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.

Mutation induced by ethylmethanesulphonate (EMS), in vitro screening for salt tolerance and plant regeneration of sweet potato ( Ipomoea batatas L.)

Abstract: Salt tolerant cultivars of sweet potato (Ipomoea batatas L.) can be obtained from induced mutation. The objective of the present study was to induce mutation for salt tolerance using ethylmethanesulphonate (EMS) in calli of sweet potato, followed by cell line selection and subsequent plant regeneration. Calli initiated from leaf explants were treated with 0.5% EMS for 0, 1, 1.5, 2, 2.5 and 3 h, followed by rinsing with sterile distilled water for four times. Preliminary experiments showed that 200 mM NaCl could be used as selection pressure. Salt tolerant calli were sub-cultured on medium supplemented with 200 mM NaCl for selection of mutant cell lines and this process repeated 5 times (20 days each). The selected calli were transferred onto somatic embryo formation medium, which was Murashige and Skoog (MS) medium supplemented with 4 mg l−1 abscisic acid (ABA), 10 mg l−1 gibberellic acid (GA). After 15 days, somatic embryos were transferred onto MS medium supplemented with 0.05 mg l−1 ABA, 0.2 mg l−1 zeatin (ZT) for regeneration. Plants designated as ML1, ML2 and ML3 were regenerated from the somatic embryos formed by calli treated with 0.5% EMS for 2 and 2.5 h. After propagation, salt tolerance of these mutants was investigated. Data suggested the mutants were more salt tolerant than control plants.

Regeneration of plants from leaf explants of micropropagated clonal Eucalyptus grandis

Abstract: Callus production along with caulogenesis was obtained from leaf explants of micropropagated clonal Eucalyptus grandis after six to twelve weeks of culture. Out of eight clones tested, six were amenable to shoot production using simple media containing naphthaleneacetic acid and either 6-benzyladenine or zeatin. Differences in growth regulator requirements for organogenesis were observed between different clones. These shoots were then elongated on a medium containing gibberellic acid and rooted using media derived from the micropropagation medium. Light conditions were also found to be important for regeneration. This protocol is the first published on regeneration from nonseedling material and it will facilitate the Agrobacterium tumefaciens -mediated transformation of selected clonal Eucalyptus grandis.

Adenine phosphoribosyltransferase isoforms of Arabidopsis and their potential contributions to adenine and cytokinin metabolism

Abstract: Adenine phosphoribosyltransferase (APT; EC 2.4.2.7) is a constitutively expressed enzyme involved in the one-step salvage of adenine to AMP. The Arabidopsis thaliana genome contains five sequences annotated as encoding APT or APT-like enzymes. Three of these have now been cloned, over-expressed and compared using kinetic analyses. At a cytosolic pH, all bind adenine efficiently based on their Km values (0.8–2.6 µM), although APT1 metabolizes adenine at a rate 31–53 times faster than APT2 and APT3, respectively. Since APT also has a possible role in the interconversion of cytokinin bases to nucleotides, we characterized the activity of each isoform on zeatin, isopentenyladenine and benzyladenine. Based on their Km values, APT2 and APT3 had much higher affinities than APT1 for all three cytokinins (15–440 µM for APT2 and 3 vs. 1.8–2.5 mM for APT1); conversely the Vmax values for APT2 and APT3 on these CK substrates showed the opposite trend, being 4- to 19-fold lower than those of APT1. Anti-peptide antibodies for APT1, APT2, and APT3 were prepared and used to examine the subcellular localization of each isoform. Based on these results, APT1 and APT3 appear to be cytosolic, while the localization of APT2 was inconclusive although sequence analysis implies that APT2 is also cytosolic. Each isoform was modelled against the crystal structure of APT from Leishmania donovani, and structural differences in substrate specificity-determining domains have been found. The estimated kinetic activities of these APTs suggest that they contribute primarily to adenine recycling, although an involvement in cytokinin interconversion cannot be discounted.

Biosynthesis of cytokinins by Azotobacter chroococcum

Abstract: Cytokinins were detected in culture nitrates of Azotobacter chroococcum, A. beijerinckii, A. vinelandii, Pseudomonas fluorescens and P. putida . The most prolific producer of cytokinins was A. chroococcum . Several purine ring constituents [adenine (ADE), adenosine, adenosine-5′-monophosphate, hypoxanthine, inosine and inosine-5′-monophosphate] and isoprenoid compounds [isopentyl alcohol (IA), 3-methyl-3-buten-1-ol, 3-methyl-2-buten-1-ol and isoprene] were tested for their suitability as physiological precursors to cytokinin biosynthesis. The isolation and quantification of zeatin riboside, dihydrozeatin riboside, t - and c -zeatin, isopentyl adenine and its riboside were monitored by high performance liquid chromatography (HPLC), u.v. spectrometry and bioassay. The stimulation of A. chroococcum to produce cytokinins by the addition of ADE and IA was monitored during the growth of the bacterium and tested under various environmental conditions in liquid media.