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Benham PM, Cicero C, Escalona M, Beraut E, Fairbairn C, Marimuthu MPA, Nguyen O, Sahasrabudhe R, King BL, Thomas WK, Kovach AI, Nachman MW, Bowie RCK. Remarkably High Repeat Content in the Genomes of Sparrows: The Importance of Genome Assembly Completeness for Transposable Element Discovery. Genome Biol Evol 2024; 16:evae067. [PMID: 38566597 PMCID: PMC11088854 DOI: 10.1093/gbe/evae067] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2023] [Revised: 03/01/2024] [Accepted: 03/23/2024] [Indexed: 04/04/2024] Open
Abstract
Transposable elements (TE) play critical roles in shaping genome evolution. Highly repetitive TE sequences are also a major source of assembly gaps making it difficult to fully understand the impact of these elements on host genomes. The increased capacity of long-read sequencing technologies to span highly repetitive regions promises to provide new insights into patterns of TE activity across diverse taxa. Here we report the generation of highly contiguous reference genomes using PacBio long-read and Omni-C technologies for three species of Passerellidae sparrow. We compared these assemblies to three chromosome-level sparrow assemblies and nine other sparrow assemblies generated using a variety of short- and long-read technologies. All long-read based assemblies were longer (range: 1.12 to 1.41 Gb) than short-read assemblies (0.91 to 1.08 Gb) and assembly length was strongly correlated with the amount of repeat content. Repeat content for Bell's sparrow (31.2% of genome) was the highest level ever reported within the order Passeriformes, which comprises over half of avian diversity. The highest levels of repeat content (79.2% to 93.7%) were found on the W chromosome relative to other regions of the genome. Finally, we show that proliferation of different TE classes varied even among species with similar levels of repeat content. These patterns support a dynamic model of TE expansion and contraction even in a clade where TEs were once thought to be fairly depauperate and static. Our work highlights how the resolution of difficult-to-assemble regions of the genome with new sequencing technologies promises to transform our understanding of avian genome evolution.
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Affiliation(s)
- Phred M Benham
- Museum of Vertebrate Zoology, University of California Berkeley, Berkeley, CA 94720, USA
- Department of Integrative Biology, University of California Berkeley, Berkeley, CA 94720, USA
| | - Carla Cicero
- Museum of Vertebrate Zoology, University of California Berkeley, Berkeley, CA 94720, USA
| | - Merly Escalona
- Department of Biomolecular Engineering, University of California Santa Cruz, Santa Cruz, CA 95064, USA
| | - Eric Beraut
- Department of Ecology and Evolutionary Biology, University of California, Santa Cruz, Santa Cruz, CA 95064, USA
| | - Colin Fairbairn
- Department of Ecology and Evolutionary Biology, University of California, Santa Cruz, Santa Cruz, CA 95064, USA
| | - Mohan P A Marimuthu
- DNA Technologies and Expression Analysis Core Laboratory, Genome Center, University of California-Davis, Davis, CA 95616, USA
| | - Oanh Nguyen
- DNA Technologies and Expression Analysis Core Laboratory, Genome Center, University of California-Davis, Davis, CA 95616, USA
| | - Ruta Sahasrabudhe
- DNA Technologies and Expression Analysis Core Laboratory, Genome Center, University of California-Davis, Davis, CA 95616, USA
| | - Benjamin L King
- Department of Molecular and Biomedical Sciences, University of Maine, Orono, ME 04469, USA
| | - W Kelley Thomas
- Department of Molecular, Cellular and Biomedical Sciences, University of New Hampshire, Durham, NH 03824, USA
| | - Adrienne I Kovach
- Department of Natural Resources and the Environment, University of New Hampshire, Durham, NH 03824, USA
| | - Michael W Nachman
- Museum of Vertebrate Zoology, University of California Berkeley, Berkeley, CA 94720, USA
- Department of Integrative Biology, University of California Berkeley, Berkeley, CA 94720, USA
| | - Rauri C K Bowie
- Museum of Vertebrate Zoology, University of California Berkeley, Berkeley, CA 94720, USA
- Department of Integrative Biology, University of California Berkeley, Berkeley, CA 94720, USA
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Bascón-Cardozo K, Bours A, Manthey G, Durieux G, Dutheil JY, Pruisscher P, Odenthal-Hesse L, Liedvogel M. Fine-Scale Map Reveals Highly Variable Recombination Rates Associated with Genomic Features in the Eurasian Blackcap. Genome Biol Evol 2024; 16:evad233. [PMID: 38198800 PMCID: PMC10781513 DOI: 10.1093/gbe/evad233] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/12/2023] [Indexed: 01/12/2024] Open
Abstract
Recombination is responsible for breaking up haplotypes, influencing genetic variability, and the efficacy of selection. Bird genomes lack the protein PR domain-containing protein 9, a key determinant of recombination dynamics in most metazoans. Historical recombination maps in birds show an apparent stasis in positioning recombination events. This highly conserved recombination pattern over long timescales may constrain the evolution of recombination in birds. At the same time, extensive variation in recombination rate is observed across the genome and between different species of birds. Here, we characterize the fine-scale historical recombination map of an iconic migratory songbird, the Eurasian blackcap (Sylvia atricapilla), using a linkage disequilibrium-based approach that accounts for population demography. Our results reveal variable recombination rates among and within chromosomes, which associate positively with nucleotide diversity and GC content and negatively with chromosome size. Recombination rates increased significantly at regulatory regions but not necessarily at gene bodies. CpG islands are associated strongly with recombination rates, though their specific position and local DNA methylation patterns likely influence this relationship. The association with retrotransposons varied according to specific family and location. Our results also provide evidence of heterogeneous intrachromosomal conservation of recombination maps between the blackcap and its closest sister taxon, the garden warbler. These findings highlight the considerable variability of recombination rates at different scales and the role of specific genomic features in shaping this variation. This study opens the possibility of further investigating the impact of recombination on specific population-genomic features.
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Affiliation(s)
- Karen Bascón-Cardozo
- MPRG Behavioural Genomics, Max Planck Institute for Evolutionary Biology, Plön 24306, Germany
| | - Andrea Bours
- MPRG Behavioural Genomics, Max Planck Institute for Evolutionary Biology, Plön 24306, Germany
| | - Georg Manthey
- Institute of Avian Research “Vogelwarte Helgoland”, Wilhelmshaven 26386, Germany
| | - Gillian Durieux
- MPRG Behavioural Genomics, Max Planck Institute for Evolutionary Biology, Plön 24306, Germany
| | - Julien Y Dutheil
- Department for Theoretical Biology, Max Planck Institute for Evolutionary Biology, Plön 24306, Germany
| | - Peter Pruisscher
- MPRG Behavioural Genomics, Max Planck Institute for Evolutionary Biology, Plön 24306, Germany
- Department of Zoology, Stockholm University, Stockholm SE-106 91, Sweden
| | - Linda Odenthal-Hesse
- Department Evolutionary Genetics, Max Planck Institute for Evolutionary Biology, Plön 24306, Germany
| | - Miriam Liedvogel
- MPRG Behavioural Genomics, Max Planck Institute for Evolutionary Biology, Plön 24306, Germany
- Institute of Avian Research “Vogelwarte Helgoland”, Wilhelmshaven 26386, Germany
- Department of Biology and Environmental Sciences, Carl von Ossietzky University of Oldenburg, Oldenburg 26129, Germany
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