VvNAC043 Delays Grape Fruit Softening by Activating VvCesA2-Mediated Cellulose Synthesis in Response to Gibberellin

Fruit softening compromises edible quality and commercial value, resulting in substantial economic losses during ripening. In grapes, a non-climacteric fruit, the molecular mechanisms governing firmness—particularly those involving cellulose metabolism in response to gibberellin—remain largely unexplored. In this study, functional analyses using transgenic and overexpression approaches revealed that VvCesA2 and VvCesA4 positively regulate fruit firmness by promoting cellulose accumulation. Electrophoretic mobility shift assays (EMSA) ,Y1H and dual-luciferase reporter assays demonstrated that VvNAC043 directly binds to elements in the VvCesA2 promoter, thereby activating its transcription. Moreover, gibberellin-induced overexpression of VvNAC043 in grape berries led to increased firmness via enhanced cellulose deposition. These findings elucidate a gibberellin-responsive regulatory network controlling grape fruit firmness and offer potential strategies for improving fruit quality and minimizing postharvest losses due to softening.