Ostrinia furnacalis serpin-3 regulates melanization cascade by inhibiting a prophenoloxidase-activating protease |
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| Affiliation: | 1. Department of Entomology, College of Agriculture and Biotechnology, China Agricultural University, Beijing, 100193, China;2. State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, 100193, China;1. State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing 400716, China;2. Vitamin D Research Institute, Shannxi University of Technology, Hanzhong 723001, Shannxi Province, China;3. School of Management, Shannxi University of Technology, Hanzhong 723001, Shannxi Province, China;1. Department of Entomology, College of Agriculture and Biotechnology, China Agricultural University, Beijing, China;2. State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, China;1. State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing, 100101, China;2. University of Chinese Academy of Sciences, Beijing, 100049, China;3. School of Life Sciences, Jinggangshan University, Ji''an, 343009, China;1. College of Veterinary Medicine, Gansu Agricultural University, Lanzhou, 730070, China;2. Product R & D,Lanzhou Weitesen Biological Technology Co. Ltd., Lanzhou, 730030, China;1. Department of Plant Protection, College of Horticulture and Plant Protection, Yangzhou University, Yangzhou, Jiangsu Province 225009, China;2. State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100193, China;3. Division of Plant Sciences, University of Missouri, Columbia, MO 65211, USA |
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| Abstract: | Serine protease cascade-mediated prophenolxidase activation is a prominent innate immune response in insect defense against the invading pathogens. Serpins regulate this reaction to avoid excessive activation. However, the function of serpins in most insect species, especially in some non-model agriculture insect pests, is largely unknown. We here cloned a full-length cDNA for a serpin, named as serpin-3, from Asian corn borer, Ostrinia furnacalis (Guenée). The open reading frame of serpin-3 encodes 462-amino acid residue protein with a 19-residue signal peptide. It contains a reactive center loop strikingly similar to the proteolytic activation site in prophenoloxidase. Sequence comparison indicates that O. furnacalis serpin-3 is an apparent ortholog of Manduca sexta serpin-3, a defined negative regulator of melanization reaction. Serpin-3 mRNA and protein levels significantly increase after a bacterial or fungal injection. Recombinant serpin-3 efficiently blocks prophenoloxidase activation in larval plasma in a concentration-dependent manner. It forms SDS-stable complexes with serine protease 13 (SP13), and prevents SP13 from cleaving prophenoloxidase. Injection of recombinant serpin-3 into larvae results in decreased fungi-induced melanin synthesis and reduced the expression of attacin, cecropin, gloverin, and peptidoglycan recognition protein-1 genes in the fat body. Altogether, serpin-3 plays important roles in the regulation of prophenoloxidase activation and antimicrobial peptide production in O. furnacalis larvae. |
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