1,675 research outputs found

    Causes and Consequences of Genome Expansion in Fungi

    Get PDF
    Fungi display a large diversity in genome size and complexity, variation that is often considered to be adaptive. But because nonadaptive processes can also have important consequences on the features of genomes, we investigated the relationship of genetic drift and genome size in the phylum Ascomycota using multiple indicators of genetic drift. We detected a complex relationship between genetic drift and genome size in fungi: genetic drift is associated with genome expansion on broad evolutionary timescales, as hypothesized for other eukaryotes; but within subphyla over smaller timescales, the opposite trend is observed. Moreover, fungi and bacteria display similar patterns of genome degradation that are associated with initial effects of genetic drift. We conclude that changes in genome size within Ascomycota have occurred using two different routes: large-scale genome expansions are catalyzed by increasing drift as predicted by the mutation-hazard model of genome evolution and small-scale modifications in genome size are independent of drift

    Identification of SVA-Mediated 3’ and 5’ Transductions in Human Genome Sequences

    Get PDF
    Transposable elements (TEs) are sequences of DNA that can move, or transpose, within a genome. Retrotransposons are TEs that propagate via a “copy and paste” mechanism where the elements are transposed to a new genomic location via an RNA intermediate. Short interspersed element (SINE)-VNTR-Alu elements (SVAs) are non-autonomous retrotransposons that use long interspersed element 1 proteins to mobilize. SVAs are currently active in the human genome and often are characterized by the mobilization of sequences adjacent to the 3’ and 5’ ends of insertions, known as transduction events (TDs). TDs were a focus of this study due to their contribution to genome expansion, exon shuffling, and gene duplication. We analyzed 547 SVA elements across 35 genetically diverse individuals from the Human Genome Structural Variation Consortium. We identified 187 full-length elements, 12 of which carried 3’ TDs, 13 harbored 5’ TDs, and five held both 3’ and 5’ TDs. Four TDs contained exons of genes, including HGSNAT, UQCRC1, and RP11-137H2.4. Utilizing TDs, we screened the dataset for source elements, i.e., active TEs capable of producing offspring, by querying the human reference genome (GRCh38) using BLAT to identify the origin of the TDs and SVA source elements. We found that Chromosomes 3, 10, and 11 showed enrichment for active SVA elements. Novel TDs were identified and can be used to study genome expansion due to their ability to take additional sequences from each genomic location. Source elements can cause insertions that drive disease and genome expansion, exemplifying their significance

    Metamorphosis Imposes Variable Constraints on Genome Expansion through Effects on Development

    Get PDF
    Genome size varies ∼100,000-fold across eukaryotes and has long been hypothesized to be influenced by meta- morphosis in animals. Transposable element accumulation has been identified as a major driver of increase, but the nature of constraints limiting the size of genomes has remained unclear, even as traits such as cell size and rate of development co-vary strongly with genome size. Salamanders, which possess diverse metamorphic and non-metamorphic life histories, join the lung- fish in having the largest vertebrate genomes—3 to 40 times that of humans—as well as the largest range of variation in genome size. We tested 13 biologically-inspired hypotheses exploring how the form of metamorphosis imposes varying constraints on genome expansion in a broadly representative phylogeny containing 118 species of salamanders. We show that metamorphosis during which animals undergo the most extensive and synchronous remodeling imposes the most severe constraint against genome expansion, with the severity of constraint decreasing with reduced extent and synchronicity of remodeling. More generally, our work demonstrates the potential for broader interpretation of phylogenetic comparative analysis in exploring the balance of multiple evolutionary pressures shaping phenotypic evolution

    Gene duplication drives genome expansion in a major lineage of Thaumarchaeota

    Get PDF
    Acknowledgements This work and P.O.S. were financially supported by UKRI through the NERC grant NE/R001529/1. In addition, C.G.-R. and T.A.W. were both supported by a Royal Society University Research Fellowship (URF150571 and UF140626). C.Q. was funded through an MRC fellowship (MR/M50161X/1) as part of the CLoud Infrastructure for Microbial Genomics (CLIMB) consortium (MR/L015080/1). S.R. was funded through the BBSRC grant BB/R015171/1. The Thames Metagenome Database was funded through the NERC grants NE/M011674/1, NE/M011259/1 and NE/M01133X/1. We thank Dr Tony Travis for his support with Biolinux and acknowledge Prof Jim Prosser for his critical reading of the manuscript. The authors would also like to acknowledge the support of the Maxwell computer cluster funded by the University of Aberdeen.Peer reviewedPublisher PD

    Assessing the Gene Content of the Megagenome: Sugar Pine (Pinus lambertiana).

