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Villegas LI, Ferretti L, Wiehe T, Waldvogel A, Schiffer PH. Parthenogenomics: Insights on mutation rates and nucleotide diversity in parthenogenetic Panagrolaimus nematodes. Ecol Evol 2024; 14:e10831. [PMID: 38192904 PMCID: PMC10771965 DOI: 10.1002/ece3.10831] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2023] [Revised: 12/11/2023] [Accepted: 12/13/2023] [Indexed: 01/10/2024] Open
Abstract
Asexual reproduction is assumed to lead to the accumulation of deleterious mutations, and reduced heterozygosity due to the absence of recombination. Panagrolaimid nematode species display different modes of reproduction. Sexual reproduction with distinct males and females, asexual reproduction through parthenogenesis in the genus Panagrolaimus, and hermaphroditism in Propanagrolaimus. Here, we compared genomic features of free-living nematodes in populations and species isolated from geographically distant regions to study diversity, and genome-wide differentiation under different modes of reproduction. We firstly estimated genome-wide spontaneous mutation rates in a triploid parthenogenetic Panagrolaimus, and a diploid hermaphroditic Propanagrolaimus via long-term mutation accumulation lines. Secondly, we calculated population genetic parameters including nucleotide diversity, and fixation index (F ST) between populations of asexually and sexually reproducing nematodes. Thirdly, we used phylogenetic network methods on sexually and asexually reproducing Panagrolaimus populations to understand evolutionary relationships between them. The estimated mutation rate was slightly lower for the asexual population, as expected for taxa with this reproductive mode. Natural polyploid asexual populations revealed higher nucleotide diversity. Despite their common ancestor, a gene network revealed a high level of genetic differentiation among asexual populations. The elevated heterozygosity found in the triploid parthenogens could be explained by the third genome copy. Given their tendentially lower mutation rates it can be hypothesized that this is part of the mechanism to evade Muller's ratchet. Our findings in parthenogenetic triploid nematode populations seem to challenge common expectations of evolution under asexuality.
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Affiliation(s)
| | | | - Thomas Wiehe
- Institute for GeneticsUniversity of CologneKölnGermany
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Abstract
The nematode Caenorhabditis elegans has shed light on many aspects of eukaryotic biology, including genetics, development, cell biology, and genomics. A major factor in the success of C. elegans as a model organism has been the availability, since the late 1990s, of an essentially gap-free and well-annotated nuclear genome sequence, divided among 6 chromosomes. In this review, we discuss the structure, function, and biology of C. elegans chromosomes and then provide a general perspective on chromosome biology in other diverse nematode species. We highlight malleable chromosome features including centromeres, telomeres, and repetitive elements, as well as the remarkable process of programmed DNA elimination (historically described as chromatin diminution) that induces loss of portions of the genome in somatic cells of a handful of nematode species. An exciting future prospect is that nematode species may enable experimental approaches to study chromosome features and to test models of chromosome evolution. In the long term, fundamental insights regarding how speciation is integrated with chromosome biology may be revealed.
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Affiliation(s)
- Peter M Carlton
- Graduate School of Biostudies, Kyoto University, Kyoto 606-8501, Japan
| | - Richard E Davis
- Department of Biochemistry and Molecular Genetics, University of Colorado School of Medicine, Denver, CO 80045, USA.,RNA Bioscience Initiative, University of Colorado School of Medicine, Aurora, CO 80045, USA
| | - Shawn Ahmed
- Department of Genetics, University of North Carolina, Chapel Hill, NC 27599, USA.,Department of Biology, University of North Carolina, Chapel Hill, NC 27599, USA
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Daugavet MA, Shabelnikov SV, Podgornaya OI. Amino acid sequence associated with bacteriophage recombination site helps to reveal genes potentially acquired through horizontal gene transfer. BMC Bioinformatics 2020; 21:305. [PMID: 32703190 PMCID: PMC7379824 DOI: 10.1186/s12859-020-03599-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2020] [Accepted: 06/10/2020] [Indexed: 12/04/2022] Open
Abstract
Background Horizontal gene transfer, i.e. the acquisition of genetic material from nonparent organism, is considered an important force driving species evolution. Many cases of horizontal gene transfer from prokaryotes to eukaryotes have been registered, but no transfer mechanism has been deciphered so far, although viruses were proposed as possible vectors in several studies. In agreement with this idea, in our previous study we discovered that in two eukaryotic proteins bacteriophage recombination site (AttP) was adjacent to the regions originating via horizontal gene transfer. In one of those cases AttP site was present inside the introns of cysteine-rich repeats. In the present study we aimed to apply computational tools for finding multiple horizontal gene transfer events in large genome databases. For that purpose we used a sequence of cysteine-rich repeats to identify genes potentially acquired through horizontal transfer. Results HMMER remote similarity search significantly detected 382 proteins containing cysteine-rich repeats. All of them, except 8 sequences, belong to eukaryotes. In 124 proteins the presence of conserved structural domains was predicted. In spite of the fact that cysteine-rich repeats are found almost exclusively in eukaryotic proteins, many predicted domains are most common for prokaryotes or bacteriophages. Ninety-eight proteins out of 124 contain typical prokaryotic domains. In those cases proteins were considered as potentially originating via horizontal transfer. In addition, HHblits search revealed that two domains of the same fungal protein, Glycoside hydrolase and Peptidase M15, have high similarity with proteins of two different prokaryotic species, hinting at independent horizontal gene transfer events. Conclusions Cysteine-rich repeats in eukaryotic proteins are usually accompanied by conserved domains typical for prokaryotes or bacteriophages. These proteins, containing both cysteine-rich repeats, and characteristic prokaryotic domains, might represent multiple independent horizontal gene transfer events from prokaryotes to eukaryotes. We believe that the presence of bacteriophage recombination site inside cysteine-rich repeat coding sequence may facilitate horizontal genes transfer. Thus computational approach, described in the present study, can help finding multiple sequences originated from horizontal transfer in eukaryotic genomes.
