Saliva Mucin-like Protein Is Required for Feeding and Induces Rice Defences.

The white-backed planthopper (WBPH), , is one of the most important piercing-sucking pests of rice () in Asia. Mucin-like salivary protein (SFMLP) is highly expressed in the salivary glands of WBPH, which plays an important role in WBPH feeding. In this study, WBPH injected with had difficulty in sucking phloem sap from rice plants, which significantly reduced their food intake, weight, and survival. In contrast, the knockdown of the gene had only a marginal effect on the survival of WBPH fed an artificial diet. Further studies showed that silencing resulted in the short and single-branched salivary sheaths secretion and less formation of salivary flanges in rice. These data suggest that is involved in the formation of the salivary sheath and is essential for feeding in WBPH. Overexpression of the gene in rice plants promoted the feeding of WBPH, whereas silencing the gene in rice plants significantly decreased WBPH performance. Additionally, it was found that overexpression of in rice plants elicited the signalling pathway of SA (salicylic acid) while suppressing JA (jasmonic acid); in contrast, silencing of the gene in rice plants showed the opposite results. This study clarified the function of in WBPH feeding as well as mediating rice defences.