title: Scavenger receptor mediates systemic RNA interference in ticks.
abstract: RNA interference is an efficient method to silence gene and protein expressions. Here, the class B scavenger receptor CD36 (SRB) mediated the uptake of exogenous dsRNAs in the induction of the RNAi responses in ticks. Unfed female Haemaphysalis longicornis ticks were injected with a single or a combination of H. longicornis SRB (HlSRB) dsRNA, vitellogenin-1 (HlVg-1) dsRNA, and vitellogenin receptor (HlVgR) dsRNA. We found that specific and systemic silencing of the HlSRB, HlVg-1, and HlVgR genes was achieved in ticks injected with a single dsRNA of HlSRB, HlVg-1, and HlVgR. In ticks injected first with HlVg-1 or HlVgR dsRNA followed 96 hours later with HlSRB dsRNA (HlVg-1/HlSRB or HlVgR/HlSRB), gene silencing of HlSRB was achieved in addition to first knockdown in HlVg-1 or HlVgR, and prominent phenotypic changes were observed in engorgement, mortality, and hatchability, indicating that a systemic and specific double knockdown of target genes had been simultaneously attained in these ticks. However, in ticks injected with HlSRB dsRNA followed 96 hours later with HlVg-1 or HlVgR dsRNAs, silencing of HlSRB was achieved, but no subsequent knockdown in HlVgR or HlVg-1 was observed. The Westernblot and immunohistochemical examinations revealed that the endogenous HlSRB protein was fully abolished in midguts of ticks injected with HlSRB/HlVg-1 dsRNAs but HlVg-1 was normally expressed in midguts, suggesting that HlVg-1 dsRNA-mediated RNAi was fully inhibited by the first knockdown of HlSRB. Similarly, the abolished localization of HlSRB protein was recognized in ovaries of ticks injected with HlSRB/HlVgR, while normal localization of HlVgR was observed in ovaries, suggesting that the failure to knock-down HlVgR could be attributed to the first knockdown of HlSRB. In summary, we demonstrated for the first time that SRB may not only mediate the effective knock-down of gene expression by RNAi but also play essential roles for systemic RNAi of ticks.
authors.affiliation: Department of Pathological and Preventive Veterinary Science, The United Graduate School of Veterinary Science, Yamaguchi University, Yoshida, Yamaguchi, Japan.
authors.forename: Kyaw Min
authors.initials: KM
authors.lastname: Aung
authors.forename: Damdinsuren
authors.initials: D
authors.lastname: Boldbaatar
authors.forename: Rika
authors.initials: R
authors.lastname: Umemiya-Shirafuji
authors.forename: Min
authors.initials: M
authors.lastname: Liao
authors.forename: Xuan
authors.initials: X
authors.lastname: Xuenan
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Suzuki
authors.forename: Remil Linggatong
authors.initials: RL
authors.lastname: Galay
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Tanaka
authors.forename: Kozo
authors.initials: K
authors.lastname: Fujisaki
mesh_terms: D000818:Animals; D015153:Blotting, Western; D004527:Egg Proteins / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism; D005260:Female; D005455:Fluorescent Antibody Technique; D020868:Gene Silencing; D010053:Ovary / Q000378:metabolism* / Q000473:pathology; D034622:RNA Interference; D012330:RNA, Double-Stranded / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics; D034741:RNA, Small Interfering / Q000235:genetics*; D011817:Rabbits; D060888:Real-Time Polymerase Chain Reaction; D011956:Receptors, Cell Surface / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism; D051116:Receptors, Scavenger / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism; D013984:Tick Infestations / Q000235:genetics* / Q000378:metabolism / Q000401:mortality; D013987:Ticks / Q000472:pathogenicity
chemical_list: D004527:Egg Proteins; D012330:RNA, Double-Stranded; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D011956:Receptors, Cell Surface; D051116:Receptors, Scavenger; C030474:vitellogenin receptor