Functional Analysis of GhRNG1L Reveals Its Positive Role in Drought Tolerance Mediated by GhDREB2B in Cotton.

Drought stress is a major abiotic factor limiting cotton yield and quality. RING-type E3 ubiquitin ligases play central regulatory roles in plant stress responses; however, the functions and regulatory networks of this gene family in cotton drought response remain largely unclear. In this study, we characterized the RING-type E3 ubiquitin ligase gene GhRNG1L from upland cotton (Gossypium hirsutum L.) and demonstrated its role in enhancing drought tolerance in cotton, and we successfully identified its upstream transcription factor GhDREB2B. Functional assays showed that overexpression of GhRNG1L significantly increased catalase (CAT) activity and reduced hydrogen peroxide (H2O2) accumulation in Arabidopsis, thereby improving plant drought tolerance, whereas silencing GhRNG1L produced the opposite phenotype. Further molecular analysis confirmed that GhDREB2B directly binds to the promoter of GhRNG1L and activates its transcription. Collectively, our findings reveal, for the first time, the positive regulatory role of the GhDREB2B-GhRNG1L module in cotton drought response, providing a clear upstream regulatory target and theoretical basis for molecular breeding of drought-tolerant cotton.