Alternative oxidase pathway inhibits PuWRKY7–PuHDAC15 complex to promote ester aroma synthesis in Nanguo pear

Volatile esters are key contributors to the characteristic aroma in fruit, and their accumulation directly dictates fruit quality and consumer acceptance. Alternative oxidase pathway is known to its role in regulating fruit quality, but its molecular mechanism in ester aroma accumulation remains unclear. Here, we demonstrated that the alternative oxidase pathway acts as the dominant respiratory pathway in Nanguo pear (Pyrus ussuriensis) during ripening, and promotes ester aroma accumulation by increasing histone acetylation levels of PuAAT1 (alcohol acetyltransferase 1), the key gene governing ester synthesis. Further, we identified PuHDAC15 as a critical histone deacetylase that modulates acetylation levels and interacts with the transcription factor PuWRKY7. Mechanistically, PuWRKY7 directly binds to the W-box elements in the PuAAT1 promoter. The PuHDAC15–PuWRKY7 complex acts synergistically to repress PuAAT1 transcription, thereby decreasing its histone acetylation levels and gene expression, and consequently inhibiting ester aroma accumulation in Nanguo pear. This study reveals how the alternative oxidase pathway integrates into fruit aroma formation via epigenetic regulation and gene expression, thereby providing a scientific basis for targeted improvement of fruit quality.