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  • Zea mays  (138)
  • Springer  (138)
  • American Geophysical Union
  • American Meteorological Society
  • Oxford University Press
  • 1995-1999  (95)
  • 1990-1994  (43)
  • 1996  (45)
  • 1995  (50)
  • 1992  (43)
Collection
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  • Springer  (138)
  • American Geophysical Union
  • American Meteorological Society
  • Oxford University Press
  • Wiley-Blackwell  (1)
Years
  • 1995-1999  (95)
  • 1990-1994  (43)
Year
  • 1
    Electronic Resource
    Electronic Resource
    Inheritance of resistance in maize silks to the corn earworm (1995)
    Springer
    Entomologia experimentalis et applicata 77 (1995), S. 315-321 
    Details
    ISSN: 1570-7458
    Keywords: Insecta ; Helicoverpa zea ; Zea mays ; resistance inheritance ; joint scaling test ; additive-dominance model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The corn earworm,Helicoverpa zea (Boddie), is a perennial economic pest of field crops in the United States. Maize,Zea mays L., is the major host crop promoting the build-up of devastating corn earworm populations that limit full production of cotton, soybean, peanut, and grain sorghum. Resistance to the corn earworm in maize and in particular sweet maize, would provide an environmentally safe, economical method of control for this pest insect. Antibiotic effects of corn silks on this insect are: small larvae, extended developmental period, and reduced fecundity. Silks from individual maize plants of resistant and susceptible lines and progeny in six generations consisting of parents (P1, P2), F1, F2, and backcrosses BC1.1 (F1 × P1) and BC1.2 (F1 × P2) from each of four crosses were used to determine the genetic basis of the antibiotic resistance of silks to the corn earworm. In the cross of Zapalote Chico × PI340856, genes controlling resistance in the silks to the corn earworm larvae are dominant in PI340856 to those in Zapalote Chico. The cross of Zapalote Chico × GT114 involves parents differing in degree of resistance, and possibly differing for the genetic mechanism by which the resistance is inherited. The inheritance of resistance may involve non-additive (dominance and epistasis) genetic variance. A digenic 6-parameter model indicated (1) the resistance in this cross is controlled by more than one pair of genes and (2) some or all of the genes interact to cause non-allelic interaction. Thus, the resistance in this cross may be controlled by both dominant and recessive genes. The resistance of Zapalote Chico × CI64, an intermediate inbred, is influenced by additive gene effects. The digenic model adequately predicts all generation means of the cross of GT3 × PI340856 except for the F1. Thus, it appears that the additive-dominance model is not satisfactory for this cross involving susceptible and resistant parents. Generation mean analysis indicates that resistance to silk-feeding by corn earworm larvae is under genetic control, but gene action differs from one type of cross to another.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02383066
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  • 2
    Electronic Resource
    Electronic Resource
    Effects of a vesicular-arbuscular mycorrhizal fungus and other soil microorganisms on growth, mineral nutrient acquisition and root exudation of soil-grown maize plants (1995)
    Springer
    Mycorrhiza 5 (1995), S. 321-327 
    Details
    ISSN: 1432-1890
    Keywords: Glomus mosseae ; Zea mays ; Mineral uptake ; Root exudation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Maize (Zea mays L. cv. Alize) plants were grown in a calcareous soil in pots divided by 30-μm nylon nets into three compartments, the central one for root growth and the outer ones for hyphal growth. Sterle soil was inoculated with either (1) rhizosphere microorganisms other than vesicular-arbuscular mycorrhizal (VAM) fungi, (2) rhizosphere microorganisms together with a VAM fungus [Glomus mosseae (Nicol. and Gerd.) Gerdemann and Trappel], or (3) with a gamma-irradiated inoculum as control. Plants were grown under controlled-climate conditions and harvested after 3 or 6 weeks. VAM plants had higher shoot∶root ratios than non-VAM plants. After 6 weeks, the concentrations of P, Zn and Cu in roots and shoots had significantly increased with VAM colonization, whereas Mn concentrations had significantly decreased. Root exudates were collected on agar sheets placed on the interface between root and hyphal compartments. Six-week-old VAM and non-VAM plants had similar root exudate compositions of 72–73% reducing sugars, 17–18% phenolics, 7% organic acids and 3% amino acids. In another experiment in which root exudates were collected on agar sheets with or without antibiotics, the amounts of amino acids and carbohydrates recovered were similar in VAM and non-VAM plants. However, threeto sixfold higher amounts of carbohydrates, amino acids and phenolics were recovered when antibiotics were added to the agar sheets. Thus, the high microbial activity in the rhizosphere and on the rhizoplane limits the exudates recovered from roots.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00207404
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  • 3
    Electronic Resource
    Electronic Resource
    Effects of a vesicular-arbuscular mycorrhizal fungus and other soil microorganisms on growth, mineral nutrient acquisition and root exudation of soil-grown maize plants (1995)
    Springer
    Mycorrhiza 5 (1995), S. 321-327 
    Details
    ISSN: 1432-1890
    Keywords: Key words Glomus mosseae ; Zea mays ; Mineral uptake ; Root exudation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Maize (Zea mays L. cv. Alize) plants were grown in a calcareous soil in pots divided by 30-μm nylon nets into three compartments, the central one for root growth and the outer ones for hyphal growth. Sterile soil was inoculated with either (1) rhizosphere microorganisms other than vesicular-arbuscular mycorrhizal (VAM) fungi, (2) rhizosphere microorganisms together with a VAM fungus [Glomus mosseae (Nicol. and Gerd.) Gerdemann and Trappel], or (3) with a gamma-irradiated inoculum as control. Plants were grown under controlled-climate conditions and harvested after 3 or 6 weeks. VAM plants had higher shoot : root ratios than non-VAM plants. After 6 weeks, the concentrations of P, Zn and Cu in roots and shoots had significantly increased with VAM colonization, whereas Mn concentrations had significantly decreased. Root exudates were collected on agar sheets placed on the interface between root and hyphal compartments. Six-week-old VAM and non-VAM plants had similar root exudate compositions of 72–73% reducing sugars, 17–18% phenolics, 7% organic acids and 3% amino acids. In another experiment in which root exudates were collected on agar sheets with or without antibiotics, the amounts of amino acids and carbohydrates recovered were similar in VAM and non-VAM plants. However, three- to sixfold higher amounts of carbohydrates, amino acids and phenolics were recovered when antibiotics were added to the agar sheets. Thus, the high microbial activity in the rhizosphere and on the rhizoplane limits the exudates recovered from roots.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s005720050079
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  • 4
    Electronic Resource
    Electronic Resource
    Bioavailability of heavy metals and abundance of arbuscular mycorrhiza in a soil polluted by atmospheric deposition from a smelter (1995)
    Springer
    Biology and fertility of soils 19 (1995), S. 22-28 
    Details
    ISSN: 1432-0789
    Keywords: Arbuscular mycorrhiza ; Limed silty loam Heavy metals ; Pb-Zn smelter ; Root colonization Spore numbers ; Tolerance ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The bioavailability of heavy metals (Cd, Zn, Pb, Cu) and the abundance of arbuscular mycorrhiza (AM) were studied in two agricultural fields close to a Pb-Zn smelter and three fields outside the pollution zone all cultivated with maize (Zea mays L.). Metal extractability with ethylenediaminetetraacetic acid (EDTA)-NH4OAc and Ca(NO3)2, plant metal uptake, and mycorrhizal parameters (spore number, root colonization) were assessed at two growth stages (six-leaf and maturity). Despite regular liming, the availability of Cd, Zn, and Pb was markedly higher in the two metal-polluted fields than in the three uncontaminated fields. However, the AM abundance was not correlated with metal availability. Root colonization and spore numbers in the metal polluted fields were relatively high, though at plant maturity the former was significantly lower than in one of the uncontaminated fields. The very low AM abundance in the two other unpolluted fields was related to other factors, particular soil and plant P status and soil pH. AM root colonization did not substantially prevent plant metal accumulation, since the metal concentrations in maize grown on the polluted fields strongly exceeded normal values, and for Cd and Pb reached the limits of toxicity for animal feed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00336342
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  • 5
    Electronic Resource
    Electronic Resource
    Growth and nitrogen nutrition of maize (Zea mays L.) in soil treated with the nitrification-inhibiting insecticide Baythroid (1996)
    Springer
    Biology and fertility of soils 23 (1996), S. 161-165 
    Details
    ISSN: 1432-0789
    Keywords: Key words ANI ; Baythroid ; Cyfluthrin ; Insecticide ; 15N ; Nitrification ; N uptake ; Synthetic pyrethroid ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A pot experiment was conducted to compare the uptake and dry matter production potential of NH+ 4 and NO– 3 and to study the effect of Baythroid, a contact poison for several insect pests of agricultural crops, on growth and N uptake of maize (Zea mays L.). Nitrogen was applied as (15NH4)2SO4, K15NO3, or 15NH4NO3 and in one treatment Baythroid was combined with 15NH4NO3. Source of N had, in general, a nonsignificant effect on dry matter and N yield, but uptake of NO– 3 was significantly higher than that of NH+ 4 when both N sources were applied together. Substantial loss of N occurred from both the sources, with NH+ 4 showing greater losses. Baythroid was found to have a significant positive effect on dry matter yield of both root and shoot; N yield also increased significantly. Uptake of N from both the applied and native sources increased significantly in the presence of Baythroid and a substantial added nitrogen interaction (ANI) was determined. The positive effect of Baythroid was attributed to: (1) a prolonged availability of NH+ 4 due to inhibition of nitrification, (2) an increased availability of native soil N through enhanced mineralization, and (3) an enhanced root proliferation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00336057
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  • 6
    Electronic Resource
    Electronic Resource
    Influence of management practices on soil organic matter, microbial biomass and cotton yield in Alabama's “Old Rotation” (1996)
    Springer
    Biology and fertility of soils 23 (1996), S. 353-358 
    Details
    ISSN: 1432-0789
    Keywords: Soil carbon ; Crop rotation ; Legumes ; Cover crop ; Nitrogen fertilization ; Microbial biomass ; Soil health ; Gossypium hirsutum ; Zea mays ; Trifolium incarnatum ; Glycine max
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The “Old Rotation” cotton experiment was designed to aid farm managers in implementing rotation schemes that not only increase yield, but also improve soil quality. Six different crop rotation treatments were imposed since 1896. Rotations were: IA, cotton (Gossypium hirsutum L.) grown every year without a winter legume and without N fertilization; IB, cotton grown every year with a winter legume and without N fertilization; IC, cotton grown every year without a winter legume and with 134 kg N as NH4NO3 ha-1 year-1; IIA, 2-year cotton-corn (Zea mays L.) rotation with a winter legume and without N fertilization; IIB, 2-year cotton-corn rotation with a winter legume and with 134 kg N ha-1 year-1 as NH4NO3; and III, 3-year cotton-corn- alternating soybean [Glycine max (L.) Merr.] or rye (Secale cereale L.) rotation with a winter legume and with 134 g N as NH4NO3 ha-1 year-1. Crimson clover (Trifolium incarnatum L.) was the winter legume cover crop. The 2-year cotton-corn rotation with a winter legume and with 134 kg N ha-1 year-1 (IIB) and the 3-year cotton-corn soybean/rye rotation with a winter legume and with 134 kg N ha-1 year-1 (III) had higher amounts of soil organic matter, soil microbial biomass C and crop yield than the other four treatments. The cotton grown every year without a winter legume or N fertilizer (IA) had a lower amount of soil organic matter, soil microbial biomass C and N and cotton seed yield than all other rotations. In 1988 and 1992 cotton seed and legume yield were correlated in positive, curvilinear relationships with soil organic matter (r 2 ranged from 0.72 to 0.87). In most months, soil microbial biomass C and N was lower in the cotton grown every year without winter legumes or fertilizer (IA) than the other five rotations. In 1994, microbial biomass C and the Cmic:Corg ratio correlated in positive, curvilinear relationships with seed cotton yield (r 2=0.87 and 0.98, respectively). After 99 years of management the “Old Rotation” cotton experiment indicates that winter legumes increase amounts of both C and N in soil, which ultimately contribute to higher cotton yields. Microbial biomass C and the Cmic:Corg ratio are poor predictors of annual crop yield but may be an accurate indicator of soil health and a good predictor of long-term crop yield.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00335906
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  • 7
    Electronic Resource
    Electronic Resource
    Influence of management practices on soil organic matter, microbial biomass and cotton yield in Alabama‘s ’’Old Rotation’ (1996)
    Springer
    Biology and fertility of soils 23 (1996), S. 353-358 
    Details
    ISSN: 1432-0789
    Keywords: Key words Soil carbon ; Crop rotation ; Legumes ; Cover crop ; Nitrogen fertilization ; Microbial biomass ; Soil health ; Gossypium hirsutum ; Zea mays ; Trifolium ; incarnatum ; Glycine max
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The “Old Rotation” cotton experiment was designed to aid farm managers in implementing rotation schemes that not only increase yield, but also improve soil quality. Six different crop rotation treatments were imposed since 1896. Rotations were: IA, cotton (Gossypium hirsutum L.) grown every year without a winter legume and without N fertilization; IB, cotton grown every year with a winter legume and without N fertilization; IC, cotton grown every year without a winter legume and with 134 kg N as NH4NO3 ha–1 year–1; IIA, 2-year cotton-corn (Zea mays L.) rotation with a winter legume and without N fertilization; IIB, 2-year cotton-corn rotation with a winter legume and with 134 kg N ha–1 year–1 as NH4NO3; and III, 3-year cotton-corn- (alternating soybean [Glycine max (L.) Merr.] or rye (Secale cereale L.) rotation with a winter legume and with 134g N as NH4NO3 ha–1 year–1. Crimson clover (Trifolium incarnatum L.) was the winter legume cover crop. The 2-year cotton-corn rotation with a winter legume and with 134 kg N ha–1 year–1 (IIB) and the 3-year cotton-corn soybean/rye rotation with a winter legume and with 134 kg N ha–1 year–1 (III) had higher amounts of soil organic matter, soil microbial biomass C and crop yield than the other four treatments. The cotton grown every year without a winter legume or N fertilizer (IA) had a lower amount of soil organic matter, soil microbial biomass C and N and cotton seed yield than all other rotations. In 1988 and 1992 cotton seed and legume yield were correlated in positive, curvilinear relationships with soil organic matter (r 2 ranged from 0.72 to 0.87). In most months, soil microbial biomass C and N was lower in the cotton grown every year without winter legumes or fertilizer (IA) than the other five rotations. In 1994, microbial biomass C and the Cmic:Corg ratio correlated in positive, curvilinear relationships with seed cotton yield (r 2=0.87 and 0.98, respectively). After 99 years of management the “Old Rotation” cotton experiment indicates that winter legumes increase amounts of both C and N in soil, which ultimately contribute to higher cotton yields. Microbial biomass C and the Cmic:Corg ratio are poor predictors of annual crop yield but may be an accurate indicator of soil health and a good predictor of long-term crop yield.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003740050182
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  • 8
    Electronic Resource
    Electronic Resource
    Nitrogen use in maize-grain legume cropping systems in semi-arid Kenya (1995)
    Springer
    Biology and fertility of soils 20 (1995), S. 57-62 
    Details
    ISSN: 1432-0789
    Keywords: Nitrogen use ; Nitrogen fertilizer recovery ; Zea mays ; Phaseolus vulgaris ; Vigna unguiculata ; Nitrogen fixation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Locally suitable cultivars of maize, beans, and cowpeas were grown in field experiments for four seasons in semi-arid Kenya. For three seasons, the dry matter production and grain yield of maize and beans were not increased by N fertilizer additions up to 120 kg N ha-1. Fertilizer recoveries measured by 15N isotope dilution techniques were low, less than 20%. Inoculated and uninoculated beans failed to fix N2. By contrast the cowpea derived 50% of its N from fixation, equivalent to 197 kg N ha-1. The N content of the grain generally exceeded 40 kg N ha-1, and the N content of the seeds from the grain legumes were greater than those from the cereals. Large inputs of N fertilizer or N by fixation are required if maize-grain legume cropping system in semiarid Kenya are to be sustained in the long term.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00307842
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  • 9
    Electronic Resource
    Electronic Resource
    Growth and nitrogen nutrition of maize (Zea mays L.) in soil treated with the nitrification-inhibiting insecticide Baythroid (1996)
    Springer
    Biology and fertility of soils 23 (1996), S. 161-165 
    Details
    ISSN: 1432-0789
    Keywords: ANI ; Baythroid ; Cyfluthrin ; Insecticide ; 15N ; Nitrification ; N uptake ; Synthetic pyrethroid ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A pot experiment was conducted to compare the uptake and dry matter production potential of NH inf4 sup+ and NO inf3 sup- and to study the effect of Baythroid, a contact poison for several insect pests of agricultural crops, on growth and N uptake of maize (Zea mays L.). Nitrogen was applied as (15NH4)2SO4, K15NO3, or 15NH4NO3 and in one treatment Baythroid was combined with 15NH4NO3. Source of N had, in general, a nonsignificant effect on dry matter and N yield, but uptake of NO inf3 sup- was significantly higher than that of NH inf4 sup+ when both N sources were applied together. Substantial loss of N occurred from both the sources, with NH inf4 sup+ showing greater losses. Baythroid was found to have a significant positive effect on dry matter yield of both root and shoot; N yield also increased significantly. Uptake of N from both the applied and native sources increased significantly in the presence of Baythroid and a substantial added nitrogen interaction (ANI) was determined. The positive effect of Baythroid was attributed to: (1) a prolonged availability of NH inf4 sup+ due to inhibition of nitrification, (2) an increased availability of native soil N through enhanced mineralization, and (3) an enhanced root proliferation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00336057
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  • 10
    Electronic Resource
    Electronic Resource
    Sequential development of pathogens in the maize tarspot disease complex (1992)
    Springer
    Mycopathologia 117 (1992), S. 157-161 
    Details
    ISSN: 1573-0832
    Keywords: Phyllachora maydis ; Monographella maydis ; Coniothyrium phyllachorae ; Zea mays ; tarspot complex
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The tarspot complex is caused by the interaction of Phyllachora maydis and Monographella maydis. Coniothyrium phyllachorae, possibly a mycoparasite, is found in older ascostromata of P. maydis, which always appears first causing tarspot. M. maydis follows and is responsible for the damaging “fisheye” symptom. The fisheye symptom is always associated with a tarspot in the center of the lesion, whereas 12 to 20% of the Phyllachora ascostromata remained free of M. maydis. Inoculations of maize leaves with the Microdochium anamorph of the Monographella (usually produced in lesions) failed to produce infections. Some infections with M. maydis were, however, obtained under unusual conditions in the field. Inoculations onto tarspots in the laboratory were unsuccessful, but in field experiments inoculations with conidia of M. maydis enhanced severity of the tarspot complex. Fisheye symptoms of the complex naturally appear 2 to 7 days after the manifestation of P. maydis. This is followed a week later by the appearance of M. maydis which became predominant in the lesions and is associated with empty perithecia of P. maydis. In the early stages of the tarspots pycnidia of the anamorph of P. maydis, Linochora sp., could occasionally be observed. Ascomata of M. maydis were rare in the field. Of the 36 genetic materials of CIMMYT tested, 30 developed the fisheye symptom, 4 tarspots only and 2 remained free of symptoms
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00442777
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  • 11
    Electronic Resource
    Electronic Resource
    The effects of aflatoxin B1 on immature germinating maize (Zea mays) embryos (1992)
    Springer
    Mycopathologia 119 (1992), S. 181-190 
    Details
    ISSN: 1573-0832
    Keywords: aflatoxin B1 ; electron microscopy ; in vitro ; immature maize embryo ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Immature maize (Zea mays L.) embryos were treated with aflatoxin B1 concentrations, ranging from 0.1 μg ml−1 to 25 μg ml−1. Below 5 μg ml−1 aflatoxin B1, root and shoot elongation was not significantly inhibited. Ultrastructurally, root tip cells showed little deterioration, except a possible diffused clearing in mitochondria and plastids. As the toxin concentration was increased above 5 μgml−1, shoot, and particularly root elongation, was progressively inhibited. Associated with this, there was an apparent decrease in the ribosome population. Furthermore, membranes, particularly the vacuolar membrane, became abnormal and vacuolar distension occurred. At 20 and 25 μg ml−1, these effects were exacerbated, and mitochondria and plastid structure was disrupted. At these concentrations, there was evidence of a disruption in lipid metabolism. The results are discussed in the context of known aflatoxin effects on cellular control mechanisms and ultrastructure in animal systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00448817
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  • 12
    Electronic Resource
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    Enterobacter cloacae is an endophytic symbiont of corn (1995)
    Springer
    Mycopathologia 129 (1995), S. 117-125 
    Details
    ISSN: 1573-0832
    Keywords: Biological control ; Corn seedling disease ; Enterobacter cloacae ; Fusarium moniliforme ; Maize ; Seedling blight ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The bacteriumEnterobacter cloacae is presently used for biocontrol of postharvest diseases of fruits and vegetables and as a preplant seed treatment for suppression of damping-off. This bacterium has apparent affinities for several grass species, but it is not considered to be an endophyte. While screening corn for fungi and bacteria with potential for biocontrol of various corn diseases, the surface-sterilized kernels of one unknown Italian corn cultivar produced fungus-free corn seedlings with roots endophytically infected byE. cloacae. This paper describes the microscopic nature ofE. cloacae RRC 101 with corn, and the in vitro control ofFusarium moniliforme and other fungi with this bacterium. Light and electron microscopy determined that this isolate ofE. cloacae was biologically associated with corn seedling roots, where it was distributed intercellularly within the cortex and stele. This is a first report of a strain of this bacterium as an endophytic symbiont of roots. Following a topical application ofE. cloacae to kernels, and upon germination this bacterium readily infected roots of two other corn cultivars. The bacterium was observed within the endosperm of germinating corn seedling, but germination was not affected. Further, the bacterium was isolated from leaves and stems of 3- to 6-week-old seedlings indicating that the above ground portions of corn were also colonized. There was no evidence of damage to cells of the root during a three to four week observation period. This bacterium was antagonistic to several isolates of the corn pathogenFusarium moniliforme, and to two other species of fungi, all of which produce mycotoxins on corn.
