Hemolin modulates IMD-related immune responses and promotes cellular immunity in Ostrinia furnacalis

Ostrinia furnacalis is one of the most destructive Lepidopteran pests in Asia and worldwide, reducing yields of corn and other grain crops. Hemolin, an immunoglobulin-like protein with both developmental and immunological functions, has been implicated in protecting insects from pathogen infections. However, the specific regulatory mechanism by which Hemolin modulates innate immunity in O. furnacalis remains unknown. In this study, the full-length Of-Hemolin cDNA sequence was obtained by rapid amplification of cDNA ends and characterized through bioinformatic analysis. Expression levels of Of-Hemolin in different tissues and developmental stages of O. furnacalis were analyzed by quantitative real-time PCR. The transcript levels of Of-Hemolin and immune-related genes in O. furnacalis larvae were detected after bacterial infection or dsHem injection. Of-Hemolin knockdown altered the expression of IMD pathway-related genes and antimicrobial peptides, suggesting that Of-Hemolin modulates IMD signaling-associated immune responses at the transcriptional level. As an opsonin, Of-Hemolin also substantially augments cellular immune reactions, including phagocytosis, encapsulation and nodulation, demonstrating its critical contribution to cellular immunity. These findings elucidate Of-Hemolin's function and suggest it may be a candidate target for green pest control.