Orange-spotted grouper (Epinephelus coioides) toll-like receptor 22: molecular characterization, expression pattern and pertinent signaling pathways.
The toll-like receptors (TLRs) are an important gene family in host innate immunologic surveillance. The TLR22 gene is an essential member of the TLRs that is only found in aquatic animals and has been detected in some bony fish. Here, a TLR22 homolog, EcTLR22, was characterized in the orange-spotted grouper (Epinephelus coioides) via homology cloning. The 3321 bp full-length cDNA sequence of EcTLR22 was obtained, which included an open reading frame of 2880 bp encoding a putative peptide of 960 amino acids containing three highly typical domains with the characteristics of TLR family members. The deduced amino acid sequence of EcTLR22 showed a relatively high similarity to flounder TLR22. Phylogenetic analysis showed that the orange-spotted grouper TLR22 sequence was clustered with those of Perciforme, such as flounder and croaker. Real-time quantitative PCR analysis revealed broad expression of EcTLR22, with relatively high expression detected in the head kidney, trunk kidney, spleen, peripheral blood leukocytes (PBLs) and heart of orange-spotted grouper. After injection with Vibrio alginolyticus, there was significant up-regulation of the expression of EcTLR22 in the spleen. In evaluating unstimulated/stimulated head kidney leukocytes and spleen leukocytes, a significant increase in EcTLR22 mRNA expression was detected, which implied a sensitive immune response. Furthermore, four important molecules for signal transduction, MyD88, TRIF, TNF-α and IRF3, were chosen to analyze the role of the EcTLR22 signaling pathway in anti-pathogen responses. Upon LPS or Poly I:C challenge, expression of the four genes was induced, with an increasing tendency detected in head kidney leukocytes, suggesting that the four genes might work with EcTLR22 in host defense against pathogenic microbes.
State Key Laboratory of Biocontrol, Institute of Aquatic Economic Animals, College of Life Sciences, Sun Yat-Sen-Zhongshan University, Guangzhou 510275, People's Republic of China.
Xu
X
Ding
Dan-qi
DQ
Lu
Qing-hua
QH
Hou
Shui-sheng
SS
Li
Xiao-chun
XC
Liu
Yong
Y
Zhang
Hao-ran
HR
Lin
D000595:Amino Acid Sequence; D000818:Animals; D001492:Bass / Q000235:genetics* / Q000378:metabolism* / Q000382:microbiology; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000235:genetics / Q000378:metabolism; D029941:Fish Proteins / Q000737:chemistry / Q000235:genetics* / Q000276:immunology / Q000378:metabolism*; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D008070:Lipopolysaccharides / Q000494:pharmacology; D009928:Organ Specificity; D010802:Phylogeny; D011070:Poly I-C / Q000008:administration & dosage; D060888:Real-Time Polymerase Chain Reaction; D017385:Sequence Homology; D015398:Signal Transduction; D051193:Toll-Like Receptors / Q000737:chemistry / Q000235:genetics* / Q000276:immunology / Q000378:metabolism*; D044149:Vibrio alginolyticus / Q000502:physiology
D018076:DNA, Complementary; D029941:Fish Proteins; D008070:Lipopolysaccharides; D051193:Toll-Like Receptors; D011070:Poly I-C