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31.
Monovalent cations and growth regulation. I. Growth responses in cucumber hypocotyl segments 下载免费PDF全文
Purves WK 《Plant physiology》1966,41(2):230-233
The elongation of etiolated cucumber (Cucumis sativus L.) hypocotyl segments was stimulated by KCl and a number of other potassium salts at a concentration of 0.02 n K+. The effect of KCl was not evident until 14 hours after the beginning of treatment. 相似文献
32.
Sulphate deprivation depresses the transport of nitrogen to the xylem and the hydraulic conductivity of barley (Hordeum vulgare L.) roots 总被引:1,自引:0,他引:1
Jadu Lal Karmoker David T. Clarkson Leslie R. Saker Joy M. Rooney Judith V. Purves 《Planta》1991,185(2):269-278
During the first 4 d after the removal of SO
4
2-
from cultures of young barley plants, the net uptake of 15N-nitrate and the transport of labelled N to the shoot both decline. This occurred during a period in which there was no measurable change in plant growth rate and where the incorporation of [3H]leucine into membrane and soluble proteins was unaffected. Reduced N translocation was associated with six- to eightfold increases in the level of asparagine and two- to fourfold increases in glutamine in root tissue; during the first 4 d of SO
4
2-
deprivation there were no corresponding increases in amides in leaf tissue. The provision of 1 mol · m–3 methionine halted, and to some extent reversed the decline in NO
3
-
uptake and N translocation which occurred during continued SO
4
2-
deprivation. This treatment had relatively little effect in lowering amide levels in roots. Experiments with excised root systems indicated that SO
4
2-
deprivation progressively lowered the hydraulic conductivity, Lp, of roots; after 4 d the Lp of SO
4
2-
-deprived excised roots was only 20% of that of +S controls. In the expanding leaves of intact plants, SO
4
2-
deprivation for 5 d was found to lower stomatal conductance, transpiration and photosynthesis, in the order given, to 33%, 37% and 18% of control values. The accumulation of amides in roots is probably explained by a failure to export either the products of root nitrate assimilation or phloem-delivered amino-N. This may be correlated with the lowered hydraulic conductivity. Enhanced glutamine and-or asparagine levels probably repressed net uptake of NO
3
-
and 13NO
3
-
influx reported earlier (Clarkson et al. 1989, J. Exp. Bot. 40, 953–963). Attention is drawn to the similar hydraulic signals occurring in the early stages of several different types of mineral-nutrient stresses.Abbreviations Asn
asparagine
- Gln
glutamine
- Lp
hydraulic conductivity
J.L.K. is extremely grateful to the British Council for supporting his working visit to Long Ashton. We thank John Radin for helpful discussion and encouragement. 相似文献
33.
Role of alpha-transinducing factor (VP16) in the induction of alpha genes within the context of viral genomes. 下载免费PDF全文
In herpes simplex virus 1, the five alpha genes are induced by alpha-transinducing factor (alpha TIF; VP16), a virion protein, acting in concert with Oct-1 and other cellular proteins on a cis-acting site in the promoter domain of alpha genes. Because alpha TIF is an essential virion protein, its function as an inducer can best be evaluated only by mutating the cis-acting site. Earlier we reported on a series of 17 mutations in and around the cis-acting site of a 275-bp alpha 27 promoter fused to a reporter gene and recombined into the viral genome. These recombinant viruses were tested in Vero cells in the presence of cycloheximide, and we demonstrated that mutations in the sequence required for Oct-1 binding abolished transactivation whereas mutations in the alpha TIF-dependent GARAT sequence decreased but did not abolish transactivation. We now report that (i) in limited-passage human embryonic lung cells, alpha gene expression from promoters mutated in the GARAT sequences is often higher and more variable than in Vero cells, (ii) in the absence of cycloheximide, the mutant viruses show less significant impairment of reporter gene expression, (iii) Oct-1 can bind either to the overlapping octamer element or to various TAATGARAT sequences with differing degrees of binding strength and these relative binding levels correlate well with levels of gene expression observed in infected cells, (iv) in the cis-acting site upstream of the alpha 4 gene, no degenerate overlapping Oct-1 sequence exists, and therefore in this instance Oct-1 must be binding directly to the TAATGARAT sequence, (v) extension of the alpha 27 promoter by an additional 1,334 bp results in much higher expression of the reporter gene as a result of additional upstream cis-acting sites, and (vi) obliteration of the most proximal Oct-1 binding element within the 275-bp promoter dramatically reduces gene expression even in the presence of the additional upstream cis-acting sites. 相似文献
34.
Earlier studies have shown that a herpes simplex virus 1 (HSV-1) open reading frame, US3, encodes a novel protein kinase and have characterized the cognate amino acid sequence which is phosphorylated by this enzyme. This report identifies an apparently essential viral phosphoprotein whose posttranslational processing involves the viral protein kinase. Analyses of viral proteins phosphorylated in the course of productive infection revealed a phosphoprotein whose mobility was viral protein kinase and serotype dependent. Thus, the corresponding HSV-1 and HSV-2 phosphoproteins differ in their electrophoretic mobilities, and the phosphoprotein specified by the HSV-1 mutant deleted in US3 (R7041) differs from that of the corresponding HSV-1 and HSV-2 proteins. Analyses of HSV-1 x HSV-2 recombinants mapped the phosphoprotein between 0.42 and 0.47 map units on the prototype HSV-1 DNA map. Within this region, the UL34 open reading frame was predicted to encode a protein of appropriate molecular weight which would also contain the consensus target site for phosphorylation by the viral protein kinase as previously defined with synthetic peptides. Replacement of the native UL34 gene with a UL34 gene tagged with a 17-amino-acid epitope from the alpha 4 protein identified this gene as encoding the phosphoprotein. Finally, mutagenesis of the predicted phosphorylation site on UL34 in the viral genome, and specifically the substitution of threonine or serine with alanine in the product of the UL34 gene, yielded phosphoproteins whose electrophoretic mobilities could not be differentiated from that of the US3- mutant. We conclude that the posttranslational processing of the UL34 gene product to its wild-type phenotype requires the participation of the viral protein kinase. While the viral protein kinase is not essential for viral replication in cells in culture, the UL34 gene product itself may not be dispensable. 相似文献
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38.
Drosophila Bcl-2 proteins participate in stress-induced apoptosis, but are not required for normal development 总被引:1,自引:0,他引:1
Sevrioukov EA Burr J Huang EW Assi HH Monserrate JP Purves DC Wu JN Song EJ Brachmann CB 《Genesis (New York, N.Y. : 2000)》2007,45(4):184-193
Many developing tissues require programmed cell death (PCD) for proper formation. In mice and C. elegans, developmental PCD is regulated by the Bcl-2 family of proteins. Two bcl-2 genes are encoded in the Drosophila genome (debcl/dBorg1/Drob-1/dBok and buffy/dBorg2) and previous RNAi-based studies suggested a requirement for these in embryonic development. However, we report here that, despite the fact that many tissues in fruit flies are shaped by PCD, deletion of the bcl-2 genes does not perturb normal development. We investigated whether the fly bcl-2 genes regulate non-apoptotic processes that require caspases, but found these to be bcl-2 gene-independent. However, irradiation of the mutants demonstrates that DNA damage-induced apoptosis, mediated by Reaper, is blocked by buffy and that debcl is required to inhibit buffy. Our results demonstrate that developmental PCD regulation in the fly does not rely upon the Bcl-2 proteins, but that they provide an added layer of protection in the apoptotic response to stress. 相似文献
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40.
Lois DW Arnold 《International breastfeeding journal》2006,1(1):1-8