The CsRAP2.12–CsERF113L/CsRAP2.7 module positively regulates chlorophyll degradation to impair saline–alkali tolerance in cucumber

Soil salinization poses a global threat to agricultural productivity by degrading arable land. Preventing the rapid degradation of chlorophyll caused by saline–alkali stress is a crucial means to improve plant resistance and productivity. In this study, RNA sequencing identified CsPPH , a pheophytinase‐encoding gene that functions as a negative regulator of both photosynthesis and saline–alkali tolerance in cucumber ( Cucumis sativus L.). Saline–alkali stress rapidly induces the expression of related to APETALA2 2.12 ( CsRAP2.12 ). Subsequently, CsRAP2.12 activates the transcription of both ethylene response factor 113‐like ( CsERF113L ) and CsRAP2.7 , while CsERF113L further transcriptionally regulates CsRAP2.7 . CsERF113L promotes chlorophyll degradation and reactive oxygen species (ROS) accumulation both through direct transcriptional upregulation of CsPPH , chlorophyll b reductase ( CsNYC1 ), and chlorophyllase 2 ( CsCLH2 ) and by indirectly stimulating ethylene synthesis via upregulation of 1‐aminocyclopropane‐1‐carboxylic acid synthase 6/9/10 ( CsACS6/9/10 ), thereby impairing photosynthesis and accelerating senescence. CsRAP2.7 indirectly promotes saline–alkali stress‐induced chlorophyll degradation and photosynthetic inhibition by facilitating CsERF113L‐mediated transcriptional activation of CsPPH , CsCLH2 , and CsACS6/9/10 . Therefore, knockout of either CsRAP2.12 , CsERF113L , or CsRAP2.7 significantly alleviated chlorophyll degradation and enhanced photosynthetic performance under saline–alkali stress, ultimately improving antioxidant capacity and stress tolerance. These findings reveal that the CsRAP2.12–CsERF113L/CsRAP2.7 module promotes saline–alkali stress‐induced chlorophyll degradation and photosynthetic inhibition via a dual regulatory mechanism. Genetic disruption of this module significantly improves cucumber tolerance to saline–alkali stress.