Functional characterization of a B-type cell cycle switch 52 in rice (OsCCS52B)

Plant growth and development depend on a precise coordination between cell division and cell expansion. In this study, a rice cell cycle switch 52 B ( OsCCS52B ) was functionally characterized using two approaches: overexpression of the gene product in fission yeast and characterization of an insertion mutant line 1B-10423. In wild-type plants, OsCCS52B is highly expressed in generative organs such as flowers and kernels. Overexpression of OsCCS52B induces cell elongation and slower cell proliferation in fission yeast. Characterization of the mutant line 1B-10423 revealed that the mutant exhibits semi-dwarf and smaller kernel phenotypes. In addition, microscopic analysis of mutant kernels showed that the reduced kernel size was due to a reduced cell size. However, the nuclear size and ploidy level were unaffected. These results suggest that OsCCS52B may be involved in cell expansion regulation in rice endosperm.