Evolutionary Genomics of Prokaryotic Viruses

Evolutionary history of biological entities is recorded within their nucleic acid sequences and can (sometimes) be deciphered by thorough genomic analysis. In this study we sought to gain insights into the diversity and evolution of bacterial and archaeal viruses. Our primary interest was pointed towards those virus groups/families for which comprehensive genomic analysis was not previously possible due to the lack of sufficient amount of genomic data. During the course of this work twenty-five putative proviruses integrated into various prokaryotic genomes were identified, enabling us to undertake a comparative genomics approach. This analysis allowed us to test the previously formulated evolutionary hypotheses and also provided valuable information on the molecular mechanisms behind the genome evolution of the studied virus groups.

Evolutionary genomics of the Fox genes: origin of gene families and the ancestry of gene clusters

Over the past decade genomic approaches have begun to revolutionise the study of animal diversity. In particular, genome sequencing programmes have spread beyond the traditional model species to encompass an increasing diversity of animals from many different phyla, as well as unicellular eukaryotes that are closely related to the animals. Whole genome sequences allow researchers to establish, with reasonable confidence, the full complement of any particular family of genes in a genome. Comparison of gene complements from appropriate genomes can reveal the evolutionary history of gene families, indicating when both gene diversification and gene loss have occurred. More than that, however, assembled genomes allow the genomic environment in which individual genes are found to be analysed and compared between species. This can reveal how gene diversification occurred. Here, we focus on the Fox genes, drawing from multiple animal genomes to develop an evolutionary framework explaining the timing and mechanism of origin of the diversity of animal Fox genes. Ancient linkages between genes are a prominent feature of the Fox genes, depicting a history of gene clusters, some of which may be relevant to understanding Fox gene function.

Evolutionary Genomics and Conservation of the Endangered Przewalski's Horse.

Przewalski's horses (PHs, Equus ferus ssp. przewalskii) were discovered in the Asian steppes in the 1870s and represent the last remaining true wild horses. PHs became extinct in the wild in the 1960s but survived in captivity, thanks to major conservation efforts. The current population is still endangered, with just 2,109 individuals, one-quarter of which are in Chinese and Mongolian reintroduction reserves [1]. These horses descend from a founding population of 12 wild-caught PHs and possibly up to four domesticated individuals [2-4]. With a stocky build, an erect mane, and stripped and short legs, they are phenotypically and behaviorally distinct from domesticated horses (DHs, Equus caballus). Here, we sequenced the complete genomes of 11 PHs, representing all founding lineages, and five historical specimens dated to 1878-1929 CE, including the Holotype. These were compared to the hitherto-most-extensive genome dataset characterized for horses, comprising 21 new genomes. We found that loci showing the most genetic differentiation with DHs were enriched in genes involved in metabolism, cardiac disorders, muscle contraction, reproduction, behavior, and signaling pathways. We also show that DH and PH populations split ∼45,000 years ago and have remained connected by gene-flow thereafter. Finally, we monitor the genomic impact of ∼110 years of captivity, revealing reduced heterozygosity, increased inbreeding, and variable introgression of domestic alleles, ranging from non-detectable to as much as 31.1%. This, together with the identification of ancestry informative markers and corrections to the International Studbook, establishes a framework for evaluating the persistence of genetic variation in future reintroduced populations.

Evolutionary genomics of Staphylococcus aureus: Insights into the origin of methicillin-resistant strains and the toxic shock syndrome epidemic

An emerging theme in medical microbiology is that extensive variation exists in gene content among strains of many pathogenic bacterial species. However, this topic has not been investigated on a genome scale with strains recovered from patients with well-defined clinical conditions. Staphylococcus aureus is a major human pathogen and also causes economically important infections in cows and sheep. A DNA microarray representing >90% of the S. aureus genome was used to characterize genomic diversity, evolutionary relationships, and virulence gene distribution among 36 strains of divergent clonal lineages, including methicillin-resistant strains and organisms causing toxic shock syndrome. Genetic variation in S. aureus is very extensive, with ≈22% of the genome comprised of dispensable genetic material. Eighteen large regions of difference were identified, and 10 of these regions have genes that encode putative virulence factors or proteins mediating antibiotic resistance. We find that lateral gene transfer has played a fundamental role in the evolution of S. aureus. The mec gene has been horizontally transferred into distinct S. aureus chromosomal backgrounds at least five times, demonstrating that methicillin-resistant strains have evolved multiple independent times, rather than from a single ancestral strain. This finding resolves a long-standing controversy in S. aureus research. The epidemic of toxic shock syndrome that occurred in the 1970s was caused by a change in the host environment, rather than rapid geographic dissemination of a new hypervirulent strain. DNA microarray analysis of large samples of clinically characterized strains provides broad insights into evolution, pathogenesis, and disease emergence.