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    URL: http://dx.doi.org/10.1007/BF01103471
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  • 13
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    The phytotoxicity of selected mycotoxins on mature, germinatingZea mays embryos (1995)
    Springer
    Mycopathologia 132 (1995), S. 173-183 
    Details
    ISSN: 1573-0832
    Keywords: Deoxynivalenol ; Embryo ; Mature ; Ochratoxin ; Plantlet ; Zearalenone ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Mature maize (Zea mays) embryos were exposed to 5, 10 and 25 µg ml−1 of deoxynivalenol (DON), zearalenone (ZEA), ochratoxin A (OA) and a mixture of zearalenone and deoxynivalenol (ZEA/DON) for 9 days. DON and the ZEA/DON combination were consistently more inhibitory of the measured parameters than either ZEA or OA. Based on the predicted additive values, it would appear that, in combination, ZEA and DON act synergistically to inhibit root and shoot growth. For ZEA alone, a concentration of 5 µg ml−1 ZEA was generally inhibitory of root and shoot elongation and fresh mass accumulation, while at 10 and 25 µg ml−1, this toxin had a stimulatory effect on these parameters. For OA, the measured effects on root and shoot growth at 5 and 25 µg ml−1 were stimulatory, while at 10 µg ml−1 OA, an inhibitory effect was observed. For all toxins, inhibitory/stimulatory effects were generally more marked for root parameters than for shoot elongation or mass.
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    URL: http://dx.doi.org/10.1007/BF01103984
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  • 14
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    Nitrogen availability alters patterns of accumulation of heat stress-induced proteins in plants (1996)
    Springer
    Oecologia 105 (1996), S. 413-418 
    Details
    ISSN: 1432-1939
    Keywords: Zea mays ; Heat-stress ; Heat-shock proteins ; Photosynthesis ; Nutrients
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Mounting evidence suggests that heat-shock proteins (HSPs) play a vital role in enhancing survival at high temperature. There is, however, considerable variation in patterns of HSP production among species, and even among and within individuals of a species. It is not known why this variation exists and to what extent variation in HSPs among organisms might be related to differences in thermotolerance. One possibility is that production of HSPs confers costs and natural selection has worked towards optimizing the cost-to-benefits of HSP synthesis and accumulation. However, the costs of this production have not been determined. If HSP production confers significant nitrogen (N) costs, then we reasoned that plants grown under low-N conditions might accumulate less HSP than high-N plants. Furthermore, if HSPs are related to thermotolerance, then variation in HSPs induced by N (or other factors) might correlate with variation in thermotolerance, here measured as short-term effects of heat stress on net CO2 assimilation and photosystem II (PSII) function. To test these predictions, we grew individuals of a single variety of corn (Zea mays L.) under different N levels and then exposed the plants to acute heat stress. We found that: (1) high-N plants produced greater amounts of mitochondrial Hsp60 and chloroplastic Hsp24 per unit protein than their low-N counterparts; and (2) patterns of HSP production were related to PSII efficiency, as measured by F v/F m. Thus, our results indicate that N availability influences HSP production in higher plants suggesting that HSP production might be resource-limited, and that among other benefits, chloroplast HSPs (e.g., Hsp24) may in some way limit damage to PSII function during heat stress.
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    URL: http://dx.doi.org/10.1007/BF00328745
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  • 15
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    Electroporation and PEG delivery of DNA into maize microspores (1992)
    Springer
    Plant cell reports 11 (1992), S. 567-570 
    Details
    ISSN: 1432-203X
    Keywords: Microspore ; Electroporation ; Transformation ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The ability to deliver and detect reporter gene activity in maize microspores was tested. Tested expression vectors contained the chloramphenicol acetyl transferase (CAT) gene and one of the following promoter-intron combinations: 1) cauliflower mosaic virus (CaMV 35S), 2) CaMV 35S + maize alcohol dehydrogenase 1 intron 6 (Adh1-I6), 3) maize alcohol dehydrogenase 1 + intron 1 (Adh1-I1), or 4) maize ubiquitin 1 + intron 1 (Ubiq 1-I1) promoter + intron. The expression vectors were delivered into maize microspores using electroporation or polyethylene glycol (PEG). Both methods were effective for delivering free DNA into microspores. Although all four promoters were active in maize protoplasts, only two promoters were active in maize microspores. The CaMV 35S and the Adh1 promoters did not promote gene expression in maize microspore. The CaMV 35S + Adh1-I6 and Ubiq1-I1 promoters produced high levels of CAT activity in maize microspores.
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    URL: http://dx.doi.org/10.1007/BF00233094
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    Cleavage polyembryony in maize (1992)
    Springer
    Sexual plant reproduction 5 (1992), S. 224-226 
    Details
    ISSN: 1432-2145
    Keywords: Zea mays ; Maize ; Polyembryony
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Two types of cleavage polyembryony are described in the inbred line VIR 17 of maize. Suspensorial embryony was observed to occur spontaneously. Typical cleavage of the zygotic proembryo occurred spontaneously, but could also be induced by treating the developing caryopses with 2,4-Dichlorophenoxyacetic acid (2,4-D) on the second day after pollination. 2,4-D was active as a decorelative factor also evoking the expression of totipotency in individual proembryonal cells.
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    URL: http://dx.doi.org/10.1007/BF00189815
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    Deleterious effect of minimal enzymatic treatments on the development of isolated maize embryo sacs in culture (1995)
    Springer
    Sexual plant reproduction 8 (1995), S. 313-317 
    Details
    ISSN: 1432-2145
    Keywords: Embryo sac ; Zea mays ; Enzymatic isolation ; Zygotic embryogenesis ; Microinjection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The long-term viability of isolated embryo sacs was studied in maize. Fertilised embryo sacs were digested in order to remove most of the nucellus cells present on their surfaces and then transferred to culture. Experiments on 161 embryo sacs showed that isolation treatments using even minimal enzymatic digestion affected the further development of the embryo sacs. Few embryo sacs survived in culture and those produced only abnormal embryos; they produced no plants. We concluded that embryo sacs isolated through enzymatic digestion may offer limited prospects for long-term studies where normal embryogenic development is required. Alternative strategies are discussed for maize.
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    URL: http://dx.doi.org/10.1007/BF00229389
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  • 18
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    Analysis of pollen-tube growth in cultured maize silks (1992)
    Springer
    Sexual plant reproduction 5 (1992), S. 227-231 
    Details
    ISSN: 1432-2145
    Keywords: Zea mays ; Maize ; Pollen-tube growth regulation ; In vitro pollination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary In vitro pollen-tube growth in maize was studied using an in vitro pollination system. In the ‘cut-silk’ method, ovaries with silks were placed on medium in vitro, whereafter the silk was cut and the upper part of the silk was pollinated. Pollen tubes were not able to bridge the space between the two silk parts. Even when silk parts were tightly connected, pollen tubes still were not able to pass the cut ends and reach the lower silk part. Pollen-tube growth rates and the direction of tube growth were not influenced by the presence or absence of an ovary. Prepollination did not have any influence on pollen-tube growth rate. Measurements of pollen-tube growth rate also showed that there was no ‘population effect’, i.e. growth rate was not stimulated by pollination with an excess of pollen grains. We found that the direction in which maize pollen grew was determined only by the positioning of the silk hairs.
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    URL: http://dx.doi.org/10.1007/BF00189816
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  • 19
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    Effects of calcium, magnesium, potassium and boron on sperm cells isolated from pollen of Zea mays L. (1995)
    Springer
    Sexual plant reproduction 8 (1995), S. 113-122 
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    ISSN: 1432-2145
    Keywords: Zea mays ; Calcium ; Cell integrity ; Cell viability ; Sperm cell
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Our previous studies showed that Brewbaker and Kwack salts, which have been widely used in pollen germination and sperm isolation, are not appropriate for the maintenance of isolated maize (Zea mays L.) sperm cells. In the present study, we have characterized the effects of each BKS component salt on the integrity of isolated sperm cells using hemacytometry. At 0.01 and 0.1 mM, there were no differences in cell number between control and any salt-treated cells except a 22% decrease with 0.1 mM MgSO4 at 48 h. At the 1 mM level, cell number decreased with time in the presence of Ca(NO3)2 and MgSO4, with loss of integrity of most cells at 48 h, while KNO3 and H3BO3 had little or no effect. Further characterization of calcium-induced reduction in cell integrity using flow cytometry showed that depletion of possible residual free calcium by addition of EGTA to the suspension medium improved cell longevity and viability. Exposure of isolated sperm cells to 1 mM calcium had no effect on cell integrity and viability in 5 h; however, only 12% of cells remained intact at 24 h. The reduction in cell integrity was hastened when cells were pretreated with the calcium ionophore A23187 prior to exposure to 1 mM calcium, with a 54% reduction in cell number at 1 h and complete cell lysis at 24 h. However, depletion of cytosolic free calcium by pretreatment of cells with the calcium ionophore followed by resuspension in the presence of EGTA resulted in rapid reduction of cell integrity as well. These results collectively suggest that maize sperm cells are sensitive to exogenous free calcium; however, a certain level of cytosolic free calcium is necessary for maintenance of integrity. Mechanisms of calcium-induced reduction in cell integrity are discussed along with possible roles of the sensitivity of sperm cells to calcium in fertilization.
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    URL: http://dx.doi.org/10.1007/BF00230898
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    New lights in early steps of in vitro fertilization in plants (1996)
    Springer
    Sexual plant reproduction 9 (1996), S. 324-329 
    Details
    ISSN: 1432-2145
    Keywords: Key words In vitro fertilization ; Gamete recognition ; Gamete fusion ; Egg activation ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Studies using in vitro fertilization systems in animals and lower plants have led to a better understanding of the initial steps of fertilization and their underlying mechanisms. These mechanisms remain to be elucidated in flowering plants. Recent progress related to the development of in vitro fertilization systems using maize as a plant model is presented in this review. Their potential for leading to a better understanding of the process of gametic recognition and fusion and of the early events triggering egg activation and zygote formation are also discussed.
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    URL: http://dx.doi.org/10.1007/s004970050050
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  • 21
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    New lights in early steps of in vitro fertilization in plants (1996)
    Springer
    Sexual plant reproduction 9 (1996), S. 324-329 
    Details
    ISSN: 1432-2145
    Keywords: In vitro fertilization ; Gamete recognition ; Gamete fusion ; Egg activation ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Studies using in vitro fertilization systems in animals and lower plants have led to a better understanding of the initial steps of fertilization and their underlying mechanisms. These mechanisms remain to be elucidated in flowering plants. Recent progress related to the development of in vitro fertilization systems using maize as a plant model is presented in this review. Their potential for leading to a better understanding of the process of gametic recognition and fusion and of the early events triggering egg activation and zygote formation are also discussed.
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    URL: http://dx.doi.org/10.1007/BF02441950
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    Maturation of maize pollen in vitro (1992)
    Springer
    Plant cell reports 11 (1992), S. 535-539 
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    ISSN: 1432-203X
    Keywords: Zea mays ; in vitro culture ; in vitro pollen ; pollen germination ; fertilization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Maturation of maize pollen was obtained in male reproductive structures cultured in vitro. Immature tassels containing microspores at the mid-uninucleate to late-binucleate stage of development were excised and spikelets, anthers, and/or isolated microspores were cultured on a medium capable of supporting pollen maturation. Microspore mitosis, culminating in the production of starch-filled, trinucleate pollen capable of germination, was observed after 7–15 days, depending on the genotype and stage at which the cultures were initiated. Up to 100%, 70%, and 20% of the cultured spikelets, anthers, and isolated microspores, respectively, produced mature pollen, which germinated, however, at different frequencies (i.e., spikelets, 50–70%; anthers, 5–10%; microspores, 〈1%). Mature kernels were produced following fertilization with pollen from cultured spikelets and anthers. These procedures provide methods for the in vitro manipulation of a significant phase of the maize life cycle.
