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  • 1
    Electronic Resource
    Electronic Resource
    A 23-kDa, root exudate polypeptide co-segregates with aluminum resistance in Triticum aestivum (1999)
    Copenhagen : Munksgaard
    Physiologia plantarum 106 (1999), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: We previously reported that treatment with aluminum (Al) leads to the accumulation of several polypeptides (12-, 23-, and 43.5-kDa) in root exudates of an Al-resistant cultivar of Triticum aestivum. In this report, we examine the segregation of the 23-kDa, Al-induced polypeptide and the Al-resistant phenotype in single F2 plants arising from a cross between Al-resistant and Al-sensitive doubled-haploid (DH) lines. Single plants and plant populations were screened for sensitivity/resistance to Al using synthesis of 1,3-β-glucans (callose) as a sensitive marker for Al injury. Callose production in the Al-sensitive cv. Katepwa was approximately 3-fold higher than observed in the Al-resistant cv. Maringa, or a near-isogenic line derived from Katepwa and Maringa (Alikat), over a broad range of Al concentrations (0–100 μM). Similar results were observed with DH lines developed from cv. Katepwa, which produced two–four times more callose than DH lines developed from cv. Alikat. When single plants from F1 and F2 populations derived from a cross between DH Katepwa and DH Alikat were scored for Al-induced callose production after 4 days exposure to 100 μM Al, all F1 plants were Al-resistant and F2 plants segregated approximately 3:1 for Al-resistance/sensitivity. A backcross population derived from crossing Al-resistant F1 with Al-sensitive Katepwa, segregated 1:1 for Al-resistance/sensitivity. Thus, the Al-resistant phenotype is inherited in a monogenic, dominant fashion in our DH lines. Enhanced accumulation of the Al-induced, 23-kDa polypeptide in root exudates was a trait which co-segregated with the Al-resistant phenotype in F2 populations. This polypeptide was strongly labeled with S-methionine after 3 days of Al exposure and 6 h labeling. When root exudate polypeptides were separated by immobilized metal ion affinity chromatography, the 23-kDa polypeptide demonstrated significant Al-binding capacity. This polypeptide has been purified to near-homogeneity, providing an opportunity to isolate the gene(s) encoding this polypeptide.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1034/j.1399-3054.1999.106108.x
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  • 2
    Electronic Resource
    Electronic Resource
    Aluminum resistance in wheat (Triticum aestivum) is associated with rapid, Al-induced changes in activities of glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase in root apices (1996)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 98 (1996), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: We have investigated the effect of aluminum (Al) on the activity of glucose-6-phosphate dehydrogenase (G6PDH; EC 1.1.1.49) and 6-phosphogluconate dehydrogenase (6PGDH; EC 1.1.1.44) isolated from 5-mm root apices of 4-day-old wheat (Triticum aestivum) cultivars differing in resistance to Al. Rapid increases in G6PDH and 6PGDH activities were observed in Al-resistant cultivars (PT741 and Atlas 66) during the first 10 h of treatment with 100 μM Al, while no change in the activity of either enzyme was observed in Al-sensitive cultivars (Katepwa and Neepawa) during a 24-h exposure to Al. The Al-induced increases in enzyme activities observed in the Al-resistant PT741 appear to reflect an induction of protein synthesis since the increases were completely abolished by 1 mM cycloheximide. No differences in G6PDH and 6PGDH activities were observed between the Al-sensitive and the Al-resistant genotypes when Al was supplied in vitro. Under these conditions, an increase in Al concentration from 0 to 1.4 mM caused a gradual decrease in activity of both enzymes, irrespective of the Al-resistance of whole seedlings. Aluminum-sensitive and aluminum-resistant cultivars also differed in the rate and extent of accumulation of slowly-exchanging Al in 5-mm root apices. During the first 6 h of Al treatment, Al accumulation was only 10% more rapid in Katepwa than in PT741. After 24-h exposure, accumulation in the Al-sensitive Katepwa, was two-fold higher. A decline in Al accumulation in a slowly-exchanging compartment as well as a decrease in activities of G6PDH and 6PGDH were found in the Al-resistant PT741, when seedlings were transferred to Al-free treatment solutions after 16-h exposure to 100 μM Al. These results suggest that rapid induction of G6PDH and 6PGDH in the Al-resistant line PT741 by Al may play a role in the mechanism of Al resistance, possibly by regulation of the pentose phosphate pathway.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1996.tb05702.x
