Abstract Plants possess conserved immune systems to defend against herbivorous insects. In response, insects secrete saliva to manipulate host cell biology, with many salivary proteins being species-specific. The mechanisms by which different insects, armed with distinct salivary components, counteract the conserved plant immune systems are not well understood. Here, we describe how two salivary effectors from the brown planthopper Nilaparvata lugens and the bean bug Riptortus pedestris target pathogenesis-related germin-like proteins (GLPs) in rice and soybean. In N. lugens, NlGTSP is expressed exclusively in the salivary glands and is secreted into host plants during feeding. Its knockdown significantly reduces phloem feeding and reproduction, whereas overexpression in rice enhances insect performance and rescues NlGTSP deficiency. NlGTSP partly modulates defenses by interacting with plant GLPs and inhibiting their enzymatic activity. In R. pedestris, the salivary protein RpGDSP lacks sequence or structural similarity to NlGTSP but also targets GLPs, promoting their degradation via the ubiquitin pathway to enhance feeding. Collectively, our findings reveal a functional analogy between salivary effectors from different insects that regulate core plant defense genes through distinct mechanisms.
Huang et al. (Sat,) studied this question.