The MhNF-YA3-like-MhMSI4-like module regulates apple drought tolerance by activating the expression of <i>MhAAO3</i>

Drought significantly impairs the growth, yield, and quality of apple (Malus domestica Borkh.). Nuclear factor-Y (NF-Y) transcription factors have well-documented functions in regulating stress tolerance in various plants. However, the specific functions and molecular mechanisms of NF-Ys in conferring drought tolerance in apples remain largely unexplored. Here, we identified and characterized a NF-Y transcription factor, MhNF-YA3-like, from Malus hupehensis, the expression of which is upregulated by drought stress and abscisic acid (ABA). Overexpressing MhNF-YA3-like enhanced tolerance to drought stress, while silencing MhNF-YA3-like increased susceptibility to drought stress. Further research demonstrated that MhNF-YA3-like directly binds to the promoter of MhAAO3 and activates its transcription. Notably, the interaction between MhNF-YA3-like and MhMSI4-like further amplified the regulatory effect of MhNF-YA3-like on MhAAO3, promoting the synthesis of ABA, which consequently improved drought stress tolerance. This study provides insights into how the MhNF-YA3-like-MhMSI4-like module finely tunes apple drought tolerance.