title: Identification and characterization of a novel Toll-like receptor 2 homologue in the large yellow croaker Larimichthys crocea.
abstract: Toll-like receptors (TLRs) are key components of innate immunity that play significant roles in immune defence against pathogen invasion. In the present study, we identified a novel TLR2 homologue (LycTLR2b) in large yellow croaker (Larimichthys crocea) that shared low sequence identity with the previously reported large yellow croaker TLR2 (tentatively named LycTLR2a). The full-length cDNA of LycTLR2b was 2926 nucleotides (nt) long and encoded a protein consisting of 797 amino acids (aa). The deduced LycTLR2b protein exhibited a typical TLR domain architecture including a signal peptide, seven leucine-rich repeats (LRRs) in the extracellular region, a transmembrane domain, and a Toll-Interleukin 1 receptor (TIR) domain in the cytoplasmic region. Phylogenetic analysis showed that both LycTLR2a and LycTLR2b fall into a major clade formed by all TLR2 sequences, and are divided into two distinct branches. Genomic organization revealed that the LycTLR2b gene lacks intron, which is similar to zebrafish and human TLR2 genes, whereas the LycTLR2a gene contains multiple introns, as found in damselfish TLR2a and Fugu TLR2 genes. Syntenic analysis suggested that the occurrence of LycTLR2a and LycTLR2b may result from a relatively recent genome duplication event. LycTLR2b mRNA was constitutively expressed in all tissues examined although at different levels. Following bacterial vaccine challenge, LycTLR2b expression levels were significantly up-regulated in both spleen and head kidney tissues. Taken together, these results indicated that two different TLR2 homologues, which may play roles in antibacterial immunity, exist in large yellow croaker.
authors.affiliation: Key Laboratory of Marine Biogenetic Resources, Third Institute of Oceanography, State Oceanic Administration, Xiamen 361005, PR China; Fujian Collaborative Innovation Center for Exploitation and Utilization of Marine Biological Resources, Xiamen 361005, PR China; Collaborative Innovation Center of Deep Sea Biology, Third Institute of Oceanography, State Oceanic Administration, Daxue Road 178, Xiamen 361005, PR China.
authors.forename: Jingqun
authors.initials: J
authors.lastname: Ao
authors.affiliation: Key Laboratory of Marine Biogenetic Resources, Third Institute of Oceanography, State Oceanic Administration, Xiamen 361005, PR China; Fujian Collaborative Innovation Center for Exploitation and Utilization of Marine Biological Resources, Xiamen 361005, PR China; Collaborative Innovation Center of Deep Sea Biology, Third Institute of Oceanography, State Oceanic Administration, Daxue Road 178, Xiamen 361005, PR China.
authors.forename: Yinnan
authors.initials: Y
authors.lastname: Mu
authors.affiliation: Key Laboratory of Marine Biogenetic Resources, Third Institute of Oceanography, State Oceanic Administration, Xiamen 361005, PR China; Fujian Collaborative Innovation Center for Exploitation and Utilization of Marine Biological Resources, Xiamen 361005, PR China; Collaborative Innovation Center of Deep Sea Biology, Third Institute of Oceanography, State Oceanic Administration, Daxue Road 178, Xiamen 361005, PR China.
authors.forename: Kunru
authors.initials: K
authors.lastname: Wang
authors.affiliation: Key Laboratory of Marine Biogenetic Resources, Third Institute of Oceanography, State Oceanic Administration, Xiamen 361005, PR China; Fujian Collaborative Innovation Center for Exploitation and Utilization of Marine Biological Resources, Xiamen 361005, PR China; Collaborative Innovation Center of Deep Sea Biology, Third Institute of Oceanography, State Oceanic Administration, Daxue Road 178, Xiamen 361005, PR China.
authors.forename: Min
authors.initials: M
authors.lastname: Sun
authors.affiliation: Key Laboratory of Marine Biogenetic Resources, Third Institute of Oceanography, State Oceanic Administration, Xiamen 361005, PR China; Fujian Collaborative Innovation Center for Exploitation and Utilization of Marine Biological Resources, Xiamen 361005, PR China; Collaborative Innovation Center of Deep Sea Biology, Third Institute of Oceanography, State Oceanic Administration, Daxue Road 178, Xiamen 361005, PR China.
authors.forename: Xianhui
authors.initials: X
authors.lastname: Wang
authors.affiliation: Key Laboratory of Marine Biogenetic Resources, Third Institute of Oceanography, State Oceanic Administration, Xiamen 361005, PR China; Fujian Collaborative Innovation Center for Exploitation and Utilization of Marine Biological Resources, Xiamen 361005, PR China; Collaborative Innovation Center of Deep Sea Biology, Third Institute of Oceanography, State Oceanic Administration, Daxue Road 178, Xiamen 361005, PR China. Electronic address: chenxinhua@tio.org.cn.
authors.forename: Xinhua
authors.initials: X
authors.lastname: Chen
mesh_terms: D000333:Aeromonas / Q000276:immunology; D000818:Animals; D001428:Bacterial Vaccines / Q000276:immunology; D029941:Fish Proteins / Q000235:genetics / Q000276:immunology; D060226:Head Kidney / Q000276:immunology; D010473:Perciformes / Q000235:genetics / Q000276:immunology; D013154:Spleen / Q000276:immunology; D051195:Toll-Like Receptor 2 / Q000235:genetics / Q000276:immunology; D015164:Vaccines, Inactivated / Q000276:immunology; D014733:Vibrio / Q000276:immunology
chemical_list: D001428:Bacterial Vaccines; D029941:Fish Proteins; D051195:Toll-Like Receptor 2; D015164:Vaccines, Inactivated
keywords: Gene expression patterns; Large yellow croaker (Larimichthys crocea); Syntenic analysis; Toll-like receptor 2