Abstract
Starch is an important form of carbon reserve in plants. While initiation of glycogen synthesis in yeast and animal has been well characterized, mechanism of initiating starch synthesis in plants remained largely inconclusive. The expression trend of rice (Oryza sativa L.) glycogenin glucosyltransferase (OsGGT) was tightly linked to that of starch biosynthesis during the day and night in the rice cultivar Nipponbare. While repressing OsGGT expression led to clear reduction in starch contents in GGT mutant line (ggt), transgenic rice plants overexpressing OsGGT showed 1.3 folds higher starch contents compared to WT plants. Moreover, after two days of complete submergence, OsGGT overexpressing plants maintained 61% of its original starch contents prior to submergence compared to only 34% in WT plants. These results provide supporting evidence that OsGGT is the starch initiating protein in rice and its overexpression provide new strategy to increase starch contents in rice with greater tolerance to submergence