Introductory Editorial: Evolutionary Genomics

This supplement is intended to focus on evolutionary genomics. Evolutionary Bioinformatics aims to provide researchers working in this complex, quickly developing field with online, open access to highly relevant scholarly articles by leading international researchers. In a field where the literature is ever-expanding, researchers increasingly need access to up-to-date, high quality scholarly articles on areas of specific contemporary interest. This supplement aims to address this by presenting high-quality articles that allow readers to distinguish the signal from the noise. The editor in chief hopes that through this effort, practitioners and researchers will be aided in finding answers to some of the most complex and pressing issues of our time.

What are we missing about marine invasions? Filling in the gaps with evolutionary genomics

Research on invasion biology has been largely dominated by studies on the ecological effects of invasion events, although recently, evolutionary processes have been shown to be important to invasion success. This is largely attributed to novel genomic tools that provide new opportunities to unravel the natural history, taxonomy, and invasion pathways of invasive species, as well as the genetic basis of adaptive traits that allow them to expand within and beyond their native range. Despite these advances and the growing literature of genomic research on terrestrial pests, these tools have not been widely applied to marine invasive species. This is in part due to the perception that high levels of dispersal and connectivity in many invasive marine species can limit the opportunity for local adaptation. However, there is growing evidence that even in species with high dispersal potential, significant site-specific adaptation can occur. We review how these “omic” tools provide unprecedented opportunities to characterise the role of adaptive variation, physiological tolerance, and epigenetic processes in determining the success of marine invaders. Yet, rapid range expansion in invasions can confound the analysis of genomic data, so we also review how data should be properly analysed and carefully interpreted under such circumstances. Although there are a limited number of studies pioneering this research in marine systems, this review highlights how future studies can be designed to integrate ecological and evolutionary information. Such datasets will be imperative for the effective management of marine pests.

Convergence and divergence during the adaptation to similar environments by an Australian Groundsel

Adaptation to replicate environments is often achieved through similar phenotypic solutions. Whether selection also produces convergent genomic changes in these situations remains largely unknown. The variable groundsel, Senecio lautus, is an excellent system to investigate the genetic underpinnings of convergent evolution, because morphologically similar forms of these plants have adapted to the same environments along the coast of Australia. We compared range-wide patterns of genomic divergence in natural populations of this plant and searched for regions putatively affected by natural selection. Our results indicate that environmental adaptation followed complex genetic trajectories, affecting multiple loci, implying both the parallel recruitment of the same alleles and the divergence of completely different genomic regions across geography. An analysis of the biological functions of candidate genes suggests that adaptation to coastal environments may have occurred through the recruitment of different genes participating in similar processes. The relatively low genetic convergence that characterizes the parallel evolution of S. lautus forms suggests that evolution is more constrained at higher levels of biological organization.

