Publication details

Effects of light intensity on modulation of morphogenesis by cytokinins in Arabidopsis seedlings



Year of publication 2008
Type Article in Proceedings
Conference XII. pracovní setkání biochemiků a molekulárních biologů
MU Faculty or unit

Faculty of Science

Field Genetics and molecular biology
Keywords cytokinins; hypocotyl
Description The participation of many environmental and hormonal cues notably influences the plant morphology. The hypocotyl is a very plastic organ, strongly influenced by both external and internal cues known to regulate cell elongation, such as light, hormones, temperature and gravity. The extension of the hypocotyl is regulated by a network of interacting factors as light and plant hormones. Light is one of the most important environmental factors for plants, as it provides photomorphogenetic signal. Cytokinins, as the members of the phytohormones, are the plant growth regulators that among others inhibit hypocotyl elongation in darkness. Conflicting results have been published regarding effects of cytokinins on hypocotyl elongation in light. The first reports concluded absence of any notable effects of cytokinins on hypocotyl elongation in Arabidopsis seedlings grown in light. Recently, stimulation of hypocotyl elongation by cytokinins was reported in Arabidopsis, however, the effect of cytokinins was found to be mediated by ethylene. We have been focused on the influence of light quantity (fluence) on hypocotyl elongation in transgenic A. thaliana seedlings (pOp-ipt-GUS::LhG4) with increased levels of endogenous cytokinins. At low fluence (lower than 20 umol photons m-2 s-1) hypocotyls of ipt overexpressing seedlings were significantly longer compared to controls. Interestingly, the effect was not influenced by inhibitors of ethylene biosynthesis and signaling providing the first evidence of a direct stimulation of hypocotyl elongation by cytokinins. Further, it was observed that the level of endogenous cytokinins play a role in the phenotype variability in ipt overexpressing plants. The increased cytokinin levels evoke several various abnormal phenotypes, on the one hand larger leaf rosette compared to control plants, on the other hand dwarfish plants.
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