A MYB-WRKY feedback module activates MdAAT2‑like to regulate aromatic ester biosynthesis during apple ripening

Aromatic esters are key determinants of apple fruit aroma and consumer preference. Here, we investigated the molecular mechanisms underlying ester biosynthesis by characterizing MdAAT2-like, a critical ester-synthesizing gene in apple. MdAAT2-like expressions were significantly upregulated during fruit ripening and positively correlated with ester accumulation. Functional validation in apple and tomato demonstrated that MdAAT2-like overexpression enhanced ester contents, while silencing or knockout reduced ester production. Enzymatic assays revealed that MdAAT2-like exhibits higher catalytic efficiency for medium- and short-chain acyl-CoAs compared to other AAT family members. Two transcription factors, MdMYB98-like and MdWRKY21, were identified as direct activators of MdAAT2-like. Both factors bind its promoter and synergistically enhance transcription through protein interaction. Notably, we uncovered a positive feedback model wherein MdMYB98-like and MdWRKY21 reciprocally activate each other's expression, reinforcing rapid ester synthesis during ripening. This study reveals a MYB-WRKY regulatory module controlling ester biosynthesis in apple.