SlMES1 modulates methyl salicylate to influence fruit volatile profiles in tomato

Methyl salicylate (MeSA), known as phloem-based mobile signal, has been identified as undesirable volatile compounds for tomato fruits due to its medicinal and wintergreen aroma properties. However, the response of most volatile compounds to endogenous MeSA are still unclarified. In this work, we found the concentration of MeSA can be regulated by salicylic acid methyl esterase 1 (SlMES1). We used CRISPR/Cas9 and GC-MS strategies to investigate the effect of SlMES1 on the biosynthesis of flavor compounds during tomato fruit ripening. Our results showed that the loss of function of SlMES1 significantly increased the MeSA content by altering the flux of MeSA and SA interconversion. Although the increased endogenous MeSA did not affect the fruit ripening process, it altered the concentration and proportion of fruit volatiles, mainly reducing the concentration of soluble sugar and volatile substances derived from amino acids and carotenoids. Additionally, the reduction of soluble sugars and volatiles was associated with downregulated the gene encoding Sucrose synthase (SuSy), Alcohol dehydrogenase (ADH), Phenylalanine ammonia lyase (PAL), and β - Carotene hydroxylase (CHY-β) when compared with control. Taken together, SlMES1 plays a crucial role in regulating the MeSA content during fruit ripening and could become a breeding target for improving fruit flavor quality.