Transcriptional Activation and Phosphorylation of OsCNGC9 Confer Enhanced Chilling Tolerance in Rice

Abstract Low temperature is a major environmental factor limiting plant growth and productivity. Although transient elevation of cytoplasmic calcium has long been recognized as a critical signal for plant cold tolerance, the calcium channels responsible for this process have remained largely elusive. Here, we reported that OsCNGC9, a cyclic nucleotide-gated channel, positively regulates chilling tolerance by mediating cytoplasmic calcium elevation in rice (Oryza sativa). We showed that the loss-of-function mutant of OsCNGC9 is defective in cold-induced calcium influx and more sensitive to prolonged cold treatment while OsCNGC9 overexpression confers enhanced cold tolerance. Mechanistically, we showed that in response to chilling stress, OsSAPK8, a homolog of Arabidopsis thaliana OST1, phosphorylates and activates OsCNGC9 to trigger Ca2+ influx. In addition, transcription of OsCNGC9 is activated by a rice dehydration responsive element binding transcription factor, OsDREB1A. Together, our results suggested that OsCNGC9 enhances chilling tolerance in rice through regulating cold-induced calcium influx and cytoplasmic calcium elevation.