OsGF14f, OsbZIP23 and OsFLZ20 form a hierarchical positive regulatory module to enhance drought tolerance in rice.

Abstract

Drought stress severely restricts global rice production, making the improvement of drought tolerance a central goal in rice breeding. Here, we identify the rice FCS-like zinc finger protein 20 (OsFLZ20) as a previously unrecognized client of the 14-3-3 protein OsGF14f, a recently characterized and promising target for engineering drought-tolerant rice cultivars. OsFLZ20 transcription is rapidly and robustly induced by drought, and transgenic analyses show that it does not affect normal growth or yield but instead acts as a positive regulator of drought tolerance by increasing soluble sugar accumulation and alleviating oxidative damage. OsGF14f and OsFLZ20 co-regulate a broad suite of drought-responsive genes, with OsGF14f serving as a positive modulator of OsFLZ20-driven transcriptional reprogramming. Mechanistically, OsGF14f interacts with OsFLZ20 at Ser-64 and increases its protein abundance. In parallel, the OsGF14f-OsbZIP23 module enhances the transcriptional activation of OsFLZ20 under drought stress. Further genetic analyses reveal that full OsFLZ20 function in drought tolerance requires a functional OsGF14f, whereas loss of OsFLZ20 compromises the drought tolerance conferred by OsGF14f, indicating mutual interdependence of these two regulators within the drought response network. Collectively, these findings establish the OsGF14f-OsbZIP23-OsFLZ20 module as a previously unrecognized determinant of rice drought tolerance and provide valuable genetic resources and molecular insights for crop improvement under water-limited conditions.