Horizontal gene transfer as the source of evolutionary innovation in eukaryotes

项目总结 水平基因转移(HGT)代表了细菌进化的主导力量，但它在塑造 真核生物基因组的进化过程一直是一个激烈争论的主题。Bdelloidae类的 轮虫门，一个大型的无脊椎动物分类群，包括近500个描述的物种，到目前为止经受住了任何 挑战质疑它们基因组中报告的大量来自非后生动物来源的HGT， 并且仍然是后生动物中外源基因比例的纪录保持者，HGT 候选序列至少占所有编码序列的8%。他们中的许多人都获得了剪接体内含子 并以四重组的形式出现，这表明它们在超过6000万年的全基因组复制之前到来 在蜈蚣类的共同祖先中。另一些则明显代表较新的生物，缺乏内含子和 倾向于亚端粒定位，可能达不到固定。同时能够捕获和保留外国 基因是蜈蚣血统的显著特征，因为它与姊妹系不同。 类，但还没有系统地分析它随时间的连续动态，因为 与核心基因组相比，远端染色体区域不完整。古老的HGT事件， 可被认为是在整个蜈蚣进化过程中通过净化选择而维持的 对于整个分类群来说，这是有选择的优势，然而，它们的分子功能并不总是被推断出来 仅是同源性的基础。在这项建议中，我们寻求调查最近和古代的HGT病例，在 聚合和单独。预计将在目标1中一瞥最近HGT病例的全人群分布 发现它们在适应饮食偏好或有毒物质等过程中的短期适应价值 在不断变化的环境中获取物质，并阐明它们最近获得的机制。深入了解 分别在目标2和目标3中探讨从细菌和真菌中建立的古代HGT事件的分类群范围， 应该澄清这些收购对蜈蚣的价值以及它们在进化历史上的足迹，通过 聚焦于这些蛋白质在不同类群中功能作用的分子基础，包括 致病真菌，其中一些基因可能代表治疗靶点。

PROJECT SUMMARY Horizontal gene transfer (HGT) represents a dominant force in bacterial evolution, however its role in shaping the evolutionary processes in eukaryotic genomes has been a subject of intense debate. Class Bdelloidea of the phylum Rotifera, a large invertebrate taxon comprising close to 500 described species, has so far withstood any challenges questioning the massive amounts of HGT from non-metazoan sources reported in their genomes, and remain the record-holders among Metazoa with regard to the proportion of foreign genes, with HGT candidates comprising at least 8% of all coding sequences. Many of them have acquired spliceosomal introns and occur in quartets, which is indicative of their arrival prior to whole-genome duplication over 60 million years ago in the common ancestor of bdelloids. Others apparently represent more recent arrivals, lacking introns and favoring subtelomeric localization, and may not reach fixation. While the ability to capture and retain foreign genes has been the distinguishing characteristic of the bdelloid lineage since its divergence from the sister classes, its continuous dynamics over time has not been analyzed in a systematic fashion, due to the incompleteness of distal chromosome regions in comparison with the core genome. The ancient HGT events, which have been maintained by purifying selection throughout the course of bdelloid evolution, can be regarded as selectively advantageous for the entire taxon, however their molecular function cannot always be inferred on the basis of homology alone. In this proposal, we seek to investigate both recent and ancient HGT cases, in aggregate and individually. A glimpse into population-wide distribution of recent HGT cases in Aim 1 is expected to uncover their short-term adaptive value in processes such as adaptation to dietary preferences or toxic substances in changing environments and shed light on the mechanisms of their recent acquisition. An in-depth look into taxon-wide establishment of ancient HGT events from bacteria and fungi, in Aims 2 and 3 respectively, should clarify the value of these acquisitions for bdelloids and their footprint on their evolutionary history, by zeroing in on molecular underpinnings of the functional role of these proteins in diverse taxa, including pathogenic fungi where some of these genes may represent therapeutic targets.