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    URL: http://dx.doi.org/10.1007/BF00236273
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    Matrix-associated DNA from maize is enriched in repetitive sequences (1992)
    Springer
    Plant cell reports 11 (1992), S. 355-358 
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    ISSN: 1432-203X
    Keywords: Zea mays ; Matrix-associated ; DNA ; repetitive sequences ; DNA loops
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In order to elucidate some features of the topological organization of DNA within the plant nucleus, DNA fragments involved in the attachment of the DNA loops to the nuclear matrix in maize were studied. The matrix-associated DNA from dry embryo and meristematic cells after extensive digestion with DNase I and high salt treatment was about 2% of the total DNA, sized within the range of 50 and 250 bp. This DNA was found to be enriched in repetitive DNA sequences, both for nuclei from dry embryo and meristematic cells. The loop size of the DNA in cells of Zea mays appeared to be between 5 and 25 kbp.
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    Field evaluation of N2 fixation and N partitioning in climbing bean (Phaseolus vulgaris L.) using 15N (1992)
    Springer
    Biology and fertility of soils 13 (1992), S. 142-146 
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    ISSN: 1432-0789
    Keywords: A value ; Common bean ; N remobilization ; Soil N balance ; Atom% 15N excess ; Phaseolus vulgaris ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The common bean (Phaseolus vulgaris L.) is generally regarded as a poor N2 fixer. This study assessed the sources of N (fertilizer, soil, and fixed N), N partitioning and mobilization, and soil N balance under field conditions in an indeterminate-type climbing bean (P. vulgaris L. cv. Cipro) at the vegetative, early pod-filling, and physiological maturity stages, using the A-value approach. This involved the application of 10 and 100 kg N ha-1 of 15N-labelled ammonium sulphate to the climbing bean and a reference crop, maize (Zea mays L.). At the late pod-filling stage (75 days after planting) the climbing bean had accumulated 119 kg N ha-1, 84% being derived from fixation, 16% from soil, and only 0.2% from the 15N fertilizer. N2 fixation was generally high at all stages of plant growth, but the maximum fixation (74% of the total N2 fixed) occurred during the interval between early (55 days after planting) and late podfilling. The N2 fixed between 55 and 75 days after planting bas a major source (88%) of the N demand of the developing pod, and only about 11% was contributed from the soil. There was essentially no mobilization of N from the shoots or roots for pod development. The cultivation of common bean cultivars that maintain a high N2-fixing capacity especially during pod filling, satisfying almost all the N needs of the developing pod and thus requiring little or no mobilization of N from the shoots for pod development, may lead to a net positive soil N balance.
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    URL: http://dx.doi.org/10.1007/BF00336269
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    Odors influence choice of oviposition sites byDiabrotica virgifera virgifera (Coleoptera: Chrysomelidae) (1992)
    Springer
    Journal of chemical ecology 18 (1992), S. 1227-1237 
    Details
    ISSN: 1573-1561
    Keywords: Western corn rootworm ; Diabrotica virgifera virgifera ; Coleoptera ; Chrysomelidae ; bacteria ; carbon dioxide ; pheromone ; semiochemicals ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract FemaleDiabrotica virgifera virgifera LeConte were allowed to choose between oviposition substrates that were and those that were not associated with potential sources of semiochemicals. Females deposited over five times more eggs on moist towelettes that were treated with homogenates of female abdomens than on towelettes treated with distilled water. Similar results were obtained when screening separated the homogenates from the towelettes, indicating that odors alone could elicit the response. In contrast, females did not choose towelettes that had previously been used for oviposition or towelettes containing eggs over unused towelettes. Further tests with homogenates of abdomens and a bacteriostatic agent (sorbate) indicated that the females were probably responding to bacterial odors rather than an oviposition-enhancing pheromone. Four strains of bacteria were isolated from a homogenate of female abdomens; females deposited 4 to 16 times more eggs on substrates with odors of the bacteria than on substrates with odors of uninoculated nutrient agar. In no-choice tests, bacterial odors did not increase the number of eggs deposited per female beetle; however, in choice tests with dishes that tended to retain any beetles that entered, there were more eggs per female (but not more beetles) after 24 hr in dishes with bacterial odors than in those without the odors. Females also chose dishes with odors of excised maize (Zea mays L.) roots or elevated levels of carbon dioxide over “control” dishes.
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    Mutational analysis of the ‘conserved region’ of maize streak virus suggests its involvement in replication (1992)
    Springer
    Plant molecular biology 19 (1992), S. 601-610 
    Details
    ISSN: 1573-5028
    Keywords: geminivirus ; agroinfection ; Zea mays ; large intergenic region (LIR)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Maize streak virus as well as other geminiviruses contain a potential hairpin structure with the conserved sequence TAATATTAC in the loop. We assessed the possible involvement of this structure in replication and symptom induction of the virus. A series of insertion and deletion mutants were analyzed by agroinfection. Deletion of the hairpin or insertions in the conserved sequence abolished symptom development. Viral DNA could not be detected in the infected tissue. However, a mutant with a point mutation in the ‘conserved’ sequence, isolated after inoculation of maize plants with an insertion mutant, was able to replicate and to induce symptoms.
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    An mRNA that specifically accumulates in maize roots delineates a novel subset of developing cortical cells (1992)
    Springer
    Plant molecular biology 20 (1992), S. 821-831 
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    ISSN: 1573-5028
    Keywords: cortex ; developmental regulation ; in situ hybridization ; organ-specific gene expression ; roots ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A near full-length cDNA clone (pZRP3) corresponding to an mRNA that accumulates specifically in roots of maize was isolated. The ZRP3 mRNA is ca. 600 nucleotides in length. The amino acid sequence of the predicted polypeptide is rich in leucine (16%), proline (11%), and cysteine (8.5%). The zrp3 gene appears to be expressed exclusively in roots, whereas other ZRP3-related genes are expressed in additional organs of the maize plant. In situ hybridization shows that ZRP3 mRNA accumulation is largely confined to the cells of the cortical ground meristem. Furthermore, accumulation of this mRNA occurs within a distinct subset of cortical cells, the inner three to four cell layers.
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    A DNA polymerase from maize axes: its purification and possible role (1992)
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    Plant molecular biology 20 (1992), S. 1159-1168 
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    ISSN: 1573-5028
    Keywords: DNA polymerase ; germination ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Three different DNA polymerase activities can be resolved by passing a protein extract from 24 h imbibed maize axes through DEAE-cellulose. These activities have been numbered 1, 2 and 3, according to their elution order. One of them, DNA polymerase 2, elutes at 100–120 mM phosphates. This enzyme was further purified by passing it through Heparin-Sepharose, Sephacryl S-300 and DNA cellulose. Purification was nearly 5000-fold. The enzyme needs Mg2+, is stimulated by K+, has an optimum pH of 7.0 and its optimum temperature is 30–37 °C. Specific inhibitors for different types of polymerases, such as aphidicolin, dideoxythymidine triphosphate and N-ethyl maleimide, gave intermediate values of inhibition, making impossible the definition of the type of enzyme purified by its inhibitory pattern. SDS-PAGE indicated the presence of several bands of molecular masses of 28–40, 56 and 15 kDa. Most of these bands could be visualized when proteins from crude extracts were analyzed by western blot, using an antibody against calf thymus DNA polymerase α. A high molecular mass (around 500 kDa) was calculated by western blot of native gels using the same antibody. Finally, specific activity of this enzyme increased 100-fold during maize germination whereas polymerase 3 virtually did not increase. Furthermore, immunoprecipitation experiments with the antipolymerase α-antibody showed a decrease in DNA polymerase activity by 70%. The possibility that polymerase 2 is a replicative enzyme is discussed.
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    Stress responses in maize: Sequence analysis of cDNAs encoding glycine-rich proteins (1992)
    Springer
    Plant molecular biology 18 (1992), S. 847-849 
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    ISSN: 1573-5028
    Keywords: cDNA ; nucleotide sequence ; glycine-rich proteins ; chemical stress ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
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    URL: http://dx.doi.org/10.1007/BF00020034
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    Multiple ocs-like elements required for efficient transcription of the mannopine synthase gene of T-DNA in maize protoplasts (1992)
    Springer
    Plant molecular biology 20 (1992), S. 219-233 
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    ISSN: 1573-5028
    Keywords: promoter ; electroporation ; protoplasts ; transient assay ; Agrobacterium ; Ti plasmid ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Regulatory elements controlling transcriptional activity of the mannopine synthase 2′ promoter (mas 2′) were defined by analysis of deletion mutants in transient expression assays in maize protoplasts. Deletion of the region between −305 and −290 containing sequence similarity to the octopine synthase (ocs) promoter element reduced activity by 67% compared to wild type activity. Less than 1% of the activity remained in 5′ deletions downstream of −153. Inclusion of various heterologous enhancer-like sequences immediately upstream of position −325 increased activity by up to 7.5-fold. Insertion of the −325 to −275 sequence alone, or in combination with heterologous enhancer-like elements, restored activity of some of the 5′-deletion mutants. Restoration of activity was not obtained with mutants deleted past position −127. Our results suggest that a single class of nuclear proteins from maize interact with high affinity at elements designated mas b (−306 to −275; mas 1′ element), d (−127 to −108), and e (−82 to −39; mas 2′ element) as well as the 20 bp element from the ocs promoter. Although the binding site at mas d only appears to accommodate a single protein, this element has the potential to make a weak, but positive, contribution to the activity of the mas 2′ promoter. The binding of nuclear proteins could not be demonstrated at mas a and c, both of which showed limited homology to the ocs element. Mutational evidence suggested that mas a and c may also contribute to mas 2′ transcription.
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    A Zea mays GTP-binding protein of the ARF family complements an Escherichia coli mutant with a temperature-sensitive malonyl-coenzyme A:acyl carrier protein transacylase (1995)
    Springer
    Plant molecular biology 27 (1995), S. 629-633 
    Details
    ISSN: 1573-5028
    Keywords: GTP binding ; ADP ribosylation ; Zea mays ; Escherichia coli ; fatty acid biosynthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In an attempt to isolate a plant malonyl-coenzyme A:acyl carrier protein transacylase cDNA clone, by direct genetic selection in an Escherichia coli fabD mutant (LA2-89) with a maize cDNA expression library, a Zea mays cDNA clone encoding a GTP-binding protein of the ARF family was isolated. Complementation of a mutation affecting bacterial membrane lipid biosynthesis by a plant ARF protein, could indicate the existence of as yet unidentified bacterial equivalents of this ubiquitous eucaryotic GTP-binding protein.
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    The involvement of Opaque 2 on β-prolamin gene regulation in maize and Coix suggests a more general role for this transcriptional activator (1995)
    Springer
    Plant molecular biology 27 (1995), S. 1015-1029 
    Details
    ISSN: 1573-5028
    Keywords: β-prolamin ; Coix lacryma-jobi ; different O2-binding sites ; Opaque 2 ; transcriptional regulation ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The maize opaque 2 (o2) mutation is known to have numerous pleiotropic effects. Some polypeptides have their expression depressed while others are enhanced. The best characterized effects of the o2 mutation are those exerted on endosperm genes encoding the storage protein class of the 22 kDa α-zeins and the ribosome inactivating protein b-32. The Opaque 2 (O2) locus encodes a basic domain-leucine zipper DNA-binding factor, O2, which transcriptionally regulates these genes. In the maize-related grass Coix lacryma-jobi, an O2-homologous protein regulates the 25 kDa α-coixin gene family. We show in this paper that O2 transcriptionally regulates the structurally and developmentally different class of the β-prolamins. A new O2-binding box was identified in β-prolamin genes from maize and Coix that, together with the boxes previously identified in other endosperm expressed genes, forms a curious collection of O2 cis elements. This may have regulatory implications on the role of O2 in the mechanism that controls coordinated gene expression in the developing endosperm. Considering that the O2 locus controls at least three distinct classes of genes in maize endosperm, we propose that the O2 protein may play a more general role in maize endosperm development than previously conceived.
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    Molecular cloning, characterization and expression of an elongation factor 1α gene in maize (1995)
    Springer
    Plant molecular biology 29 (1995), S. 611-615 
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    ISSN: 1573-5028
    Keywords: elongation factor 1α ; EF-1α ; Zea mays ; cDNA sequence ; gene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A cDNA (zmEF1A) and the corresponding genomic clone (zmgEF1A) of a member of the gene family encoding the α subunit of translation elongation factor 1 (EF-1α) have been isolated from maize. The deduced amino acid sequence is 447 residues long interrupted by one intron. Southern blot analysis reveals that the cloned EF-1α gene is one member out of a family consisting of at least six genes. As shown by northern hybridizations in leaves the mRNA level increases at low temperature whereas time-course experiments over 24 h at 5°C show that in roots the overall mRNA level of EF-1α is transiently decreased. These results indicate that the expression of EF-1α is differently regulated in leaves and roots under cold stress.
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    Nucleotide sequence of a region of maize chloroplast DNA containing the 3′ end of clpP, exon 1 of rps12 and rpl20 and their cotranscription (1992)
    Springer
    Plant molecular biology 18 (1992), S. 415-418 
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    ISSN: 1573-5028
    Keywords: ribosomal protein ; rps12 ; rpl20 ; clpP ; chloroplast genome ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
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    URL: http://dx.doi.org/10.1007/BF00034970
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    Nitrate reductase transcript is expressed in the primary response of maize to environmental nitrate (1992)
    Springer
    Plant molecular biology 18 (1992), S. 55-64 
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    ISSN: 1573-5028
    Keywords: cycloheximide ; leaf ; nitrate induction ; nitrate reductase transcript ; root ; scutellum ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The nitrate induction of NADH:nitrate reductase mRNA in maize roots, scutella and leaves was investigated in the presence and absence of inhibitors of protein synthesis. In the absence of inhibitors, nitrate treatment caused a fairly rapid (2 to 3 h) increase in the level of the nitrate reductase transcript in all tissues. When cytoplasmic protein synthesis was inhibited by cycloheximide, nitrate reductase mRNA was induced by nitrate in all tissues to levels equal to or greater than those found with nitrate treatment alone. Treatment of maize tissues with cycloheximide in the absence of nitrate had only a small effect on the accumulation of the nitrate reductase mRNA. Inhibition of organellar protein synthesis with chloramphenicol also had little or no effect on nitrate-induced nitrate reductase mRNA accumuiation in roots and scutella, but did appear to partially inhibit appearance of transcript in leaves. Excision of scutella in the absence of nitrate was sufficient to cause some accumulation of the nitrate reductase transcript. Since cytoplasmic protein synthesis was not required for expression of nitrate reductase transcripts, induction of these transcripts by nitrate is a primary response of maize to this environmental signal. Thus, it appears that the signal transduction system mediating this response is constitutively expressed in roots, scutella and leaves of maize.
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    cDNA clones encoding Arabidopsis thaliana and Zea mays mitochondrial chaperonin HSP60 and gene expression during seed germination and heat shock (1992)
    Springer
    Plant molecular biology 18 (1992), S. 873-885 
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    ISSN: 1573-5028
    Keywords: Arabidopsis thaliana ; ATPase ; cpn60 ; developmental regulation ; molecular chaperones ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Mitochondria contain a nuclear-encoded heat shock protein, HSP60, which functions as a chaperonin in the post-translational assembly of multimeric proteins encoded by both nuclear and mitochondrial genes. We have isolated and sequenced full-length complementary DNAs coding for this mitochondrial chaperonin in Arabidopsis thaliana and Zea mays. Southern-blot analysis indicates the presence of a single hsp60 gene in the genome of A. thaliana. There is a high degree of homology at the predicted amino acid levels (43 to 60%) between plant HSP60s and their homologues in prokaryotes and other eukaryotes which indicates that these proteins must have similar evolutionarily conserved functions in all organisms. Northern- and western-blot analyses indicate that the expression of the hsp60 gene is developmentally regulated during seed germination. It is also heat-inducible. Developmental regulation of the (β-subunit) of F1-ATPase, an enzyme complex that is involved in the cyanide-sensitive mitochondrial electron transport system, indicates that imbibed embryos undergo rapid mitochondrial biogenesis through the early stages of germination. Based on the functional role of HSP60 in macromolecular assembly, these data collectively suggest that the presence of higher levels of HSP60 is necessary during active mitochondrial biogenesis, when the need for this protein is greatest in assisting the rapid assembly of the oligomeric protein structures.
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    URL: http://dx.doi.org/10.1007/BF00019202
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    Dissection of a pollen-specific promoter from maize by transient transformation assays (1992)
    Springer
    Plant molecular biology 18 (1992), S. 211-218 
    Details
    ISSN: 1573-5028
    Keywords: pollen-specific gene expression ; promoter analysis ; transient assays ; Tradescantia ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We have previously reported the isolation and characterization of a gene (Zm 13) from Zea mays which shows a pollen-specific pattern of expression. Stably transformed tobacco plants containing a reporter gene linked to portions of the Zm 13 5′ flanking region show correct temporal and spatial expression of the gene. Here we present a more detailed analysis of the 5′ regions responsible for expression in pollen by utilizing a transient expression system. Constructs containing the β-glucuronidase (GUS) gene under the control of various sized fragments of the Zm13 5′ flanking region were introduced into Tradescantia and Zea mays pollen via high-velocity microprojectile bombardment, and monitored both visually and with a fluorescence assay. The results suggest that sequences necessary for expression in pollen are present in a region from −100 to −54, while other sequences which amplify that expression reside between −260 and −100. The replacement of the normal terminator with a portion of the Zm13 3′ region containing the putative polyadenylation signal and site also increased GUS expression. While the −260 to −100 region contains sequences similar to other protein-binding domains reported for plants, the −100 to −54 region appears to contain no significant homology to other known promoter fragments which direct pollen-specific expression. The microprojectile bombardment of Tradescantia pollen appears to be a good test system for assaying maize and possibly other monocot promoter constructs for pollen expression.