新基因的从头起源与几种重要物种的进化基因组学研究

自然界丰富的生物多样性不断地激发着包括达尔文在内所有生物学家的研 究热情。自从达尔文进化论提出以来，进化生物学所要回答的一个基本问题就 是生物是如何从一个共同祖先进化到如此丰富多样的。随着分子生物学中心法 则的发现和基因组时代的到来，比较不同物种的基因组（即通过进化基因组学 研究）找出进化过程中发生的遗传变异成为求解这一基本进化生物学问题的重 要方法。 通过比较不同物种的基因组可以发现新基因的诞生是在进化过程中普遍存 在的基本过程，对生物的进化发挥着重要的作用。大量前人的研究认为新基因 主要通过老基因的重复产生，新基因的从头起源很少发生或根本不存在。直至 最近在果蝇中发现了新基因从头起源事件才改变了人们的这种看法，然而这些 研究缺少功能的证据。我们通过比较酿酒酵母近缘种的基因组序列发现了酿酒 酵母中进化出的一个从头起源的新基因BSC4，并且提供了群体遗传学、转录 组、蛋白质组学和表型水平的证据支持这个基因的生物学功能和蛋白编码能 力。同时我们在其近缘种中发现其直系同源的非编码序列拥有RNA 水平的表达 活性，由此我们提出了一个蛋白基因从头起源的两步模型。我们认为一个非编 码DNA 序列进化为蛋白编码基因需要经历两个步骤：第一，DNA 序列先进化出 顺式元件来招募转录机器变成有RNA 转录活性的序列；第二，转录的序列通过 突变获得开放读码框并加入到翻译机器中。 进一步的分析提示BSC4 可能在酿 酒酵母转换到营养贫瘠的环境中并进入生长停滞期时对酿酒酵母的适应性作出 了贡献。酿酒酵母是一种对人类生活十分重要的微生物，它进行发酵的能力在 工业生产中具有重要应用价值。生长停滞期是酿酒酵母实际生产应用中频繁经 ii 历的过程，对这一阶段的适应性进化也对其工业应用有重要意义。 大熊猫是我国的国宝。它是一种具有独特特性的熊科动物，进化上属于食 肉目类群，食性确以竹子为主。为了适应其食性，其前掌的籽骨还发育出了著 名的“伪拇指”来帮助其进食。然而这些性状是如何进化出来的确一直是个未 解之谜。进化基因组学为解决这些问题提供了一个重要的思路和方法。我们通 过应用第二代测序技术对大熊猫基因组进行了从头测序和组装，通过和其它基 因组比较分析发现了大熊猫基因组中不存在编码降解纤维素酶的基因，提示了 大熊猫特殊食性的进化机制很可能是通过其肠道微生物的改变而发生的。同 时，我们也发现了大熊猫鲜味受体的退化，这很可能是一个伴随其食性进化而 发生的变异。 长雄野生稻是栽培稻的近缘种，它和栽培稻同属于AA 基因组。由于它具有 以发达的地下茎为生理表型的多年生特性和自交不亲和性，研究这些特性背后 的遗传机制对改良栽培稻一年生为多年生和构建自交不亲和的新杂交稻育种体 系有重要意义。我们从头测序并组装了长雄野生稻的基因组，通过和栽培稻基 因组的比较分析，在前人工作的基础上找出了决定上述两个重要性状的可能的 基因组区域，为进一步的实验验证提供了候选的基因。同时我们的序列提供了 对其它野生稻特性研究的重要基础。

La génomique évolutive mitochondriale révèle des échanges génétiques et la ségrégation chez les Gloméromycètes

Les champignons mycorhiziens à arbuscules (CMA) sont des organismes microscopiques du sol qui jouent un rôle crucial dans les écosystèmes naturels et que l’on retrouve dans tous les habitats de la planète. Ils vivent en relation symbiotique avec la vaste majorité des plantes terrestres. Ils sont des biotrophes obligatoires, c'est-à-dire qu'ils ne peuvent croître qu'en présence d'une plante hôte. Cette symbiose permet entre autres à la plante d'acquérir des nutriments supplémentaires, en particulier du phosphore et du nitrate. Malgré le fait que cette symbiose apporte des services importants aux écosystèmes, la richesse des espèces, la structure des communautés, ainsi que la diversité fonctionnelle des CMA sont mal connues et l'approfondissement des connaissances dans ces domaines dépend d’outils de diagnostic moléculaire. Cependant, la présence de polymorphisme nucléaire intra-isolat combiné à un manque de données génomiques dans différents groupes phylogénétique de ces champignons complique le développement de marqueurs moléculaires et la détermination de l'affiliation évolutive à hauts niveaux de résolution (c.a.d. entre espèces génétiquement similaires et/ou isolats de la même espèce). . Pour ces raisons, il semble une bonne alternative d’utiliser un système génétique différent en ciblant le génome mitochondrial, qui a été démontré homogène au sein d'un même isolat de CMA. Cependant, étant donné le mode de vie particulier de ces organismes, une meilleure compréhension des processus évolutifs mitochondriaux est nécessaire afin de valoriser l'utilisation de tels marqueurs dans des études de diversité et en génétique des populations. En ce sens, mon projet de doctorat consistait à investiguerétudier: i) les vecteurs de divergences inter-isolats et -espèces génétiquement rapprochéesphylogénétiquement apparentées, ii) la plasticité des génomes mitochondriaux, iii) l'héritabilité mitochondriale et les mécanismes potentiels de ségrégation, ainsi que iv) la diversité mitochondriale intra-isolat in situ. À l'aide de la génomique mitochondriale comparative, en utilisant le séquençage nouvelle génération, on a démontré la présence de variation génétique substantielle inter-isolats et -espèces, engendrées par l'invasion d'éléments mobiles dans les génomes mitochondriaux des CMA, donnant lieu à une évolution moléculaire rapide des régions intergéniques. Cette variation permettait de développer des marqueurs spécifiques à des isolats de la même espèce. Ensuite, à l'aide d'une approche analytique par réseaux de gènes sur des éléments mobiles, on a été en mesure de démontrer des évènements de recombinaisons homologues entre des haplotypes mitochondriaux distincts, menant à des réarrangements génomiques. Cela a permis d'ouvrir les perspectives sur la dynamique mitochondriale et l'hétéroplasmie dans un même isolatsuggère une coexistence de différents haplotypes mitochondriaux dans les populations naturelles et que les cultures monosporales pourraient induirent une sous-estimation de la diversité allélique mitochondriale. Cette apparente contradiction avec l'homogénéité mitochondriale intra-isolat généralement observée, a amené à investiguer étudier les échanges génétiques à l'aide de croisements d'isolats génétiquement distincts. Malgré l'observation de quelques spores filles hétéroplasmiques, l'homoplasmie était le statut par défaut dans toutes les cultures monosporales, avec un biais en faveur de l'un des haplotypes parentaux. Ces résultats suggèrent que la ségrégation opère durant la formation de la spore et/ou le développement de la coloniedu mycélium. De plus, ils supportent la présence d'une machinerie protéique de ségrégation mitochondriale chez les CMAAMF, où l'ensemble des gènes impliqués dans ce mécanisme ont été retrouvé et sont orthologues aux autres champignons. Finalement, on est revenue aux sources avecon a étudié le polymorphisme mitochondrial intra-isolat à l'aide d'une approche conventionnelle de PCR en utilisant une Taq polymérase de haute fidélité, suivie de clonage et de séquençage Sanger, sur deux isolats de R. irregularis. Cela a permis l'observation d'hétéroplasmie in situ, ainsi que la co-expression de variantes de variantes de protéines'ARNm dans une souche in vitro. Les résultats suggèrent que d'autres études basées sur le séquençage nouvelle génération aurait potentiellement ignorée cette variation, offrant ainsi plusieurs nouveaux arguments permettant de considérer les CMA comme des organismes possédant une population de génomes mitochondriaux et nucléaires distincts.

