The role of the uncharacterized gene TuPSEG in host plant adaptation of Tetranychus urticae (Trombidiformes: Tetranychidae) and its potential for RNA interference-based control

Tetranychus urticae Koch (Acari: Tetranychidae) is a globally distributed agricultural pest with a broad host range and a high propensity for developing pesticide resistance, urgently requiring novel control strategies based on molecular targets. In this study, comparative transcriptomic analysis identified a previously uncharacterized gene, TuPSEG, which is specifically highly expressed in mite proterosomas and is induced by host plants. Sequence analysis revealed that TuPSEG encodes a hydrophilic secreted protein containing a signal peptide, with no known conserved domains, and exhibits high conservation only among closely related Tetranychus species. Developmental expression profiling showed that TuPSEG expression peaks in adult females, and its transcript levels significantly increase with prolonged feeding, with stronger induction observed after transfer to non-adapted hosts such as Citrus sinensis (L.) Osbeck and Solanum lycopersicum (L.). RNAi-mediated silencing of TuPSEG reduced feeding damage area on Glycine max leaves by 53.58% and resulted in a corrected mortality rate of 30.82% over 10 d, whereas survival was unaffected under artificial diet feeding, indicating that this gene specifically participates in plant feeding. Off-target assessment demonstrated that dsRNA targeting TuPSEG poses a minimal predicted risk to non-target organisms (natural enemies and crops) while exhibiting high specificity toward closely related spider mite species. In conclusion, TuPSEG plays a key role in host adaptation of spider mites, and its species-specificity offers a potential target for developing RNAi-based precision control technologies.