Peanut 9-cis-epoxycarotenoid Dioxygenase Enhances Salt and Drought Stress Tolerance by Regulating ROS Homeostasis

Peanut (Arachis hypogaea L.), a vital oilseed and cash crop, faces yield limitations due to abiotic stresses. The 9-cis-epoxycarotenoid dioxygenase (NCED) enzyme, a key enzyme in abscisic acid (ABA) biosynthesis regulating plant development and stress responses, remains mechanistically uncharacterized in peanut abiotic stress tolerance. In this study, we isolated a novel gene, AhNCED4, from the salt-tolerant mutant M24. The expression of AhNCED4 was strongly induced by NaCl, PEG6000, and ABA in peanut huayu20. Overexpression of AhNCED4 enhanced salt and drought tolerance in Arabidopsis. Transgenic overexpression of AhNCED4 improved salt and stress resistance through upregulated ROS-scavenging genes superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) with elevated enzymatic activities while reducing malondialdehyde (MDA), superoxide anion (O^2-), and hydrogen peroxide (H₂O₂) accumulation compared to wild-type plants. Further research showed that the chlorophyll fluorescence parameters of transgenic lines were significantly increased, while light damage was significantly reduced. These findings establish AhNCED4 as a critical regulator of stress adaptation and an excellent candidate gene for resistance breeding in peanut.