Helicoverpa armigera Transcriptome or Gene expression. Helicoverpa armigera

Cotton bollworm, Helicoverpa armigera, is one of the most destructive pests all around the world, and comparison of immunity-related genes expression profiles at different developmental stages is not reported. Here, we conducted the transcriptome analysis of second instar larvae infected with entomopathogen Beauveria bassiana. We found that only 250 genes were regulated significantly in second instar larvae after fungal infection. This number was much less than that from fat body and hemocytes of fifth instar larvae from previous study. Only seven out of 233 immunity-related genes expressed differently in second instar larvae after B. bassiana infection, while the number in fat body and hemocytes of fifth instar larvae were 68 and 56 respectively. There are 42 immunity-related genes were up-regulate at fifth instar but not second instar. Among this gene cohorts, C-type lectin 14 (CTL14) is a fungal-induced pattern recognition receptor. Recombinant CTL14 protein could bind to zymosan and B. bassiana in vitro and co-localize with fungi on hemocytes in vivo. Immunoprecipitation demonstrated that CTL14 interacted with serine proteinases (SP), serine proteinase inhibitor (serpin), prophenoloxidases (PPO) and vitellogenin (Vg) under the condition of fungal infection. Depletion of CTL14 using dsRNA interference dramatically decreased the expression level of Vg and melanization genes (PPO1, cSP6, cSPH11, and SPH50). Conversely, mRNA abundance of SP inhibitor, serpin-3, was up-regulated. Furthermore, CTL14 depleted H. armigera decreased the resistance to fungal challenge. Taken together, our study proved direct involvement of CTL14 in the anti-fungal immunity in H. armigera, which explained the stronger immune responses in the fifth instar compared to second instar larvae.