A new spider mite elicitor triggers plant defenses and promotes resistance to herbivores.

Herbivore-associated elicitors (HAEs) are active molecules produced by herbivorous insects. Recognition of HAEs by plants induces defenses that resist herbivore attacks. We previously demonstrated that the tomato red spider, Tetranychus evansi, triggered defenses in Nicotiana benthamiana. However, our knowledge of HAEs from T. evansi remains limited. Here, we characterize a novel HAE, Te16, from T. evansi and dissect its function in mite-plant interactions. We investigate the effects of Te16 on spider mites and plants by heterologous expression, virus-induced gene silencing assay and RNA interference. Te16 induces cell death and ROS accumulation, callose deposition and JA-related responses in N. benthamiana leaves. Te16-mediated cell death requires calcium signaling pathway, cytoplasmic localization, plant co-receptor BAK1 and signaling components SGT1 and HSP90. The active region of Te16-induced cell death is located at amino acids 114-293. Moreover, silencing the Te16 gene in T. evansi reduces spider mite survival and hatchability, but expressing Te16 in N. benthamiana leaves enhances plant resistance to herbivores. Finally, the Te16 gene is specific to Tetranychidae species and highly conserved in activating plant immunity. Our findings reveal a novel salivary protein produced by spider mites that elicits plant defenses and resistance to insects, which provides valuable clues for pest management.