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Affiliation(s)
| | | | - Olga I Podgornaya
- Institute of Cytology, St. Petersburg, Russia, 194064.,School of Biomedicine, Far Eastern Federal University, Vladivostok, Russia, 690090.,Department of Cytology and Histology, St. Pb State University, St. Petersburg, Russia, 199034
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Jouet A, Saunders DGO, McMullan M, Ward B, Furzer O, Jupe F, Cevik V, Hein I, Thilliez GJA, Holub E, van Oosterhout C, Jones JDG. Albugo candida race diversity, ploidy and host-associated microbes revealed using DNA sequence capture on diseased plants in the field. THE NEW PHYTOLOGIST 2019; 221:1529-1543. [PMID: 30288750 DOI: 10.1111/nph.15417] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/17/2018] [Accepted: 07/20/2018] [Indexed: 05/28/2023]
Abstract
Physiological races of the oomycete Albugo candida are biotrophic pathogens of diverse plant species, primarily the Brassicaceae, and cause infections that suppress host immunity to other pathogens. However, A. candida race diversity and the consequences of host immunosuppression are poorly understood in the field. We report a method that enables sequencing of DNA of plant pathogens and plant-associated microbes directly from field samples (Pathogen Enrichment Sequencing: PenSeq). We apply this method to explore race diversity in A. candida and to detect A. candida-associated microbes in the field (91 A. candida-infected plants). We show with unprecedented resolution that each host plant species supports colonization by one of 17 distinct phylogenetic lineages, each with an unique repertoire of effector candidate alleles. These data reveal the crucial role of sexual and asexual reproduction, polyploidy and host domestication in A. candida specialization on distinct plant species. Our bait design also enabled phylogenetic assignment of DNA sequences from bacteria and fungi from plants in the field. This paper shows that targeted sequencing has a great potential for the study of pathogen populations while they are colonizing their hosts. This method could be applied to other microbes, especially to those that cannot be cultured.
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Affiliation(s)
- Agathe Jouet
- The Sainsbury Laboratory, Norwich Research Park, Norwich, NR4 7UH, UK
- School of Environmental Sciences, University of East Anglia, Norwich Research Park, Norwich, NR4 7TJ, UK
| | | | - Mark McMullan
- The Earlham Institute, Norwich Research Park, Norwich, NR4 7UZ, UK
| | - Ben Ward
- School of Environmental Sciences, University of East Anglia, Norwich Research Park, Norwich, NR4 7TJ, UK
- The Earlham Institute, Norwich Research Park, Norwich, NR4 7UZ, UK
| | - Oliver Furzer
- The Sainsbury Laboratory, Norwich Research Park, Norwich, NR4 7UH, UK
- University of North Carolina, Chapel Hill, NC, 27599-2200, USA
| | - Florian Jupe
- The Sainsbury Laboratory, Norwich Research Park, Norwich, NR4 7UH, UK
- Plant Molecular and Cellular Biology Laboratory, Salk Institute, La Jolla, CA, 92037, USA
| | - Volkan Cevik
- The Sainsbury Laboratory, Norwich Research Park, Norwich, NR4 7UH, UK
- The Milner Centre for Evolution, Department of Biology and Biochemistry, University of Bath, Bath, BA2 7AY, UK
| | - Ingo Hein
- The James Hutton Institute, CMS, Dundee, DD2 5DA, UK
- Division of Plant Sciences at the James Hutton Institute, the University of Dundee, Dundee, DD2 5DA, UK
| | - Gaetan J A Thilliez
- The James Hutton Institute, CMS, Dundee, DD2 5DA, UK
- Quadram Institute Bioscience, Norwich Research Park, Colney Lane, NR4 7UH, Norwich, UK
| | - Eric Holub
- School of Life Sciences, Warwick Crop Centre, University of Warwick, Warwick, CV35 9EF, UK
| | - Cock van Oosterhout
- School of Environmental Sciences, University of East Anglia, Norwich Research Park, Norwich, NR4 7TJ, UK
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