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  • 3
    Electronic Resource
    Electronic Resource
    Aluminum-induced alterations in lipid composition of microsomal membranes from an aluminum-resistant and an aluminum-sensitive cultivar of Triticum aestivum (1996)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 96 (1996), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: We have studied the effect of aluminum (Al) on the lipid composition of microsomal membranes isolated from 5-mm root tips of an Al-resistant (T 741) and an Al-sensitive (Katepwa) cultivar of Triticum aestivum L. Exposure of both genotypes to 10 and 50 μM AeCl3 for 1 day had no effect on lipid composition; however, decreases in phospholipids and increases in monogalactosyl diacylglycerols, free sterols, free fatty acids and triacylglycerols were observed with prolonged exposure (3 days) to 5O μM AlCe3. Several genotype-specific changes were also observed under these conditions. The content of digalactosyl diacylglycerols increased by 66.7% in Katepwa. but decreased slightly in PT 741. Thus, the ratio of rnonogalactosyl diacylglycerols to digalactosyl diacylglycerols increased by 46.2% in PT 741, but decreased by 21.3% in Katepwa. Genotype-specific differences were also observed in steryl lipids. Treatment with Al induced a 70.2% increase in sterylglucosides and a 23.3% increase in acylated sterylglucosides in Katepwa. In contrast, a 18.9% decrease in acylated sterylglucosides and no changes in sterylglucosides were observed in PT 741. Our limited understanding of the effect of membrane composition on membrane structure and function makes it difficult to predict how these changes relate to Al toxicity and resistance. While it is possible that many changes reflect the toxic effects of Al, we believe that changes observed only in the Al-resistant genotype could contribute to continuous growth in the face of Al stress.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1996.tb00243.x
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  • 4
    Electronic Resource
    Electronic Resource
    The effects of excess manganese on photosynthetic rate and concentration of chlorophyll in Triticum aestivum grown in solution culture (1992)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 85 (1992), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Manganese toxicity, which involves a broad array of physiological responses, has been identified as an important factor limiting plant growth on acid soils. In the experiments reported here, we examined the toxic effects of Mn on chlorophyll content, photosynthesis and respiration in two cultivars (Norquay and Columbus) of Triticum aestivum (wheat) which differ in tolerance of Mn. When grown over a range of concentrations of Mn (0–1 000 μM), the Mn-tolerant cultivar maintained higher rates of photosynthesis and respiration, and higher concentrations of chlorophyll a and chlorophyll b, than did the Mn-sensitive cultivar, despite greater accumulations of Mn in leaf tissues. After 5 days growth with 1 000 μM Mn in solution, the photosynthetic rate fell to 25% of control in the sensitive cultivar and to only 75% of control in the tolerant cultivar. The concentration of chlorophyll a fell to 50% of control in the sensitive cultivar, but did not differ from control in the tolerant cultivar. Greater effects were seen on concentrations of chlorophyll b. which fell to 35% and 55% of control in the sensitive and tolerant cultivars, respectively. Rates of photosynthesis decreased in both cultivars as concentrations of chlorophyll decreased; however, the photosynthetic rate per unit chlorophyll remained constant or increased in the tolerant cultivar and decreased in the sensitive cultivar as concentrations of Mn in solution increased. Thus, in the sensitive cv. Columbus, Mn seemed to have a toxic effect on both chlorophyll content and photosynthesis per unit chlorophyll. In the tolerant cv. Norquay, the only clear effect of Mn was a reduction in chlorophyll content, although direct inhibition of photosynthesis could not be discounted.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1992.tb05813.x
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  • 5
    Electronic Resource
    Electronic Resource