Certain observations concerning the effects of epistasis on complex traits and the evolution of genomes.

Thesis (Ph.D.)--University of Washington, 2016-05

Integrating cytogenetics and genomics in comparative evolutionary studies of cichlid fish

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

De-DUFing the DUFs: Deciphering distant evolutionary relationships of Domains of Unknown Function using sensitive homology detection methods

Background: In the post-genomic era where sequences are being determined at a rapid rate, we are highly reliant on computational methods for their tentative biochemical characterization. The Pfam database currently contains 3,786 families corresponding to ``Domains of Unknown Function'' (DUF) or ``Uncharacterized Protein Family'' (UPF), of which 3,087 families have no reported three-dimensional structure, constituting almost one-fourth of the known protein families in search for both structure and function. Results: We applied a `computational structural genomics' approach using five state-of-the-art remote similarity detection methods to detect the relationship between uncharacterized DUFs and domain families of known structures. The association with a structural domain family could serve as a start point in elucidating the function of a DUF. Amongst these five methods, searches in SCOP-NrichD database have been applied for the first time. Predictions were classified into high, medium and low-confidence based on the consensus of results from various approaches and also annotated with enzyme and Gene ontology terms. 614 uncharacterized DUFs could be associated with a known structural domain, of which high confidence predictions, involving at least four methods, were made for 54 families. These structure-function relationships for the 614 DUF families can be accessed on-line at http://proline.biochem.iisc.ernet.in/RHD_DUFS/. For potential enzymes in this set, we assessed their compatibility with the associated fold and performed detailed structural and functional annotation by examining alignments and extent of conservation of functional residues. Detailed discussion is provided for interesting assignments for DUF3050, DUF1636, DUF1572, DUF2092 and DUF659. Conclusions: This study provides insights into the structure and potential function for nearly 20 % of the DUFs. Use of different computational approaches enables us to reliably recognize distant relationships, especially when they converge to a common assignment because the methods are often complementary. We observe that while pointers to the structural domain can offer the right clues to the function of a protein, recognition of its precise functional role is still `non-trivial' with many DUF domains conserving only some of the critical residues. It is not clear whether these are functional vestiges or instances involving alternate substrates and interacting partners. Reviewers: This article was reviewed by Drs Eugene Koonin, Frank Eisenhaber and Srikrishna Subramanian.

Evolutionary characteristics of exons expressed at different abundance levels in mammals

With comparative genomics approaches, we evaluated the evolutionary characteristics of conservation of exons which are expressed abundantly, moderately or lowly in mammals. Using non-coding regions and pseudogenes as controls, sequence identity, phastCons