title: The nuclear actin-related protein ARP6 is a pleiotropic developmental regulator required for the maintenance of FLOWERING LOCUS C expression and repression of flowering in Arabidopsis.
abstract: Actin-related proteins (ARPs) are found in the nuclei of all eukaryotic cells, but their functions are generally understood only in the context of their presence in various yeast and animal chromatin-modifying complexes. Arabidopsis thaliana ARP6 is a clear homolog of other eukaryotic ARP6s, including Saccharomyces cerevisiae ARP6, which was identified as a component of the SWR1 chromatin remodeling complex. We examined the subcellular localization, expression patterns, and loss-of-function phenotypes for this protein and found that Arabidopsis ARP6 is localized to the nucleus during interphase but dispersed away from the chromosomes during cell division. ARP6 expression was observed in all vegetative tissues as well as in a subset of reproductive tissues. Null mutations in ARP6 caused numerous defects, including altered development of the leaf, inflorescence, and flower as well as reduced female fertility and early flowering in both long- and short-day photoperiods. The early flowering of arp6 mutants was associated with reduced expression of the central floral repressor gene FLOWERING LOCUS C (FLC) as well as MADS AFFECTING FLOWERING 4 (MAF4) and MAF5. In addition, arp6 mutations suppress the FLC-mediated late flowering of a FRIGIDA-expressing line, indicating that ARP6 is required for the activation of FLC expression to levels that inhibit flowering. These results indicate that ARP6 acts in the nucleus to regulate plant development, and we propose that it does so through modulation of chromatin structure and the control of gene expression.
authors.affiliation: Department of Genetics, Davison Life Sciences Complex, University of Georgia, Athens, GA 30602, USA.
authors.forename: Roger B
authors.initials: RB
authors.lastname: Deal
authors.forename: Muthugapatti K
authors.initials: MK
authors.lastname: Kandasamy
authors.forename: Elizabeth C
authors.initials: EC
authors.lastname: McKinney
authors.forename: Richard B
authors.initials: RB
authors.lastname: Meagher
mesh_terms: D000199:Actins / Q000235:genetics / Q000378:metabolism*; D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002467:Cell Nucleus / Q000235:genetics / Q000378:metabolism; D002843:Chromatin / Q000235:genetics; D017124:Conserved Sequence; D035264:Flowers / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D018506:Gene Expression Regulation, Plant / Q000235:genetics; D026161:MADS Domain Proteins / Q000235:genetics / Q000378:metabolism*; D008840:Microfilament Proteins / Q000235:genetics / Q000378:metabolism*; D008938:Mitosis / Q000235:genetics; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D010802:Phylogeny; D010937:Plant Growth Regulators / Q000235:genetics / Q000378:metabolism*; D050436:Regulatory Elements, Transcriptional / Q000235:genetics; D029702:Schizosaccharomyces pombe Proteins / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid
chemical_list: C507995:ARP6 protein, Arabidopsis; D000199:Actins; D029681:Arabidopsis Proteins; C498984:Arp6 protein, S pombe; D002843:Chromatin; C418902:At5g10140 protein, Arabidopsis; C414613:FRI protein, Arabidopsis; D026161:MADS Domain Proteins; D008840:Microfilament Proteins; D009687:Nuclear Proteins; D010937:Plant Growth Regulators; D029702:Schizosaccharomyces pombe Proteins