Publication details

Opposing regulation of hypocotyl elongation by cytokinins at low intensity of white and red light



Year of publication 2010
Type Article in Proceedings
Conference Book of Abstracts of XXIVth Genetic Days 2010
MU Faculty or unit

Faculty of Science

Field Genetics and molecular biology
Description Cytokinins (CKs) were reported not to affect hypocotyl elongation in Arabidopsis seedlings grown in the white light, and CK reportedly promoted hypocotyl elongation in the white light when ethylene action or auxin transport was blocked. Here we re-investigated the effects of CKs on hypocotyl elongation in Arabidopsis. While only a marginal effect of CKs on hypocotyl length was observed at a standard white light intensity (80 umol m-2 s-1), a pronounced stimulation of hypocotyl elongation by CKs was found when the seedlings were cultivated at a decreased white light intensity (20 umol m-2 s-1). The CK effect on hypocotyl length was due to cell elongation. The stimulation of hypocotyl elongation was observed for all four principal CKs (t-Z, iP, BA, TDZ) and was dose-dependent in the nanomolar range. The stimulatory effect of the CKs was antagonized by PI-55. Mutant and transgenic plant analysis indicated that the canonical two-component response pathway is necessary for this process with prevailing contribution of cytokinin receptors AHK2 and AHK3. This CK action was independent of ethylene signaling and partially inhibited by IAA. In contrary, inhibition of hypocotyl elongation by CKs was observed at a decreased red light intensity (20 umol m-2 s-1). Mutant analysis revealed that this effect is mediated by AHK3. Supported by grant Nos. LC06034, 1M06030, AV0Z50040507 and AV0Z50040702.
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