The miR172/IDS1 signaling module confers salt tolerance through maintaining ROS homeostasis in cereal crops

Salt stress triggers the overdose accumulation of reactive oxygen species (ROS) in crop plants, leading to severe oxidative damage to living tissues. MicroRNAs (miRNAs) act as master regulators orchestrating the stress responsive regulatory networks as well as salt tolerance. However, the fundamental roles of miRNAs in modulating salt tolerance in cereal crops, especially in salt-triggered ROS scavenging remain largely unknown. Through small RNA sequencing, a salt-responsive miRNA, miR172 was identified in rice. Further, by generating the miR172-overexpression or MIR172 gene loss-of-function mutant lines, the biological significance of miR172 and its downstream signaling pathways related to salt tolerance were defined. We demonstrated that miR172 is a positive regulator of salt tolerance in both rice and wheat. More interestingly, miR172a and miR172b, but not miR172c or miR172d are involved in salt stress response, emphasizing the functional differentiation within miR172 family members. Further evidence uncovers a novel miR172/IDS1 regulatory module that functions as a crucial molecular rheostat in maintaining ROS homeostasis during salt stress, mainly through balancing the expression of a group of ROS-scavenging genes. Our findings establish a direct molecular link between miRNAs and detoxification response in cereal crops for improving salt tolerance.