Laboratory for Marine Living Resources and Molecular Engineering, College of Marine Science, Zhejiang Ocean University, Zhoushan 316000, PR China.
Fish Shellfish Immunol. 2013 Jan;34(1):119-28. doi: 10.1016/j.fsi.2012.10.008. Epub 2012 Oct 13.
Toll-like receptor 2 (TLR2) is a member of an ancient pattern recognition receptor family, conserved from insects to mammals and it is best known as a receptor for recognizing conserved components of Gram-positive bacteria. In present study, the genomic structure of TLR2 gene from miiuy croaker was identified and characterized. It comprises twelve exons and eleven introns. The lengths of exons 3 to 10 of miiuy croaker TLR2 and exons 2 to 9 of fugu and pufferfish TLR2 are exactly the same, but most importantly, both of fugu and pufferfish have only eleven exons and ten introns. An intron insert event probably happened on exon 1 of miiuy croaker TLR2 after its divergence from ancestor of zebrafish, and an intron loss event probably happened on those of Tetraodontiformes TLR2 after the divergence with ancestor of miiuy croaker. Our study showed the direct evidence and strongly supported the intron insert and loss on fish TLR2. The pathogen injection experiments indicated that TLR2 might not be an important responder to Gram-negative bacteria in miiuy croaker. Molecular evolutionary analyses indicated TLR2 genes were under strong purifying selection pressure, showing a quite strong functional constraint in both of fish and mammals, despite of their distinct living environment conditions.
Toll 样受体 2（TLR2）是古老的模式识别受体家族的成员，从昆虫到哺乳动物都有保守，它最著名的是识别革兰氏阳性菌的保守成分的受体。在本研究中，鉴定并表征了米氏黄鱼 TLR2 基因的基因组结构。它包含十二个外显子和十一个内含子。米氏黄鱼 TLR2 的外显子 3 到 10 和河豚和翻车鱼 TLR2 的外显子 2 到 9 的长度完全相同，但最重要的是，河豚和翻车鱼都只有十一个外显子和十个内含子。米氏黄鱼 TLR2 的外显子 1 可能在其与斑马鱼祖先分化后发生了内含子插入事件，而 Tetraodontiformes TLR2 的内含子丢失事件可能在其与米氏黄鱼祖先分化后发生。我们的研究提供了鱼类 TLR2 发生内含子插入和缺失的直接证据，并提供了有力支持。病原体注射实验表明，TLR2 可能不是米氏黄鱼中革兰氏阴性菌的重要应答者。分子进化分析表明，TLR2 基因受到强烈的净化选择压力，尽管它们生活在不同的环境条件下，但在鱼类和哺乳动物中都表现出很强的功能约束。
