Clip domain prophenoloxidase activating protease is required for Ostrinia furnacalis Guenée to defend against bacterial infection. (October 2018)

• Record Type: Journal Article
• Authors: Feng, Congjing; Zhao, Ya; Chen, Kangkang; Zhai, Huifeng; Wang, Zhenying; Jiang, Haobo; Wang, Yingjuan; Wang, Libao; Zhang, Yiqiang; Tang, Tai
• Is Part Of: Developmental and comparative immunology. Volume 87(2018)
• Page Start: 204
• Page End: 215
• Publication Date: 2018-10
• Subjects: Insect immunity -- Hemolymph protein -- RNA interference -- Melanization -- Bacterial challenge; Immunology -- Periodicals; Developmental immunology -- Periodicals; 616.079
• DOI: 10.1016/j.dci.2018.06.014
• Languages: English
• ISSNs: 0145-305X

Abstract

Abstract: The prophenoloxidase (PPO) activating system in insects plays an important role in defense against microbial invasion. In this paper, we identified a PPO activating protease (designated Of PAP) containing a 1203 bp open reading frame encoding a 400-residue protein composed of two clip domains and a C-terminal serine protease domain from Ostrinia furnacalis . SignalP analysis revealed a putative signal peptide of 18 residues. The mature Of PAP was predicted to be 382 residues long with a calculated M r of 44.8 kDa and pI of 6.66. Multiple sequence alignment and phylogenetic analysis indicated that Of PAP was orthologous to the PAPs in the other lepidopterans. A large increase of the transcript levels was observed in hemocytes at 4 h post injection (hpi) of killed Bacillus subtilis, whereas its level in integument increased continuously from 4 to 12 hpi in the challenged larvae and began to decline at 24 hpi. After OfPAP expression had been silenced, the median lethal time (LT50 ) of Escherichia coli -infected larvae (1.0 day) became significantly lower than that of E. coli- infected wild-type (3.0 days, p < 0.01). A 3.5-fold increase in E. coli colony forming units occurred in larval hemolymph of the OfPAP knockdown larvae, as compared with that of the control larvae not injected with dsRNA. There were notable decreases in PO and IEARase activities in hemolymph of the OfPAP knockdown larvae. In summary, we have demonstrated that Of PAP is a component of the PPO activation system, likely by functioning as a PPO activating protease in O. furnacalis larvae. Highlights: cDNA isolation of Ostrinia furnacalis PAP. A large increase of OfPAP mRNA in hemocytes at 4 h post injection of killed Bacillus subtilis. Notably lower LT50 of OfPAP -RNAi larvae than that after Escherichia coli infection. Significant reduction in PO and IEARase activities of hemolymph of the OfPAP knockdown larvae.