A phosphoinositide‐specific phospholipase C pathway elicits stress‐induced Ca 2+ signals and confers salt tolerance to rice

Summary In animal cells, phospholipase C ( PLC ) isoforms predominantly hydrolyze phosphatidylinositol‐4,5‐biphosphates [PtdIns(4,5)P 2 ] into the second messengers diacylglycerol ( DAG ) and inositol 1,4,5‐trisphosphate [Ins(1,4,5)P 3 ] to regulate diverse biological processes. By contrast, the molecular mechanisms and physiological significance of PLC signaling in plants still awaits full elucidation. Here, we identified a rice ( Oryza sativa cv) PI ‐ PLC , Os PLC 1, which preferred to hydrolyze phosphatidylinositol‐4‐phosphate (PtdIns4P) and elicited stress‐induced Ca 2+ signals regulating salt tolerance. Analysis by ion chromatography revealed that the concentration of PtdIns4P was c . 28 times of that of PtdIns(4,5)P 2 in shoots. Os PLC 1 not only converted PtdIns(4,5)P 2 but also – and even more efficiently – converted PtdIns4P into DAG and Ins(1,4,5)P 3 in vitro and in vivo . Salt stress induced the recruitment of Os PLC 1 from cytoplasm to plasma membrane, where it hydrolyzed PtdIns4P. The stress‐induced Ca 2+ signaling was dependent on Os PLC 1, and the PLC ‐mediated Ca 2+ signaling was essential for controlling Na + accumulation in leaf blades, thus establishing whole plant salt tolerance. Our work identifies a conversion pathway and physiological function for PtdIns4P pools in rice and reveals the connection between phosphoinositides and Ca 2+ signals mediated by PLC during salt stress responses.