Arabidopsis ARP7 is an essential actin-related protein required for normal embryogenesis, plant architecture, and floral organ abscission

Abstract

The actin-related proteins (AKPs) that are localized to the nucleus are present as components of various chromatin-modifying complexes involved in chromatin dynamics and transcriptional regulation. Arabidopsis (Arabidopsis thaliana) AKP7 is a constitutively expressed nuclear protein belonging to a novel plant-specific AKP class. In this study, we demonstrate a vital role for AKP7 protein in embryogenesis and plant development. Knocking out the expression of AKP7 in an arp7-1 T-DNA mutant produced morphologically aberrant, homozygous embryos that were arrested at or before the torpedo stage of development Hence, the arp7-1 null mutation is homozygous lethal. Knocking down the expression levels of AKP7 protein with KNA interference produced viable Arabidopsis lines affected in multiple developmental pathways and induced dosage-dependent, heritable defects in plant architecture. The transgenic plants containing greatly reduced levels of ARP7 in the nucleus were severely dwarfed with small rosette leaves that are defective in cell expansion and trichome morphology. Moreover, the AKP7-deficient KNA interference plants exhibited retarded root growth, altered flower development, delayed perianth abscission, and reduced fertility. These pleiotropic phenotypic changes suggest a critical role for the Arabidopsis AKP7 protein in the regulation of various phases of plant development through chromatin-mediated, global regulation of gene expression. © 2005 American Society of Plant Biologists.