Salivary protein FoDESP8 serving as an effector to restrain plant resistance causing exacerbated damage by western flower thrips under elevated CO2.

Salivary proteins of herbivorous insects are essential for their infestation in host plants. While previous studies have mainly focused on confirming the functions of salivary proteins, there is limited understanding of how environmental factors affect plant-herbivorous insect interactions through salivary proteins. Therefore, this study utilized proteomic analysis to identify salivary proteins that were expressed differently in western flower thrips (Frankliniella occidentalis) under ambient CO2 (400 ppm; i.e., aCO2) and elevated CO2 (800 ppm; i.e., eCO2) to pinpoint the key salivary active protein. Then, changes in the defense response of kidney bean (Phaseolus vulgaris) mediated by the key salivary proteins were further clarified to explore the mechanism of salivary protein-based aggravation of damage by thrips under eCO2. The results revealed that a total of 30 differentially expressed salivary proteins (i.e., DESPs) were obtained from the comparative proteomic analysis between aCO2 and eCO2. One of these proteins, FoDESP8, functioned as a salivary effector that suppressed H2O2 and jasmonic acid (JA) accumulation in kidney bean leaves, with stronger inhibition under eCO2 than aCO2. This is conducive to the feeding and reproduction of thrips under eCO2, potentially leading to the aggravated damage on kidney beans by thrips.