title: In vivo study of Dicer-2-mediated immune response of the small interfering RNA pathway upon systemic infections of virulent and avirulent viruses in Bombus terrestris.
abstract: Recent studies suggest a potent role of the small interfering RNA (siRNA) pathway in the control of bee viruses and its usefulness to tackle these viral diseases. However, the involvement of the siRNA pathway in the defense against different bee viruses is still poorly understood. Therefore, in this report, we comprehensively analyzed the response of the siRNA pathway in bumblebees of Bombus terrestris to systemic infections of the virulent Israeli acute paralysis virus (IAPV) and the avirulent slow bee paralysis virus (SBPV). Our results showed that IAPV and SBPV infections induced the expression of Dicer-2. IAPV infections also triggered the production of predominantly 22 nt-long virus-derived siRNAs (vsiRNAs). Intriguingly, these 22 nt-long vsiRNAs showed a high proportion of antigenomic IAPV sequences. Conversely, these predominantly 22 nt-long vsiRNAs of SBPV were not detected in SBPV infected bees. Furthermore, an "RNAi-of-RNAi" experiment on Dicer-2 did not result in altered genome copy numbers of IAPV (n = 17-18) and also not of SBPV (n = 11-12). Based on these results, we can speculate about the importance of the siRNA pathway in bumblebees for the antiviral response. During infection of IAPV, this pathway is probably recruited but it might be insufficient to control viral infection in our experimental setup. The host can control SBPV infection, but aside from the induction of Dicer-2 expression, no further evidence of the antiviral activity of the siRNA pathway was observed. This report may also enhance the current understanding of the siRNA pathway in the innate immunity of non-model insects upon different viral infections.
authors.affiliation: Department of Crop Protection, Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, B-9000 Ghent, Belgium.
authors.forename: Jinzhi
authors.initials: J
authors.lastname: Niu
authors.affiliation: Department of Crop Protection, Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, B-9000 Ghent, Belgium.
authors.forename: Guy
authors.initials: G
authors.lastname: Smagghe
authors.affiliation: Laboratory for Pharmaceutical Biotechnology, Faculty of Pharmaceutical Sciences, Ghent University, Ottergemsesteenweg 460, B-9000 Ghent, Belgium.
authors.forename: Dieter I M
authors.initials: DI
authors.lastname: De Coninck
authors.affiliation: Laboratory for Pharmaceutical Biotechnology, Faculty of Pharmaceutical Sciences, Ghent University, Ottergemsesteenweg 460, B-9000 Ghent, Belgium.
authors.forename: Filip
authors.initials: F
authors.lastname: Van Nieuwerburgh
authors.affiliation: Laboratory for Pharmaceutical Biotechnology, Faculty of Pharmaceutical Sciences, Ghent University, Ottergemsesteenweg 460, B-9000 Ghent, Belgium.
authors.forename: Dieter
authors.initials: D
authors.lastname: Deforce
authors.affiliation: Department of Crop Protection, Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, B-9000 Ghent, Belgium. Electronic address: ivan.meeus@ugent.be.
authors.forename: Ivan
authors.initials: I
authors.lastname: Meeus
mesh_terms: D000818:Animals; D001516:Bees / Q000276:immunology / Q000821:virology*; D020868:Gene Silencing; D007304:Insect Viruses / Q000472:pathogenicity*; D020365:RNA Helicases / Q000235:genetics / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000235:genetics*; D014774:Virulence
chemical_list: D034741:RNA, Small Interfering; D020365:RNA Helicases
keywords: Bee immunity; Dicistroviridae; Iflaviridae; RNAi; Small RNA sequencing; dsRNA