Tomato Spotted Wilt Virus Promotes Offspring and Egg Production of Its Vector, Frankliniella occidentalis, by Suppressing Plant Defences Induced by a Thrips Salivary Elicitor.

Western flower thrips (Frankliniella occidentalis) are among the most significant invasive pests worldwide. In addition to causing direct plant damage, they transmit tomato spotted wilt virus (TSWV) (species Orthotospovirus tomatomaculae; genus Orthotospovirus), a member of the genus Orthotospovirus. Although numerous studies have examined virus-insect-host plant interactions, research on the TSWV-thrips-plant tripartite interaction remains limited. In this study, we found that F. occidentalis can induce plant defence responses. FoCSP1, a chemosensory protein from F. occidentalis, was identified as a salivary elicitor capable of inducing serial plant defence responses in Nicotiana benthamiana. Our results revealed that the FoCSP1-induced plant defence responses did not affect thrips feeding preference but significantly inhibited both offspring and egg production. Moreover, TSWV impairs these defence responses through its encoded proteins, N and NSs, thereby alleviating the FoCSP1-mediated suppression of thrips offspring and egg production. Collectively, these findings indicate that TSWV promotes the offspring and egg production of its thrips vector by inhibiting plant defences induced by FoCSP1, providing new insights into the TSWV-thrips-plant tripartite interaction.