| Summary: | The SWR1 complex (SWR1-C) is important for the deposition of histone variant H2A.Z into chromatin to regulate gene expression. Characterization of SWR1-C subunits in <i>Arabidopsis thaliana</i> has revealed their role in variety of developmental processes. <i>Oryza sativa</i> actin related protein 6 (OsARP6) is a subunit of rice SWR1-C. Its role in rice plant development is unknown. Here, we examined the subcellular localization, expression patterns, and loss of function phenotypes for this protein and found that OsARP6 is a nuclear localized protein, and is broadly expressed. OsARP6 interacted with OsPIE1, a central ATPase subunit of rice SWR1-C. The <i>osarp6</i> knockout mutants displayed pleiotropic phenotypic alterations in vegetative and reproductive traits, including semi-dwarf phenotype, lower tillers number, short leaf length, changes in spikelet morphology, and seed abortion. Microscopic thin sectioning of the top internode revealed that the dwarf phenotype of <i>osarp6</i> was due to reduced number of cells rather than reduced cell length. The altered transcript level of genes involved in cell division suggested that <i>OsARP6</i> affects cell cycle regulation. In addition, H2A.Z levels were reduced at the promoters and transcription start sites (TSS) of the regulated genes in <i>osarp6</i> plants. Together, these results suggest that OsARP6 is involved in rice plant development, and H2A.Z deposition.
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