OsANN3, a calcium-dependent lipid binding annexin is a positive regulator of ABA-dependent stress tolerance in rice.

Annexin is a multigene family that plays critical roles in plant stress responses and various cellular processes. Here, we reported the cloning and functional characterization of a novel rice annexin protein, OsANN3. We found that expression of OsANN3 was induced by polyethylene glycol (PEG) and abscisic acid (ABA) treatments. Overexpression of OsANN3 in rice significantly increased survival rates under drought stress, while knocking down OsANN3 resulted in sensitivity to drought. Meanwhile, OsANN3 overexpression showed enhanced sensitivity to exogenous ABA. Together with its Ca2+ and phospholipid binding activity, we proposed that when plants were subjected to drought stress, OsANN3 might mediate Ca2+ influx by binding to phospholipid to activate ABA signaling pathways. In addition, overexpression OsANN3 showed better growth under drought stress comparing to wild type, such as longer root length and more stomata closure for reducing water loss by regulating ABA-dependent stress response pathways.