Abstract

SUMMARY In plants, C2 domain-containing proteins (C2DPs) constitute a large Ca 2+ -binding family involved in development and abiotic stress response. However, how it regulates the abscisic acid (ABA) signaling under chilling in rice is largely unknown. Here, we identified OsERG1, encoding a small C2 domain protein with binding Ca 2+ in vitro , was induced obviously by cold stress and negatively regulated chilling tolerance in rice seedlings. An ABA receptor OsPYL10 was screened out from a yeast two-hybrid (Y2H) cDNA library using OsERG1 as bait. Furthermore, OsERG1 specifically interacted with OsPYL10 in both Ca 2+ - and ABA-dependent manners in vitro and in vivo . Moreover, both OsERG1 and OsPP2C09 interacted with the CL2 loop of OsPYL10 in the Y2H assay; OsERG1 was able to compete with OsPP2C09 for the interaction with OsPYL10 in the competitive in vitro pull-down assay. In addition, overexpression of OsERG1 and ospyl10 mutation showed a similar hyposensitive response of shoot growth to ABA application during the germination stage, suggesting the interrupting role of OsERG1 in the OsPYL10-OsPP2C09 module in rice. RNA-seq analysis confirmed that OsERG1 and OsPYL10 differentially regulated the expression of candidate genes in the ABA biosynthesis and ABA signaling, including OsNAC5 , OsbZIP62 , and OsbZIP46 under chilling. These findings provide the regulatory role of OsERG1 to the OsPYL10-OsPP2C09 module, and reveal new insight into the mechanism of chilling stress signaling and response in rice seedlings.