Abstract：
The yellow catfish (Pelteobagrus fulvidraco) is one of the most economically important freshwater species in Asia. However, pathogenic bacterial infections often cause high rates of mortality and economic losses in practical aquaculture. Previous studies in mammals have shown that Toll-like receptor 2 (TLR2) and Toll-like receptor 5 (TLR5) are involved in the recognition of cell wall components such as lipopolysaccharides and flagella of various bacteria, thereby acting as key regulators in the innate immunity response. However, TLR2 and TLR5 in yellow catfish have not been characterized. In the present study, TLR2 and TLR5 were examined through comparative genomic approaches. The gene structure, collinearity, protein spatial structure, and phylogenetic relationships were compared with those in multiple representative vertebrates. Meanwhile, quantitative real-time PCR was conducted to explore transcriptional changes in TLR2 and TLR5 in immune tissues after infection with exogenous A. hydrophila and E. tarda. The results demonstrated the presence of TLR2 and TLR5 in yellow catfish. However, a systematic analysis showed that TLR2 was not associated with the arrangement of diverse neighboring genes. The expression of hybrid yellow catfish TLR2 transcripts in multiple tissues (including liver, spleen, kidney, and intestine) was significantly up-regulated after infection with A. hydrophila and E. tarda, suggesting that hybrid yellow catfish TLR2 and TLR5 may participate in the immune process. Taken together, the results indicate that TLR2 and TLR5 are conserved in terms of evolution and possess significant antibacterial activity as well as regulatory properties in immune-related tissues and thus play key roles in host defense against pathogen invasion.
摘要：
黄cat鱼（Pelteobagrusfulvidraco）是亚洲经济上最重要的淡水物种之一。然而,在实际水产养殖中，病原菌感染往往会导致高死亡率和经济损失。先前在哺乳动物中的研究表明，Toll样受体2（TLR2）和Toll样受体5（TLR5）参与识别细胞壁成分，例如各种细菌的脂多糖和鞭毛，从而充当先天免疫反应的关键调节因子。然而,黄鲶鱼中的TLR2和TLR5尚未被表征。在本研究中,通过比较基因组方法检查TLR2和TLR5。基因结构，共线性,蛋白质空间结构，并将系统发育关系与多个代表性脊椎动物的系统发育关系进行了比较。同时,采用实时定量PCR方法研究外源性嗜水菌和大肠杆菌感染后免疫组织中TLR2和TLR5的转录变化。结果证明了TLR2和TLR5在黄鲶鱼中的存在。然而,系统分析显示TLR2与不同邻近基因的排列无关。杂交黄鲶鱼TLR2转录本在多个组织(包括肝脏、脾,脾肾,和肠）在感染嗜水菌和大肠杆菌后显著上调，提示杂交黄鲶鱼TLR2和TLR5可能参与免疫过程。一起来看,结果表明，TLR2和TLR5在进化方面是保守的，并且在免疫相关组织中具有显着的抗菌活性和调节特性，因此在宿主防御病原体入侵中起关键作用。
