The LbNAM2-LbZDS module enhances drought resistance in wolfberry (Lycium barbarum) by participating in ABA biosynthesis

Wolfberry (Lycium barbarum L.) fruit, renowned for its high carotenoid content, is extensively used in traditional Chinese herbal medicine and cuisine. Drought is a significant global challenge to crop production, with carotenoids playing crucial roles in enhancing drought resistance in higher plants. ζ-Carotene desaturase (ZDS), a key enzyme in the carotenoid biosynthesis pathway, catalyzes the conversion of ζ-carotene to lycopene. However, the molecular mechanisms by which LbZDS responds to drought stress remain largely unexplored. In this study, we demonstrated that LbZDS transcription is induced by PEG, NaCl, and abscisic acid (ABA) treatments. Overexpression of LbZDS in both wolfberry and tomato plants conferred enhanced drought tolerance by promoting ABA synthesis. We further identified that the NAC transcription factor LbNAM2 directly binds to the promoter region of LbZDS and activates its expression, as evidenced by electrophoretic mobility shift assays, yeast one-hybrid assays, and dual-luciferase assays. Silencing LbNAM2, or dual silencing of LbNAM2 and LbZDS via virus-induced gene silencing (VIGS), severely compromised drought tolerance in wolfberry plants. Additionally, overexpression of LbZDS resulted in a marked increase in carotenoid content, while silencing either LbZDS, LbNAM2, or both together led to reduced carotenoid levels. In conclusion, our study provides critical insights into the functional roles and regulatory mechanisms of the LbNAM2–LbZDS module in drought stress response and carotenoid biosynthesis in wolfberry.