A VIN3-like Protein OsVIL1 Is Involved in Grain Yield and Biomass in Rice.

In chromatin remodeling, the post-translational modification of histone proteins is mediated by multimeric protein complexes. VERNALIZATION INSENSITIVE3 (VIN3) forms a complex with Polycomb Repressive Complex 2 (PRC2), which mediates the trimethylation of H3K27 to repress target gene expression. In rice, four genes (OsVIL1-OsVIL4) encoding the VIN3-like proteins are expressed ubiquitously in various tissues. Null mutants of display pleiotropic phenotypes such as altered flowering time, floral organ defects, and reduced tiller size. In contrast, mutants did not show significant phenotypes except in fertilization compared with the wild type. However, transgenic plants overexpressing showed phenotypes of increased biomass and grain yield. Cross-sections of the basal region of elongating stems revealed that the increased biomass was mediated by inducing cell proliferation in the meristem. Chromatin immunoprecipitation assay indicated that OsVIL1 repressed expression of cytokinin oxidase/dehydrogenase gene () by binding to the promoter and genic regions of . We also observed that OsVIL1 modified the levels of H3K27me3 in the chromatin. Because encodes an enzyme that degrades active cytokinin, we conclude that OsVIL1 functions in the regulation of endogenous active cytokinin levels, thereby increasing plant height and productivity.