OsEIN2-OsEIL1/2 pathway negatively regulates chilling tolerance by attenuating OsICE1 function in rice.

Low temperature severely affects rice development and yield. Ethylene signal is essential for plant development and stress response. Here, we reported that the OsEIN2-OsEIL1/2 pathway reduced OsICE1-dependent chilling tolerance in rice. The overexpressing plants of OsEIN2, OsEIL1 and OsEIL2 exhibited severe stress symptoms with excessive reactive oxygen species (ROS) accumulation under chilling, while the mutants (osein2 and oseil1) and OsEIL2-RNA interference plants (OsEIL2-Ri) showed the enhanced chilling tolerance. We validated that OsEIL1 and OsEIL2 could form a heterxodimer and synergistically repressed OsICE1 expression by binding to its promoter. The expression of OsICE1 target genes, ROS scavenging- and photosynthesis-related genes were downregulated by OsEIN2 and OsEIL1/2, which were activated by OsICE1, suggesting that OsEIN2-OsEIL1/2 pathway might mediate ROS accumulation and photosynthetic capacity under chilling by attenuating OsICE1 function. Moreover, the association analysis of the seedling chilling tolerance with the haplotype showed that the lower expression of OsEIL1 and OsEIL2 caused by natural variation might confer chilling tolerance on rice seedlings. Finally, we generated OsEIL2-edited rice with an enhanced chilling tolerance. Taken together, our findings reveal a possible mechanism integrating OsEIN2-OsEIL1/2 pathway with OsICE1-dependent cascade in regulating chilling tolerance, providing a practical strategy for breeding chilling-tolerant rice.