title: R1R2R3-Myb proteins positively regulate cytokinesis through activation of KNOLLE transcription in Arabidopsis thaliana.
abstract: G2/M phase-specific gene transcription in tobacco cells is mediated by R1R2R3-Myb transcriptional activators, NtmybA1 and NtmybA2, which bind to mitosis-specific activator (MSA) elements. We show here that two structurally related genes, MYB3R1 and MYB3R4, which encode homologs of NtmybA1 and NtmybA2, play a partially redundant role in positively regulating cytokinesis in Arabidopsis thaliana. The myb3r1 myb3r4 double mutant often fails to complete cytokinesis, resulting in multinucleate cells with gapped walls and cell wall stubs in diverse tissues. These defects correlate with the selective reduction of transcript levels of several G2/M phase-specific genes, which include B2-type cyclin (CYCB2), CDC20.1 and KNOLLE (KN). These genes contain MSA-like motifs in their promoters and were activated by MYB3R4 in transient expression assays in tobacco cells. The KN gene encodes a cytokinesis-specific syntaxin that is essential for cell plate formation. The cytokinesis defects of myb3r1 myb3r4 double mutants were partially rescued by KN gene expression from heterologous promoters. In addition, a kn heterozygous mutation enhanced cytokinesis defects resulting from heterozygous or homozygous mutations in the MYB3R1 and MYB3R4 genes. Our results suggest that a pair of structurally related R1R2R3-Myb transcription factors may positively regulate cytokinesis mainly through transcriptional activation of the KN gene.
authors.affiliation: Graduate School of Bioagricultural Sciences, Nagoya University, Chikusa, Nagoya 464-8601, Japan.
authors.forename: Nozomi
authors.initials: N
authors.lastname: Haga
authors.forename: Kiichi
authors.initials: K
authors.lastname: Kato
authors.forename: Masatake
authors.initials: M
authors.lastname: Murase
authors.forename: Satoshi
authors.initials: S
authors.lastname: Araki
authors.forename: Minoru
authors.initials: M
authors.lastname: Kubo
authors.forename: Taku
authors.initials: T
authors.lastname: Demura
authors.forename: Kaoru
authors.initials: K
authors.lastname: Suzuki
authors.forename: Isabel
authors.initials: I
authors.lastname: Müller
authors.forename: Ute
authors.initials: U
authors.lastname: Voss
authors.forename: Gerd
authors.initials: G
authors.lastname: Jürgens
authors.forename: Masaki
authors.initials: M
authors.lastname: Ito
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000502:physiology*; D048749:Cytokinesis / Q000235:genetics*; D018506:Gene Expression Regulation, Plant; D008969:Molecular Sequence Data; D010802:Phylogeny; D050765:Qa-SNARE Proteins / Q000235:genetics*; D015534:Trans-Activators / Q000235:genetics / Q000502:physiology*; D015533:Transcriptional Activation
chemical_list: D029681:Arabidopsis Proteins; C097724:KNOLLE protein, Arabidopsis; C520423:MYB3R1 protein, Arabidopsis; C520424:MYB3R4 protein, Arabidopsis; D050765:Qa-SNARE Proteins; D015534:Trans-Activators