title: A Venom Serpin Splicing Isoform of the Endoparasitoid Wasp Pteromalus puparum Suppresses Host Prophenoloxidase Cascade by Forming Complexes with Host Hemolymph Proteinases.
abstract: To ensure successful parasitism, parasitoid wasps inject venom along with their eggs into their hosts. The venom serves to suppress host immune responses, including melanization. Venom from Pteromalus puparum, a pupal endoparasitoid, inhibits melanization of host hemolymph in vitro in a dose-dependent manner. Using assay-guided fractionation, a serpin splicing isoform with phenoloxidase inhibitory activity was identified as P puparum serpin-1, venom isoform (PpS1V). This serpin gene has 16 predicted splicing isoforms that differ only in the C-terminal region. RT-PCR results show that the specific serpin isoform is differentially expressed in the venom gland. Recombinant PpS1V (rPpS1V) suppresses host prophenoloxidase (PPO) activation rather than inhibiting the phenoloxidase directly. Pulldown assays show that PpS1V forms complexes with two host hemolymph proteins, here named Pieris rapae hemolymph proteinase 8 (PrHP8) and P. rapae prophenoloxidase-activating proteinase 1 (PrPAP1), based on gene sequence blasting and phylogenetic analysis. The role of rPrPAP1 in the PPO activation cascade and its interaction with rPpS1V were confirmed. The stoichiometry of inhibition of PrPAP1 by PpS1V is 2.3. PpS1V also inhibits PPO activation in a non-natural host, Ostrinia furnacalis, through forming a complex with O. furnacalis serine protease 13 (OfSP13), an ortholog to PrPAP1. Our results identify a venom-enriched serpin isoform in P. puparum that inhibits host PPO activation, probably by forming a complex with host hemolymph proteinase PrPAP1.
authors.affiliation: From the State Key Laboratory of Rice Biology and Ministry of Agriculture Key Laboratory of Agricultural Entomology, Institute of Insect Sciences, Zhejiang University, Hangzhou 310058, China.
authors.forename: Zhichao
authors.initials: Z
authors.lastname: Yan
authors.affiliation: From the State Key Laboratory of Rice Biology and Ministry of Agriculture Key Laboratory of Agricultural Entomology, Institute of Insect Sciences, Zhejiang University, Hangzhou 310058, China.
authors.forename: Qi
authors.initials: Q
authors.lastname: Fang
authors.affiliation: From the State Key Laboratory of Rice Biology and Ministry of Agriculture Key Laboratory of Agricultural Entomology, Institute of Insect Sciences, Zhejiang University, Hangzhou 310058, China.
authors.forename: Yang
authors.initials: Y
authors.lastname: Liu
authors.affiliation: From the State Key Laboratory of Rice Biology and Ministry of Agriculture Key Laboratory of Agricultural Entomology, Institute of Insect Sciences, Zhejiang University, Hangzhou 310058, China.
authors.forename: Shan
authors.initials: S
authors.lastname: Xiao
authors.affiliation: From the State Key Laboratory of Rice Biology and Ministry of Agriculture Key Laboratory of Agricultural Entomology, Institute of Insect Sciences, Zhejiang University, Hangzhou 310058, China.
authors.forename: Lei
authors.initials: L
authors.lastname: Yang
authors.affiliation: From the State Key Laboratory of Rice Biology and Ministry of Agriculture Key Laboratory of Agricultural Entomology, Institute of Insect Sciences, Zhejiang University, Hangzhou 310058, China.
authors.forename: Fei
authors.initials: F
authors.lastname: Wang
authors.affiliation: the Department of Entomology, College of Agriculture and Biotechnology, China Agricultural University, Beijing 100193, China, and.
authors.forename: Chunju
authors.initials: C
authors.lastname: An
authors.affiliation: the Department of Biology, University of Rochester, Rochester, New York 14627.
authors.forename: John H
authors.initials: JH
authors.lastname: Werren
authors.affiliation: From the State Key Laboratory of Rice Biology and Ministry of Agriculture Key Laboratory of Agricultural Entomology, Institute of Insect Sciences, Zhejiang University, Hangzhou 310058, China, chu@zju.edu.cn.
authors.forename: Gongyin
authors.initials: G
authors.lastname: Ye
mesh_terms: D017398:Alternative Splicing / Q000502:physiology*; D000818:Animals; D004156:Catechol Oxidase / Q000378:metabolism*; D004792:Enzyme Precursors / Q000378:metabolism*; D006458:Hemolymph / Q000378:metabolism*; D019476:Insect Proteins / Q000378:metabolism*; D020033:Protein Isoforms / Q000378:metabolism; D015843:Serpins / Q000378:metabolism*; D014862:Wasp Venoms / Q000378:metabolism*; D014863:Wasps
chemical_list: D004792:Enzyme Precursors; D019476:Insect Proteins; D020033:Protein Isoforms; D015843:Serpins; D014862:Wasp Venoms; C038451:pro-phenoloxidase; D004156:Catechol Oxidase
keywords: alternative splicing; insect immunity; melanization; parasitoid wasp; parasitology; proteinase; serpin; venom