Abstract
Plant genome contains a lot of Myb genes, but most of which encode for Myb proteins that contain only two repeats in the Myb domain. In contrast, much fewer number of plant genes, like mammalian c-Myb gene, encode for Myb proteins with three repeats. We previously reported that, in tobacco, the three-repeat Myb proteins bind to the cell cycle-regulated cis element called MSA in cyclin B promoter, and regulate G2/M phase-specific transcription. Arabidopsis genome contains 5 genes encoding for such three-repeat Myb proteins. Here we isolated and analyzed knockout mutants for these Myb genes in Arabidopsis. We found that a double knockout mutation for two related three-repeat Myb genes caused severe defects in embryogenesis, inflorescence architecture, and cytokinesis in epidermal cells. Some of these defects are consistent with our previous finding that a group of genes involved in cell plate formation during cytokinesis are the targets of three-repeat Myb factors.