    Get PDF
    Sugar pine (Pinus lambertiana Douglas) is within the subgenus Strobus with an estimated genome size of 31 Gbp. Transcriptomic resources are of particular interest in conifers due to the challenges presented in their megagenomes for gene identification. In this study, we present the first comprehensive survey of the P. lambertiana transcriptome through deep sequencing of a variety of tissue types to generate more than 2.5 billion short reads. Third generation, long reads generated through PacBio Iso-Seq have been included for the first time in conifers to combat the challenges associated with de novo transcriptome assembly. A technology comparison is provided here to contribute to the otherwise scarce comparisons of second and third generation transcriptome sequencing approaches in plant species. In addition, the transcriptome reference was essential for gene model identification and quality assessment in the parallel project responsible for sequencing and assembly of the entire genome. In this study, the transcriptomic data were also used to address questions surrounding lineage-specific Dicer-like proteins in conifers. These proteins play a role in the control of transposable element proliferation and the related genome expansion in conifers

    Analysis of the giant genomes of Fritillaria (Liliaceae) indicates that a lack of DNA removal characterizes extreme expansions in genome size.

    Get PDF
    This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.Plants exhibit an extraordinary range of genome sizes, varying by > 2000-fold between the smallest and largest recorded values. In the absence of polyploidy, changes in the amount of repetitive DNA (transposable elements and tandem repeats) are primarily responsible for genome size differences between species. However, there is ongoing debate regarding the relative importance of amplification of repetitive DNA versus its deletion in governing genome size. Using data from 454 sequencing, we analysed the most repetitive fraction of some of the largest known genomes for diploid plant species, from members of Fritillaria. We revealed that genomic expansion has not resulted from the recent massive amplification of just a handful of repeat families, as shown in species with smaller genomes. Instead, the bulk of these immense genomes is composed of highly heterogeneous, relatively low-abundance repeat-derived DNA, supporting a scenario where amplified repeats continually accumulate due to infrequent DNA removal. Our results indicate that a lack of deletion and low turnover of repetitive DNA are major contributors to the evolution of extremely large genomes and show that their size cannot simply be accounted for by the activity of a small number of high-abundance repeat families.Thiswork was supported by the Natural Environment ResearchCouncil (grant no. NE/G017 24/1), the Czech Science Fou nda-tion (grant no. P501/12/G090), the AVCR (grant no.RVO:60077344) and a Beatriu de Pinos postdoctoral fellowshipto J.P. (grant no. 2011-A-00292; Catalan Government-E.U. 7thF.P.)

    Whole genome duplication and transposable element proliferation drive genome expansion in Corydoradinae catfishes

    Get PDF
    Genome size varies significantly across eukaryotic taxa and the largest changes are typically driven by macro-mutations such as whole genome duplications (WGDs) and proliferation of repetitive elements. These two processes may affect the evolutionary potential of lineages by increasing genetic variation and changing gene expression. Here we elucidate the evolutionary history and mechanisms underpinning genome size variation in a species rich group of Neotropical catfishes (Corydoradinae) with extreme variation in genome size - 0.6pg to 4.4 pg per haploid cell. Firstly, genome size was quantified in 65 species and mapped onto a novel fossil-calibrated phylogeny. Two evolutionary shifts in genome size were identified across the tree - the first between 43-49 Mya (95% highest posterior density (HPD) 36.2-68.1 Mya) and the second at ~19 Mya (95% HPD 15.3-30.14 Mya). Secondly, RAD sequencing was used to identify potential WGD events and quantify transposable element abundance in different lineages. Evidence of two lineage scale WGDs were identified across the phylogeny, the first event occurring between 54-66 Mya (95% HPD 42.56-99.5 Mya) and the second at 20-30 Mya (95% HPD 15.3-45 Mya) based on haplotype numbers per contig and between 35-44 Mya (95% HPD 30.29-64.51 Mya) and 20-30 Mya (95% HPD 15.3-45 Mya) based on SNP read ratios. Transposable element abundance increased considerably in parallel with genome size, with a single TE-family (TC1-IS630-Pogo) showing several increases across the Corydoradinae, with the most recent at 20-30 Mya (95% HPD 15.3-45 Mya) and an older event at 35-44 Mya (95% HPD 30.29-64.51 Mya). We identified signals congruent with two WGD duplication events, as well as an increase in TE abundance across different lineages, making the Corydoradinae an excellent model system to study the effects of WGD and TEs on genome and organismal evolution
    corecore