Background: The interaction and co-evolution between the gut microbiome and the host play important roles in the host’s physiology, nutrition, and health. Diet is considered an important driver of differences in the gut microbiota; however, research on the relationship between the gut microbiota and diet in Asian elephants remains limited. Methods: In this study, we explored the gut microbiota structure and its relationship with diet in different populations of Asian elephants through metagenomic sequencing, combined with previously published dietary data. Results: This study found that the dominant gut microbiota of Asian elephants includes the phyla Bacillota (29.85% in BP, 22.79% in RC, 21.89% in SM, 31.67% in ML, and 33.00% in NGH), Bacteroidota (25.25% in BP, 31.44% in RC, 16.44% in SM, 25.73% in ML, and 23.74% in NGH), and Spirochaetota (3.49% in BP, 6.18% in RC, 1.71% in SM, 2.69% in ML, and 3.52% in NGH), with significant differences in the gut microbiota among different populations. Correlation analysis between the gut microbiota and diet revealed that dietary diversity did not directly affect the alpha diversity of the gut microbiota. However, specific food types might play a key role in shaping the gut microbiota structure by regulating the abundance of certain microbiota. Conclusions: This study reveals significant differences in the gut microbiota structure among different populations of Asian elephants and explores the impact of diet on the structure. The results provide foundational data for a deeper understanding of the gut microbiota structure of Asian elephants and offer important references for the scientific conservation and precise management strategies of this species.

Star anise, an economically and medicinally important crop, is highly susceptible to infestation by Oides leucomelaena Weise, leading to significant yield losses. This study employed transcriptome sequencing and bioinformatic analysis to systematically identify detoxification genes (CYP, GST, and CarE) in O. leucomelaena and evaluated their binding potential with star anise volatiles via molecular docking. A total of 64 CYP, 21 GST, and 44 CarE genes were identified, with several genes showing high expression across multiple tissues. Molecular docking revealed strong binding affinity between seven CYP proteins and star anise volatiles, notably the antennae-specific CYP, which exhibited robust binding with multiple volatiles. Detoxification genes in O. leucomelaena may mediate host adaptation by metabolizing star anise volatiles, providing potential targets for eco-friendly pest control.

Dendrolimus kikuchii Matsumura (D. kikuchii) is a serious pest of coniferous trees. Bacillus thuringiensis (Bt) has been widely studied and applied as a biological control agent for a variety of pests. Here, we found that the mortality rate of D. kikuchii larvae after being fed Bt reached 95.33% at 24 h; the midgut membrane tissue was ulcerated and liquefied, the MDA content in the midgut tissue decreased and the SOD, CAT and GPx enzyme activities increased, indicating that Bt has toxic effects on D. kikuchii larvae. In addition, transmission electron microscopy showed that Bt infection caused severe deformation of the nucleus of the midgut tissue of D. kikuchii larvae, vacuoles in the nucleolus, swelling and shedding of microvilli, severe degradation of mitochondria and endoplasmic reticulum and decreased number. Surprisingly, metabolomics and transcriptome association analysis revealed that four metabolic-related signaling pathways, Nicotinate and nicotinamide metabolism, Longevity regulating pathway—worm, Vitamin digestion and absorption and Lysine degradation, were co-annotated in larvae. More surprisingly, Niacinamide was a common differential metabolite in the first three signaling pathways, and both Niacinamide and L-2-Aminoadipic acid were reduced. The differentially expressed genes involved in the four signaling pathways, including NNT, ALDH, PNLIP, SETMAR, GST and RNASEK, were significantly down-regulated, but only SLC23A1 gene expression was up-regulated. Our results illustrate the effects of Bt on the 5th instar larvae of D. kikuchii at the tissue, cell and molecular levels, and provide theoretical support for the study of Bt as a new biological control agent for D. kikuchii.