MhNF-YA1-Like-MhDnaJC76-MhAAO3 Transcriptional Cascade Enhances ABA Biosynthesis and Drought Tolerance in Apple

Drought, the most unfavorable and widespread environmental factor among abiotic stresses, has become a significant global issue that severely crop growth and yield. Nuclear factor-Y (NF-Y) transcription factors have well-documented functions in regulating stress tolerance in plants. However, the specific functions and molecular mechanisms of NF-YS in conferring drought tolerance in apples remain largely unexplored. Here, we reported that the NF-Y transcription factor MhNF-YA1-like positively modulates drought stress tolerance in apple (Malus domestica Borkh.). MhNF-YA1-like is transcriptionally upregulated in response to drought and abscisic acid (ABA) treatments. Overexpression of MhNF-YA1-like enhances drought tolerance in apples, whereas its silencing results in weakened drought tolerance. Further investigation reveals that MhNF-YA1-like directly binds to the promoter of MhAAO3 and activates its expression. Additionally, we identified MhDnaJC76 as an interacting protein of MhNF-YA1, and MhDnaJC76 positively modulates apple drought tolerance. Furthermore, the interaction between MhNF-YA1-like and MhDnaJC76 significantly amplifies the regulatory effect of MhNF-YA1-like on MhAAO3, thereby promoting ABA accumulation and consequently enhancing apple drought tolerance. Taken together, our findings elucidate a molecular framework by which the MhNF-YA1-like-MhDnaJC76 complex modulates drought tolerance in apples, thereby providing targets for developing drought-tolerant crops.