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1

Electronic Resource

DNA replication and the development of preprophase bands in soybean protoplast cultures (1991)

Wang, Hong ; Cutler, Adrian J. ; Fowke, Larry C.

Oxford, UK : Blackwell Publishing Ltd

Physiologia plantarum 82 (1991), S. 0

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ISSN: 1399-3054

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology

Notes: Nuclear DNA replication and the development of preprophase bands (PPBs) are two chronologically close processes during the higher plant cell cycle. However, it is not clear whether occurrence of PPBs is coupled with DNA replication. A soybean protoplast culture with a high frequency of PPBs was used to study the relationship between the two processes when treated with aphidicolin, a potent and specific inhibitor of eukaryotic DNA polymerase-α. When DNA replication was partially inhibited by 10 mg l-1 aphidicolin, both the percentage of cells with PPBs and the mitotic index (MI) decreased in absolute terms, but there were proportionately more PPBs than mitoses. Since PPBs change in appearance as they develop, they were divided into categories of early (interphase associated) and late (prophase associated). The increased PPB/MI ratio was associated with an increased proportion of early stage PPBs relative to late stage PPBs. When DNA replication was completely blocked by 50 mg l-1 aphidicolin, both MI and the percentage of cells with PPBs were close to zero. These results suggest that development of PPBs was to a large extent coupled DNA replication. We propose that the increased PPB/MI ratio at 10 mg l-1 aphidicolin was due to a linkage between the duration of interphase and the time period in which early stage PPBs are visible. The increased duration of early PPBs partially compensates for the reduced number of nuclei reaching the stage of PPB initiation. Furthermore, in cultures containing aphidicolin, the percentage of PPBs with simultaneous perinuclear fluorescence (PNF, accumulation of microtubules on nuclear envelope) was reduced and whenever PNF was prominent and dense on the nuclear envelope the nucleus showed chromatin condensation. These observations indicated that the transition from PPB to PNF and then to the prophase spindle is closely related to the progress of the nuclear cycle.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1399-3054.1991.tb00074.x

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2

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Promoters from kin1 and cor6.6, two Arabidopsis thaliana low-temperature-and ABA-inducible genes, direct strong β-glucuronidase expression in guard cells, pollen and young developing seeds (1995)

Wang, Hong ; Cutler, Adrian J.

Springer

Plant molecular biology 28 (1995), S. 619-634

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ISSN: 1573-5028

Keywords: Arabidopsis ; low-temperature-induced genes ; developmental regulation ; osmolarity ; promoter ; transgenic

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract The ability of most higher plants to withstand freezing can be enhanced by cold acclimation, although the freezing tolerance of plant tissues is also affected by their developmental stage. In addition, low temperature has pleiotropic effects on many plant developmental processes such as vernalization. The interaction between plant development and low temperature implies that some genes are regulated by both environmental factors and developmental cues. Although a number of cold-inducible genes from plants have been identified, information concerning their regulation during plant development is limited. In order to understand their developmental regulation and obtain possible clues as to function, the promoters of kin1 and cor6.6, two cold- and abscisic acid (ABA)-regulated genes from Arabidopsis thaliana, were fused to the β-glucuronidase (GUS)-coding sequence and the resulting constructs were used to transform tobacco and A. thaliana. Transgenic plants with either the kin1 or cor6.6 promoter showed strong GUS expression in pollen, developing seeds, trichomes and, most interestingly, in guard cells. During pollen development, maximum GUS activity was found in mature pollen. In contrast, the maximum GUS activity during seed development was during early embryogenesis. These patterns of expression distinguish kin1 and cor6.6 from related lea genes which are strongly expressed during late embryogenesis. There was no major qualitative difference in patterns of GUS expression between kin1 and cor6.6 promoters and the results were similar for transgenic tobacco and Arabidopsis. Considering the results described, as well as those in an accompanying paper Wang et al., 1995, Plant Mol Biol 28: 605–617 (this issue), we suggest that osmotic potential might be a major factor in regulating the expression of kin1 and cor6.6 during several developmental processes. The implication of the results for possible function of the gene products is discussed.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00021188

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3

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Promoters from kin1 and cor6.6, two homologous Arabidopsis thaliana genes: transcriptional regulation and gene expression induced by low temperature, ABA, osmoticum and dehydration (1995)

Wang, Hong ; Datla, Raju ; Georges, Fawzy ; [et al.]

