(E)-2-Hexenyl acetate improved carotenoid synthesis in tomato fruits by reducing (E)-2-hexenal biosynthesis and activating jasmonic acid pathway

(E)-2-hexenyl acetate (E2HA) is the esterification product of (E)-2-hexenal (E2H), which is generated by lipoxygenase (LOX) during the degradation of polyunsaturated fatty acids. As a green leaf volatile, E2HA is released in large quantities during the ripening or stress of fruits, forming a unique aroma of fruits and helping to resist stress, however, its the effect on fruit quality is still unclear. In this study, E2HA significantly affected the colour change process in tomato by activating carotenoid synthesis pathways (PDS, ZDS, LCY-β), resulting in increased lycopene and β-carotene contents while maintaining chlorophyll levels. E2HA upregulated LOX expression and activity, thereby promoting polyunsaturated fatty acid degradation. As a downstream product of E2H, E2HA reduces hydroperoxide lyase (HPL) gene expression and enzyme activity, thereby decreasing the endogenous E2H content. Concurrently, E2HA activated the jasmonic acid (JA) synthesis pathway (AOS, AOC, OPR3, COI-1, MYC2), leading to elevated endogenous JA levels. By redirecting LOX pathway flux toward JA biosynthesis, E2HA increased carotenoid accumulation. These findings suggest that E2HA is a natural compound for improving fruit quality, with promising applications in preharvest horticulture.