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    URL: http://dx.doi.org/10.1007/BF00034950
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    The maize GapC4 promoter confers anaerobic reporter gene expression and shows homology to the maize anthocyanin regulatory locus C1 (1995)
    Springer
    Plant molecular biology 29 (1995), S. 1293-1298 
    Details
    ISSN: 1573-5028
    Keywords: anaerobiosis ; BMS cells ; glyceraldehyde-3-phosphate dehydrogenase ; transient gene expression ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The cytosolic glyceraldehyde-3-phosphate dehydrogenase (GapC) gene family of maize is differentially expressed in response to anaerobic stress. While GapC1 and GapC2 are downregulated, GapC3 and GapC4 are anaerobically induced. We have sequenced and analyzed a 3073 bp promoter fragment of GapC4. The promoter confers anaerobic induction of a reporter gene construct in a transient gene expression system in maize. Deletion analysis of the GapC4 promoter revealed a 270 bp long DNA region required for anaerobic induction. This region contains sequence motifs resembling the cis-acting sequences of the anaerobically induced maize Adh1 and Adh2 genes. Furthermore, the 3073 bp GapC4 promoter fragment displays homology to long terminal repeats of maize retrotransposons and to the 3′ region of the maize anthocyanin regulatory locus C1.
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    URL: http://dx.doi.org/10.1007/BF00020469
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    Characterization of a maize ribosomal P2 protein cDNA and phylogenetic analysis of the P1/P2 family of ribosomal proteins (1996)
    Springer
    Plant molecular biology 30 (1996), S. 655-658 
    Details
    ISSN: 1573-5028
    Keywords: cDNA ; evolution ; p2 protein ; ribosome ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The nucleotide sequence of a full-length ribosomal P2 protein cDNA from maize was determined and used for a sequence comparison with the P2 and P1 proteins from other organisms. The integration of these data into a phylogenetic tree shows that the P proteins separated into the subspecies P1 and P2 before the eukaryotic kingdoms including plants developed from their ancestor.
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    URL: http://dx.doi.org/10.1007/BF00049340
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  • 40
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    Molecular cloning and characterization of six cDNAs expressed during glucose starvation in excised maize (Zea mays L.) root tips (1995)
    Springer
    Plant molecular biology 28 (1995), S. 473-485 
    Details
    ISSN: 1573-5028
    Keywords: carbon catabolite repression ; cDNA ; gene expression ; stress-induced genes ; glucose-starvation ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In order to isolate glucose-starvation-related cDNAs in maize (Zea mays L.) root tips, a cDNA library was constructed with poly(A)+ mRNA from 24 h starved root tips. After differential screening of the library, we isolated six different cDNAs (named pZSS2 and pZSS7) which were expressed during glucose starvation. Time course analysis revealed that maximum expression of five of these genes occurs 30 h after the onset of the starvation treatment. On the contrary, the expression of mRNAs corresponding to pZSS4 was maximal at an early stage of starvation and then dramatically decreased. The expression of this gene did not seem to be specific for glucose starvation. The pattern of induction of the genes corresponding to pZSS2, pZSS3, pZSS5, pZSS6 and pZSS7 revealed that non-metabolizable sugars such as L-glucose and mannitol induce mRNA transcription similarly to glucose starvation. When D-glucose or any other metabolizable sugar was supplied, the level of transcripts was reduced. Nucleotide sequence analyses of the six cDNAs allowed identification of five of them by comparison with sequence data bases. The protein encoded by clone pZSS2 is analogous to a wound-induced protein from barley. Clones pZSS4 to pZSS7 encode, respectively, a transmembrane protein, a cysteine protease, a metallothionein-like protein and a chymotrypsin/subtilisin-like protease inhibitor. Clone pZSS3 shares no significant homology with any known sequence.
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    URL: http://dx.doi.org/10.1007/BF00020395
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    Intron-dependent transient expression of the maize GapA1 gene (1995)
    Springer
    Plant molecular biology 28 (1995), S. 667-676 
    Details
    ISSN: 1573-5028
    Keywords: gene expression ; promoter ; glyceraldehyde-3-phosphate dehydrogenase ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Transient expression experiments show that the maize GapA1 promoter exhibits a requirement for sequences contained within intron 1 and surrounding exon border regions for expression in maize Black Mexican Sweet cells. Maize GapA1-promoter constructs lacking intron 1 are inactive. Intron 1 and its exon border sequences, when reintroduced into constructs lacking introns, restore gene activity whereas intron 2 and its exon borders to not. The minimal promoter so defined encompasses roughly 250 bp upstream of the in vivo transcription start and appears also to include intron 1. An octameric sequence was identified in intron 1 of maize GapA1 which is similar to sequence motifs found in other maize introns known to increase transient expression. Partial restoration of gene expression in GapA1 constructs lacking intron 1 was achieved through insertion of the identified octameric sequence.
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    URL: http://dx.doi.org/10.1007/BF00021192
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  • 42
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    PCR-generated cDNA library of transition-stage maize embryos: cloning and expression of calmodulin genes during early embryogenesis (1995)
    Springer
    Plant molecular biology 27 (1995), S. 105-113 
    Details
    ISSN: 1573-5028
    Keywords: calmodulin ; cDNA library ; embryogenesis ; PCR ; transition stage ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract One hundred maize zygotic embryos microdissected at the transition stage were used to construct a cDNA library after non-selective PCR (NS-PCR) amplification of whole cDNA populations. The library contains 2.3 × 105 recombinants and two different calmodulin cDNAs were cloned using a heterologous probe from petunia. Calmodulin expression was confirmed throughout maize embryogenesis at the mRNA, amplified cDNA and protein levels. Sequence analysis suggests a maize origin for both clones and negligible nucleotide changes linked to PCR. This library is the first described for early plant embryos and represents a breakthrough to isolate genes involved in embryo differentiation.
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    URL: http://dx.doi.org/10.1007/BF00019182
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    Evidence for the thiamine biosynthetic pathway in higher-plant plastids and its developmental regulation (1995)
    Springer
    Plant molecular biology 29 (1995), S. 809-821 
    Details
    ISSN: 1573-5028
    Keywords: Zea mays ; thiamine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Thiamine or vitamin B-1, is an essential constituent of all cells since it is a cofactor for two enzyme complexes involved in the citric acid cycle, pyruvate dehydrogenase and α-ketoglutarate dehydrogenase. Thiamine is synthesized by plants, but it is a dietary requirement for humans and other animals. The biosynthetic pathway for thiamine in plants has not been well characterized and none of the enzymes involved have been isolated. Here we report the cloning and characterization of two cDNAs representing members of the maize thi1 gene family encoding an enzyme of the thiamine biosynthetic pathway. This assignment was made based on sequence homology to a yeast thiamine biosynthetic gene and by functional complementation of a yeast strain in which the endogenous gene was inactivated. Using immunoblot analysis, the thi1 gene product was found to be located in a plastid membrane fraction. RNA gel blot analysis of various tissues and developmental stages indicated thi1 expression was differentially regulated in a manner consistent with what is known about thiamine synthesis in plants. This is the first report of cDNAs encoding proteins involved in thiamine biosynthesis for any plant species.
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    URL: http://dx.doi.org/10.1007/BF00041170
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    ZmHox: a novel class of maize homeobox genes (1996)
    Springer
    Plant molecular biology 30 (1996), S. 439-453 
    Details
    ISSN: 1573-5028
    Keywords: Zea mays ; homeobox gene family ; gene expression ; DNA-binding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Clones of two highly related genes, ZmHox2a and ZmHox2b (Zea mays homeobox), were isolated from maize embryo cDNA libraries by screening with the ZmHox1a homeobox sequence. The genes map to chromosomes 3 and 8, respectively, and encode mRNA transcripts of 6 kb. The encoded proteins, ZmHox2a and b, share 84% sequence identity and exhibit a modular structure with several novel plant-specific protein domains. Interestingly, each ZmHox2 gene product contains two complete homeodomains which, for Zmhox2a, were both shown to be functional DNA-binding motifs in vitro. Not only probes encoding the homeobox but also DNA fragments corresponding to other ZmHox2 domains hybridize to multiple bands in genomic Southern blots, indicating that related protein domains may be conserved in other maize genes. The ZmHox2a/b genes, therefore, are members of a novel and large class of maize genes, some of which can be expected to encode new transcription factors.
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    URL: http://dx.doi.org/10.1007/BF00049323
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    Structure and regulation of the maize Bronze2 promoter (1996)
    Springer
    Plant molecular biology 32 (1996), S. 599-609 
    Details
    ISSN: 1573-5028
    Keywords: anthocyanin ; Bronze2 gene ; transcriptional regulation ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The maize Bronze2 (Bz2) gene encodes a glutathione S-transferase that is required for anthocyanin pigment accumulation. Two classes of regulatory proteins, R and C1, are required for transcriptional activation of Bz2 and several additional structural genes. Functional domains of the Bz2 promoter were identified using Bz2 promoterdriven luciferase reporter genes electroporated into maize protoplasts together with R and C1 expression plasmids. Complete regulation was conferred by 224 nt of the Bz2 promoter. Within this region at least two separable regions are independently capable of conferring regulation by R and C1. Predicted regulatory elements corresponding to two classes of sequence motifs, the Myb-box homologous ‘C1-motif’, TAACTG/CAGTTA, and the G-box and E-box homologous ‘R-motif’, CACGTG, were shown to be important for full R and C1 activation of the Bz2 promoter. Expression of reconstructed Bz2 genes with mutated promoters was quantified using RNase protection, and this analysis confirmed results obtained using reporter genes.
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    URL: http://dx.doi.org/10.1007/BF00020201
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    Manipulating cytoplasmic pH under anoxia: A critical test of the role of pH in the switch from aerobic to anaerobic metabolism (1995)
    Springer
    Planta 195 (1995), S. 324-330 
    Details
    ISSN: 1432-2048
    Keywords: Anoxia ; Biochemical pH-stat ; Cytoplasmic pH ; Ethanol production ; Pyruvate decarboxylase ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Ethanol production by maize (Zea mays L.) root tips, measured by an enzymic assay of the suspending medium, was correlated with changes in the cytoplasmic pH, determined by in-vivo 31P nuclear magnetic resonance (NMR) spectroscopy, following the onset of anoxia. Strong evidence for the role of the cytoplasmic pH in triggering the switch to ethanol production under anoxia was obtained by: (i) varying the pH of the suspending medium between pH 4 and pH 10; and (ii) using the permeant weak base methylamine to combat the acidification of the cytoplasm induced by the anoxic conditions. Experimentally, it proved to be much easier to manipulate the cytoplasmic pH under anoxia after the pH had stabilised, rather than during the initial rapid acidification that occurred following the onset of anoxia, and in the presence of methylamine, it was possible to impose a normal aerobic cytoplasmic pH value on tissue that was metabolising anaerobically. By this means it was possible to demonstrate the reversibility of the pH effect on ethanol production under anoxia and thus to provide good evidence in support of the biochemical pH-stat model of the anoxic response. The NMR measurement of the cytoplasmic pH in the presence of methylamine was achieved by using a manganese pretreatment technique to eliminate interference between the cytoplasmic and vacuolar Pi signals, and it seems likely that the experimental approach used here will have further applications in studies of the metabolic response to anoxia.
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    URL: http://dx.doi.org/10.1007/BF00202588
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    Transport and dynamics of molecules dissolved in maize root cortex membranes (1995)
    Springer
    The journal of membrane biology 143 (1995), S. 19-28 
    Details
    ISSN: 1432-1424
    Keywords: Plant membrane ; Lipid domain ; Fluorescence photobleaching recovery ; Electron paramagnetic resonance ; Temperature stress ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Translational diffusion of a fluorescent sterol probe was measured in the plasma membranes of protoplasts isolated from cortical cells of the primary root of maize seedlings. The apparent lateral diffusion coefficient was typically observed to be nearly insensitive to temperature, while the mobile fraction increased with increasing temperature. These fluorescence photobleaching recovery (FPR) measurements were compared with the electron paramagnetic resonance (EPR) spectra of the methyl ester of 13-doxyl palmitic acid in membranes of corn root tissue in situ. The complex spectra observed with this probe were analyzed as weighted sums of simpler spectra of various order parameters and rotational correlation times. The reconstituted spectra calculated from the model show that EPR also detects a mobile (less ordered, fluid) fraction, distinguished by the order parameter S=0.1 to 0.2, which becomes more abundant as temperature increases and is qualitatively comparable to the mobile fraction determined by the FPR method. The observed results on the mobile fractions and the diffusion rates for translational (FPR) as well as rotational (EPR) motions are interpreted in terms of membrane organization, thus providing information on the population and structural patterns of the coexisting domains with a special emphasis on the response of the membrane to temperature changes.
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    URL: http://dx.doi.org/10.1007/BF00232520
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    Detection of the apomictic mode of reproduction in maize-Tripsacum hybrids using maize RFLP markers (1995)
    Springer
    Theoretical and applied genetics 90 (1995), S. 1198-1203 
    Details
    ISSN: 1432-2242
    Keywords: Diplospory ; RFLP ; Bulk-segregant analysis ; Genome similarity ; Intergeneric hybrids ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Polyploid plants in the genus Tripsacum, a wild relative of maize, reproduce through gametophytic apomixis of the diplosporous type, an asexual mode of reproduction through seed. Moving gene(s) responsible for the apomictic trait into crop plants would open new areas in plant breeding and agriculture. Efforts to transfer apomixis from Tripsacum into maize at CIMMYT resulted in numerou intergeneric F1 hybrids obtained from various Tripsacum species. A bulk-segregant analysis was carried out to identify molecular markers linked to diplospory in T. dactyloides. This was possible because of numerous genome similarities among related species in the Andropogoneae. On the basis of maize RFLP probes, three restriction fragments co-segregating with diplospory were identified in one maize-Tripsacum dactyloides F1 population that segregated 1∶1 for the mode of reproduction. The markers were also found to be linked in the maize RFLP map, on the distal end of the long arm of chromosome 6. These results support a simple inheritance of diplospory in Tripsacum. Manipulation of the mode of reproduction in maize-Tripsacum backcross generations, and implications for the transfer of apomixis into maize, are discussed.
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    URL: http://dx.doi.org/10.1007/BF00222943
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    Comparative mapping in F2∶3 and F6∶7 generations of quantitative trait loci for grain yield and yield components in maize (1996)
    Springer
    Theoretical and applied genetics 92 (1996), S. 817-826 
    Details
    ISSN: 1432-2242
    Keywords: Zea mays ; RFLPs ; Plant breeding ; Genetics ; Recombination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract This study was conducted to compare maize quantitative trait loci (QTL) detection for grain yield and yield components in F2∶3 and F6∶7 recombinant inbred (RI) lines from the same population. One hundred and eighty-six F6∶7 RIs from a Mo17×H99 population were grown in a replicated field experiment and analyzed at 101 loci detected by restriction fragment length polymorphisms (RFLPs). Single-factor analysis of variance was conducted for each locus-trait combination to identify QTL. For grain yield, 6 QTL were detected accounting for 22% of the phenotypic variation. A total of 63 QTL were identified for the seven grain yield components with alleles from both parents contributing to increased trait values. Several genetic regions were associated with more than one trait, indicating possible linked and/or pleiotropic effects. In a comparison with 150 F2∶3 lines from the same population, the same genetic regions and parental effects were detected across generations despite being evaluated under diverse environmental conditions. Some of the QTL detected in the F2∶3 seem to be dissected into multiple, linked QTL in the F6∶7 generation, indicating better genetic resolution for QTL detection with RIs. Also, genetic effects at QTL are smaller in the F6∶7 generation for all traits.
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    URL: http://dx.doi.org/10.1007/BF00221893
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    Chromosomal and cell size analysis of cold tolerant maize (1992)
    Springer
    Theoretical and applied genetics 84 (1992), S. 798-802 
    Details
    ISSN: 1432-2242
    Keywords: Zea mays ; C-banding ; Cell size ; Chloroplast number ; Cold tolerance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary C-band number, guard cell length, and chloroplast number per guard cell were determined for eight maize populations. These populations consisted of maize selected for cold tolerance at the University of Nebraska as well as the original unselected populations. The genome size of these populations had previously been determined. C-band number fluctuated concertedly with the changes in genome size indicating that deletions and additions of constitutive heterochromatin occurred during selection, resulting in altered genome sizes. Guard cell size of all the cold tolerant populations was greater than the cell size of the respective nonselected populations. Chloroplast number per guard cell was also higher in all the cold tolerant populations than in their parental populations, but the increases were not statistically significant. The results indicate that changes in genome size that occurred during selection for cold tolerance are the result of changes in amounts of C-band heterochromatin and that the selection process results in an increase in cell size in the cold tolerant populations.
