Horizontal gene transfer as the source of evolutionary innovation in eukaryotes

项目摘要 水平基因转移（HGT）代表了细菌进化中的主导力量，但它在塑造细菌中的作用是非常重要的。 真核生物基因组的进化过程一直是激烈争论的主题。蛭总科 轮虫门是一个大型的无脊椎动物分类单元，包括近500个描述的物种，迄今为止已经经受住了任何 质疑在其基因组中报告的来自非后生动物来源的大量HGT的挑战， 并且保持了后生动物中外源基因比例的记录保持者，HGT 候选者包括所有编码序列的至少8%。它们中的许多已经获得剪接体内含子 并且以四联体的形式出现，这表明它们在6000万年前的全基因组复制之前就已经出现了。 在蛭形类动物的共同祖先中。另一些显然代表了更近的到来，缺乏内含子， 有利于亚端粒定位，并且可能达不到固定。虽然捕捉和留住外国人的能力 自从与姐妹谱系分歧以来，基因一直是蛭形谱系的显着特征 类，其随时间的连续动态尚未以系统的方式进行分析，由于 与核心基因组相比，远端染色体区域不完整。古老的HGT事件， 在蛭形动物进化的整个过程中， 对于整个分类群是选择性有利的，然而，它们的分子功能并不总是根据 仅仅是同源性的基础。在这个建议中，我们试图调查最近和古代的HGT案件， 总体和个人。希望能对Aim 1中最近HGT病例的全人群分布情况有所了解 揭示它们在适应饮食偏好或毒性等过程中的短期适应价值， 物质在不断变化的环境中，并阐明其最近收购的机制。深入 分别在目标2和目标3中研究细菌和真菌的古HGT事件的分类群范围建立， 应该澄清这些收购的价值蛭类及其足迹对他们的进化历史， 将注意力集中在这些蛋白质在不同分类群中的功能作用的分子基础上，包括 病原真菌，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.