title: Cloning and expression analysis of a Toll-like receptor 22 (tlr22) gene from turbot, Scophthalmus maximus.
abstract: Toll-like receptor 22 (TLR22) exists exclusively in aquatic animals and recognizes double stranded RNA (dsRNA). In the present study, a tlr22 gene and its 5'-flanking sequence were cloned from turbot, Scophthalmus maximus, its immune responsive expression was subsequently studied in vivo. The turbot (sm)tlr22 gene spans over 5.6 kb with a structure of 4 exon-3 intron and encodes 962 amino acids. The deduced protein shows the highest sequence identity (76.7%) to Japanese flounder Tlr22 and possesses a signal peptide sequence, a leucine-rich repeat (LRR) domain composed of 27 LRR motifs, a transmembrane region and a Toll/interleukin-1 receptor (TIR) domain. Phylogenetic analysis grouped it with other teleost Tlr22s. The interferon-stimulated response element (ISRE) and signal transducer and activator of transcription (STAT) binding site important for the basal transcriptional activity of TLR3 were predicted in the 5'-flanking sequence of smtlr22 gene. Quantitative real-time PCR (qPCR) analysis demonstrated the constitutive expression of smtlr22 mRNA in all examined tissues with higher levels in the head kidney, kidney and spleen. Further, smtlr22 expression was significantly up-regulated following challenge with polyinosinic: polycytidylic acid (poly I:C), lipopolysaccharide (LPS) or turbot reddish body iridovirus (TRBIV) in the gills, head kidney, spleen and muscle, with maximum increases ranging from 2.56 to 6.24 fold upon different immunostimulants and organs. These findings suggest a possible role of Smtlr22 in the immune responses to the infections of a broad range of pathogens that include DNA and RNA viruses and Gram-negative bacteria.
authors.affiliation: College of Marine Life Sciences, Ocean University of China, Qingdao 266003, China; Institute of Evolution & Marine Biodiversity, Ocean University of China, Qingdao 266003, China. Electronic address: huguobin@mail.ouc.edu.cn.
authors.forename: Guo-Bin
authors.initials: GB
authors.lastname: Hu
authors.affiliation: College of Marine Life Sciences, Ocean University of China, Qingdao 266003, China.
authors.forename: Shou-Feng
authors.initials: SF
authors.lastname: Zhang
authors.affiliation: College of Marine Life Sciences, Ocean University of China, Qingdao 266003, China.
authors.forename: Xi
authors.initials: X
authors.lastname: Yang
authors.affiliation: First Institute of Oceanography, State Oceanic Administration of China, Qingdao 266061, China.
authors.forename: Da-Hai
authors.initials: DH
authors.lastname: Liu
authors.affiliation: College of Marine Life Sciences, Ocean University of China, Qingdao 266003, China.
authors.forename: Qiu-Ming
authors.initials: QM
authors.lastname: Liu
authors.affiliation: College of Marine Life Sciences, Ocean University of China, Qingdao 266003, China; Institute of Evolution & Marine Biodiversity, Ocean University of China, Qingdao 266003, China.
authors.forename: Shi-Cui
authors.initials: SC
authors.lastname: Zhang
mesh_terms: D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D005412:Flatfishes / Q000235:genetics* / Q000276:immunology*; D040461:Gene Components; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation / Q000502:physiology*; D005880:Gills / Q000821:virology; D017994:Iridovirus; D008070:Lipopolysaccharides; D008969:Molecular Sequence Data; D010802:Phylogeny; D011070:Poly I-C; D060888:Real-Time Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D017385:Sequence Homology; D051193:Toll-Like Receptors / Q000235:genetics* / Q000378:metabolism*
chemical_list: D008070:Lipopolysaccharides; D051193:Toll-Like Receptors; D011070:Poly I-C
keywords: Gene expression; PAMPs; Scophthalmus maximus; Structural characteristics; Tlr22