A Rice FLO2 is Involved in Regulation of Gene Expression for Storage Substances, and Affects Rice Grain Size and Starch Quality

Abstract

Rice (Oryza sativa ) endosperm accumulates a massive amount of storage starch and storage proteins during seed development. The rice flo2 mutation resulted in reduced grain size and starch quality. The flo2 mutation decreased expression of genes involved in production of storage starch and storage proteins in the endosperm. Map-based cloning identified FLOURY ENDOSPERM 2 (FLO2) , as the gene responsible for the rice flo2 mutation. The wild-type FLO2 restored the size of grains of the flo2 mutant. FLO2 was abundantly expressed in developing seeds coincident with production of storage starch and protein, as well as in leaves. FLO2 harbors a tetratricopeptide repeat (TPR) motif, considered to mediate protein-protein interactions. As the candidate proteins of interaction with FLO2, a bHLH protein and a LEA protein was detected. These results suggest that FLO2 plays a pivotal regulatory role in the rice grain size and starch quality, by affecting storage substances accumulation in the endosperm.