Identification and expression analysis of a TLR11 family gene in the sea urchin Strongylocentrotus intermedius

In this study, a homolog of the TLR11 family gene from the sea urchin Strongylocentrotus intermedius (denoted as SiTLR11) was cloned and characterized. The full-length cDNA of SiTLR11 was 2096-bp long, which included 43 bp of 5' untranslated region (UTR), 238 bp of 3' UTR, and a putative open reading frame of 1815 bp encoding a polypeptide of 604 amino acid residues. Representative domains such as leucine-rich repeat (LRR) (residues 108-249) and a cytoplasmic Toll-interleukin-1 receptor (TIR) (residues 429-571) domains were detected in the predicted amino acid sequence of SiTLR11. SiTLR11 transcript was widely distributed in all the tested tissues, including intestine, tube feet, gonad, coelomocytes, and peristomial membrane, with the highest expression level in the coelomocytes and peristomial membrane. After the sea urchin was injected with polyinosinic:polycytidylic acid (PolyI:C), the expression level of SiTLR11 in the coelomocytes increased significantly, reaching 1.96-fold the level of the control at 12 h, but decreased to level below that of control at 24 and 48 h. Injection of peptidoglycan (PGN) also led to increased expression of SiTLR11, which peaked at 12 h, yielding an increase of 2.19-fold compared to the control group, and continued to increase at 24 and 48 h. However, almost no differences in immunological activity were found in the groups challenged with lipopolysaccharides (LPS), Zymosan A (ZOA), or Vibrio fortis compared to the control. Taken together, the results strongly suggested that SiTLR11 was functionally involved in the immune response triggered by double-stranded RNA (dsRNA) viruses and Gram-positive bacteria.