Nymphal diets boost adults’ immunity via strengthened constitutive immunity and metabolic capacity in Adelphocoris suturalis

In insects, juvenile diet strongly influences adult fitness. Yet, despite the centrality of immune function to overall organismal health, the effects of early-life diets on adult immunity remain underexplored. We showed that Adelphocoris suturalis adults, developed from nymphs fed on an omnivorous diet (NO), exhibited higher survival against Beauveria bassiana than those from a phytophagous diet (NP). Using high-throughput RNA sequencing, we profiled gene expression responses at both early and late infection stages. Integrated transcriptomic and immunological analyses revealed that NO adults exhibited a greater number of up-regulated immune-related genes, elevated phenoloxidase and prophenoloxidase activity, and higher hemocyte counts, particularly during early infection. Tracking macronutrient dynamics and associated gene expression showed that the NO group displayed up-regulation of more metabolic-related genes, which positively correlated with immune activity. These findings highlight a developmentally coordinated link between nutrition and immunity, contributing to an integrated understanding of nutritional and developmental immunology.