Arabidopsis ARP7 Is an Essential Actin-Related Protein Required for Normal Embryogenesis, Plant Architecture, and Floral Organ Abscission

Abstract

Abstract The actin-related proteins (ARPs) 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) ARP7 is a constitutively expressed nuclear protein belonging to a novel plant-specific ARP class. In this study, we demonstrate a vital role for ARP7 protein in embryogenesis and plant development. Knocking out the expression of ARP7 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 ARP7 protein with RNA 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 ARP7-deficient RNA 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 ARP7 protein in the regulation of various phases of plant development through chromatin-mediated, global regulation of gene expression.