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591.
592.
Laura Meek Ruth C. Martin Xueyan Shan P. Andrew Karplus David W. S. Mok Machteld C. Mok 《Journal of Plant Growth Regulation》2008,27(2):192-201
O-Glycosides of the cytokinin zeatin are found in many plant tissues. They provide protection against degradative enzymes
and may serve as cytokinin reserves. Two zeatin glycosyltransferase (GT) genes, an O-glucosyltransferase (ZOG1) from Phaseolus lunatus and an O-xylosyltransferase (ZOX1) from P. vulgaris, were previously isolated. Five novel bean and soybean GT genes with high sequence identity to ZOG1 were isolated, sequenced, and expressed, along with two such genes from rice and one from tomato. None of the recombinant
proteins showed GT activity with zeatin. By comparing the ZOG1 sequence to the 3D model of Medicago truncatula UGT71G1, four regions possibly important to zeatin binding were identified, and mutation studies identified one amino acid
within each region (R59, D87, L127, and F149) whose mutation strongly impaired enzyme activity. The new bean and soybean GTs
differ from ZOG1 in one (PlGT2 and GmGT2) to three (GmGT1) of these residues. Mutation of one such GT (PlGT2) to render it identical to ZOG1 at the four implicated residues conferred low enzyme activity, providing further support
for the importance of these amino acids in recognizing zeatin as substrate.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
593.
594.
A GC-ECD titration of IAA in normal auxin (2,4-D)-requiring and auxin-independent (habituated) sugarbeet callus revealed an equal amount in both tissues. A comparison of the content and pattern (through starch gel electrophoresis) of soluble, membrane and wall peroxidases indicated that normal tissues contained a higher level of isoperoxidases. Normal tissues also were found to contain higher levels of peroxidase inhibitors and auxin protectors. The hypothesized peroxidase-mediated higher rate of auxin destruction in normal sugarbeet callus is supposed to be counterbalanced by the 2,4-D-controlled auxin protectors. 相似文献
595.
596.
597.
Elevation of pheromone response threshold in almond moth males pre-exposed to pheromone spray 总被引:1,自引:0,他引:1
Abstract. High percentages of naive Cadra cautella (Walker) (Lepidoptera: Pyralidae) males not pre-exposed to pheromone flew upwind to sources containing 50 ng (83%) and 500 ng (97%) of pheromone, but not to sources containing 5 μg (23%) and 50 μg (4%).Of the naive males that flew upwind in response to 50 ng sources, 67% located and landed on the source, whereas fewer than 19% of the naive males that flew upwind in response to higher doses located and landed on the sources.A 2-minute pre-exposure of C.cautella males to a spray cloud containing 50 ng, 500 ng, 5 μg or 50 μg of pheromone, induced shifts in response levels such that in wind-tunnel bioassays performed 1 h later, there was an increase in the doses that optimally elicited upwind flight and landing on the source that was proportional to the pre-exposure dose.Few of the pre-exposed males flew upwind to (10–43%) and landed on (0–33%) 50 ng sources, whereas they now perferentially flew upwind to(58–81% and 52–73%) and landed on (33–68% and 55–60%) pheromone sources of doses of 500 ng and 5 μg, respectively.Therefore pre-exposure to pheromone promoted a shift of threshold for response, and not an overall reduction in responsiveness to pheromone. 相似文献
598.
Effects on growth, mostly of an inhibitory nature, have been attributed to phenolic compounds in vivo and in vitro. This
suggests that l-α-aminooxy-β-phenylpropionic acid (l-AOPP), a competitive inhibitor of phenylalanine ammonia-lyase (PAL), the enzyme controlling the first step in phenylpropanoid
synthesis, might stimulate growth in soybean suspension cultures (Glycine max, cv. Acme). The promotive effect of l-AOPP, measured as an increase in cell number, was more clearly detected in the growth-limiting condition of cytokinin starvation.
At least one more cell division cycle was completed in the presence of l-AOPP before growth by division ceased and growth continued by expansion only. Phenolic acids are known to conjugate with
polyamines, modulating the free levels of these plant growth substances. Thus, the effect of l-AOPP on the titers of free and conjugated polyamines (putrescine, spermidine, and spermine) was investigated by high performance
liquid chromatography in the course of cytokinin starvation. An increased level of free putrescine was detected in the presence
of l-AOPP relative to controls, especially in the initial period before growth became restricted to cell expansion. The decrease
in free putrescine associated with the cessation of cell division was temporarily delayed, suggesting that an interaction
between phenolic acids and polyamines is involved in the mechanism of growth promotion by l-AOPP.
Received July 30, 1996; accepted January 28, 1997 相似文献