Eurydema oleracea negatively affects defenses in Arabidopsis by inducing salicylic acid-mediated signaling pathway.

The study of defense mechanisms of plants against herbivorous insects can clarify the evolutionary mechanisms of these interactions and has significant implications for agriculture. The herbivore Eurydema oleracea is an invasive crop pest; however, knowledge on how it affects plant immune responses is lacking. In the present study, we demonstrate that insect feeding causes the induction of both salicylic acid (SA) and jasmonic acid (JA)-mediated signaling pathways in infested Arabidopsis plants. Using transgenic SA-deficient NahG, we show that the two phytohormones crosstalk antagonistically. In particular, the rapid and strong induction of SA-related gene expression partially suppresses the JA-dependent signaling pathway. This results in increased plant susceptibility to the herbivore, evidenced by an increase of leaf damage inflicted by the adult insects and increased development of the nymphs. Our findings suggest that E. oleracea manipulates hormone signaling components of Arabidopsis as a strategy of attack to suppress plant defense traits. Our work contributes to knowledge on the adaptation of insect pests to plant responses, and is useful for developing management strategies to combat harmful herbivores in agriculture.