Metagenomic Analysis of Gut Bacteria in Different Developmental Instars of the Spodoptera litura

Spodoptera litura, a globally distributed agricultural pest, whose gut microbiota significantly influences host feeding, digestion, immunity, and development. We used whole metagenomic sequencing to analyze the diversity and functional roles of gut bacteria at different developmental stages (eggs, 1st-6th instar larvae, pupae and adults). Findings revealed that Pseudomonadota predominated at the phylum level, with notable differences across instars: Bacillota was dominated in young larvae, whereas Verrucomicrobiota was added in older larvae, eggs, pupae, and adults. At the genus level, Pseudomonas dominated, Enterococcus was prevalent in larvae and Rickettsia in eggs, pupae, and adults. Metagenomic analysis identified numerous carbohydrate-active enzymes (CAZy database) aiding in plant cell wall polysaccharide digestion. KEGG pathway analysis indicated differential gene expression in metabolism and xenobiotic degradation across instars, with metabolic gene annotation levels declining as development progressed. Detoxification-related enzyme genes were predominantly expressed in early instar larvae and adults, uncovering microbial origins of these enzymes. This research enhances understanding of S. litura gut microbiota-host interactions and supports novel pest control strategies targeting gut microbiota.