The miR396f-GRF7 Module Confers Thermotolerance in Rice

Heat stress is one of the major threats to global rice production globally. Uncovering key genetic regulators of thermotolerance is crucial for breeding climate-resilient crops. While microRNA396 (miR396) is known to be heat-responsive, the function and mechanism of its specific member, miR396f, remain elusive. Here, we report that miR396f is a heat-induced miRNA exhibiting predominantly in vascular bundles. Its transcriptional induction was more pronounced in a thermotolerant variety (HT54) than in a heat-sensitive one (HT14), correlating with natural variation in its promoter sequence. Through a multi-step screening, we identified growth-regulation factor 7 (GRF7) as its direct target under heat stress. Genetic evidence demonstrated that the miR396f-GRF7 module positively regulates thermotolerance at both the seedling and flowering stages: miR396f knockout lines (396fKO) were heat-sensitive, whereas GRF7 knockout lines (grf7) exhibited enhanced thermotolerance. Transcriptome analysis of grf7 mutant under heat stress suggested its potential involvement in sugar metabolism pathways. Our study unveils the miR396f-GRF7 module as a novel positive regulator of rice thermotolerance, providing valuable genetic targets for future breeding programs.