Clip domain prophenoloxidase activating protease is required for Ostrinia furnacalis Guenee to defend against bacterial infection

文献类型： 外文期刊

第一作者： Zhao, Ya

作者： Zhao, Ya;Chen, Kangkang;Zhai, Huifeng;Wang, Yingjuan;Wang, Libao;Zhang, Yiqiang;Tang, Tai;Wang, Zhenying;Jiang, Haobo

作者机构：

关键词： Insect immunity; Hemolymph protein; RNA interference; Melanization; Bacterial challenge

期刊名称：DEVELOPMENTAL AND COMPARATIVE IMMUNOLOGY （ 影响因子：3.636； 五年影响因子：3.654 ）

ISSN： 0145-305X

年卷期： 2018 年 87 卷

页码：

收录情况： SCI

摘要： 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 OfPAP) 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 OfPAP 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 OfPAP 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. con-infected wild-type (3.0 days, p < 0.01). A 3.5-fold increase in E. coil 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 OfPAP is a component of the PPO activation system, likely by functioning as a PPO activating protease in O. furnacalis larvae.

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