CmALDH2B7 and CmALDH7B4 positively regulate the osmotic stress tolerance in melon (Cucumis melo L.).

Abstract

Aldehyde dehydrogenases (ALDHs) play critical roles in detoxifying reactive aldehydes and maintaining cellular redox homeostasis under stress conditions. In this study, 17 ALDH genes were identified in melon (Cucumis melo L.). Most CmALDH genes harbor multiple cis-regulatory elements associated with abiotic stress responses and hormone signaling, implicating their roles in environmental adaptation. Subsequently, CmALDH2B7 and CmALDH7B4 were selected for further expression and functional analyses. Both CmALDH2B7 and CmALDH7B4 were highly expressed in flowers, flower buds, and roots, and were strongly induced by osmotic stress. Overexpression of CmALDH2B7 or CmALDH7B4 enhanced the osmotic stress resistance of Arabidopsis plants, while silencing of either gene compromised the osmotic stress tolerance of melon seedlings, as evidenced by accelerated wilting, elevated malondialdehyde (MDA) accumulation, and reduced activities of catalase (CAT), superoxide dismutase (SOD), and peroxidase (POD). Protein interaction assays revealed that CmALDH2B7 directly interacts with the catalase CmCAT1, whereas CmALDH7B4 does not. This study provides a foundation for understanding the functional diversification of the ALDH superfamily and identifies promising targets for improving drought stress tolerance in melon.