Data_Sheet_1_Divergent Evolution of TRC Genes in Mammalian Niche Adaptation.zip

Mammals inhabit a wide variety of ecological niches, which in turn can be affected by various ecological factors, especially in relation to immunity. The canonical TRC repertoire (TRAC, TRBC, TRGC, and TRDC) codes C regions of T cell receptor chains that form the primary antigen receptors involved in the activation of cellular immunity. At present, little is known about the correlation between the evolution of mammalian TRC genes and ecological factors. In this study, four types canonical of TRC genes were identified from 37 mammalian species. Phylogenetic comparative methods (phyANOVA and PGLS) and selective pressure analyses among different groups of ecological factors (habitat, diet, and sociality) were carried out. The results showed that habitat was the major ecological factor shaping mammalian TRC repertoires. Specifically, trade-off between TRGC numbers and positive selection of TRAC and the balanced evolutionary rates between TRAC and TRDC genes were speculated as two main mechanisms in adaption to habitat and sociality. Overall, our study suggested divergent mechanisms for the evolution of TRCs, prompting mammalian immunity adaptions within diverse niches.

哺乳动物栖息于多种多样的生态位中，而其生态位亦会受到各类生态因素的调控，其中与免疫相关的因素尤为关键。经典TRC基因库（TRAC、TRBC、TRGC及TRDC）编码T细胞受体（T cell receptor）链的恒定区，该恒定区是构成细胞免疫激活过程中核心抗原受体的关键组分。目前，学界对哺乳动物TRC基因的演化与生态因素之间的关联尚缺乏深入认知。本研究从37个哺乳动物物种中鉴定出4类经典TRC基因，采用系统发育比较方法（phyANOVA与系统发育广义最小二乘法PGLS），并针对不同生态因素类群（栖息地、食性及社会性）开展了选择压力分析。结果显示，栖息地是塑造哺乳动物TRC基因库的主要生态因素。具体而言，研究推测TRGC基因数量与TRAC基因正选择之间的权衡效应，以及TRAC与TRDC基因间的演化速率平衡，是哺乳动物适应栖息地与社会性的两大核心机制。综上，本研究揭示了TRC基因演化的多样化机制，助力哺乳动物在多样生态位中实现免疫适应性演化。