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

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 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 Mr 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. 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 OfPAP is a component of the PPO activation system, likely by functioning as a PPO activating protease in O. furnacalis larvae.

• Authors: Congjing Feng, Ya Zhao, Kangkang Chen, Huifeng Zhai, Zhenying Wang, Haobo Jiang, Yingjuan Wang, Libao Wang, Yiqiang Zhang, Tai Tang
• Journal: Developmental and comparative immunology (Dev Comp Immunol) Vol. 87 Pg. 204-215 (10 2018) ISSN: 1879-0089 [Electronic] United States
• PMID: 30017863 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't)
• Copyright: Copyright © 2018 Elsevier Ltd. All rights reserved.

Chemical References

• Enzyme Precursors
• Insect Proteins
• pro-phenoloxidase
• Catechol Oxidase

Topics

• Amino Acid Sequence
• Animals
• Base Sequence
• Binding Sites (genetics)
• Catechol Oxidase (classification, genetics, immunology)
• Disease Resistance (genetics, immunology)
• Enzyme Activation (genetics, immunology)
• Enzyme Precursors (classification, genetics, immunology)
• Escherichia coli (immunology, physiology)
• Gene Expression Regulation, Enzymologic (immunology)
• Hemocytes (enzymology, immunology, microbiology)
• Hemolymph (enzymology, immunology, microbiology)
• Insect Proteins (classification, genetics, immunology)
• Larva (genetics, immunology, microbiology)
• Moths (genetics, immunology, microbiology)
• Phylogeny
• RNA Interference
• Sequence Homology, Amino Acid