A Stinkbug Salivary Protein Is Indispensable for Insect Feeding and Activates Plant Immunity

Salivary proteins secreted by phytophagous insects play pivotal roles in plant-insect interactions. A salivary protein RpSP27, from the stinkbug Riptortus pedestris, a devastating pest on soybean, was selected for studying due to its ability to induce cell death and activate immune responses in plants. RpSP27 localized to the endoplasmic reticulum and triggered reactive oxygen species burst. Virus-induced gene silencing assays showed RAR1 plays an essential role in RpSP27-induced cell death in Nicotiana benthamiana. Expression analyses revealed that RpSP27 is predominantly expressed in R. pedestris salivary glands. RNA interference-mediated silencing of RpSP27 in R. pedestris significantly reduced insect survival rates and altered feeding behavior by decreasing the formation of salivary sheaths on soybeans and reducing probing and feeding duration. Furthermore, the silencing of RpSP27 in R. pedestris mitigated the staygreen syndrome in soybeans, characterized by delayed senescence and pod abnormalities. This study elucidated the role of RpSP27 in the interaction between R. pedestris and soybean, presenting a potential target for pest management strategies to protect soybean crops from the detrimental effects of R. pedestris feeding.