Functional Characterization of TaNCED1 in Regulating Drought Stress Tolerance in Transgenic Wheat

The ABA signaling pathway is essential for plant growth, development, and responses to diverse abiotic stresses. 9-cis-epoxycarotenoid dioxygenases (NCEDs) are key functional enzymes involved in this pathway. In the present study, we investigated the biological roles and underlying molecular mechanisms of the TaNCED1 gene in wheat under drought stress treatment, using two materials: TaNCED1-overexpressing transgenic wheat plants and the nced1 knockout mutants. Phenotypic and physiological results demonstrated that TaNCED1 overexpression significantly enhanced wheat drought tolerance, whereas the knockout mutants clearly reduced the drought resistance. Mechanistically, TaNCED1 positively modulates wheat drought tolerance by maintaining higher leaf relative water content (RWC), accumulating more soluble sugars and proline, and reducing malondialdehyde (MDA) accumulation and electrolytic leakage. Moreover, the catalase (CAT) activity accumulated to higher levels exclusively under drought stress, and this antioxidant enzyme serves as a core mediator of drought tolerance conferred by TaNCED1 overexpression. Transcriptomic profiling of drought-challenged transgenic and WT plants further confirmed that TaNCED1 initiates a suite of stress-responsive regulatory cascades and robustly upregulates key drought resistance genes in wheat.