title: A primitive Toll-like receptor signaling pathway in mollusk Zhikong scallop Chlamys farreri.
abstract: As a member of pattern-recognition receptors (PRRs), the Toll-like receptor (TLR) and its signaling pathway play pivotal roles in recognizing various pathogen-associated molecular patterns (PAMPs), and buildup the front-line against invading pathogens. In the present study, the sequence features and mRNA expression profiles of five key genes involved in TLR signal pathway were characterized, and their functions in the immune responses were also investigated in order to validate the TLR signaling pathway and its potential roles in the immune defense of Zhikong scallop Chlamys farreri. These five genes, including CfTLR, CfMyD88, CfTRAF6, CfIκB and CfNFκB, exhibited significant similarity with their homologues from other model organisms, and contained the typical motifs. A strong interaction between the TIR domain from CfTLR and CfMyD88 protein was revealed via ELISA assays. The mRNA transcripts of these five genes were all up-regulated after LPS stimulation, indicating that they were involved in the immune response against LPS. When CfTLR expression was inhibited by RNAi technology, the mRNA expression level of CfMyD88, CfTRAF6, CfIκB, CfNFκB and G-type lysozyme were all decreased, while those of superoxide dismutase and catalase were increased. After Listonella anguillara challenge, the apoptosis level of those CfTLR-suppressed scallops was significantly lower than that in control groups (p<0.05) at the beginning of bacteria challenge, while the cumulative mortality was significantly higher than that of control groups (p<0.05). These results collectively favored that a rather canonical MyD88-dependent TLR pathway existed in scallop and this pathway was involved in immune signaling to active the diverse downstream reaction including anti-oxidant, anti-bacteria and apoptosis.
authors.affiliation: The Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, 7 Nanhai Rd., Qingdao 266071, Shandong, China.
authors.forename: Mengqiang
authors.initials: M
authors.lastname: Wang
authors.forename: Jialong
authors.initials: J
authors.lastname: Yang
authors.forename: Zhi
authors.initials: Z
authors.lastname: Zhou
authors.forename: Limei
authors.initials: L
authors.lastname: Qiu
authors.forename: Lingling
authors.initials: L
authors.lastname: Wang
authors.forename: Huan
authors.initials: H
authors.lastname: Zhang
authors.forename: Yang
authors.initials: Y
authors.lastname: Gao
authors.forename: Xingqiang
authors.initials: X
authors.lastname: Wang
authors.forename: Li
authors.initials: L
authors.lastname: Zhang
authors.forename: Jianmin
authors.initials: J
authors.lastname: Zhao
authors.forename: Linsheng
authors.initials: L
authors.lastname: Song
mesh_terms: D000818:Animals; D049897:Pectinidae / Q000276:immunology* / Q000378:metabolism*; D034622:RNA Interference; D015398:Signal Transduction; D051193:Toll-Like Receptors / Q000276:immunology* / Q000378:metabolism
chemical_list: D051193:Toll-Like Receptors