    Alternation of plasma membrane lipids in aluminum-resistant and aluminum-sensitive wheat genotypes in response to aluminum stress (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 99 (1997), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: We have studied the effect of aluminum (A1) on lipid composition of plasma membranes from roots of an A1-resistant (PT741) and an A1-sensitive (Katepwa) cultivar of Triticum aestivum L. Several genotype–specific changes were observed in phospholipids and steryl lipids. While exposure to 20 μM AICI3 for 3 days had no effect on total phospholipids in either genotype, the most abundant phospholipid, phosphatidylcholine, increased significantly in the A1-sensitive Katepwa. Aluminum also decreased steryl lipids (mainly free sterols) in PT741. Such changes were not observed in Katepwa. As a result of differential changes in lipid composition, the relative abundance of one lipid class to another changed. The ratio of steryl lipids to phospholipids decreased in PT741, with no change in Katepwa. While limited information on the relationship between membrane function and lipid composition makes it difficult to relate these changes to A1 toxicity and resistance, changes observed only in the A1–resistant genotype could contribute to continued plant growth in the face of A1 stress.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1997.tb05416.x
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  • 6
    Electronic Resource
    Electronic Resource
    Antagonistic and synergistic interactions between aluminum and manganese on growth of Vigna unguiculata at low ionic strength (1998)
    Copenhagen : Munksgaard International Publishers
    Physiologia plantarum 104 (1998), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Concentrations of soluble aluminum (Al) and manganese (Mn) frequently reach phytotoxic levels in acid soils. While dose response relationships for these metals are well documented, the effects of combined exposure have received less attention. We have examined the effect of combinations of Al and Mn on growth and metal accumulation in Vigna unguiculata (L.) Walp. grown in solution culture under conditions of low ionic strength (conductivities typically 〈 100 µS cm−1). The nature of interaction between these metals varied with the specific physiological response, the part of the plant investigated, and the relative amount of stress imposed. Analysis of growth data provided evidence for amelioration of metal toxicity (antagonistic effects), although this effect was dose dependent. Analysis of metal content data provided evidence for antagonistic and synergistic (exacerbation of toxicity) effects, again depending on dose. Analysis of foliar symptoms also provided evidence for antagonisms and synergisms, with the nature of the response dependent on the specific physiological response and specific plant part investigated. In contrast with previous reports, evidence for antagonistic, synergistic, and multiplicative effects on growth, metal uptake, and expression of foliar symptoms have been obtained under physiologically and environmentally relevant conditions. These results suggest a more detailed analysis of the potential for interactions between metals in the environment is required.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1034/j.1399-3054.1998.1040206.x
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  • 7
    Electronic Resource
    Electronic Resource
    Vacuolar H+-ATPase, but not mitochondrial F1F0-ATPase, is required for NaCl tolerance in Saccharomyces cerevisiae (2002)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 208 (2002), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Salt tolerance in Saccharomyces cerevisiae is a complex trait, involving regulation of membrane polarization, Na+ efflux and sequestration of Na+ in the vacuole. Since transmembrane transport energized by H+-adenosine triphosphatases (ATPases) is common to all of these tolerance mechanisms, the objective of this study was to characterize the responses of the plasma membrane H+-ATPase, vacuolar H+-ATPase and mitochondrial F1F0-ATPase to NaCl stress. We hypothesized that since the vacuolar ATPase is responsible for generating the proton motive force required for import of cations (such as Na+) into the vacuole, strains lacking this activity should be hypersensitive to NaCl. We found that strains lacking vacuolar ATPase activity were in fact hypersensitive to NaCl, while strains lacking ATP synthase were not. This effect was specific to the ionic component of NaCl stress, since the mutant strains were indistinguishable from wild-type and complemented strains in the presence of sorbitol.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.2002.tb11086.x
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  • 8
    Electronic Resource
    Electronic Resource
