Oliveira Tatiana Maia de, Burlamaqui Tibério Cesar Tortola, Sá André Luiz Alves de, Breaux Breanna, Luna Fábia de Oliveira, Attademo Fernanda Löffler Niemeyer, Klautau Alex Garcia Cavalleiro de Macedo, Oliveira Jairo Moura, Sena Leonardo, Criscitiello Michael F, Schneider Maria Paula Cruz
Universidade Federal do Pará, Instituto de Ciências Biológicas, Belém, PA, Brazil.
Universidade Federal Rural da Amazônia, Instituto Socioambiental e dos Recursos Hídricos, Laboratório de Genética Aplicada, Belém, PA, Brazil.
Genet Mol Biol. 2021 Apr 9;44(2):e20190252. doi: 10.1590/1678-4685-GMB-2019-0252. eCollection 2021.
Amazonian (Trichechus inunguis) and West Indian (Trichechus manatus) manatees are aquatic mammals vulnerable to extinction found in the Amazon basin and the coastal western Atlantic. Toll-like receptors (TLR) play a key role in recognizing pathogen-associated molecular patterns using leucine-rich repeats (LRRs). We described the diversity of TLR4 and TLR8 genes in these two species of manatee. Amazonian manatee showed seven SNPs in TLR4 and the eight in TLR8, while West Indian manatee shared four and six of those SNPs, respectively. In our analysis, TLR4 showed one non-conservative amino acid replacement substitution in LRR7 and LRR8, on the other hand, TLR8 was less variable and showed only conserved amino acid substitutions. Selection analysis showed that only one TLR4 site was subjected to positive selection and none in TLR8. TLR4 in manatees did not show any evidence of convergent evolution compared to species of the cetacean lineage. Differences in TLR4 and TLR8 polymorphism may be related to distinct selection by pathogens, population reduction of West Indian manatees, or an expected consequence of population expansion in Amazonian manatees. Future studies combining pathogen association and TLR polymorphism may clarify possible roles of these genes and be used for conservation purposes of manatee species.
亚马逊海牛（Trichechus inunguis）和西印度海牛（Trichechus manatus）是生活在亚马逊盆地和西大西洋沿岸的易濒危水生哺乳动物。Toll样受体（TLR）利用富含亮氨酸的重复序列（LRR）在识别病原体相关分子模式中起关键作用。我们描述了这两种海牛中TLR4和TLR8基因的多样性。亚马逊海牛在TLR4中有7个单核苷酸多态性（SNP），在TLR8中有8个SNP，而西印度海牛分别有其中的4个和6个SNP。在我们的分析中，TLR4在LRR7和LRR8中显示出一个非保守氨基酸替换，另一方面，TLR8的变异性较小，仅显示保守氨基酸替换。选择分析表明，只有一个TLR4位点受到正选择，而TLR8中没有。与鲸类谱系的物种相比，海牛的TLR4没有显示出任何趋同进化的证据。TLR4和TLR8多态性的差异可能与病原体的不同选择、西印度海牛种群减少或亚马逊海牛种群扩张的预期结果有关。未来结合病原体关联和TLR多态性的研究可能会阐明这些基因的可能作用，并用于海牛物种的保护目的。