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    Cytological and molecular characterization of oat x maize partial hybrids (1996)
    Springer
    Theoretical and applied genetics 93 (1996), S. 123-135 
    Details
    ISSN: 1432-2242
    Keywords: Avena sativa ; Zea mays ; Wide hybridization ; Genomic in situ hybridization ; Cytogenetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In cereals, interspecific and intergeneric hybridizations (wide crosses) which yield karyotypically stable hybrid plants have been used as starting points to widen the genetic base of a crop and to construct stocks for genetic analysis. Also, uniparental genome elimination in karyotypically unstable hybrids has been utilized for cereal haploid production. We have crossed hexaploid oat (2n=6x=42, Avena sativa L.) and maize (2n=2x=20, Zea mays L.) and recovered 90 progenies through embryo rescue. Fifty-two plants (58%) produced from oatxmaize hybridization were oat haploids (2n=3x=21) following maize chromosome elimination. Twenty-eight plants (31%) were found to be stable partial hybrids with 1–4 maize chromosomes in addition to a haploid set of 21 oat chromosomes (2n=21+1 to 2n=21+4). Ten of the ninety plants produced were found to be apparent chromosomal chimeras, where some tissues in a given plant contained maize chromosomes while other tissues did not, or else different tissues contained a different number of maize chromosomes. DNA restriction fragment length polymorphisms (RFLPs) were used to identify the maize chromosome(s) present in the various oat-maize progenies. Maize chromosomes 2, 3, 4, 5, 6, 7, 8, and 9 were detected in partial hybrids and chromosomal chimeras. Maize chromosomes 1 and 10 were not detected in the plants analyzed to-date. Furthermore, partial self-fertility, which is common in oat haploids, was also observed in some oat-maize hybrids. Upon selfing, partial hybrids with one or two maize chromosomes showed nearly complete transmission of the maize chromosome to give self-fertile maize-chromosome-addition oat plants. Fertile lines were recovered that contained an added maize chromosome or chromosome pair representing six of the ten maize chromosomes. Four independently derived disomic maize chromosome addition lines contained chromosome 4, one line carried chromosome 7, two lines had chromosome 9, one had chromosome 2, and one had chromosome 3. One maize chromosome-8 monosomic addition line was also identified. We also identified a double disomic addition line containing both maize chromosomes 4 and 7. This constitutes the first report of the production of karyotypically stable partial hybrids involving highly unrelated species from two subfamilies of the Gramineae (Pooideae — oat, and Panicoideae — maize) and the subsequent recovery of fertile oat-maize chromosome addition lines. These represent novel material for gene/ marker mapping, maize chromosome manipulation, the study of maize gene expression in oat, and the transfer of maize DNA, genes, or active transposons to oat.
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    URL: http://dx.doi.org/10.1007/BF00225737
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    Cytological and molecular characterization of oat×maize partial hybrids (1996)
    Springer
    Theoretical and applied genetics 93 (1996), S. 123-135 
    Details
    ISSN: 1432-2242
    Keywords: Key wordsAvena sativa ; Zea mays ; Wide hybridization ; Genomic in situ hybridization ; Cytogenetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In cereals, interspecific and intergeneric hybridizations (wide crosses) which yield karyotypically stable hybrid plants have been used as starting points to widen the genetic base of a crop and to construct stocks for genetic analysis. Also, uniparental genome elimination in karyotypically unstable hybrids has been utilized for cereal haploid production. We have crossed hexaploid oat (2n=6x=42, Avena sativa L.) and maize (2n=2x=20, Zea mays L.) and recovered 90 progenies through embryo rescue. Fifty-two plants (58%) produced from oat×maize hybridization were oat haploids (2n=3x=21) following maize chromosome elimination. Twenty-eight plants (31%) were found to be stable partial hybrids with 1–4 maize chromosomes in addition to a haploid set of 21 oat chromosomes (2n=21+1 to 2n=21+4). Ten of the ninety plants produced were found to be apparent chromosomal chimeras, where some tissues in a given plant contained maize chromosomes while other tissues did not, or else different tissues contained a different number of maize chromosomes. DNA restriction fragment length polymorphisms (RFLPs) were used to identify the maize chromosome(s) present in the various oat-maize progenies. Maize chromosomes 2, 3, 4, 5, 6, 7, 8, and 9 were detected in partial hybrids and chromosomal chimeras. Maize chromosomes 1 and 10 were not detected in the plants analyzed to-date. Furthermore, partial self-fertility, which is common in oat haploids, was also observed in some oat-maize hybrids. Upon selfing, partial hybrids with one or two maize chromosomes showed nearly complete transmission of the maize chromosome to give self-fertile maize-chromosome-addition oat plants. Fertile lines were recovered that contained an added maize chromosome or chromosome pair representing six of the ten maize chromosomes. Four independently derived disomic maize chromosome addition lines contained chromosome 4, one line carried chromosome 7, two lines had chromosome 9, one had chromosome 2, and one had chromosome 3. One maize chromosome-8 monosomic addition line was also identified. We also identified a double disomic addition line containing both maize chromosomes 4 and 7. This constitutes the first report of the production of karyotypically stable partial hybrids involving highly unrelated species from two subfamilies of the Gramineae (Pooideae – oat, and Panicoideae – maize) and the subsequent recovery of fertile oat-maize chromosome addition lines. These represent novel material for gene/ marker mapping, maize chromosome manipulation, the study of maize gene expression in oat, and the transfer of maize DNA, genes, or active transposons to oat.
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    Binding sites for maize nuclear proteins in the subterminal regions of the transposable elementActivator (1996)
    Springer
    Molecular genetics and genomics 251 (1996), S. 428-435 
    Details
    ISSN: 1617-4623
    Keywords: Transposable element ; Ac ; Zea mays ; Host factor ; DNase I protection assay
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Genetic data suggest that transposition of the maize elementActivator (Ac) is modulated by host factors. Using gel retardation and DNase I protection assays we identified maize proteins which bind to seven subterminal sites in both ends ofAc. Four DNase I-protected sites contain a GGTAAA sequence, the other three include either GATAAA or GTTAAA. The specificity of the maize protein binding toAc was verified by using a synthetic fragment containing four GGTAAA motifs as probe and competitor in gel retardation assays. All seven binding sites are located within regions requiredin cis for transposition. A maize protein binding site with the same sequence has previously been identified in the terminal inverted repeats of the maizeMutator element. Thus, the protein, that recognizes this sequence is a good candidate for a regulatory host factor forAc transposition.
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    URL: http://dx.doi.org/10.1007/BF02172371
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    Intron-specific stimulation of anaerobic gene expression and splicing efficiency in maize cells (1996)
    Springer
    Molecular genetics and genomics 251 (1996), S. 252-258 
    Details
    ISSN: 1617-4623
    Keywords: Key words Anaerobiosis ; Glyceraldehyde-3-phosphate dehydrogenase ; Introns ; Transientgene expression ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Most of the glyceraldehyde-3-phosphate dehydrogenase (GAPDH) genes characterized in plants and algae to date have one intron very close to the 5′ end of the gene. To study the functional relevance of some of these introns for gene expression we have analysed the influence of three 5′ introns on transient gene expression of the anaerobically inducible maize GapC4 promoter in maize cells. Under aerobic conditions, reporter gene expression is increased in the presence of the first introns of the GapC4 and GapC1 genes, and the first intron of the nuclear encoded chloroplast-specific GapA1 gene. In contrast, the GapC4 intron increases anaerobic gene expression above the level obtained for the intronless construct, while anaerobic expression of constructs harboring the GapA1 and GapC1 introns was similar to the anaerobic expression level of the intronless construct. Splicing analysis revealed that the GapC4 intron is processed more efficiently under anaerobic conditions, while no change in splicing efficiency is observed for the GapC1 and the GapA1 introns when subjected to anaerobic conditions. These results suggest that an increase in splicing efficiency contributes to the anaerobic induction of the maize GapC4 gene.
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    URL: http://dx.doi.org/10.1007/BF02172925
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    Intron-specific stimulation of anaerobic gene expression and splicing efficiency in maize cells (1996)
    Springer
    Molecular genetics and genomics 251 (1996), S. 252-258 
    Details
    ISSN: 1617-4623
    Keywords: Anaerobiosis ; Glyceraldehyde-3-phosphate dehydrogenase ; Introns ; Transient gene expression ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Most of the glyceraldehyde-3-phosphate dehydrogenase (GAPDH) genes characterized in plants and algae to date have one intron very close to the 5′ end of the gene. To study the functional relevance of some of these introns for gene expression we have analysed the influence of three 5′ introns on transient gene expression of the anaerobically inducible maizeGapC4 promoter in maize cells. Under aerobic conditions, reporter gene expression is increased in the presence of the first introns of theGapC4 andGapC1 genes, and the first intron of the nuclear encoded chloroplast-specificGapA1 gene. In contrast, theGapC4 intron increases anaerobic gene expression above the level obtained for the intronless construct, while anaerobic expression of constructs harboring theGapA1 andGapC1 introns was similar to the anaerobic expression level of the intronless construct. Splicing analysis revealed that theGapC4 intron is processed more efficiently under anaerobic conditions, while no change in splicing efficiency is observed for theGapC1 and theGapA1 introns when subjected to anaerobic conditions. These results suggest that an increase in splicing efficiency contributes to the anaerobic induction of the maizeGapC4 gene.
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    URL: http://dx.doi.org/10.1007/BF02172925
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    Mechanical release and lectin labeling of maize root protoplasts (1992)
    Springer
    Protoplasma 169 (1992), S. 49-56 
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    ISSN: 1615-6102
    Keywords: Lectin ; Plasma membrane ; Protoplast isolation ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary An improved method for the mechanical release of protoplasts from plant tissues is described. The historically-low yield of mechanically-released protoplasts is greatly increased by use of a simple electrically-driven tissue sheer and by optimization of various other steps in the procedure. As counted by light microscopy of a purified preparation, the number of mechanically-released protoplasts obtained is about 6×104 per gram fresh weight of cortical tissue from the primary root of maize (Zea mays L. WF9×Mo 17) seedlings. Nuclear staining of the preparation, however, shows that about half of these protoplasts lack a nucleus and thus are actually subprotoplasts. Comparison of lectin binding to the plasma membranes of mechanically-and enzymatically-released protoplasts shows that both types contain binding sites forRicinus communis agglutinin. Binding sites for peanut (Arachis hypogaea) agglutinin are not naturally present on mechanically-released protoplasts but are generated by exposure to a mixture of Cellulysin and Pectolyase Y-23, the cell wall-degrading enzymes used to prepare enzymatically-released protoplasts.
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    URL: http://dx.doi.org/10.1007/BF01343369
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    Plant cell wall architecture is revealed by rapid-freezing and deep-etching (1992)
    Springer
    Protoplasma 167 (1992), S. 33-42 
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    ISSN: 1615-6102
    Keywords: Daucus carota ; Zea mays ; Vigna radiata ; Helicoidal cell walls ; Polylamellate cell walls ; Rapid-freeze deep-etch
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary This paper reports on preliminary investigations into the structure of cell walls of varying complexity as revealed by the rapidfreeze deep-etch technique. Three cell types from different species were examined in order to compare the three-dimensional arrangement of random, polylamellate and helicoidal walls. Each cell type displayed a distinctive level of organisation with respect to the cellulose microfibrils and the matrix material. In polylamellated walls, the microfibrils within each layer were linked to each other by 16–20 nm long side chains regularly spaced along the length of the microfibril. In helicoidal walls, the shifting of the microfibrils could cleary be seen, yet no recognisable structures were observed which could mediate this movement.
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    URL: http://dx.doi.org/10.1007/BF01353578
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    Developmental SEM observations on an extracellular matrix in embryogenic calli ofDrosera rotundifolia andZea mays (1995)
    Springer
    Protoplasma 186 (1995), S. 45-49 
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    ISSN: 1615-6102
    Keywords: Drosera rotundifolia ; Embryogenic callus ; Extracellular matrix ; Scanning electron microscopy ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Primary embryogenic callus ofDrosera rotundifolia and long-term cultured embryogenic callus ofZea mays possess a conspicuous extracellular matrix (ECM) around and between embryogenic cells. The structural arrangement of ECM depends on the developmental stage of the embryogenic cells. Single embryoid cells were covered with, and connected by net-like material. However, surface cells of young globular embryoids were covered with a coherent layer of ECM which forms bridges with net-like material between the cells which was gradually reduced to coarse strands. When protodermis was formed on the surface of globular embryoids, the ECM disappeared completely. The ECM network was never observed on the surface of heart- and torpedo-shaped embryoids. Safranine (especially 0.1%) stabilized the structure of ECM. Digestion with pronase E and proteinase K indicated that the ECM contains proteinaceous components. Similar developmental patterns of ECM were observed in dicotyledonous and monocotyledonous examples. The ECM represents a stable morphological structure even during long-term embryogenic culture in maize.
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    URL: http://dx.doi.org/10.1007/BF01276934
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    From in vitro fertilization to early embryogenesis in maize (1995)
    Springer
    Protoplasma 187 (1995), S. 3-12 
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    ISSN: 1615-6102
    Keywords: Gamete protoplasts ; In vitro fertilization ; Early embryogenesis ; Developmental mutations ; Polymerase chain reaction ; cDNA libraries ; Gene cloning ; Angiosperm ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The development of in vitro fertilization methods in plants, the characterization of developmental mutants, and the adaptation of molecular biology techniques to construct cDNA libraries from minute samples, all represent important recent technical break-throughs. They allow the study of fertilization and early embryogenesis at a molecular level and considerable improvement in the under-standing of higher plant reproduction can be predicted over the next few years. Important biological questions, such as polyspermy, gamete fusion physiology, asymmetrical cell division, embryo axis formation, can now be addressed experimentally in maize, which appears as a major study model in this area.
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    URL: http://dx.doi.org/10.1007/BF01280227
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    uidA gene transfer and expression in maize microspores using the biolistic method (1995)
    Springer
    Protoplasma 187 (1995), S. 138-143 
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    ISSN: 1615-6102
    Keywords: Biolistics ; Microspores ; GUS-expression ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The ability to recover male gametophyte derived plants, which is necessary to get transformed haploid plants, was verified for a hybrid of maize. Using the isolated microspore culture technique, a 9 × 10−5 plant regeneration frequency was obtained. Maize microspores were bombarded with tungsten particles using a PDS He/1000 apparatus. GUS expression in the microspores was maximum with 1.1 μm diameter tungsten microprojectiles for 1100 and 1350 psi helium pressures at a 6 cm distance between the launch point and the target cells. Increasing the amount of DNA coated on the microparticles from 1.66 to 4 μg DNA/mg of particles allowed a two-fold and four-fold increase of the GUS-expressing microspore frequency for 1100 and 1350 psi helium pressure bombardment, respectively. Optimal concentration of solidifying agent in the bombardment support culture medium was found to be 1%. Cell density ranging from 25000 microspores/bombardment to 100000 microspores/bombardment did not affect the frequency of GUS-expressing microspores. Using these optimal conditions, the maximum frequency of GUS-expressing microspores was found to be about 9 × 10−4, while maintaining an embryo formation frequency about 5 × 10−4.
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    URL: http://dx.doi.org/10.1007/BF01280242
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    Effect of thefloury-2 locus on protein body formation during maize endosperm development (1992)
    Springer
    Protoplasma 171 (1992), S. 123-133 
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    ISSN: 1615-6102
    Keywords: Endosperm ; Floury-2 ; Immunocytochemistry ; Protein bodies ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The seed storage proteins of maize (Zea mays L.) are synthesized during endosperm development on membrane-bound polyribosomes. These proteins, collectively called zeins, are translocated into the lumen of the rough endoplasmic reticulum, where they assemble into protein bodies. Protein body formation in normal genotypes occurs via an ordered deposition of the various types of zeins, and leads to the formation of spherical structures with a diameter of about 1 μm. These structures consist of a central core that contains predominantly α-zein; this central region is surrounded by a peripheral layer of β- and γ-zeins, and the entire structure is bounded by rough endoplasmic reticulum. In the endosperm mutant floury-2 the levels of all classes of zeins are reduced; these kernels exhibit an opaque phenotype instead of the vitreous phenotype observed in normal genotypes. In contrast to the discrete, spherical protein bodies which are formed in normal maize endosperm, the protein bodies within floury-2 endosperm are irregular and the zeins are disorganized; patches of β- and γ-zeins occur within irregularly lobed clusters of α-zein within the lumen of the rough endoplasmic reticulum. The implications of this aberrant distribution are discussed, both with respect to protein body development and kernel characteristics.