    Vacuolar H+-ATPase, but not mitochondrial F1F0-ATPase, is required for aluminum resistance in Saccharomyces cerevisiae (2001)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 205 (2001), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: It was recently shown that vacuolar ATPase and mitochondrial F1F0-ATPase activities are induced by aluminum (Al) in an Al-resistant cultivar of wheat, suggesting that induction of these enzymes could be an adaptive trait involved in Al resistance. To test this hypothesis, we used the Saccharomyces cerevisiae model system. In yeast, unlike wheat, the activity, transcript and protein levels of mitochondrial F1F0-ATPase, but not vacuolar ATPase, are induced by Al, while plasma membrane P-ATPase activity is inhibited. However, yeast vacuolar ATPase mutant strains are hypersensitive to Al, while F1F0-ATPase mutant strains exhibit wild-type growth. These data suggest that vacuolar ATPase activity is involved in Al resistance, with ATP required for this activity supplied by mitochondrial F1F0-ATPase or fermentation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.2001.tb10953.x
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  • 9
    Electronic Resource
    Electronic Resource
    A comparison of the kinetics of aluminum (Al) uptake and distribution in roots of wheat (Triticum aestivum) using different aluminum sources. A revision of the operational definition of symplastic Al (1996)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 98 (1996), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The lack of information about the movement of aluminum (Al) across the plasma membrane presents a significant barrier to the elucidation of resistance mechanisms which may involve exclusion of Al from the symplast. An understanding of mechanistic aspects of exclusion requires the estimation of symplastic Al levels. Such measurements may be achievable through the use of a kinetic approach. A kinetic protocol was developed to characterize the accumulation and distribution of Al in various cellular compartments in roots of wheat (Triticum aestivum L.). The kinetics of uptake and desorption were similar when Al was supplied as AIK(SO4)2 or as AlCl3. When both salts were supplied at low concentration (50 μM), Al bound to a purified cell wall fraction could be reduced to less than 10–20% of non-exchangeable Al, if roots were washed for 30 min in citric acid following exposure. In contrast, when AlK(SO4)2 was supplied at a high concentration (200 μM), a strong linear phase of uptake into cell wall material was observed, which accounted for approximately 48% of non-exchangeable Al in roots. These results suggest that the use of low concentrations of Al in simple salt solutions is required to minimize accumulation of non-exchangeable Al in the apoplasm. A series of multiple-desorption experiments confirmed that citric acid was effective in removing Al from the cell wall compartment of roots exposed to Al for short periods (3 h). However, long exposures (48 h) appeared to create conditions conducive to the accumulation of non-exchangeable Al in the cell wall. In experiments where uptake from solutions containing 50 μM AlCl3 was followed by desorption in citric acid, non-exchangeable Al in microsomal membrane fractions represented less than 4% of total non-exchangeable Al. Thus, we can exclude the plasma membrane and cell wall as major sites for accumulation of non-exchangeable Al in short exposure studies. Although we cannot provide unequivocal evidence for the localization of Al within the symplast, use of simple salt solutions followed by desorption in citric acid provides the best kinetic technique currently available for the quantitation of Al in the symplasm.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1996.tb05714.x
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  • 10
    Electronic Resource
    Electronic Resource
    Measuring the effect of an abiotic stress on competition (1994)
    Springer
    Oecologia 100 (1994), S. 221-228 
    Details
    ISSN: 1432-1939
    Keywords: Triticum aestivum ; Competition ; Abiotic stress ; Multiplicative interactions ; Nickel toxicity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Using recently developed solution culture techniques, the effect of a non-resource abiotic stress, nickel toxicity, was tested on intraspecific nutrient competition among wheat. The choice of an appropriate statistical model was of paramount importance in interpreting these effects. We argue that a multiplicative model is more appropriate for experiments on interactions of competition and abiotic stress. By such an analysis, nickel had no relative effect on the ability of competition to reduce plant size in two experiments, and caused a small reduction in competition in another. These results are contrary to other reports of the effect of a non-resource abiotic stress on competition and appear to be due to an increased demand for nutrients in the presence of toxic levels of nickel. The effects of an abiotic stress on competition may thus be specitic to the stress and not generalized across all abiotic stresses.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00316948
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