The Order Chiroptera comprises more than 1,400 species, each with its evolutionary history and under unique selective pressures, among which are the host–pathogen interactions. Bats have coped with complex interactions with a broad spectrum of microbes throughout their evolutionary history, prompting the development of unique adaptations that allow them to co-exist with microbes with pathogenic potential more efficiently than other nonadapted species. In this sense, an extraordinary immune system with unique adaptations has been hypothesized in bats. To explore this, we focused on the major histocompatibility complex (MHC), which plays a crucial role in pathogen recognition and presentation to T cells to trigger the adaptive immune response. We analyzed MHC class I transcripts in five species, each from different families of New World bats. From RNA-seq data, we assembled a partial region of the MHC-I comprising the α1 and α2 domains, which are responsible for peptide binding and recognition. We described five putative functional variants, two of which have two independent insertions at the α2 domain. Our results suggest that this insertion appeared after the divergence of the order Chiroptera and may have an adaptive function in the defense against intracellular pathogens, providing evidence of positive selection and trans-specific polymorphism on the peptide-binding sites.

中文翻译：

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转录组学分析阐明了新热带蝙蝠主要组织相容性复合物 I 类的进化

翼手目包括 1,400 多个物种，每个物种都有其进化历史并处于独特的选择压力下，其中包括宿主-病原体相互作用。蝙蝠在其整个进化历史中一直在应对与广泛微生物的复杂相互作用，这促使它们发展出独特的适应性，使它们能够比其他不适应的物种更有效地与具有致病潜力的微生物共存。从这个意义上说，已经在蝙蝠中假设了一种具有独特适应性的非凡免疫系统。为了探索这一点，我们专注于主要组织相容性复合物 (MHC)，它在病原体识别和呈递给 T 细胞以触发适应性免疫反应中起着至关重要的作用。我们分析了五个物种的 MHC I 类转录物，每个物种来自不同的新大陆蝙蝠家族。从 RNA-seq 数据中，我们组装了 MHC-I 的部分区域，包括负责肽结合和识别的 α1 和 α2 结构域。我们描述了五个推定的功能变体，其中两个在 α2 域有两个独立的插入。我们的研究结果表明，这种插入出现在翼翅目分化之后，并且可能在防御细胞内病原体方面具有适应性功能，为肽结合位点的正选择和反式特异性多态性提供了证据。