Comparative gene expression analyses reveal developmental stage dependent immune adaptations of Spodoptera frugiperda

The fall armyworm, Spodoptera frugiperda , is a major agricultural pest responsible for substantial crop damage worldwide. Several critical physiological functions, including high reproductive and migratory abilities, a broad plant host range, coupled to the development of high resistance to various chemical pesticides, and a strong immune response to microbial pathogens, has made this insect particularly difficult to control. While various innate immune pathways are assumed to play crucial roles in microbial pathogen defense, a comprehensive analysis across different developmental stages has been lacking. This is particularly important as different developmental stages of S. frugiperda display differential sensitivity to chemical pesticides and/or microbial pathogens. Here, we performed a comparative transcriptomic analysis of S. frugiperda across ten developmental stages: egg, six larval instars (1–6), pupa, and adult (both female and male). We identified 56 gene families associated with insect immunity, with several exhibiting variable expression patterns across the developmental stages. Our findings provide new insights into the global gene expression landscape forming innate immune responses throughout development and between sexes in S. frugiperda . These results help explain the disparate innate immune responses of different developmental stages and provides clues for devising more effective pest control strategies.