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Combinatorial Microarray Analysis Revealing Arabidopsis Genes Implicated in Cytokinin Responses through the His[rightwards arrow]Asp Phosphorelay Circuitry

Kiba, Takatoshi, Naitou, Takahito, Koizumi, Nobuya, Yamashino, Takafumi, Sakakibara, Hitoshi, Mizuno, Takeshi
Plant & cell physiology 2005 v.46 no.2 pp. 339-355
Arabidopsis thaliana, transgenic plants, plant response, plant proteins, transcription factors, gene expression regulation, signal transduction, microarray technology, cytokinins, histidine, aspartic acid, nucleotide sequences
In Arabidopsis thaliana, the immediate early response of plants to cytokinin is formulated as the multistep histidine kinase (AHK)[rightwards arrow]histidine-containing phosphotransmitter (AHP)[rightwards arrow]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[rightwards arrow]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[rightwards arrow]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[rightwards arrow]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[rightwards arrow]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[rightwards arrow]Asp phosphorelay in A. thaliana.