title: A viral histone H4 suppresses insect insulin signal and delays host development.
abstract: Parasitization by an endoparasitoid wasp, Cotesia plutellae, alters host development of Plutella xylostella by extending larval period and preventing metamorphosis. Insulin signal plays a crucial role in mediating insect development and controlling blood sugar level in insects. In this study, three insulin-like peptide genes (PxILP1-3) were predicted from the genome of P. xylostella. However, only PxILP1 was confirmed to be expressed in P. xylostella. Starvation suppressed the expression level of PxILP1 and up-regulated plasma trehalose level. RNA interference against PxILP1 mimicked starvation effect and extended the larval period of P. xylostella. Parasitized larvae exhibited significantly lower levels of PxILP1 expression compared to nonparasitized larvae. Injection of wasp-symbiotic polydnavirus C. plutellae bracovirus (CpBV) also suppressed PxILP1 expression and extended the larval period. Injection of a viral segment (CpBV-S30) containing a viral histone H4 (CpBV-H4) also suppressed PxILP1 expression. Co-injection of CpBV-S30 and double-stranded RNA (dsCpBV-H4) specific to CpBV-H4 rescued the suppression of PxILP1 expression. Injection of CpBV-S30 significantly extended larval development. Co-injection of CpBV-S30 with dsCpBV-H4 rescued the delay of larval development. Injection of a bovine insulin to parasitized larvae prevented parasitoid development. These results indicate that parasitism of C. plutellae can down-regulate host insulin signaling with the help of parasitic factor CpBV-H4.
authors.affiliation: Department of Bioresource Sciences, Andong National University, Andong 36729, South Korea.
authors.forename: Sunil
authors.initials: S
authors.lastname: Kumar
authors.affiliation: College of Plant Protection, Fujian Agriculture and Forestry University, Fuzhou 350002, China.
authors.forename: Xiaojun
authors.initials: X
authors.lastname: Gu
authors.affiliation: Department of Bioresource Sciences, Andong National University, Andong 36729, South Korea. Electronic address: hosanna@andong.ac.kr.
authors.forename: Yonggyun
authors.initials: Y
authors.lastname: Kim
mesh_terms: D000818:Animals; D004266:DNA Virus Infections / Q000276:immunology*; D006657:Histones / Q000378:metabolism*; D006790:Host-Parasite Interactions; D007328:Insulin / Q000235:genetics / Q000378:metabolism*; D007814:Larva; D008675:Metamorphosis, Biological; D009036:Moths / Q000276:immunology* / Q000821:virology; D018071:Polydnaviridae / Q000276:immunology*; D034741:RNA, Small Interfering / Q000235:genetics; D013217:Starvation; D014764:Viral Proteins / Q000378:metabolism*; D014863:Wasps / Q000276:immunology* / Q000821:virology
chemical_list: D006657:Histones; D007328:Insulin; D034741:RNA, Small Interfering; D014764:Viral Proteins
keywords: Histone H4; Insulin; Parasitism; Polydnavirus; Trehalose