Two genes with similarity to bacterial response regulators are rapidly and specifically induced by cytokinin in Arabidopsis.
Cytokinins are central regulators of plant growth and development, but little is known about their mode of action. By using differential display, we identified a gene, IBC6 (for induced by cytokinin), from etiolated Arabidopsis seedlings, that is induced rapidly by cytokinin. The steady state level of IBC6 mRNA was elevated within 10 min by the exogenous application of cytokinin, and this induction did not require de novo protein synthesis. IBC6 was not induced by other plant hormones or by light. A second Arabidopsis gene with a sequence highly similar to IBC6 was identified. This IBC7 gene also was induced by cytokinin, although with somewhat slower kinetics and to a lesser extent. The pattern of expression of the two genes was similar, with higher expression in leaves, rachises, and flowers and lower transcript levels in roots and siliques. Sequence analysis revealed that IBC6 and IBC7 are similar to the receiver domain of bacterial two-component response regulators. This homology, coupled with previously published work on the CKI1 histidine kinase homolog, suggests that these proteins may play a role in early cytokinin signaling.
Brandstatter
I
I
Department of Biological Sciences, Laboratory for Molecular Biology, University of Illinois at Chicago, Chicago, Illinois 60607, USA.
Kieber
J J
JJ
D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics / Q000502:physiology*; D029681:Arabidopsis Proteins; D001426:Bacterial Proteins / Q000737:chemistry*; D001483:Base Sequence; D003583:Cytokinins / Q000494:pharmacology*; D017931:DNA Primers; D004926:Escherichia coli / Q000502:physiology; D018506:Gene Expression Regulation, Plant / Q000187:drug effects / Q000502:physiology*; D017343:Genes, Plant; D008565:Membrane Proteins / Q000737:chemistry; D000072236:Methyl-Accepting Chemotaxis Proteins; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000096:biosynthesis* / Q000737:chemistry; D012333:RNA, Messenger / Q000096:biosynthesis; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D014158:Transcription, Genetic / Q000187:drug effects
C113359:ARR4 protein, Arabidopsis; D029681:Arabidopsis Proteins; D001426:Bacterial Proteins; D003583:Cytokinins; D017931:DNA Primers; C113358:IBC6 protein, Arabidopsis; D008565:Membrane Proteins; D000072236:Methyl-Accepting Chemotaxis Proteins; D010940:Plant Proteins; D012333:RNA, Messenger