Submitted to: Plant and Cell Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/18/2025
Publication Date: 7/7/2025
Citation: Sorg, A.M., Mendoza, J.S., Liu, H., Roy, K.M., Gorman, Z.J., Tieman, D.M., Mckenzie, C.L., Basset, G.J., Block, A.K. 2025. A herbivore-induced salicylic acid carboxyl methyl transferase produces methyl salicylate in tomato to mediate defense signaling and deter pests. Plant and Cell Physiology. pcaf066. https://doi.org/10.1093/pcp/pcaf066.
DOI: https://doi.org/10.1093/pcp/pcaf066

Interpretive Summary: Methyl salicylate is an airborne plant odor that affects relationships between plants and the insects in their environment. In a new study, ARS scientists showed that methyl salicylate boosts tomato plants' ability to defend themselves by repelling insects that would otherwise feed on them. The scientists also demonstrated that methyl salicylate plays a role in regulating other chemical processes, including hormone signaling, that helps plants defend themselves by boosting a range of defense mechanisms. Understanding the airborne odors, such as methyl salicylate, that plants use to deter herbivores can help promote natural pest resistance and reduce the use of chemical pesticides in agriculture.

Technical Abstract: Methyl salicylate (MeSA) is a component of the herbivore-induced plant volatile blend of tomato (Solanum lycopersicum), and an intermediate in long distance salicylic acid (SA) signaling. The role of MeSA in plant-insect interactions can vary widely between species. In this study, we used transgenic tomato lines that were antisense (AS) or overexpressors (OE) of the tomato SA carboxyl methyl transferase SlSAMT1, which under- or over-produce MeSA respectively, to investigate the role of MeSA in interactions between tomato and the lepidopteran pests Helicoverpa zea and Manduca sexta. AS plants produced less MeSA and were more susceptible to both insects compared to wild-type, while OE plants had elevated MeSA production but displayed increased resistance only to M. sexta. Pairwise choice and toxicity assays revealed that MeSA itself impacted the larvae as a deterrent rather than toxin, and phytohormone profiling indicated that increased susceptibility in the AS lines may be related to repression of herbivore-induced jasmonate defense signaling. To expand beyond Lepidoptera, the settling preference of the piercing-sucking fly Bemisia tabaci was also examined and demonstrated a strong preference for lines with less MeSA. These data indicate that MeSA plays an important and complex role in the defense of tomato against insect pests.