Shuai Cao

This study aimed to explore the effects of different host tea cultivars on population fitness, as well as the abundance and diversity of gut bacteria of Ectropis grisescens Warren. The feeding preference, survival rate, body length and body weight of E. grisescens larvae were determined on six tea cultivars. Furthermore, 16S rRNA high-throughput sequencing technology was adopted to analyze the community structure and diversity of gut bacteria in larvae fed on Camellia sinensis cv. ‘Xinyang 10’, Camellia sinensis cv. ‘Fudingdabaicha’ and Camellia sinensis cv. ‘Wuniuzao’, and correlation analysis was performed between gut bacterial data and larval growth-development indices. The results revealed significant differences in feeding preference and adaptability of E. grisescens larvae across different tea cultivars. Larvae feeding on C. sinensis cv. ‘Xinyang 10’ achieved the highest survival rate, body length and body weight, showing the optimal fitness; larvae fed on C. sinensis cv. ‘Wuniuzao’ exhibited the lowest values for all measured indices and the poorest fitness. Gut microbiota analysis indicated that Proteobacteria and Firmicutes constituted the core bacterial taxa, yet their relative abundances differed significantly among host treatments. Serratia marcescens was the core gut bacterium in larvae feeding on C. sinensis cv. ‘Xinyang 10’ and C. sinensis cv. ‘Wuniuzao’, whereas Enterococcus flavescens ATCC 49996 dominated the gut of larvae reared on C. sinensis cv. ‘Fudingdabaicha’. Functional profiles demonstrated that gut bacteria of larvae were mainly involved in carbon metabolism, amino acid metabolism, membrane transport, energy metabolism and other pathways. Correlation analysis showed that larval growth-development indices were positively correlated with Serratia marcescens. Collectively, host tea cultivars shape the adaptability of E. grisescens, and the underlying mechanism is potentially associated with the composition, abundance and function of gut bacteria. This research provides a theoretical foundation for deciphering the interaction mechanism between tea pests and their hosts from the perspective of gut bacteria and developing novel pest-management strategies.

Insects employ various types of gustatory receptors (GRs) to identify nutrient‐rich food and avoid toxic substances. The larval gustatory system is the critical checkpoint for food acceptance or rejection. As a specialist herbivore, the larvae of Bactrocera minax feed only on unripe citrus fruits. However, how larvae use GRs to check and adapt to the secondary metabolites in unripe citrus fruits remains unknown. In this study, we first performed developmental expression profiles showing that most BminGRs genes were highly expressed in 1st and 2nd instar larvae and that tissue‐specific expression indicated high expression of most BminGRs genes in the mouthparts of 2nd instar larvae. Furthermore, we found that silencing BminGR59f by RNA interference (RNAi) affected the growth of 2nd instar B. minax larvae. Hesperidin and naringin were screened as ligands of BminGR59f via RNAi and cell calcium imaging, and the combination of these two flavones increased the body weight of larvae. In summary, we identified a novel gustatory perception pattern in B. minax for detecting hesperidin and naringin, which boosted the growth of B. minax larvae. These results shed light on how specialist herbivores detect and adapt to host metabolites in adverse environments depending on larval GRs.