Silencing beta-1,3-glucan binding protein enhances the susceptibility of Plutella xylostella to entomopathogenic fungus Isaria cicadae

BACKGROUND: The diamondback moth, Plutella xylostella is a notorious pest of brassicaceae crops globally and has developed serious resistance to insecticide. Insects primarily rely on their innate immunity to defense against various pathogens. In this study, we investigated the immunological functions of a beta-1,3-glucan binding protein from P. xylostella (Px beta GBP) and evaluated its potential for biocontrolling P. xylostella. RESULTS: The open reading frame of Px beta GBP is 1422 bp encoding 473 amino acids residues. Px beta GBP contained a CBM39 domain, a PAC domain and a GH16 domain and shared evolutionary conservation with other lepidoptera beta GRPs. Px beta GBP was strongly expressed in the third instar larvae and fat body. Px beta GBP transcript levels increased significantly after the challenge with microbes, including Isaria cicadae, Escherichia coli and Staphylococcus aureus. Px beta GBP was identified in P. xylostella larvae challenged by I cicadae, but not in the naive insects. Recombinant Px beta GBP can directly bind fungal and bacterial cells, and also agglutinate the cells of I cicadae, S. aureus and E coli in a zinc-dependent manner. Knockdown of Px beta GBP via RNA interference significantly down-regulated the expression of antimicrobial peptide gene gloverin, and enhanced the susceptibility of P. xylostella to I. cicadae infection, leading to high mortality. CONCLUSION: These results indicated that Px beta GBP plays an important role in the immune response of P. xylostella against I. cicadae infection, and could serve as a potential novel target for pest control. (C) 2022 Society of Chemical Industry.