Combinatorial microarray analysis revealing arabidopsis genes implicated in cytokinin responses through the His->Asp Phosphorelay circuitry.
In Arabidopsis thaliana, the immediate early response of plants to cytokinin is formulated as the multistep histidine kinase (AHK)-->histidine-containing phosphotransmitter (AHP)-->response regulator (ARR) phosphorelay signaling circuitry, which is initiated by the cytokinin receptor histidine protein kinases. In the hope of finding components (or genes) that function downstream of the cytokinin-mediated His-->Asp phosphorelay signaling circuitry, we carried out genome-wide microarray analyses. To this end, we used a combinatorial microarray strategy by employing not only wild-type plants, but also certain transgenic lines in which the cytokinin-mediated His-->Asp phosphorelay signaling circuitry has been genetically manipulated. These transgenic lines employed were ARR21-overexpressing and ARR22-overexpressing plants, each of which exhibits a characteristic phenotype with regard to the cytokinin-mediated His-->Asp phosphorelay. The results of extensive microarray analyses with these plants allowed us systematically to identify a certain number of genes that were up-regulated at the level of transcription in response to cytokinin directly or indirectly. Among them, some representatives were examined further in wild-type plants to support the idea that certain genes encoding transcription factors are rapidly and specifically induced at the level of transcription by cytokinin in a manner similar to that of the type-A ARR genes, which are the hallmarks of the His-->Asp phosphorelay signaling circuitry. Several interesting transcription factors were thus identified as being cytokinin responsive, including those belonging to the AP2/EREBP family, MYB family, GATA family or bHLH family. Including these, the presented list of cytokinin-up-regulated genes (214) will provide us with valuable bases for understanding the His-->Asp phosphorelay in A. thaliana.
Kiba
Takatoshi
T
Laboratory of Molecular Microbiology, School of Agriculture, Nagoya University, Chikusa-ku, Nagoya, 464-8601 Japan.
Naitou
Takahito
T
Koizumi
Nobuya
N
Yamashino
Takafumi
T
Sakakibara
Hitoshi
H
Mizuno
Takeshi
T
D017360:Arabidopsis / Q000235:genetics*; D001224:Aspartic Acid / Q000378:metabolism; D002478:Cells, Cultured; D003583:Cytokinins / Q000378:metabolism* / Q000494:pharmacology; D030541:Databases, Genetic; D018506:Gene Expression Regulation, Plant / Q000187:drug effects / Q000502:physiology*; D006639:Histidine / Q000378:metabolism; D020411:Oligonucleotide Array Sequence Analysis / Q000379:methods*; D010766:Phosphorylation; D010937:Plant Growth Regulators / Q000494:pharmacology; D015398:Signal Transduction / Q000235:genetics*; D015854:Up-Regulation / Q000235:genetics
D003583:Cytokinins; D010937:Plant Growth Regulators; D001224:Aspartic Acid; D006639:Histidine