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.

Leaf Senescence and Protein Metabolism in Creeping Bentgrass Exposed to Heat Stress and Treated with Cytokinins

Abstract: Heat stress induces leaf senescence and causes changes in protein metabolism. The objective of this study was to investigate effects of exogenous application of a synthetic form of cytokinin, zeatin riboside (ZR), on protein metabolism associated with leaf senescence under heat stress for a cool-season grass species. Creeping bentgrass (Agrostis stolonifera L.) (cv. Penncross) plants were exposed to optimum temperature control (20/15 8C, day/night) and heat stress (35/30 8C) in growth chambers. Before heat stress treatments, foliage was sprayed with 10 mmol ZR or water (untreated) for 3 days and then once per week during 35 days of heat stress. Leaf chlorophyll content, photo- chemical efficiency (Fv/Fm), and soluble protein content declined, whereas protease activity increased during heat stress. Treatments with ZR helped maintain higher leaf chlorophyll content, Fv/Fm, and soluble protein content under heat stress. Protease activity in ZR-treated plants was lower than that of untreated plants. Zeatin riboside-treated plants had less severe degradation of ribulose-1,5-bisphosphate carboxylase proteins than untreated plants exposed to heat stress. In addition, ZR treatment upregulated the expression of 32- and 57-kDa proteins under heat stress conditions. These results demonstrated that the exogenous application of ZR ameliorated the negative effects of heat stress, as manifested by suppression or delay of leaf senescence. Cytokinins may have helped to alleviate heat stress injury, probably by slowing down the action of protease and by induction or upregulation of heat-shock proteins.

Endogenous cytokinin accumulation and cytokinin oxidase activity during shoot organogenesis of Petunia hybrida

Abstract: Changes in endogenous cytokinin content and cytokinin oxidase activity were characterized in leaf explants from two Petunia hybrida Vilm. genetic lines which differed in their shoot organogenic response to exogenous N 6 -benzyladenine (BA). Endogenous cytokinin content in leaf explants of the highly shoot organogenic line, St40, increased 1.7-fold during the shoot induction phase (days 6-10) and had an additional 2.6-fold cytokinin increase correlated with the shift from induction to the shoot development phase. The cytokinins isopentenyl adenine (iP) and isopentenyl adenosine (iPAR) increased, while the cytokinins zeatin, zeatin riboside and dihydrozeatin remained at consistently low levels. In contrast, isoprenoid cytokinins did not accumulate in petunia TLV1 leaf explants which were incapable of shoot induction during 12 days of culture with BA. Cytokinin oxidase activity continuously increased in leaf explants of both petunia genotypes in response to BA, with a larger increase in St40. These results suggest that the differences in organogenic response in the two petunia genotypes may be the result of differences in BA uptake and metabolism which subsequently affects the accumulation of isoprenoid cytokinins and the activity of cytokinin oxidase in the early stages of shoot development.

The effect of stratification on endogenous cytokinin levels in seeds of Acer saccharum.

Abstract: Stratification of sugar maple seed resulted in high levels of cytokinins after 20 days. A further increase in the chilling period led to a decrease in cytokinins. Most of the cytokinin activity detected was due to compound(s) that co-chromatographed with zeatin.

Changes in cis‐zeatin and cis‐zeatin riboside levels and biological activity during potato tuber dormancy

Abstract: The effects of postharvest storage duration and temperature on endogenous cis-zeatin (cis-Z) and cis-zeatin riboside (cis-ZR) levels in potato (Solanum tuberosum L.) tubers were determined in relation to tuber bud dormancy. The tubers used in these studies were completely dormant for at least 81 days of storage. Thereafter, tuber bud dormancy diminished gradually and after 165 days of postharvest storage, the tubers were completely non-dormant. Immediately after harvest, endogenous levels of cis-Z and cis-ZR were approximately 25 pmol (g fresh weight)−1 and 8 pmol (g fresh weight)−1, respectively. In tubers exiting dormancy but stored at a growth-inhibiting temperature (3°C), endogenous levels of cis-Z rose over threefold after 25 days of storage and remained elevated for the duration of the study. Levels of cis-ZR remained essentially constant during this same period. In tubers transferred to a growth permissive temperature (20°C) prior to use, the rise in endogenous cis-Z was less dramatic and more protracted; increasing twofold after 53 days of storage. No change in cis-Z riboside content was observed in these tubers during this period. Dose-response studies using either cis-Z or trans-Z demonstrated a time-dependent increase in cytokinin sensitivity during postharvest storage. Immediately after harvest, dormant tubers were insensitive to both zeatin isomers. Thereafter, tubers exhibited a dose-dependent increase in premature sprouting following injection with either cytokinin isomer. After injection into dormant tubers, cis-[8-14C]-zeatin was metabolized primarily to adenine/adenosine and cis-Z riboside. Seven days after injection, less than 10% of the recovered radioactivity was associated with trans-ZR. These results are consistent with a role for endogenous cis-Z (and its derivatives) in the regulation of potato tuber dormancy.

Characterization and regeneration of wheat (Triticum aestivum L.) embryogenic cell suspension cultures.

Abstract: Stable cell suspension cultures were established from two types of calli (one compact, nodular and embryogenic, the other friable and embryogenic) derived from cultured immature embryos of wheat (cv FLA302). Only aged calli, which had been subcultured for at least 5–8 months, formed suspensions comprised mainly of groups of small, round, densely cytoplasmic, starch-containing cells. Only the embryogenic suspension derived from the aged, compact and nodular callus formed distinct somatic embryos when plated on regeneration media containing IAA and zeatin. Upon subsequent transfer to fresh regeneration medium more than 200 green rooted plants were obtained.