Heat Shock 70 kDa Protein Cognate 3 of Brown Planthopper Is Required for Survival and Suppresses Immune Response in Plants

SIMPLE SUMMARY: Heat shock 70 kDa protein cognate 3 (NlHSC70-3) of brown planthopper (BPH) is important to the growth and development of BPH. However, if it also regulates plant physiological processes remain unclear. In this study, NlHSC70-3 is identified from a compared protein profile of Nipponbare tissues after BPH infestation. The predicted signal peptide and high levels of transcription in salivary glands and ovaries supported that it is a secreted protein. Function analysis demonstrates that NlHSC70-3 is required for the survival of BPH on rice. Plant immune responses, including flg22-induced ROS bursts and the expression of defense-related genes, are suppressed by NlHSC70-3 in Nicotiana benthamiana. Thus, NlHSC70-3 is secreted into rice by BPH and may interfere with plant defense responses to facilitate its survival. ABSTRACT: The brown planthopper (Nilaparvata lugens) is a monophagous pest of rice (Oryza sativa), which threatens food security around the world. Insect Heat shock proteins 70 kDa (Hsp70s) play a key role in insect growth and development, however, if they also modulate the plant physiological processes is still unclear. In this study, we identified the Heat shock 70 kDa protein cognate 3 (NlHSC70-3) of BPH from compared protein profiles of Nipponbare tissues after BPH infestation via LC/MS. NlHSC70-3 has a predicted signal peptide and displays high transcription levels in the salivary glands, which further supported that it is secreted into plants by BPH during the feeding process. Using RNA interference (RNAi), we showed that NlHSC70-3 is indispensable for the survival of BPH on rice. Most importantly, NlHSC70-3 mediates the plant immune responses including cell death, flg22-induced ROS burst and defense-related gene expression in N. benthamiana. These results demonstrate that NlHSC70-3 may function as an effector manipulating plant physiological processes to facilitate pest survival on rice, which provides a new potential target for future pest control.