Abstract
Starch is an important form of carbon reserve in plants whereas in animals it is the glycogen. While the mechanism of initiating glycogen synthesis is well characterized, initiating starch synthesis in plants remained largely inconclusive. Since starch is synthesized in the chloroplast, we investigated the subcellular localization of the rice glycogenin glucosyltransferase (OsGGT) which was localized to the plasmamembrane. Although transgenic rice plants overexpressing OsGGT showed 1.3 folds higher starch contents compared to wild type (WT) plants, repressing OsGGT expression did not result in complete depletion of the starch pool. 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, whereas after four days the level of the starch was similar in both plants. Our results suggest that OsGGT might be actively involved in protecting starch from the rapid depletion under submergence conditions.
