Cytokinin Regulation of Gene Expression in the AHP Gene Family in Arabidopsis thaliana

0305973 - ÚEB 2008 RIV US eng J - Journal Article
Hradilová, Jana - Malbeck, Jiří - Brzobohatý, Břetislav
Cytokinin Regulation of Gene Expression in the AHP Gene Family in Arabidopsis thaliana.
[Cytokinin Regulation of Gene Expression in the AHP Gene Family in Arabidopsis thaliana.]
Journal of Plant Growth Regulation. Roč. 26, č. 3 (2007), s. 229-244. ISSN 0721-7595. E-ISSN 1435-8107
R&D Projects: GA MŠMT LN00A081; GA MŠMT 1M06030; GA MŠMT(CZ) LC06034; GA AV ČR(CZ) IAA600380507; GA AV ČR IAA600040612
Institutional research plan: CEZ:AV0Z50380511; CEZ:AV0Z50040702
Source of funding: V - Other public resources ; V - Other public resources ; V - Other public resources ; V - Other public resources
Keywords : gene expression * AHP gene family * cytokinin signal transduction
Subject RIV: EF - Botanics
Impact factor: 2.220, year: 2007

In higher plants histidine-aspartate phosphorelays are involved in hormone and stress signaling via a two-component system of signal transduction. In this system a histidine-containing phosphotransmitter (HPt) mediates signal transmission from a sensory histidine kinase to a response regulator, providing integration and/or branching of several different signaling pathways. Five genes encoding HPts, AHP1-5, have been identified in Arabidopsis. Histidine-aspartate phosphorelays involving HPts have been at least partly implicated in cytokinin signaling. We analyzed the regulation by cytokinins of AHP gene expression. We compared the effects on steady-state levels of AHP transcripts of a short-term treatment with an aromatic cytokinin and increase in endogenous isoprenoid cytokinin levels using an activable ipt system in 8-day-old Arabidopsis seedlings. Following ipt activation, a rapid and highly preferential increase in trans-zeatin-type cytokinins was observed, whereas other isoprenoid-type cytokinins showed no or only marginal increases. The levels of cytokinin metabolites under long-term ipt activation suggest that the seedlings may have difficulties in efficiently downregulating active forms of the hormone. Using real-time RT-PCR, transient increases in steady-state levels of AHP1-4 transcripts in response to both the short-term N-6-benzyladenine treatment and the increase in endogenous trans-zeatin-type cytokinin levels were observed. In contrast, both the full and the alternatively spliced AHP5 transcripts remained unaltered. On the other hand, increases in steady-state levels of AHP1-4 transcripts observed in seedlings cultivated continuously in the presence of exogenous N-6-benzyladenine were not paralleled in seedlings with constitutively increased endogenous trans-zeatin-type cytokinins, providing further indirect evidence for distinct functions of aromatic and isoprenoid cytokinins.

Cytokinin Regulation of Gene Expression in the AHP Gene Family in Arabidopsis thaliana.
Permanent Link: http://hdl.handle.net/11104/0159094