The OsMYB30-OsADF7 Axis Modulates Rice Heat Acclimation Through Actin Microfilament Dynamics

Actin cytoskeleton is a fundamental cellular structure governing stress signal transduction and cellular homeostasis in plants. While its involvement in heat stress adaptation has been documented, the transcriptional and cytoskeletal regulatory networks underlying rice thermotolerance remain poorly defined. Here, we report that the actin-depolymerizing factor OsADF7 acts as a negative regulator of rice heat acclimation through modulating microfilament dynamics, and is transcriptionally controlled by the R2R3-MYB transcription factor OsMYB30. Heat stress markedly suppresses the expression of both OsMYB30 and OsADF7. Functional characterization demonstrated that knockout of Osadf significantly enhances heat acclimation by preserving microfilament polymerization, whereas overexpression (OE) of OsADF7 confers heat acclimation in rice seedlings. Physiological analyses including survival rate, electrolyte leakage, MDA, ROS, chlorophyll content and Fv/Fm further validated the heat acclimation phenotypes. Mechanistically, OsMYB30 directly binds to the TATCC cis-element in the OsADF7 promoter and may positively regulate OsADF7 transcription. Consequently, knockout of Osmyb30 enhances heat tolerance, while OE of OsMYB30 induces OsADF7 expression and leads to heat hypersensitivity. Genetic epistasis analyses support that the OsMYB30-OsADF7 transcriptional module may serve as a potential regulatory module involved in actin cytoskeleton-associated heat acclimation in rice. Collectively, our findings provide preliminary mechanistic clues linking MYB-related transcriptional regulation to actin cytoskeletal dynamics during rice thermotolerance responses, and provide a promising target for genetic improvement of heat-resistant rice varieties.