Exogenous methyl jasmonate-mediated physiological and transcriptomic network improves thrips tolerance in alfalfa (Medicago sativa)

Abstract

Exogenous methyl jasmonate is widely acknowledged for its role in triggering plants’ defense systems against pest invasions. Nonetheless, there has been a dearth of research exploring the elicitation of defense mechanisms by jasmonic acid in alfalfa. In order to investigate the effect of methyl jasmonate on thrips resistance in alfalfa, Medicago sativa L.cv. Caoyuan No. 4 was exogenously sprayed with different concentrations of methyl jasmonate, and thrips and Orius strigicollis (natural enemies) behavioral choice, physiological and transcriptomic analyses were performed. The results revealed a concentration-dependent inducible effect of methyl jasmonate on the behavioral choice, feeding and oviposition of thrips mediated by volatile organic compounds. Moreover, methyl jasmonate treatment at varying concentrations significantly influenced the activity levels of defense enzymes and secondary metabolites in alfalfa. Notably, the most pronounced induction effect of methyl jasmonate was observed at a concentration of 0.1 mmol/L, particularly evident in the enhanced activity of peroxidase, polyphenol oxidase, lipoxygenase and tannins. Transcriptome analysis showed that differentially expressed genes between methyl jasmonate treatment and control group (methyl jasmonate-free treatment) were mainly enriched in metabolic pathways and plant hormone signal transduction pathways such as terpenoid biosynthesis, linoleic acid metabolism and jasmonate signal transduction. Subsequent pathway analysis elucidated the potential of methyl jasmonate treatment to elevate endogenous jasmonic acid levels and instigate the activation of the jasmonate signaling pathway.