Topic
Zeatin
About: Zeatin is a research topic. Over the lifetime, 2467 publications have been published within this topic receiving 64092 citations. The topic is also known as: Zeatin & (E/Z)-zeatin.
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TL;DR: In this article, the radioactivity in the xylem sap of intact seedlings, supplied with [(3)H]zeatin via the roots, was largely due to Zeatin, dihydrozeatin and zeatin riboside.
Abstract: [(3)H]zeatin was supplied through the transpiration stream to de-rooted lupin (Lupinus angustifolius L.) seedlings. The following previously known metabolites were identified chromatographically: 5'-phosphates of zeatin riboside and dihydrozeatin riboside, adenosine-5'-phosphate, zeatin riboside, zeatin-7-glucopyranoside, zeatin-9-glucopyranoside, adenine, adenosine and dihydrozeatin. Five new metabolites were purified; four of these contain an intact zeatin moiety. Two were identified unequivocally, one as L-β-[6-(4-hydroxy-3-methylbut-trans-2-enylamino)-purin-9-yl]alanine, a metabolite now termed lupinic acid, and the second as O-β-D-glucopyranosylzeatin. These two compounds were the major metabolites formed when zeatin solution (100 μM) was supplied to the de-rooted seedlings. The radioactivity in the xylem sap of intact seedlings, supplied with [(3)H]zeatin via the roots, was largely due to zeatin, dihydrozeatin and zeatin riboside. When [(3)H]zeatin (5 μM) was supplied via the transpiration stream to de-rooted Lupinus luteus L. seedlings, the principal metabolite in the lamina was adenosine, while in the stem nucleotides of zeatin and adenine were the dominant metabolites. O-Glucosylzeatin and lupinic acid were also detected as metabolites. The level of the latter varied greatly in the tissues of the shoot, and was greatest in the lower region of the stem and in the expanding lamina. Minor metabolites also detected chromatographically were: (a) dihydrolupinic acid, (b) a partially characterized metabolite which appears to be a 9-substituted adenine (also formed in L. angustifolius), (c) glucosides of zeatin riboside and/or dihydrozeatin riboside, and (d) O-glucosyldihydrozeatin. While lupinic acid supplied exogenously to L. luteus leaves underwent little metabolism, chromatographic studies indicated that O-glucosylzeatin was converted to its riboside, the principal metabolite formed, and also to adenosine, zeatin and dihydrozeatin. A thinlayer chromatography procedure for separating zeatin, dihydrozeatin, zeatin riboside and dihydrozeatin riboside is described.
96 citations
TL;DR: There is good evidence that bacteria and fungi produce cytokinins, and some associations involving obligate parasites also exhibit such symptoms, providing circumstantial evidence that these organisms also excrete cytokinin into host tissue.
Abstract: There is good evidence that bacteria and fungi produce cytokinins. A number of microorganisms excrete cytokinin-active nucleosides and free bases into culture media. Cytokinin-active nucleosides have also been found in the tRNA of all the bacteria and fungi examined so far. The production of zeatin and its derivatives by microorganisms seems to be limited to those which cause diseases in higher plants or enter into symbioses. The symptoms of the plant-microbe interactions often resemble the effects of exogenously applied cytokinins, leading to speculation that microbes excrete cytokinins into host tissue. Some associations involving obligate parasites also exhibit such symptoms, providing circumstantial evidence that these organisms also excrete cytokinins.
95 citations
TL;DR: This study provides a novel strategy for designing plants for enhanced biomass production and insect control by releasing plant hormones or sugar esters from their conjugates stored within their chloroplasts.
Abstract: Transplastomic tobacco (Nicotiana tabacum) plants expressing β-glucosidase (Bgl-1) show modified development. They flower 1 month earlier with an increase in biomass (1.9-fold), height (1.5-fold), and leaf area (1.6-fold) than untransformed plants. Trichome density on the upper and lower leaf surfaces of BGL-1 plants increase by 10- and 7-fold, respectively, harboring 5-fold more glandular trichomes (as determined by rhodamine B staining), suggesting that BGL-1 lines produce more sugar esters than control plants. Gibberellin (GA) levels were investigated because it is a known regulator of flowering time, plant height, and trichome development. Both GA1 and GA4 levels are 2-fold higher in BGL-1 leaves than in untransformed plants but do not increase in other organs. In addition, elevated levels of other plant hormones, including zeatin and indole-3-acetic acid, are observed in BGL-1 lines. Protoplasts from BGL-1 lines divide and form calli without exogenous hormones. Cell division in protoplasts is enhanced 7-fold in the presence of exogenously applied zeatin-O-glucoside conjugate, indicating the release of active hormones from their conjugates. Whitefly (Bemisia tabaci) and aphid (Myzus persicae) populations in control plants are 18 and 15 times higher than in transplastomic lines, respectively. Lethal dose to kill 50% of the test population values of 26.3 and 39.2 μg per whitefly and 23.1 and 35.2 μg per aphid for BGL-1 and untransformed control exudates, respectively, confirm the enhanced toxicity of transplastomic exudates. These data indicate that increase in sugar ester levels in BGL-1 lines might function as an effective biopesticide. This study provides a novel strategy for designing plants for enhanced biomass production and insect control by releasing plant hormones or sugar esters from their conjugates stored within their chloroplasts.
95 citations
TL;DR: Data show that chloroplasts contain a whole spectrum of CKs and the enzymatic activity necessary for their metabolism, including a relatively high CK oxidase activity.
Abstract: Although cytokinins (CKs) affect a number of processes connected with chloroplasts, it has never been rigorously proven that chloroplasts contain CKs. We isolated intact chloroplasts from tobacco ( Nicotiana tabacum L. cv SR1) and wheat ( Triticum aestivum L. cv Ritmo) leaves and determined their CKs by liquid chromatography/tandem mass spectroscopy. Chloroplasts from both species contained a whole spectrum of CKs, including free bases (zeatin and isopentenyladenine), ribosides (zeatin riboside, and isopentenyladenosine), ribotides (isopentenyladenosine-5′-monophosphate, zeatin riboside-5′-monophosphate, and dihydrozeatin riboside-5′-monophosphate), and N -glucosides (zeatin- N 9 -glucoside, dihydrozeatin- N 9 -glucoside, zeatin- N 7 -glucoside, and isopentenyladenine- N -glucosides). In chloroplasts there was a moderately higher relative amount of bases, ribosides, and ribotides than in leaves, and a significantly increased level of N 9 -glucosides of zeatin and dihydrozeatin. Tobacco and wheat chloroplasts were prepared from leaves at the end of either a dark or light period. After a dark period, chloroplasts accumulated more CKs than after a light period. The differences were moderate for free bases and ribosides, but highly significant for glucosides. Tobacco chloroplasts from dark-treated leaves contained zeatin riboside- O -glucoside and dihydrozeatin riboside- O -glucoside, as well as a relatively high CK oxidase activity. These data show that chloroplasts contain a whole spectrum of CKs and the enzymatic activity necessary for their metabolism.
95 citations
TL;DR: A natural free radical scavenger, ascorbic acid (AsA) shows both counteractive and enhancing effects on JA‐inducible phytoalexin production, depending on its concentration, which suggests that active oxygen species (AOS) may play important roles in phy toalex in production by JA in rice leaves.
94 citations