FLOURY ENDOSPERM15 encodes a glyoxalase I involved in compound granule formation and starch synthesis in rice endosperm

Key message FLO15 encodes a plastidic glyoxalase I protein, OsGLYI7, which affects compound starch granule formation and starch synthesis in rice endosperm . Starch synthesis in rice ( Oryza sativa ) endosperm is a sophisticated process, and its underlying molecular machinery still remains to be elucidated. Here, we identified and characterized two allelic rice floury endosperm 15 ( flo15 ) mutants, both with a white-core endosperm. The flo15 grains were characterized by defects in compound starch granule development, along with decreased starch content. Map-based cloning of the flo15 mutants identified mutations in OsGLYI7 , which encodes a glyoxalase I (GLYI) involved in methylglyoxal (MG) detoxification. The mutations of FLO15 / OsGLYI7 resulted in increased MG content in flo15 developing endosperms. FLO15/OsGLYI7 localizes to the plastids, and the in vitro GLYI activity derived from flo15 was significantly decreased relative to the wild type. Moreover, the expression of starch synthesis-related genes was obviously altered in the flo15 mutants. These findings suggest that FLO15 plays an important role in compound starch granule formation and starch synthesis in rice endosperm.