The miR164b-SiNAC015 Module Regulates Drought Tolerance by Scavenging Reactive Oxygen Species in Foxtail Millet

Drought is the major abiotic stress threatening global crop yields, thus identifying potential candidates with promising breeding value has become a central goal of current breeding programmes. Here, we found that miR164b functions as a negative regulator in plant drought tolerance, whose expression is dramatically inhibited under drought stress. Overexpressing MIR164b reduced the drought tolerance, while STTM164 transgenic seedlings showed enhanced drought tolerance in foxtail millet. We further identified that NAC (NAM-ATAF1/2-CUC2) transcription factor SiNAC015 was a target of miR164b. The sinac015 mutants showed attenuated drought tolerance, whereas overexpressing mSiNAC015 (miR164b-resistant version) improved drought tolerance in foxtail millet. Genetic evidence indicated that SiNAC015 could function in the same pathway as miR164b to mediate drought response by directly repressing the expression levels of SitPRX genes, which encoded peroxidase (POD) involved in reactive oxygen species (ROS) scavenging. Additionally, the superior SiNAC015^Hap1 possessing higher SiNAC015 expression was found to be associated with enhanced drought tolerance in foxtail millet. Collectively, our study reveals that the miR164b-SiNAC015 module mediates drought stress response and provides a valuable genetic resource for drought-resistant breeding in foxtail millet.