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    URL: http://dx.doi.org/10.1007/BF01403727
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    Distribution of pectins in cell walls of maize coleoptiles and evidence against their involvement in auxin-induced extension growth (1995)
    Springer
    Protoplasma 188 (1995), S. 213-224 
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    ISSN: 1615-6102
    Keywords: Auxin ; Cell wall ; Coleoptile ; Pectin ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Aiming to elucidate the possible involvement of pectins in auxin-mediated elongation growth the distribution of pectins in cell walls of maize coleoptiles was investigated. Antibodies against defined epitopes of pectin were used: JIM 5 recognizing pectin with a low degree of esterification, JIM 7 recognizing highly esterified pectin and 2F4 recognizing a pectin epitope induced by Ca2+. JIM 5 weakly labeled the outer third of the outer epidermal wall and the center of filled cell corners in the parenchyma. A similar labeling pattern was obtained with 2F4. In contrast, JIM 7 densely labeled the whole outer epidermal wall except the innermost layer, the middle lamellae, and the inner edges of open cell corners in the parenchyma. Enzymatic de-esterification with pectin methylesterase increased the labeling by JIM 5 and 2F4 substantially. A further increase of the labeling density by JIM 5 and 2F4 and an extension of the labeling over the whole outer epidermal wall could be observed after chemical de-esterification with alkali. This indicates that both methyl- and other esters exist in maize outer epidermal walls. Thus, in the growth-controlling outer epidermal wall a clear zonation of pectin fractions was observed: the outermost layer (about one third to one half of wall thickness) contains unesterified pectin epitopes, presumably cross-linked by Ca2+ extract. Tracer experiments with3H-myo-inositol showed rapid accumulation of tracer in all extractable pectin fractions and in a fraction tightly bound to the cell wall. A stimulatory effect of IAA on tracer incorporation could not be detected in any fraction. Summarizing the data a model of the pectin distribution in the cell walls of maize coleoptiles was developed and its implications for the mechanism of auxin-induced wall loosening are discussed.
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    Chromosome endoreduplication in endosperm cells of two maize genotypes and their progenies (1995)
    Springer
    Protoplasma 189 (1995), S. 156-162 
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    ISSN: 1615-6102
    Keywords: Chromosome endoreduplication ; Endosperm ; Protein accumulation ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Chromosome endoreduplication is a very common process in higher plants but its function and genetic control are still to be clarified. In our experiments we analyzed, by Feulgen cytophotometry, chromosome endoreduplication in endosperm cells of two maize genotypes, IHP and ILP, having high and low protein content in their seed, respectively. Chromosome endoreduplication occurs in both lines within 24 days after pollination, attaining a maximum ploidy level of 384C (7 DNA replication rounds) in IHP and of 192C (6 replication rounds) in ILP. In the mature seed, endosperms of the two lines show different mean ploidy level. In reciprocal crosses between IHP and ILP the f1 endosperms have mean ploidy levels analogous to that of the maternal parent, showing that the difference in ploidy level between the two genotypes is maintained. After selfing of the f1 plants, the difference in ploidy level between the two F2 populations is reduced. In F2 the mean ploidy level is as variable as in f1, indicating the absence of genetic segregation. From our data, it is apparent that both the genetic constitution (cytoplasmic and nuclear) of the maternal parent and the genotype of the individual endosperms influence the ploidy level. An analysis of the protein content in endosperms carried out on the same seed sample as analyzed cytophotometrically showed that the protein content increases, during seed development, parallel to chromosome endoreduplication and varies, in the two lines, in reciprocal crosses and their progeny, according to the same trend as mean ploidy level, suggesting a correlation between the two parameters.
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    A novel tubular array associated with protein bodies in the rough endoplasmic reticulum ofopaque-2 maize (1996)
    Springer
    Protoplasma 195 (1996), S. 68-77 
    Details
    ISSN: 1615-6102
    Keywords: Endosperm ; Immunocytochemistry ; Opaque-2 ; Protein bodies ; Tubular arrays ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The seed storage proteins of maize (Zea mays L.) are synthesized during endosperm development on membrane-bound polyribosomes. Protein body formation in normal genotypes occurs via a sequential deposition of the various types of zeins, and leads to the formation of spherical structures with a diameter of about l μm. In the endosperm mutantopaque-2 the level of one zein class is reduced; these kernels exhibit an opaque phenotype instead of the vitreous phenotype displayed in normal genotypes, presumably due to the decrease in total zein protein at the time of desiccation. Previous microscopic examination ofopaque-2 protein bodies at 22 DAP (days after pollination) showed that the protein bodies were morphologically similar to those of normal genotypes. However, the endosperm ofopaque-2 maize at 14 DAP contains tubular arrays within the rough endoplasmic reticulum. These tubular arrays are tightly associated with the developing protein bodies. Long strands of tubules, sometimes 10 μm in length, are observed in the endosperm, and partially formed protein bodies often seem to be forming directly from these tubular arrays. No immunostaining is associated with this tubular material when any of the anti-zein antibodies are used.
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    URL: http://dx.doi.org/10.1007/BF01279187
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    Increases in binding protein (BiP) accompany changes in protein body morphology in three high-lysine mutants of maize (1992)
    Springer
    Protoplasma 171 (1992), S. 142-152 
    Details
    ISSN: 1615-6102
    Keywords: Endosperm ; Zea mays ; Immunolocalization ; Rough endoplasmic reticulum ; Binding protein ; Protein bodies
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A maize 75 kDa protein recently has been identified as a plant homolog of the mammalian binding protein (BiP). To better understand the function of BiP in protein body formation in maize endosperm, immunomicroscopy studies were conducted on three maize endosperm mutants, floury-2, Mucronate, and Defective endosperm-B 30, in which the level of BiP is highly elevated. Our results showed that protein body morphology in all three mutants was altered. In addition, BiP was localized in both the ER and peripheral regions of the abnormal protein bodies. The degree to which protein body morphology differed from normal was positively correlated with increased amounts of BiP. In addition, the accumulation of BiP in abnormal protein bodies increased with protein body maturation. In the three endosperm mutants, the arrangement of zeins within protein bodies had been perturbed, yet none of the specific zein subclasses exhibited the staining pattern found for BiP. The association of BiP with abnormal packaging of proteins in protein bodies may reflect a biological function to mediate protein folding and assembly in maize endosperm.
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    Hexacyanoferrate (III) stimulation of elongation in coleoptile segments fromZea mays L. (1995)
    Springer
    Protoplasma 184 (1995), S. 63-71 
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    ISSN: 1615-6102
    Keywords: Avena sativa ; Elongation growth ; Glycine max ; Hexacyanoferrate III (ferricyanide) ; Indole-3-acetic acid ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The influence of exogenous potassium hexacyanoferrate (III) (HCF III) on elongation of maize (Zea mays L.) coleoptile segments was investigated. Addition of HCF III led to a strong stimulation of growth both in the presence and absence of indole-3-acetic acid (IAA). The magnitude of growth stimulation was dependent on the presence of IAA, HCF III concentration, incubation time, and phase growth. The reduced form, potassium hexacyanoferrate (II), was without effect on growth. In the presence of HCF III, elongation was suppressed when coleoptile segments were treated with N,N′-dicyclohexylcarbodiimide, cycloheximide or atebrine (quinacrine). The addition of HCF III stimulated the IAA-induced proton extrusion, and the e−/H+ ratio decreased with incubation time. HCF III also strongly stimulated elongation ofAvena saliva L. coleoptile segments andGlycine max L. hypocotyl segments. These results suggested that a plasma membrane redox system (NADH oxidase type I) may be involved in the regulation of growth through the activity of the plasma membrane-bound ATPase.
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    Iron and copper in plasma membranes of maize (Zea mays L.) roots investigated by proton induced X-ray emission (1995)
    Springer
    Protoplasma 184 (1995), S. 145-150 
    Details
    ISSN: 1615-6102
    Keywords: Zea mays ; Plasma membrane ; Proton microprobe ; Copper ; Iron ; Zinc
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Plasma membranes of maize (Zea mays L., cv. Sil Anjou 18) roots were isolated by aqueous two-phase partitioning. Multi elemental analysis by proton induced X-ray emission (PIXE) was used for the investigation of elemental composition of plasma membranes. Fe, Cu, and Zn as well as P, S, and Ca were identified. We did not find significant amounts of V, Mn, Se, Mo, or W.
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    Changes in the glutathione level induced by transplasma membrane electron transport in maize (Zea mays L.) (1995)
    Springer
    Protoplasma 184 (1995), S. 238-248 
    Details
    ISSN: 1615-6102
    Keywords: Glutathione ; Plasma membrane redox acitvity ; Electron transfer ; Zea mays ; Diamide ; Buthionine-D,L-suIfoximine ; Hexacyanoferrate III ; Hexabromoiridate IV
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We investigated changes of thiols (GSH, GSSG, and cysteine) induced by transplasma membrane electron transport after addition of artificial electron acceptors and the influence of the thiol level on redox activity. GSH, GSSG, and cysteine content of maize (Zea mays L. cv. Golden Bantam) roots and coleoptile segments was determined by high performance liquid chromatography with a fluorescence detector. GSSG increased after treatment with 0.8 mM diamide, an SH-group oxidizer. GSH level of roots increased after treatment with diamide, while GSH levels of coleoptiles decreased. Incubation of roots with the GSH biosynthesis inhibitor buthionine-D,L-sulfoximine for 6 days lowered the glutathione level up to 80%. However, the GSH/GSSG ratio of maize roots remained constant after treatment with both effectors. The GSH/GSSG ratio and the glutathione level were changed by addition of artificial electron acceptors like hexacyanoferrate (III) or hexabromoiridate (IV), which do not permeate the plasma membrane. Hexacyanoferrate (III) reduction was inhibited up to 25% after the cellular glutathione level was lowered by treatment with diamide or buthionine-D,L-sulfoximine. Proton secretion induced by reduction of the electron acceptors was not affected by both modulators. The change in glutathione level is different for roots and coleoptiles. Our data are discussed with regard to the role of GSH in electron donation for a plasma membrane bound electron transport system.
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    Reactivation of Mutator transposable elements of maize by ultraviolet light (1992)
    Springer
    Molecular genetics and genomics 234 (1992), S. 353-360 
    Details
    ISSN: 1617-4623
    Keywords: Zea mays ; Somatic instability ; Bronze-2 ; Genomic shock ; Pollen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary After epigenetic loss of Mutator activity, the family of Mu elements in Zea mays becomes immobile and highly methylated; in addition, Mu9, the presumptive autonomous regulatory element, is transcriptionally silent and its copy number decreases in successive crosses to non-Mutator lines. Spontaneous reactivation, scored as restoration of somatic instability of potentially mutable alleles of Bronze-2, of such cryptic Mutator lines is rare, occurring with a frequency of about 10−4. Irradiation of pollen with 254 nm ultraviolet light increases reactivation rate in the progeny kernels by up to 40-fold. Accompanying reactivation, the copy number of Mu9 elements increased, two-fold in one line and 20 to 40-fold in a second line. Reactivation may involve direct DNA damage or immediate physiological stress in the treated pollen.
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    Endosperm-specific demethylation and activation of specific alleles of α-tubulin genes of Zea mays L. (1995)
    Springer
    Molecular genetics and genomics 246 (1995), S. 716-722 
    Details
    ISSN: 1617-4623
    Keywords: α-tubulin gene ; DNA methylation ; Endosperm ; Parental imprinting ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We have investigated the methylation status of the α-tubulin genes, and the degree of accumulation of their mRNAs in endosperm, embryo and seedling tissues of Zea mays L. We have found that many of the α-tubulin genes are differentially demethylated in the endosperm relative to the embryo and seedling. However, only for tubα2 and tubα4 could a correlation between DNA demethylation and increased RNA accumulation be detected. By analyzing the inbred lines W64A and A69Y and their reciprocal crosses, we have also identified in the endosperm two α-tubulin genes, tubα3 and tubα4, that are differentially demethylated if transmitted by the maternal germline, but that remain hypermethylated when transmitted by the paternal germline.
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    Pulsed-field gel mapping of maize mitochondrial chromosomes (1995)
    Springer
    Molecular genetics and genomics 247 (1995), S. 255-263 
    Details
    ISSN: 1617-4623
    Keywords: Zea mays ; Mitochondrial genome ; Pulsed-field gel electrophoresis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Pulsed-field gel electrophoresis (PFGE) in combination with infrequently cutting restriction enzymes was used to investigate the structure of the mitochondrial (mt) genome of the maize variety Black Mexican Sweet (BMS). The mt genome of this variety was found to resemble that of the closely related B37N variety, with one recombination and five insertion/deletion events being sufficient to account for the differences observed between the two genomes. The majority of the BMS genome is organized as a number of subgenomic chromosomes with circular restriction maps. Several large repeated sequences are found in the BMS mt genome, but not all appear to be in recombinational equilibrium. No molecules large enough to contain the entire mt genome were discernible using these techniques. The mapping approach described here provides a means of quickly analyzing the large and complex rut genomes of plants.
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    Phosphorylation/dephosphorylation steps are key events in the phytochrome-mediated enhancement of nitrate reductase mRNA levels and enzyme activity in maize (1996)
    Springer
    Molecular genetics and genomics 251 (1996), S. 599-608 
    Details
    ISSN: 1617-4623
    Keywords: Key words Nitrate reductase ; Phytochrome ; Phosphorylation ; Protein kinase C ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  We provide evidence to show that the increase in nitrate reductase (NR) transcript level stimulated by red light is mediated via a phosphorylation-dependent step. The light-stimulated enhancement of NR transcript level was significantly inhibited by H-7, a protein kinase inhibitor, whereas okadaic acid (OKA), a phosphatase inhibitor, had no effect. Phorbol myristate acetate (PMA), an activator of protein kinase C (PKC) enhanced the NR transcript level in dark-grown leaves. No correlation between changes in NR transcript level and NR activity (NRA) was observed. Inhibition of NRA by OKA and stimulation by H-7 indicated that NRA is increased by dephosphorylating the enzyme. We have identified a protein kinase (C type) that can phosphorylate the purified NR in vitro without the involvement of other accessory proteins. By in vivo labelling with 32P and immunoprecipitation of NR with NR antibodies it was found that in the presence of OKA most NR protein (NRP) was present in phosphorylated state, while with H-7 the reverse was seen. The red (R) and far-red (FR) light reversible experiments suggested that phytochrome (Pfr, an active form) stimulation of NRA is mediated by dephosphorylation of the enzyme, suggesting that Pfr regulates both NR transcription and NRA via phosphorylation/dephosphorylation steps controlled by separate signal transduction pathways.
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    Phosphorylation/dephosphorylation steps are key events in the phytochrome-mediated enhancement of nitrate reductase mRNA levels and enzyme activity in maize (1996)
    Springer
    Molecular genetics and genomics 251 (1996), S. 599-608 
    Details
    ISSN: 1617-4623
    Keywords: Nitrate reductase ; Phytochrome ; Phosphorylation ; Protein kinase C ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We provide evidence to show that the increase in nitrate reductase (NR) transcript level stimulated by red light is mediated via a phosphorylation-dependent step. The light-stimulated enhancement of NR transcript level was significantly inhibited by H-7, a protein kinase inhibitor, whereas okadaic acid (OKA), a phosphatase inhibitor, had no effect. Phorbol myristate acetate (PMA), an activator of protein kinase C (PKC) enhanced the NR transcript level in darkgrown leaves. No correlation between changes in NR transcript level and NR activity (NRA) was observed. Inhibition of NRA by OKA and stimulation by H-7 indicated that NRA is increased by dephosphorylating the enzyme. We have identified a protein kinase (C type) that can phosphorylate the purified NR in vitro without the involvement of other accessory proteins. By in vivo labelling with32P and immunoprecipitation of NR with NR antibodies it was found that in the presence of OKA most NR protein (NRP) was present in phosphorylated state, while with H-7 the reverse was seen. The red (R) and far-red (FR) light reversible experiments suggested that phytochrome (Pfr, an active form) stimulation of NRA is mediated by dephosphorylation of the enzyme, suggesting that Pfr regulates both NR transcription and NRA via phosphorylation/dephosphorylation steps controlled by separate signal transduction pathways.
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    URL: http://dx.doi.org/10.1007/BF02173650
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    Analysis of Mutator-induced mutations in the Iojap gene of maize (1996)
    Springer
    Molecular genetics and genomics 252 (1996), S. 216-220 
    Details
    ISSN: 1617-4623
    Keywords: Key wordsiojap ; Chloroplast development ; Transposon ; Robertson's Mutator ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The recessive nuclear mutation iojap (ij) in maize produces striped plants with normal chloroplasts in green sectors and poorly developed chloroplasts in the white sectors. The ij mutation is also characterized by an array of additional phenotypic affects which suggests a pivotal role for Ij in chloroplast development. The Ij gene from maize has been isolated; however, the sequence has not provided information on the action of the Ij gene product. As an extension of the analysis of the Ij gene we have generated a number of independent transposon insertion mutations using the Robertson's Mutator (Mu). Insertions were found to be distributed throughout the 5' half of the gene and all showed a similar striping pattern to that of the original ij mutation, ij-ref. While several of the new mutant alleles produced ij-homologous transcripts none produced detectable levels of the Ij polypeptide product. Chloroplast development in some cells appears to be able to proceed in the absence of the Ij polypeptide.
