title: Characterization of Venom and Oviduct Components of Parasitoid Wasp Asobara japonica.
abstract: During natural parasitization, Asobara japonica wasps introduce lateral oviduct (LO) components into their Drosophila hosts soon after the venom injection to neutralize its strong toxicity; otherwise, the host will die. Although the orchestrated relationship between the venom and LO components necessary for successful parasitism has attracted the attention of many researchers in this field, the molecular natures of both factors remain ambiguous. We here showed that precipitation of the venom components by ultracentrifugation yielded a toxic fraction that was inactivated by ultraviolet light irradiation, boiling, and sonication, suggesting that it is a virus-like entity. Morphological observation of the precipitate after ultracentrifugation showed small spherical heterogeneous virus-like particles 20-40 nm in diameter. The venom's detrimental effect on D. melanogaster larvae was not directly neutralized by the LO components but blocked by a hemolymphal neutralizing factor activated by the LO factor. Furthermore, we found that A. japonica venom and LO components acted similarly on the larvae of the common cutworm Spodoptera litura: the venom injection caused mortality but coinjection of the LO factor protected S. litura larvae from the venom's toxicity. In contrast, D. ficusphila and D. bipectinata, which are closely related to D. melanogaster but non-habitual host species of A. japonica, were not negatively affected by A. japonica venom due to an intrinsic neutralizing activity in their hemolymph, indicating that these species must have acquired a neutralizer of A. japonica venom during evolution. These results give new insights into the characteristics of both the venom and LO components: A. japonica females have utilized the virus-like toxic venom factor to exploit a wider range of host species after the evolutionary process enabled them to use the LO factor for activation of the host hemolymph neutralizer precursor, although the non-habitual host Drosophila species possess an active intrinsic neutralizer in their hemolymph.
authors.affiliation: Department of Applied Biological Sciences, Saga University, Saga 840-8502, Japan.
authors.forename: Shunsuke
authors.initials: S
authors.lastname: Furihata
authors.affiliation: Department of Applied Biological Sciences, Saga University, Saga 840-8502, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Matsumura
authors.affiliation: Department of Applied Biological Sciences, Saga University, Saga 840-8502, Japan.
authors.forename: Makiko
authors.initials: M
authors.lastname: Hirata
authors.affiliation: Research and Education Center for Prevention of Global Infectious Diseases of Animals, Tokyo University of Agriculture and Technology, Fuchu, Tokyo, 183-8509, Japan.
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Mizutani
authors.affiliation: Department of Virology II, National Institute of Infectious Diseases, Tokyo, 280-0011, Japan.
authors.forename: Noriyo
authors.initials: N
authors.lastname: Nagata
authors.affiliation: Department of Virology II, National Institute of Infectious Diseases, Tokyo, 280-0011, Japan.
authors.forename: Michiyo
authors.initials: M
authors.lastname: Kataoka
authors.affiliation: Research and Education Center for Prevention of Global Infectious Diseases of Animals, Tokyo University of Agriculture and Technology, Fuchu, Tokyo, 183-8509, Japan.
authors.forename: Yukie
authors.initials: Y
authors.lastname: Katayama
authors.affiliation: Research and Education Center for Prevention of Global Infectious Diseases of Animals, Tokyo University of Agriculture and Technology, Fuchu, Tokyo, 183-8509, Japan.
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Omatsu
authors.affiliation: Department of Applied Biological Sciences, Saga University, Saga 840-8502, Japan.
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Matsumoto
authors.affiliation: Department of Applied Biological Sciences, Saga University, Saga 840-8502, Japan.
authors.forename: Yoichi
authors.initials: Y
authors.lastname: Hayakawa
mesh_terms: D000818:Animals; D004331:Drosophila melanogaster / Q000469:parasitology*; D005260:Female; D006790:Host-Parasite Interactions / Q000502:physiology*; D010057:Oviducts / Q000378:metabolism / Q000502:physiology*; D018411:Spodoptera / Q000469:parasitology; D015996:Survival Rate; D014862:Wasp Venoms / Q000737:chemistry / Q000378:metabolism*; D014863:Wasps / Q000502:physiology*
chemical_list: D014862:Wasp Venoms