Data from: Signatures of selection acting on the innate immunity gene Toll-like receptor 2 (TLR2) during the evolutionary history of rodents

Patterns of selection acting on immune defence genes have recently been the focus of considerable interest. Yet, when it comes to vertebrates, studies have mainly focused on the acquired branch of the immune system. Consequently, the direction and strength of selection acting on genes of the vertebrate innate immune defence remain poorly understood. Here, we present a molecular analysis of selection on an important receptor of the innate immune system of vertebrates, the Toll-like receptor 2 (TLR2), across 17 rodent species. Although purifying selection was the prevalent evolutionary force acting on most parts of the rodent TLR2, we found that codons in close proximity to pathogen-binding and TLR2–TLR1 heterodimerization sites have been subject to positive selection. This indicates that parasite-mediated selection is not restricted to acquired immune system genes like the major histocompatibility complex, but also affects innate defence genes. To obtain a comprehensive understanding of evolutionary processes in host–parasite systems, both innate and acquired immunity thus need to be considered.

作用于免疫防御基因的选择模式，近来已成为学界广泛关注的研究热点。然而针对脊椎动物的相关研究，长期以来主要聚焦于免疫系统的获得性免疫分支。因此，针对脊椎动物先天免疫防御基因的选择作用方向与强度，目前仍鲜有清晰认知。本研究针对17种啮齿类动物，对脊椎动物先天免疫系统的重要受体Toll样受体2（Toll-like receptor 2, TLR2）所受的选择压力展开分子层面分析。尽管在啮齿类TLR2的大部分区域，纯化选择是占主导的进化压力，但我们发现，紧邻病原体结合位点与TLR2-TLR1异二聚化位点的密码子，受到了正选择作用。这表明，寄生虫介导的选择压力并非仅局限于主要组织相容性复合体（major histocompatibility complex, MHC）这类获得性免疫基因，同样也会作用于先天防御基因。因此，若要全面解析宿主-寄生虫互作系统中的进化过程，就必须同时兼顾先天免疫与获得性免疫两个维度。