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    URL: http://dx.doi.org/10.1007/s004389670025
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    Regulated transcription of the maize Bronze-2 promoter in electroporated protoplasts requires the C1 and R gene products (1992)
    Springer
    Molecular genetics and genomics 233 (1992), S. 379-387 
    Details
    ISSN: 1617-4623
    Keywords: Bz2 gene ; Transcriptional regulation ; Anthocyanin pathway ; Transient assay ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The putative maize transcription factor genes R and C1 are required for expression of reporter genes with promoters from the Bz1 and A1 genes, which encode enzymes required for anthocyanin biosynthesis in maize. Bz2 is another anthocyanin biosynthetic gene; we show that expression of a reporter gene from the Bz2 promoter also requires R and C1 when the fusion construct is introduced into maize kernels by particle gun bombardment. When electroporated into maize protoplasts from a suspension cell line not synthesizing anthocyanins, reporter genes with Bz2, Bz1, and A1 promoters are expressed only when both R and C1 expression plasmids are co-electroporated. Electroporation of R and C1 expression plasmids also induces the endogenous genes required for anthocyanin synthesis, resulting in pink protoplasts within 24 h. RNase protection analysis demonstrates that accumulation of mRNA from the endogenous Bzl and Bz2 genes absolutely requires introduced R and C1. In time-course experiments there is a delay of 3–6 h before the Bz2 promoter is activated, supporting the proposed role for R- and C1-encoded proteins in transcriptional control. An excess of R relative to C1 suppresses expression of A1, Bz1, and Bz2 promoters, suggesting an interaction between the R and C1 proteins.
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    URL: http://dx.doi.org/10.1007/BF00265434
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    Mechanism of Ds1 excision from the genome of maize streak virus (1992)
    Springer
    Molecular genetics and genomics 233 (1992), S. 388-394 
    Details
    ISSN: 1617-4623
    Keywords: Viral vector ; Transposable element ; Zea mays ; Agroinfection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We have previously shown that the maize transposable element Ds1 introduced into maize plants by agroinfection can be excised from the genome of geminivirus maize streak virus (MSV). Excision depended strictly on the presence of an active Ac element in the plants. In this study, the excision products or “footprints” left in the MSV genome after Ds1 excision were extensively characterized and the effects of flanking sequences on Ds1 excision were analysed. Most types of footprints obtained were comparable to those described for Ds1 excision in the maize genome, and could be explained by the models proposed for excision of plant transposable elements. In two revertants, however, some terminal sequences of the Ds1 element were found to have been left behind at the excision site. The finding of this novel type of Ds1 footprint indicated that gene conversion events occurred during and/or after Ds1 excision from the MSV genome. A partial deletion of one copy of the 8 by duplications flanking the Ds1 element had no effect on the frequency or on the types of footprints of Ds1 excision from the MSV genome. Thus, the duplicated 8 by sequences flanking the transposable element are not involved in Ds1 excision. These results, as well as a statistical analysis of the modifications of the bases flanking the Ds1 element after excision, are discussed in terms of excision models.
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    URL: http://dx.doi.org/10.1007/BF00265435
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    Functional analysis of the — 300 region of maize zein genes (1992)
    Springer
    Molecular genetics and genomics 231 (1992), S. 369-374 
    Details
    ISSN: 1617-4623
    Keywords: Zea mays ; Transcription ; Transformation ; Endosperm ; Tissue culture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A 43 by fragment containing the — 300 region upstream control element common to the endosperm expressed zein genes of Zea mays L. has been analyzed by in vivo and in vitro techniques. Transient transformation studies with protoplasts from a maize endosperm culture indicate that the element positively affects CaMV 35S promoter-driven gene expression, and that this effect is both orientation- and position-dependent. Band-shift and Southwestern blotting experiments demonstrate that the element is specifically bound by different sets of DNA-binding proteins from seedling and endosperm nuclei. A 2 by substitution within the most conserved region of the element both reduces the stimulatory effect on transcription and alters the binding of nuclear proteins from both tissues.
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    URL: http://dx.doi.org/10.1007/BF00292705
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    Structural and functional analysis of theBz2 locus ofZea mays: characterization of overlapping transcripts (1992)
    Springer
    Molecular genetics and genomics 233 (1992), S. 269-277 
    Details
    ISSN: 1617-4623
    Keywords: Zea mays ; Bz2 locus ; Natural antisense transcripts ; Transposable elements ; Gene family
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Analysis of the transcription pattern of theBz2 locus revealed that overlapping transcripts are derived from opposite DNA strands. The most abundant transcript (sense transcript) has an open reading frame coding for a protein of 241 amino acids, whilst in the antisense orientation no open reading frame has been detected; the antisense transcripts are detected only in those tissues that show high levels of sense transcript. Particle gun experiments indicate that the sense transcript is sufficient to provide theBz2 function. The promoter driving the sense transcript contains the elements usually found in front of eukaryotic genes. In addition an element with similarity to theC1 andR binding sites identified in theBz1 promoter is found. Further upstream in the promoter region a transposon-like insertion has been identified. This element has features similar to members of theAc/Ds transposable element family. The putativeBz2 protein shows similarity to various other plant proteins and to anEscherichia coli protein. All related proteins have in common the fact that they are involved in stress responses.
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    URL: http://dx.doi.org/10.1007/BF00587588
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    Binding sites for maize nuclear proteins in the subterminal regions of the transposable element Activator (1996)
    Springer
    Molecular genetics and genomics 251 (1996), S. 428-435 
    Details
    ISSN: 1617-4623
    Keywords: Key words Transposable element ; Ac ; Zea mays ; Host factor ; DNase I protection assay
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Genetic data suggest that transposition of the maize element Activator (Ac) is modulated by host factors. Using gel retardation and DNase I protection assays we identified maize proteins which bind to seven subterminal sites in both ends of Ac. Four DNase I-protected sites contain a GGTAAA sequence, the other three include either GATAAA or GTTAAA. The specificity of the maize protein binding to Ac was verified by using a synthetic fragment containing four GGTAAA motifs as probe and competitor in gel retardation assays. All seven binding sites are located within regions required in cis for transposition. A maize protein binding site with the same sequence has previously been identified in the terminal inverted repeats of the maize Mutator element. Thus, the protein, that recognizes this sequence is a good candidate for a regulatory host factor for Ac transposition.
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    URL: http://dx.doi.org/10.1007/BF02172371
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    Analysis ofMutator-induced mutations in theIojap gene of maize (1996)
    Springer
    Molecular genetics and genomics 252 (1996), S. 216-220 
    Details
    ISSN: 1617-4623
    Keywords: iojap ; Chloroplast development ; Transposon ; Robertson'sMutator ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The recessive nuclear mutationiojap (ij) in maize produces striped plants with normal chloroplasts in green sectors and poorly developed chloroplasts in the white sectors. Theij mutation is also characterized by an array of additional phenotypic affects which suggests a pivotal role forIj in chloroplast development. TheIj gene from maize has been isolated; however, the sequence has not provided information on the action of theIj gene product. As an extension of the analysis of theIj gene we have generated a number of independent transposon insertion mutations using the Robertson'sMutator (Mu). Insertions were found to be distributed throughout the 5′ half of the gene and all showed a similar striping pattern to that of the originalij mutation,ij-ref. While several of the new mutant alleles producedij-homologous transcripts none produced detectable levels of the Ij polypeptide product. Chloroplast development in some cells appears to be able to proceed in the absence of the Ij polypeptide.
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    URL: http://dx.doi.org/10.1007/BF02173223
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    Variegation patterns caused by excision of the maize transposable element Dissociation (Ds) are autonomously regulated by allele-specific Activator (Ac) elements and are not due to trans-acting modifier genes (1995)
    Springer
    Molecular genetics and genomics 246 (1995), S. 1-9 
    Details
    ISSN: 1617-4623
    Keywords: Zea mays ; Transposable elements ; Unstable mutation ; Variegation pattern ; Modifier gene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The Ac elements present in the unstable wxm7 and wx-m9 alleles of maize trigger different patterns of Ds excision in trans. To determine whether this differential regulation is a feature of the Ac alleles themselves or is mediated by genetically distinct factors, maize plants heterozygous for the wx-m7 and wx-m9 alleles were crossed to tester strains homozygous for Ds reporter alleles. Kernels showing the variegation pattern characteristic for the Ac elements carried in the wx-m7 and wx-m9 alleles were found to be present in the ratios expected from the genetic constitution of the strains. The aleurone variegation caused by excision of the Ds reporter element and the endosperm variegation caused by excision of Ac from the wx-m7 and wx-m9 alleles themselves segregated with the original wx-m alleles. In addition, stable Wx and wx derivatives of wx-m9 that have lost Ac no longer exert any trans effect on the wx-m7 allele (and vice versa). Therefore it is concluded that the observed variegation patterns are autonomously determined by specific trans effects of the particular Ac element.
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    URL: http://dx.doi.org/10.1007/BF00290127
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    Evidence for plasma membrane-associated forms of sucrose synthase in maize (1996)
    Springer
    Molecular genetics and genomics 252 (1996), S. 303-310 
    Details
    ISSN: 1617-4623
    Keywords: Zea mays ; Sucrose synthase ; Plasma membrane ; Cellulose biosynthesis ; Endosperm
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Plasma membrane fractions were isolated from maize (Zea mays L.) endosperms and etiolated kernels to investigate the possible membrane location of the sucrose synthase (SS) protein. Endosperms from seedlings at both 12 and 21 days after pollination (DAP), representing early and mid-developmental stages, were used, in addition to etiolated leaf and elongation zones from seedlings. Plasma membrane fractions were isolated from this material using differential centrifugation and aqueous two-phase partitioning. The plasma membrane-enriched fraction obtained was then analyzed for the presence of sucrose synthase using protein blots and activity measurements. Both isozymes SS1 and SS2, encoded by the lociSh1 andSus1, respectively, were detected in the plasma membrane-enriched fraction using polyclonal and monoclonal antisera to SS1 and SS2 isozymes. In addition, measurements of sucrose synthase activity in plasma membrane fractions of endosperm revealed high levels of specific activity. The sucrose synthase enzyme is tightly associated with the membrane, as shown by Triton X-100 treatment of the plasma membrane-enriched fraction. It is noteworthy that the gene products of bothSh1 andSus1 were detectable as both soluble and plasma membrane-associated forms.
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    URL: http://dx.doi.org/10.1007/BF02173776
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    In vivo demonstration of acid phosphatase activity in the rhizosphere of soil-grown plants (1992)
    Springer
    Plant and soil 144 (1992), S. 199-205 
    Details
    ISSN: 1573-5036
    Keywords: acid phosphatase ; ectoenzymes ; naphthyl phosphate ; Picea abies ; rhizosphere ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract For in vivo demonstration of acid phosphatase activity in the rhizosphere of soil-grown plants filter papers were treated with a mixture of 1-naphthyl phosphate as substrate and the diazonium salt Fast Red TR as an indicator. After enzymatic hydrolysis, 1-naphthol forms a red complex with Fast Red TR. This method was applied to 8-day old maize plants and 3-year old Norway spruce plants growing in rhizoboxes in soil under non-sterile conditions. The treated filter paper is placed at the surface of roots and soil and acid phosphatase activity is visualized as a red-coloured ‘root print’ on the filter paper. The method can be used as a qualitative analysis of acid phosphatase in the rhizosphere. It also allows a rough estimate of phosphatase activity in different root zones.
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    URL: http://dx.doi.org/10.1007/BF00012876
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    Heavy-metal uptake by crops from polluted river sediments covered by non-polluted topsoil (1995)
    Springer
    Plant and soil 175 (1995), S. 105-113 
    Details
    ISSN: 1573-5036
    Keywords: cadmium ; root distribution ; root methods ; soil pollution ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Cadmium uptake by maize from polluted river sediments covered with a clean top layer of variable thickness is discussed in relation to root distribution. Two pathways for uptake are distinguished: roots penetrating the contaminated layer or contaminants moving into the root zone. Relative Cd uptake proved to be roughly proportional to the fraction of total root length found in the contaminated layer. A deeper water table induced a deeper root development and more Cd uptake for a given thickness of clean topsoil. A model based on exponential decrease of root length density with depth is acceptable as first approximation only. Little or no evidence was found for contaminants moving into the root zone during the ten years of the experiment.
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    URL: http://dx.doi.org/10.1007/BF02413015
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    Divergent full-sib recurrent selection for germination at low temperature in a maize population (1992)
    Springer
    Euphytica 64 (1992), S. 21-29 
    Details
    ISSN: 1573-5060
    Keywords: cold tolerance ; correlated responses ; germination ; kernel type ; kernel weight ; recurrent selection ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Four cycles of divergent full-sib recurrent selection for the ability to germinate at low temperature were conducted in a maize (Zea mays L.) F2 population. The selection criterion was the high (H) or the low (L) value in algebraic terms of the difference (DG) between germination percentage at 9.5°C (G9.5) detected 19 days after sowing and germination percentage at 25°C (G 25) seven days after sowing; both traits were evaluated in a controlled environment (germinator). Direct and correlated responses estimated during the course of selection were in accordance with those evaluated at the end. Selection for H led to populations with higher DG values, while the reverse was noted for L; differences between H and L populations increased in successive selection cycles, though divergence tended to level off. Selection for H also resulted in higher G 9.5 (day 19), shorter germination time and more flinty kernels, while selection for L led to responses in the opposite direction as well as to a lower G 9.5 detected 37 days after sowing (i.e. at the end of germination). In contrast, responses were negligible for G 25 and varied erratically from one cycle to another for kernel weight.
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    Glyphosate tolerance in maize (Zea mays L.). 1. Differential response among inbred lines (1995)
    Springer
    Euphytica 82 (1995), S. 157-164 
    Details
    ISSN: 1573-5060
    Keywords: EPSP synthase ; glyphosate ; herbicide tolerance ; natural variation ; Zea mays ; maize
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Variation in susceptibility to the safe broad-spectrum herbicide glyphosate was investigated in maize. Eleven inbred lines, grown in a growth chamber, were evaluated for their tolerance to the herbicide at 2.4 mM (0.2 kg a.i. in 400 I ha-1 of water). Following treatment with glyphosate at the three-leaf stage, significant variation in damage, expressed as visual injury ratings scored 7, 14 and 21 days after the application of the herbicide, was found. Effects on dry weight and shoot height were consistent with visual scores and the carbon-exchange rate was found to be a sensitive index of differential injury. Biochemical characterization of 5-enol-pyruvyl-shikimate-3-phosphate (EPSP) synthase, the main target of the herbicide, ruled out the possibility that this differential susceptibility was due to variations in the sensitivity of the enzyme. On the contrary, a positive correlation was found between in vivo tolerance and EPSP synthase levels, measured at different stages during seedling growth. This result suggests that a naturally occurring difference in EPSP synthase levels in the tissues may contribute to the differential response observed in vivo in maize inbreds.
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    URL: http://dx.doi.org/10.1007/BF00027062
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    Improvement in selfed and random-mated generations of four subtropical maize populations through S3 recurrent selection (1995)
    Springer
    Euphytica 83 (1995), S. 1-8 
    Details
    ISSN: 1573-5060
    Keywords: Zea mays ; maize, subtropical white germplasm ; S3 recurrent selection ; inbreeding depression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary In maize (Zea mays L.) source germplasm having tolerance to inbreeding is needed for the derivation of productive inbred lines. The germplasm with non-temperature adaptation, generally suffer from large inbreeding depression (ID). the objective of the present study was to improve four white subtropical populations for tolerance to ID through S3 recurrent selection. Two cycles of selection were conducted and the effect of selection was evaluated in the first selfed (S1) and random0mated (Synthetic-2=Syn-2) generations. To complete each cycle. 200 to 250 S3 progenies were evaluated and 15 to 20 superior ones selected for recombination in each population. Selection was practiced for high grain yield, vigour and other agronomie traits. The S1 and Syn-2 generations of the original (C0) and improved (C1, C2) populations were evaluated in a split-split plot design, with populations in main plots, generations in subplots and cycles in sub-subplots. In all populations, S1 and Syn-2 generations of C2 were significantly higher yielding than the C0 and the linear gain per cycle varied from 16.3 to 28.8% in S1 generation and 5.5 to 10.7% in Syn-2 generation. Selection reduced the anthesis-silking interval but slightly increased plant height, grain moisture and days to silk. An increase in plant height was expected because of emphasis on vigour during selection. For grain yield. ID decreased from 48.4% in C0 populations to 37.9% in C2, indicating an improved tolerance to inbreeding. Further, the selection accumulated favourable alleles; and Pop. 42 seemed to be the best source populations for deriving high yielding inbred lines. It may be concluded that S3 recurrent selection was effective in improving grain yield and the improved populations would provide better germplasm sources for the derivation of productive inbred lines.
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    URL: http://dx.doi.org/10.1007/BF01677854
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    Phenotypic correlations between maize inbreds and their single cross hybrids in short season areas (1996)
    Springer
    Euphytica 89 (1996), S. 291-296 
    Details
    ISSN: 1573-5060
    Keywords: maize ; Zea mays ; phenotypic correlation ; genotype × environment interaction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary This study was conducted to determine the relationships among various agronomic traits in inbreds, hybrids and between inbreds and their progeny of maize in short season areas. Phenotypic correlations of each measured trait between as well as among hybrids and inbreds were not the same. The highest correlation coefficient (r=0.78) was obtained between days to anthesis and yield. The high yielding inbreds did not necessarily give rise to high yielding progeny. Given that days to anthesis plays an important role in two major traits (yield and moisture) for hybrids, an emphasis on optimum anthesis dates during inbred development could be a useful criterion for the prediction of hybrid performance in short season areas.
