A novel salivary effector, BtE3, is essential for whitefly performance on host plants.

The whitefly Bemisia tabaci is a piercing-sucking herbivore that reduces the yields of crops both by feeding on plants and transmitting plant viruses. Like most plant feeders, B. tabaci has evolved ways to avoid plant defense responses. For example, B. tabaci is known to secrete salivary effectors to suppress host defenses. However, the nature of B. tabaci effectors is incompletely understood. In this study, we used B. tabaci genomic and salivary gland transcriptomic data and an overexpression system to identify a previously unknown B. tabaci salivary effector, BtE3. BtE3 is specifically expressed in the head (containing primary salivary glands) and is secreted into hosts during B. tabaci feeding. In planta overexpression of BtE3 blocked Burkholderia glumae-induced hypersensitive response (HR) in both Nicotiana benthamiana and Solanum lycopersicum. Silencing of BtE3 by plant-mediated RNAi prevented whiteflies from continuously ingesting phloem sap and reduced whitefly survival and fecundity. Moreover, over-expression of BtE3 in planta upregulated the salicylic acid- (SA-) signaling pathway but suppressed the downstream jasmonic acid- (JA-) mediated defenses. Taken together, these results indicate that BtE3 is a whitefly-specific novel effector involved in whitefly-plant interactions. These findings increase our understanding of whitefly effectors and suggest novel strategies for whitefly pest management.