AUTHOR=Guan Ruobing , Hu Shaoru , Li Xiang , An Shiheng , Miao Xuexia , Li Haichao 

TITLE=A TIL-Type Serine Protease Inhibitor Involved in Humoral Immune Response of Asian Corn Borer Ostrinia furnaculis

JOURNAL=Frontiers in Immunology

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/immunology/articles/10.3389/fimmu.2022.900129

DOI=10.3389/fimmu.2022.900129

ISSN=1664-3224

ABSTRACT=<p>To elucidate the application value of insect endogenous protease and its inhibitor genes in pest control, we analyzed in detail the transcriptome sequence of the Asian corn borer, <italic>Ostrinia furnacalis</italic>. We obtained 12 protease genes and 11 protease inhibitor genes, and comprehensively analyzed of their spatiotemporal expression by qRT-PCR. In which, a previous unstudied serine protease inhibitor gene attracted our attention. It belongs to the canonical serine proteinase inhibitor family, a trypsin inhibitor-like cysteine-rich domain (TIL)-type protease inhibitor, but its TIL domain lacks two cysteine residues, and it was named as <italic>ACB-TIL</italic>. Its expression level is relatively very low in the absence of pathogen stimulation, and can be up-regulated expression induced by Gram-negative bacteria (<italic>Escherichia coli</italic>), virus (BmNPV), and dsRNA (dsEGFP), but cannot be induced by fungus spores (<italic>Metarrhizium anisopliae</italic>). Prokaryotic expressed ACB-TIL protein can significantly inhibit the melanization <italic>in vitro</italic>. Injecting this protein into insect body can inhibit the production of antimicrobial peptides of attacin, lebocin and gloverin. Inhibition of <italic>ACB-TIL</italic> by RNAi can cause the responses of other immune-, protease- and inhibitor-related genes. ACB-TIL is primarily involved in Asian corn borer humoral immunity in responses to Gram-negative bacteria and viruses. This gene can be a potential target for pest control since this will mainly affect insect immune response.</p>