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    URL: http://dx.doi.org/10.1007/BF00022284
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    Mapping QTLs in breeding for drought tolerance in maize (Zea mays L.) (1996)
    Springer
    Euphytica 91 (1996), S. 89-97 
    Details
    ISSN: 1573-5060
    Keywords: anthesis-silking interval ; drought tolerance ; grain yield ; maize ; QTL ; RFLP ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Grain yield in the maize (Zea mays L) plant is sensitive to drought in the period three weeks either side of flowering. Maize is well-adapted to the use of restriction fragment length polymorphisms (RFLPs) to identify a tight linkage between gene(s) controlling the quantitative trait and a molecular marker. We have determined the chromosomal locations of quantitative trait loci (QTLs) affecting grain yield under drought, anthesis-silking interval, and number of ears per plant. The F3 families derived from the cross SD34(tolerant) × SD35 (intolerant) were evaluated for these traits in a two replicated experiment. RFLP analysis of the maize genome included non-radioactive DNA-DNA hybridization detection using chemiluminescence. To identify QTLs underlying tolerance to drought, the mean phenotypic performances of F3 families were compared based on genotypic classification at each of 70 RFLP marker loci. The genetic linkage map assembled from these markers was in good agreement with previously published maps. The phenotypic correlations between yield and other traits were highly significant. In the combined analyses, genomic regions significantly affecting tolerance to drought were found on chromosomes 1,3,5,6, and 8. For yield, a total of 50% of the phenotypic variance could be explained by five putative QTLs. Different types of gene action were found for the putative QTLs for the three traits.
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    URL: http://dx.doi.org/10.1007/BF00035278
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    Breeding for yield, in mixtures of common beans (Phaseolus vulgaris L.) and maize (Zea mays L.) (1996)
    Springer
    Euphytica 92 (1996), S. 129-134 
    Details
    ISSN: 1573-5060
    Keywords: common bean ; correlations ; intercropping ; maize ; selection gains ; selection methods ; yields ; Phaseolus vulgaris ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Despite the growing industrialization, technification and transformation that is happening in the agriculture around the world, and despite that agricultural research has always concentrated its effort on sole crops, multiple cropping systems have historically been important for common bean production in tropical countries. The reasons for this fact, are economical and social, as well as biological. Bean breeders have always been questioned on their work, because the development of new varieties is usually done in sole crop, but the varieties are grown in either systems. This paper addresses a set of questions that are usually presented to the breeders, in light of the evidence obtained from many trials conducted in Brazil and in the U.S.A.: Will the genotypes bred for sole crop conditions, perform well when grown in intercrop; How different should a genotype be, for cultivation in intercropping compared to genotypes developed for sole crop conditions; Is there a need for special breeding programs for intercropping and How could a breeding program focus the question of multiple (associated) cropping?
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    URL: http://dx.doi.org/10.1007/BF00022837
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    Breeding widely adapted, popular maize hybrids (1996)
    Springer
    Euphytica 92 (1996), S. 163-174 
    Details
    ISSN: 1573-5060
    Keywords: adaptation ; maize breeding ; genetic diversity ; hybrid-by-environment interaction ; information systems ; performance testing ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary World trend is to more maize hectarage grown to fewer, more widely-adapted hbrids. My purpose is to document research events leading to the most popular corn hybrids, Pioneer Brand 3780 and 3732. I provide background on maize adaptedness, on the seed maize business, on commercial maize hybrid development process, and on cultural practice change. I provide historical information on the cultivars: Leaming corn, Reid Yellow Dent, and Minn. 13 were widely-adapted open-pollinated varieties. Shift from open-pollinated to hybrid maize caused a shift in emphasis from local to wider adaptation. The first widely-adapted hybrids were Iowa 939 and U.S. 13. DEKALB 404A was the first popular and most popular double-cross hybrid. Pioneer 349 was the second-most popular double-cross hybrid. The first popular single cross hybrids were DEKALB 805 in medium and DEKALB XL45 in early U.S. Corn Belt in the early-1960's. Cultural practices (higher planting density, narrower rows, more nitrogen, better pesticides, and larger equipment allowing more timely operations) changed greatly in the 1960's and 1970's; allowing fewer, more widely-adapted genotypes to prevail. First hybrid 3780, then 3732 became the most popular hybrid; each exceeded one billion (1 × 109) dollars sales. They were the result of wide-area testing, of utilizing higher plant density stress for selecting inbred lines and for screening hybrids, and of modern information management.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00022842
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  • 92
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    Effects of organic acid fractions extracted from Eucalyptus camaldulensis leaves on root elongation of maize (Zea mays) in the presence and absence of aluminium (1995)
    Springer
    Plant and soil 171 (1995), S. 189-192 
    Details
    ISSN: 1573-5036
    Keywords: aluminium toxicity ; Eucalyptus camaldulensis ; fulvic acid ; humic acid ; root elongation ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Complexes of aluminium (Al) with organic ligands are believed to represent an important detoxification mechanism in acid soils. However, relatively little is known about the particular ligands produced by decomposing vegetation or about their effects on plant growth in the presence or absence of toxic Al. This paper reports an experiment on the effects of decomposition products of Eucalyptus camaldulensis leaves on the root elongation of maize (Zea mays) cv. DK687 in the presence or absence of Al. The static solution culture experiment used fulvic acid (FA) and humic acid (HA), extracted from E. camaldulensis leaves, at three nominal concentrations, viz. 40, 120 and 360 mg C L-1, replicated 4 times in the presence and absence of 30 µM Al. In the absence of Al, root elongation was increased by 30% by HA at 40 mg C L-1 and by 36% by FA at 120 mg C L-1. In the presence of 30 µM Al, the effects of toxic Al on root elongation were negated by FA and HA at all concentrations. Aluminium was totally complexed in all treatments except FA at 40 mg C L-1 in which treatment only 2.7 µM Al was present in the monomeric form. The E. camaldulensis FA and HA at concentrations of 40 and 120 mg C L-1, either in the presence or absence of Al, stimulated maize root elongation. Aluminium was strongly complexed by the E. camaldulensis FA and HA. The present results, in which FA and HA alleviated Al toxicity limitations on root elongation of maize, are relevant to the protection afforded to plant growth in acid soils amended with organic materials. They highlight the need to focus more on the role of FA and HA.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00009586
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  • 93
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    Root colonization of maize by a Cd-sensitive and a Cd-tolerant Glomus mosseae and cadmium uptake in sand culture (1995)
    Springer
    Plant and soil 175 (1995), S. 233-238 
    Details
    ISSN: 1573-5036
    Keywords: arbuscular mycorrhiza (AM) ; Cd ; Glomus mosseae ; phytotoxicity ; tolerance ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A Cd-tolerant arbuscular mycorrhizal fungus, Glomus mosseae, isolated from a polluted soil (P2 culture), was compared with a Cd-sensitive reference Glomus mosseae (Gm) for its capacity to colonize maize (Zea mays L.) roots and to affect plant growth and Cd uptake in sand culture at increasing exposure to Cd added with the nutrient solution (0, 0.1, 1, 5 and 10 mg L-1). After eight weeks, mycorrhizal colonization by P2 culture was relatively high (50% of the control without Cd added) up to 5 mg L-1 Cd, whereas colonization by Gm was almost totally suppressed at that Cd level. However, even mycorrhizal colonization by the Cd-tolerant P2 culture appeared more sensitive to Cd than plant growth and was completely suppressed at 10 mg L-1 Cd. AM colonization did not alleviate the negative effect of Cd on plant growth compared to the non-mycorrhizal treatment. On the contrary, at the 5 mg L-1 Cd level non-mycorrhizal plants were greater than mycorrhizal plants with lower Cd concentration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00011359
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  • 94
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    Flooding-induced membrane damage, lipid oxidation and activated oxygen generation in corn leaves (1996)
    Springer
    Plant and soil 179 (1996), S. 261-268 
    Details
    ISSN: 1573-5036
    Keywords: activated oxygen ; activated oxygen scavenging system ; flooding ; lipid peroxidation ; membrane injury ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Flooding effects on membrane permeability, lipid peroxidation and activated oxygen metabolism in corn (Zea mays L.) leaves were investigated to determine if activated oxygens are involved in corn flooding-injury. Potted corn plants were flooded at the 4-leaf stage in a controlled environment. A 7-day flooding treatment resulted in a significant increase in chlorophyll breakdown, lipid peroxidation (malondialdehye content), membrane permeability, and the production of superoxide (O 2 - ) and hydrogen peroxide (H2O2) in corn leaves. The effects were much greater in older leaves than in younger ones. Spraying leaves with 8-hydroxyquinoline (an O 2 - scavenger) and sodium benzoate (an .OH scavenger) reduced the oxidative damage and enhanced superoxide dismutase (SOD) activity. A short duration flooding treatment elevated the activities of SOD, catalase, ascorbate peroxidase (AP), and glutathione reductase (GR), while further flooding significantly reduced the enzyme activities but enhanced the concentrations of ascorbic acid and reduced form glutathione (GSH). It was noted that the decline in SOD activity was greater than that in H2O2 scavengers (AP and GR). The results suggested that O 2 - induced lipid peroxidation and membrane damage, and that excessive accumulation of O 2 - is due to the reduced activity of SOD under flooding stress.
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    URL: http://dx.doi.org/10.1007/BF00009336
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  • 95
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    The influence of chlorsulfuron and metsulfuron methyl on root growth and on the ultrastructure of root tips of germinating maize seeds (1996)
    Springer
    Plant and soil 180 (1996), S. 19-28 
    Details
    ISSN: 1573-5036
    Keywords: herbicides ; chlorsulfuron ; metsulfuron methyl ; root tip ultrastructure ; root growth ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Seeds of Zea mays L., germinating in soil, were exposed to very low doses of the sulfonylurea herbicides chlorsulfuron and metsulfuron methyl. At a concentration of 0.012 mg L−1, chlorsulfuron caused 72% and metsulfuron methyl 55% growth reduction of the young primary roots. Both herbicides also caused obvious injuries to the root tips. Scanning electron microscopic observations of the root tip surfaces indicated an inhibition of slime secretion at a herbicide concentration of 1.5 mg L−1. Transmission electron microscopy revealed obvious changes to the nuclei and deformation of radial cell walls in the primary root cortex at 0.012 and 1.5 mg L−1 for both herbicides. Moreover, the secretory cells of the root cap periphery showed partially irregular deposition of premature cell wall or slime material at a concentration of 0.012 mg L−1 of both herbicides. From the results of our electron microscopic observations we conclude that the primary roots of maize seedlings are seriously affected by extremely low concentrations of even those herbicides which (as chlorsulfuron and metsulfuron methyl) have been developed to inhibit the growth of dicotyledonous weeds. Moreover, we suggest that the frequently observed growth retardation of crop seedlings is a consequence of early root tip injuries caused by herbicide residues in the soil. ei]H Lambers
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00015407
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  • 96
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    Water in aerenchyma spaces in roots. A fast diffusion path for solutes (1996)
    Springer
    Plant and soil 184 (1996), S. 131-141 
    Details
    ISSN: 1573-5036
    Keywords: aerenchyma ; cryo-microscopy ; intercellular water ; maize ; root cortex ; solute diffusion ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract During a study of the diffusivity of sulphorhodamine G in the cortical apoplast of maize roots widely discrepant rates were found between different samples. In roots which had developed large aerenchyma spaces, the diffusion in some regions was very fast, indistinguishable from the rate in water. In other regions the rate was as much as 100 times slower. Examination of frozen intact roots with the cryo-scanning electron microscope showed the presence of liquid filling some of the aerenchyma spaces, while other spaces of the same root contained air. X-ray microanalysis of the liquid (for oxygen) showed that the liquid was water with few detectable ions. Similar liquid was present in small intercellular spaces within the spoke-like radial files of cells between the large spaces, or between remnants of collapsed cell walls at the edges of the large spaces. It is proposed that regions of roots with high diffusivity are those in which some of the aerenchyma spaces are filled with water. In seeking the origin of this liquid, the progress of aerenchyma formation could be followed in the frozen tissues. The first change observed in a group of contiguous cells was a loss of vacuolar solutes and of cell turgor. Next the walls broke apart and collapsed back onto the surrounding turgid cells leaving a volume of ion-poor liquid. The liquid was probably not that found in some aerenchyma spaces of the mature roots, because the final stage of space formation was a loss of the liquid, leaving an air filled cavity surrounded by a composite lining formed from the collapsed walls of the broken cells. It is likely that the liquid in the spaces of mature aerenchyma is exuded from the remaining living cortical cells at times when the root turgor is high. This would be consistent with several recent studies which have shown periodic exudation of water from the surface of turgid roots. The spasmodic occurrence of root cortex tissue with enhanced diffusivity would have important implications for the transport of nutrient ions across the root.
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    URL: http://dx.doi.org/10.1007/BF00029283
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  • 97
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    Monitoring of haploid maize cell suspension culture conditions in bioreactors (1995)
    Springer
    Plant cell, tissue and organ culture 43 (1995), S. 123-126 
    Details
    ISSN: 1573-5044
    Keywords: bioreactor ; dissolved oxygen ; haploid cell suspension ; pH ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Maize (Zea mays L.) haploid cells were cultivated in a 1500 ml aerated and stirred batch bioreactor using modified BM medium. Cell growth was highly affected by pH and dissolved oxygen, and we observed two fairly distinct growth phases. During the first two days after inoculation at pH 5.8, oxygen consumption was high and the cells lowered the pH to a value around 4.3. After this period the pH stabilized at 4.5 and the dissolved oxygen reached a steady level. Decreasing dissolved oxygen concentration leads to lower growth rate and to higher pH. Both events mean stress conditions for the cell culture and probably result in increased genetic variability, and the loss of regeneration capacity. The stress condition during the adaptation phase can be eliminated by decreasing the pH of the medium to 4.7 before inoculation and by keeping dissolved oxygen above 40%. These conditions provide prolonged exponential growth dynamics and the cell suspensions could be the basis of large scale cultures also.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00052166
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  • 98
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    Evaluation of in vitro selection regimes for a mitochondrial trait (methomyl resistance) in cms-T maize (1992)
    Springer
    Plant cell, tissue and organ culture 28 (1992), S. 129-137 
    Details
    ISSN: 1573-5044
    Keywords: cms-T ; in vitro selection ; methomyl resistance ; mitochondrial mutation ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Several factors affecting the success of selection in plant populations were examined for their relevance to in vitro selection. Three in vitro selection schemes and two growth assessment procedures were evaluated for effectiveness in selecting for a mitochondrial trait in maize: resistance to the insecticidal compound methomyl. Regenerable maize callus was derived from immature embryos of the three-way hybrid P39/IL766A2 x W182BN containing Texas male sterile cytoplasm (cms-T). Either low, gradually increasing, or high selection pressures were used to grow callus over a period of 3–5 months. There was no significant difference in recovery of resistant plants using these 3 methods. Growth of callus on medium containing methomyl was assessed by increase in fresh weight during the final month of selection or by increase in number of callus pieces over the course of selection. These quantitative measures of growth were unreliable indicators for gain in resistance within the callus population. A procedure for recovery of methomyl resistant and male-fertile cms-T plants is suggested.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00055507
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  • 99
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    Construction of ‘compound’ rust resistance genes in maize (1996)
    Springer
    Euphytica 87 (1996), S. 45-51 
    Details
    ISSN: 1573-5060
    Keywords: sweet corn ; Rp1 ; disease resistance ; plant breeding ; complex locus ; recombination ; Puccinia ; Zea mays ; maize
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The Rp1 locus of maize is a complex rust resistance locus where multiple resistance genes are clustered. Rare recombination events between Rp1 genes or alleles can produce two or more detectable genes linked in coupling phase. Such ‘compound’ genes can then be manipulated as a single gene in breeding programs. Several compound Rp1 genes, each carrying two or three tightly linked resistance genes, were constructed to test their utility in controlling common rust. While none of the lines carrying single Rp1 genes were resistant to all of the characterized North American P. sorghi biotypes, most of the two component and all of the three component Rp1 complexes were resistant. The potential for utilization of compound resistance genes in other crop species is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00022963
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  • 100
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    Wheat embryogenesis and haploid production in wheat × maize hybrids (1996)
    Springer
    Euphytica 90 (1996), S. 315-324 
    Details
    ISSN: 1573-5060
    Keywords: embryogenesis ; wheat ; maize ; Triticum aestivum ; Zea mays ; haploidy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Embryogenesis was analyzed in wheat × maize hybrids using paraffin sectioning. Embryogenesis in wheat × maize hybrids is different from that in self-pollinated wheat plants. Development of the embryo is not accompanied by the formation of an endosperm. The endosperm nuclei remain free in the cytoplasm, fail to advance into the cellular stage, and degenerate at a later time. The antipodal cells quickly degenerate in the fertilized ovaries of wheat × maize hybrids similar to self-pollinated ovaries. The antipodal cells remain normal in unpollinated ovaries. The pre-embryo will abort if it is allowed to develop on the plant, because of a nutritional shortage in the absence of an endosperm. Therefore, embryo rescue is necessary for haploid production from a wheat × maize hybrids. Haploid polyembryos were obtained from spikelet culture of wheat × maize hybrids. The formation of polyembryos is due to the cleavage of the pre-embryo and the effect of 2,4-D. The frequency of haploid embryo production and plant regeneration is affected significantly by maize genotypes, but not by wheat genotypes. The concentration of 2,4-D affects only the size of the embryo.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00027482
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