The SlAREB–SlGPX2–SlRCCR module coordinates stomatal closure and chloroplast antioxidant defense to confer drought tolerance in tomato

Abstract

Drought stress severely constrains tomato growth and agricultural productivity. Although the core role of the abscisic acid (ABA) signaling pathway in drought response is well-established, the downstream molecular mechanisms that directly protect chloroplasts and maintain redox homeostasis remain unclear. This study identifies a chloroplast-localized glutathione peroxidase, SlGPX2, which plays a key role in tomato drought tolerance. SlGPX2-overexpression lines exhibited enhanced drought resistance, reduced stomatal aperture, and lower levels of oxidative damage, whereas knockout lines were more sensitive to drought. Mechanistically, we found that the transcription factor SlAREB directly binds to the SlGPX2 promoter, activating its transcription and thereby linking ABA signaling to downstream antioxidant defense. Furthermore, using multiple experimental approaches, we confirmed that SlGPX2 directly interacts with red chlorophyll catabolite reductase (SlRCCR), a key enzyme in the chlorophyll degradation pathway, forming a functional complex. This interaction is crucial for synergistically maintaining chloroplast structural integrity and reactive oxygen species (ROS) balance under drought stress. Collectively, our findings reveal a SlAREB–SlGPX2–SlRCCR regulatory module that systemically enhances tomato drought tolerance by coordinating stomatal movement with chloroplast antioxidant defense. These results provide a theoretical basis and molecular targets for crop stress-resistance breeding.