Transcriptomic analysis of the myb3r1 myb3r4 double mutant in Arabidopsis thaliana

R1R2R3-Myb proteins represent an evolutionarily conserved class of Myb family proteins important for cell cycle regulation and differentiation in eukaryotic cells. In plants, this class of Myb proteins are believed to play important roles in cell cycle regulation through transcriptional regulation of G2/M phase-specific genes by binding to common cis-elements, called MSA elements. In Arabidopsis thaliana, MYB3R1 and MYB3R4 act as transcriptional activators and positively regulate cytokinesis by activating transcription of KNOLLE, which encodes a cytokinesis-specific syntaxin. Here, we show that the double mutation myb3r1 myb3r4 causes pleiotropic developmental defects, some of which are due to deficiency of KNOLLE whereas other are not, suggesting multiple target genes are involved. Consistently, microarray analysis of the double mutant revealed altered expression of many genes, among which G2/M-specific genes showed significant overrepresentation of the MSA motif and a strong tendency to be down-regulated by the double mutation. Our results demonstrate, on a genome-wide level, the importance of the MYB3R-MSA pathway for regulating G2/M-specific transcription. In addition, MYB3R1 and MYB3R4 may have diverse roles during plant development by regulating G2/M-specific genes with various functions, as well as genes possibly unrelated to the cell cycle.

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Haga N, Kobayashi K, Suzuki T, Maeo K, Kubo M, Ohtani M, Mitsuda N, Demura T, Nakamura K, Jürgens G, Ito M