J Insect Physiol. 2026 Jul 16:105037. doi: 10.1016/j.jinsphys.2026.105037. Online ahead of print.

ABSTRACT

Symbiotic microbiota of insects play crucial roles in host development, metabolism, and immunity, but the molecular mechanisms underlying these interactions remain poorly understood, particularly in non-model lepidopteran pests. Traditional germ-free (GF) insect models are primarily generated using antibiotics, which may introduce confounding effects and fail to completely eliminate microbiota. Here, we present an antibiotic-free method to generate GF Spodoptera frugiperda larvae by rearing them on axenically cultured maize. The 3rd to 6th instar GF larvae exhibited significantly reduced weight and length compared to the conventionally reared (CR) larvae, and the developmental period was prolonged. Transcriptomic analysis of 3rd instar larvae revealed significant differences in gene expression between the two groups, especially in pathways related to total carbohydrate, protein, triglycerides metabolism, as well as juvenile hormone (JH) signaling pathway. In addition, three nutritional content and JH titer were tested between GF and CR larvae. Furthermore, GF groups showed lower pupation rate and eclosion rate, reduced pupal weight, and prolonged developmental period, while pupal length was not affected compare to CR groups. Additionally, the ovarian and testes sizes of GF adults were smaller than those of CR adults. Consistently, GF females laid fewer eggs with significantly lower hatching rate compared to the CR females. These findings demonstrate that microbiota profoundly influence egg, larval, pupal development and adult reproduction in S. frugiperda. This study provides a robust framework for microbiota-function research in agricultural pests and expands our understanding of lepidopteran insects and microbiota interactions.

PMID:42462808 | DOI:10.1016/j.jinsphys.2026.105037