Springer

Plant molecular biology 28 (1995), S. 605-617

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ISSN: 1573-5028

Keywords: abscisic acid ; Arabidopsis ; cold acclimation ; low temperature-induced genes ; promoter ; transgenic

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract The Arabidopsis thaliana genes kin1 and cor6.6 belong to the same family and were expressed at higher levels following low temperature and ABA treatments. In an attempt to elucidate the mechanism of gene regulation by low temperature, the relationship between low-temperature- and abscisic acid (ABA)-induced gene expression and possible differential expression of the two genes, we have cloned a 5.3 kb genomic fragment harboring kin1 and cor6.6 and their respective 5′ sequences. The putative promoters of both genes were fused to the β-glucuronidase (GUS) coding sequence and GUS expression was analysed in transgenic tobacco and Arabidopsis plants. The cor6.6 promoter produced a higher basal level of expression than the kin1 promoter in transgenic tobacco. Enzyme assays of inducible GUS activity in transgenic Arabidopsis and tobacco plants showed that GUS activity directed by both kin1 and cor6.6 promoters was significantly induced by ABA, dehydration and osmoticum, but not by low temperature. Northern analysis revealed, in contrast, that GUS mRNA was significantly induced in these transgenic plants by low temperature. Further analysis showed that, at low temperature, GUS protein synthesis from the induced GUS mRNA was inhibited. Together these results reveal induction of kin1 and cor6.6 transcription by low temperature, exogenous ABA and dehydration. However, low-temperature expression is dramatically reduced at the translational level.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00021187

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4

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Promoters from kin1 and co6.6, two Arabidopsis thaliana low-temperature- and ABA-inducible genes, direct strong β-glucuronidase expression in guard cells, pollen and young developing seeds (1995)

Wang, Hong ; Cutler, Adrian J.

Springer

Plant molecular biology 29 (1995), S. 1307-1307

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ISSN: 1573-5028

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00020472

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5

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Non-destructive, stereological estimation of plant root lengths, branching pattern and diameter distribution (1999)

Wulfsohn, Dvoralai ; Nyengaard, Jens R. ; Gundersen, Hans Jørgen G. ; [et al.]

Springer

Plant and soil 214 (1999), S. 15-26

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ISSN: 1573-5036

Keywords: Agropyron cristatum L. ; growth curves ; total vertical projections ; unbiased stereology ; variability

Source: Springer Online Journal Archives 1860-2000

Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Notes: Abstract The total length of a linear structure contained in an unbounded, transparent reference space can be estimated from ‘total vertical projections’ obtained by rotating the linear structure about an arbitrary ‘vertical’ axis, and projecting the linear structure onto a plane parallel to the axis of rotation. The total number of intersections between cycloid arcs with their minor axis perpendicular to the axis of rotation and the projected linear structure then provides an unbiased estimator of the total length of the structure. In this study, a stereological procedure based on the method of ‘total vertical projections’ was used to non-destructively estimate total root length, number of branches, diameter distribution and mean root diameter of crested wheatgrass plants (Agropyron cristatum L.) growing in a transparent medium. Root lengths, diameters, and number of branching points of various orders were determined at 3-day intervals over a 4-week growing period. The length estimator was very robust and efficient with sampling coefficients of error usually less than 5% for a total of 50–150 grid intersection counts over two projection directions per plant. Biological coefficients of variance for total length were between 30–70%, and were largely related to variation in the extent of branching.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1004642820669

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6

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Role of oxidative stress in cereal protoplast recalcitrance (1989)

Cutler, Adrian J. ; Saleem, Mohammed ; Coffey, Maxine A. ; [et al.]

Springer

Plant cell, tissue and organ culture 18 (1989), S. 113-127

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ISSN: 1573-5044

Keywords: lipoxygenase ; peroxidase ; peroxidation ; cereal protoplast ; oxidative stress

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract Cereal leaf protoplasts are often extremely unstable in culture and usually lyse within 24 hours. Using the thiobarbituric acid test and the ferrous thiocyanate test we have shown that corn (Zea mays L. cv. Market Beauty) and wheat (Triticum aestivum L. cv. Benito) leaf protoplasts accumulate peroxides and peroxide degradation products during culture. This increase correlated with an increase in lipoxygenase activity. On the other hand, enzymes involved in detoxification of peroxides such as catalase and peroxidase decreased during culture. The occurrence of lipid peroxidation in leaf protoplasts is likely to be a consequence of a temporary imbalance in the enzymes involved in oxygen metabolism. It has previously been shown that the lipoxygenase inhibitor n-propyl gallate stabilizes the protoplasts in culture and so peroxidation is likely to be the cause of leaf protoplast instability. Protoplasts obtained from suspension cultures are stable in culture and do not undergo lipid peroxidation. This stability is due to a decrease in lipoxygenase activity and increases in catalase and peroxidase activity after protoplast isolation.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00033470

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7

Electronic Resource

DNA replication in maize leaf protoplasts (1989)

Wang, H. ; Cutler, Adrian J. ; Saleem, M. ; [et al.]

