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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13 citations
TL;DR: In this article, the role of cytokinins in the senescence of G2 peas was determined using gas chromatography-mass spectroscopy following purification by HPLC, and the presence of zeatin was confirmed by its mass spectrum of its permethylated derivative.
Abstract: In G2 peas senescence only takes place in long days. In order to determine the role of cytokinins in this process the endogenous cytokinins from vegetative shoots of G2 peas were characterized using gas chromatography-mass spectroscopy following purification by HPLC. Cytokinins were extracted and purified with and without the addition of 15N labelled internal standards of several cytokinins to estimate cytokin content by isotope dilution in the mass spectra. Samples without internal standards were bioassayed after HPLC. Bioassays showed the presence of zeatin, zeatin riboside and zeatin-0-glucoside. The presence of zeatin was confirmed by its mass spectrum of its permethylated derivative. Tentative identification of zeatin riboside, zeatin-0-glucoside, dihydrozeatin, and dihydrozeatin-0-glucoside was obtained by the coincidence of the major ion for the permethylated natural and 15N labelled internal standards on GC-MS, and the similar coincidence of ions for permethylated zeatin riboside-0-glucoside by direct probe MS. There was no indication of the presence of significant quantities of zeatin-7-glucoside or zeatin-9-glucoside. The amounts in the tissue ranged from 200–1000 ng/kg fresh weight for each cytokinin and about 2–4 μg/kg fresh weight for total cytokinins. There was no apparent difference in the levels in mature but pre-senescent shoots grown in long days and short days indicating that apical senesecence in G2 peas does not appear to be induced by a decline in cytokinin level in the shoots.
13 citations
TL;DR: Regions relevant to UDPG/UDPX affinity and competition were identified using hybrid enzymes derived from domain exchanges of parental genes, and the N-terminal half of the enzyme is important in this respect.
Abstract: The substrate specificity of two recombinant enzymes, zeatin O-glucosyltransferase 1 (ZOG1) and zeatin O-xylosyltransferase 1 (ZOX1), was further characterised. ZOG1 utilises zeatin (Z), UDPG, and UDPX as substrates to form O-glucosylzeatin (OGZ) and O-xylosylzeatin (OXZ) but has higher affinity to UDPG than UDPX. ZOX1 uses only UDPX, converting Z to OXZ. Dihydrozeatin (DHZ) is also a substrate for both enzymes, but only in combination with UDPX, giving rise to O-xylosyldihydrozeatin (OXDHZ). O-Glucosyldihydrozeatin (OGDHZ) is not formed by ZOG1, possibly due to steric hindrance. Regions relevant to UDPG/UDPX affinity and competition were identified using hybrid enzymes derived from domain exchanges of parental genes. The N-terminal half of the enzyme is important in this respect. The BstEII-BstAPI segment of ZOG1 correlates with inhibition of O-xylosyltransferase activity by UDPG while the BstAPI-Eco0109 segment of ZOG1 is required for utilisation of UDPG as the sugar donor.
13 citations
TL;DR: Dihydrozeatin delayed the senescence of cut carnations while zeatin did not and both cytokinins were rapidly transtocated to the receptacle which apparently serves as a cytokinin reservoir.
13 citations
TL;DR: Plant and anther nutrient starvation did not improve the anther response to differentiation, nor did it induce haploid development, similarly as cold treatment of inflorescences or isolated anthers.
Abstract: In the present investigation, aimed at obtaining beet haploids from anthers, the effect of mineral media, potato and sugar beet extract and p-fluorophenylalanine (PFP) in combination with growth substances was tested. Nutrient-starved plants as anther-donors, anther-starvation, cold treatment and photoperiod were also analysed. On all mineral media the anthers produced callus and roots; however, the percentage depended on the combination of growth substances used. The best medium for differentiation was that of Linsmaier and Skoog with 25 µM zeatin or 6-(3-methyl-2-butenylamino)purine with 5 µM naphthalene-l-acetic acid (25.5%). The addition of PFP caused an increase in the percentage of anther differentiation (41.6%). Besides callus and roots on one of the anthers (in ca. 140000 tested), vegetative buds were formed from which numerous plants were obtained (2n). Plant and anther nutrient starvation did not improve the anther response to differentiation, nor did it induce haploid development, similarly as cold treatment of inflorescences or isolated anthers. The anthers of wild species showed lower ability to differentiate than those of sugar or fodder beets. Cytological analyses showed formation of multicellular structures until ca. the 12-th day of anther culture; afterwards, they degenerated.
13 citations