Springer

Plant cell, tissue and organ culture 18 (1989), S. 33-46

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ISSN: 1573-5044

Keywords: maize (Zea mays L.) ; DNA synthesis (replication) ; leaf protoplast ; immunofluorescence microscopy ; n-propyl gallate ; polyamines

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract Maize leaf protoplasts were investigated for their metabolic competence and capacity to synthesize DNA. When protoplasts were incubated at elevated temperatures, they exhibited a heat shock response with specific proteins being preferentially synthesized. This indicated that the protoplasts were fully metabolically functional and capable of responding to environmental stimuli. Significant DNA synthesis was observed in these protoplasts after incorporation of 3H-thymidine into chromatin by trichloroacetic acid precipitation and by incorporation of 5-bromo-2-deoxyuridine (BrdU), an analog of thymidine, detected by immunofluorescence. The immunocytochemical method revealed that about 50% of nuclei in the maize leaf protoplasts were labelled after 3 days of culture and that most of these nuclei were labelled as intensely as normal mitotic cells. Aphidicolin, an inhibitor of DNA polymerase-α, decreased the percentage of labelled nuclei, demonstrating that the labelling was substantially due to replicative DNA synthesis. However, chromosome condensation was not observed. It is proposed that these protoplasts are capable of DNA synthesis, but incapable of nuclear division. Effects of media additives on the number of nuclei entering S phase in these protoplasts were also assessed by the immunocytochemical method. Inclusion of 80mM Ca2+ in the enzyme solution increased protoplast yield and also appeared beneficial to DNA synthesis. The antioxidant, n-propyl gallate, which was used to stabilize the protoplasts, delayed the onset of DNA synthesis. Arginine and spermidine produced a slight increase in DNA synthesis.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00033463

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Long noncoding miRNA gene represses wheat β-diketone waxes (2017)

Huang, Daiqing ; Feurtado, J. Allan ; Smith, Mark A. ; [et al.]

National Academy of Sciences

In: PNAS - Proceedings of the National Academy of Sciences of the United States of America. 2017; 114(15): E3149-E3158. Published 2017 Mar 28. doi: 10.1073/pnas.1617483114.

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Publication Date: 2017-03-28

Description: The cuticle of terrestrial plants functions as a protective barrier against many biotic and abiotic stresses. In wheat and other Triticeae, β-diketone waxes are major components of the epicuticular layer leading to the bluish-white glaucous trait in reproductive-age plants. Glaucousness in durum wheat is controlled by a metabolic gene cluster at the WAX1 (W1) locus and a dominant suppressor INHIBITOR of WAX1 (Iw1) on chromosome 2B. The wheat D subgenome from progenitor Aegilops tauschii contains W2 and Iw2 paralogs on chromosome 2D. Here we identify the Iw1 gene from durum wheat and demonstrate the unique regulatory mechanism by which Iw1 acts to suppress a carboxylesterase-like protein gene, W1-COE, within the W1 multigene locus. Iw1 is a long noncoding RNA (lncRNA) containing an inverted repeat (IR) with 〉80% identity to W1-COE. The Iw1 transcript forms a miRNA precursor-like long hairpin producing a 21-nt predominant miRNA, miRW1, and smaller numbers of related sRNAs associated with the nonglaucous phenotype. When Iw1 was introduced into glaucous bread wheat, miRW1 accumulated, W1-COE and its paralog W2-COE were down-regulated, and the phenotype was nonglaucous and β-diketone–depleted. The IR region of Iw1 has 〉94% identity to an IR region on chromosome 2 in Ae. tauschii that also produces miRW1 and lies within the marker-based location of Iw2. We propose the Iw loci arose from an inverted duplication of W1-COE and/or W2-COE in ancestral wheat to form evolutionarily young miRNA genes that act to repress the glaucous trait.

Print ISSN: 0027-8424

Electronic ISSN: 1091-6490

Topics: Biology , Medicine , Natural Sciences in General