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Davison A, Chowdhury M, Johansen M, Uliano-Silva M, Blaxter M. High heteroplasmy is associated with low mitochondrial copy number and selection against non-synonymous mutations in the snail Cepaea nemoralis. BMC Genomics 2024; 25:596. [PMID: 38872121 DOI: 10.1186/s12864-024-10505-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2024] [Accepted: 06/06/2024] [Indexed: 06/15/2024] Open
Abstract
Molluscan mitochondrial genomes are unusual because they show wide variation in size, radical genome rearrangements and frequently show high variation (> 10%) within species. As progress in understanding this variation has been limited, we used whole genome sequencing of a six-generation matriline of the terrestrial snail Cepaea nemoralis, as well as whole genome sequences from wild-collected C. nemoralis, the sister species C. hortensis, and multiple other snail species to explore the origins of mitochondrial DNA (mtDNA) variation. The main finding is that a high rate of SNP heteroplasmy in somatic tissue was negatively correlated with mtDNA copy number in both Cepaea species. In individuals with under ten mtDNA copies per nuclear genome, more than 10% of all positions were heteroplasmic, with evidence for transmission of this heteroplasmy through the germline. Further analyses showed evidence for purifying selection acting on non-synonymous mutations, even at low frequency of the rare allele, especially in cytochrome oxidase subunit 1 and cytochrome b. The mtDNA of some individuals of Cepaea nemoralis contained a length heteroplasmy, including up to 12 direct repeat copies of tRNA-Val, with 24 copies in another snail, Candidula rugosiuscula, and repeats of tRNA-Thr in C. hortensis. These repeats likely arise due to error prone replication but are not correlated with mitochondrial copy number in C. nemoralis. Overall, the findings provide key insights into mechanisms of replication, mutation and evolution in molluscan mtDNA, and so will inform wider studies on the biology and evolution of mtDNA across animal phyla.
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Affiliation(s)
- Angus Davison
- School of Life Sciences, University of Nottingham, University Park, Nottingham, NG7 2RD, UK.
| | - Mehrab Chowdhury
- School of Life Sciences, University of Nottingham, University Park, Nottingham, NG7 2RD, UK
| | - Margrethe Johansen
- School of Life Sciences, University of Nottingham, University Park, Nottingham, NG7 2RD, UK
| | - Marcela Uliano-Silva
- Tree of Life, Wellcome Sanger Institute, Wellcome Genome Campus, Hinxton, Cambridge, Cambridgeshire, CB10 1SA, UK
| | - Mark Blaxter
- Tree of Life, Wellcome Sanger Institute, Wellcome Genome Campus, Hinxton, Cambridge, Cambridgeshire, CB10 1SA, UK
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Togashi T, Parker GA, Horinouchi Y. Mitochondrial uniparental inheritance achieved after fertilization challenges the nuclear-cytoplasmic conflict hypothesis for anisogamy evolution. Biol Lett 2023; 19:20230352. [PMID: 37752851 PMCID: PMC10523090 DOI: 10.1098/rsbl.2023.0352] [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: 08/02/2023] [Accepted: 09/04/2023] [Indexed: 09/28/2023] Open
Abstract
In eukaryotes, a fundamental phenomenon underlying sexual selection is the evolution of gamete size dimorphism between the sexes (anisogamy) from an ancestral gametic system with gametes of the same size in both mating types (isogamy). The nuclear-cytoplasmic conflict hypothesis has been one of the major theoretical hypotheses for the evolution of anisogamy. It proposes that anisogamy evolved as an adaptation for preventing nuclear-cytoplasmic conflict by minimizing male gamete size to inherit organelles uniparentally. In ulvophycean green algae, biparental inheritance of organelles is observed in isogamous species, as the hypothesis assumes. So we tested the hypothesis by examining whether cytoplasmic inheritance is biparental in Monostroma angicava, a slightly anisogamous ulvophycean that produces large male gametes. We tracked the fates of mitochondria in intraspecific crosses with PCR-RFLP markers. We confirmed that mitochondria are maternally inherited. However, paternal mitochondria enter the zygote, where their DNA can be detected for over 14 days. This indicates that uniparental inheritance is enforced by eliminating paternal mitochondrial DNA in the zygote, rather than by decreasing male gamete size to the minimum. Thus, uniparental cytoplasmic inheritance is achieved by an entirely different mechanism, and is unlikely to drive the evolution of anisogamy in ulvophyceans.
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Affiliation(s)
- Tatsuya Togashi
- Marine Biosystems Research Center, Chiba University, Kamogawa 299-5502, Japan
| | - Geoff A. Parker
- Department of Evolution, Ecology and Behaviour, University of Liverpool, Liverpool L69 7ZB, UK
| | - Yusuke Horinouchi
- Marine Biosystems Research Center, Chiba University, Kamogawa 299-5502, Japan
- Muroran Marine Station, Field Science Center for Northern Biosphere, Hokkaido University, Muroran 051-0013, Japan
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Li J, Cullis C. Comparative analysis of 84 chloroplast genomes of Tylosema esculentum reveals two distinct cytotypes. FRONTIERS IN PLANT SCIENCE 2023; 13:1025408. [PMID: 36798803 PMCID: PMC9927231 DOI: 10.3389/fpls.2022.1025408] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/22/2022] [Accepted: 12/21/2022] [Indexed: 06/18/2023]
Abstract
Tylosema esculentum (marama bean) is an important orphan legume from southern Africa that has long been considered to have the potential to be domesticated as a crop. The chloroplast genomes of 84 marama samples collected from various geographical locations in Namibia and Pretoria were compared in this study. The cp genomes were analyzed for diversity, including SNPs, indels, structural alterations, and heteroplasmy. The marama cp genomes ranged in length from 161,537 bp to 161,580 bp and contained the same sets of genes, including 84 protein-coding genes, 37 tRNA genes, and 8 rRNA genes. The genes rpoC2 and rpoB, and the intergenic spacers trnT-trnL and ndhG-ndhI were found to be more diverse than other regions of the marama plastome. 15 haplotypes were found to be divided into two groups, differing at 122 loci and at a 230 bp inversion. One type appears to have greater variability within the major genome present, and variations amongst individuals with this type of chloroplast genome seems to be distributed within specific geographic regions but with very limited sampling for some regions. However, deep sequencing has identified that within most of the individuals, both types of chloroplast genomes are present, albeit one is generally at a very low frequency. The inheritance of this complex of chloroplast genomes appears to be fairly constant, providing a conundrum of how the two genomes co-exist and are propagated through generations. The possible consequences for adaptation to the harsh environment in which T. esculentum survives are considered. The results pave the way for marama variety identification, as well as for understanding the origin and evolution of the bean.
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Tassé M, Choquette T, Angers A, Stewart DT, Pante E, Breton S. The longest mitochondrial protein in metazoans is encoded by the male-transmitted mitogenome of the bivalve Scrobicularia plana. Biol Lett 2022; 18:20220122. [PMID: 35673874 PMCID: PMC9174706 DOI: 10.1098/rsbl.2022.0122] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Cytochrome c oxidase subunit II (COX2) is one of the three mitochondrially encoded proteins of the complex IV of the respiratory chain that catalyses the reduction of oxygen to water. The cox2 gene spans about 690 base pairs in most animal species and produces a protein composed of approximately 230 amino acids. We discovered an extreme departure from this pattern in the male-transmitted mitogenome of the bivalve Scrobicularia plana with doubly uniparental inheritance (DUI) of mitochondrial DNA (mtDNA), which possesses an important in-frame insertion of approximately 4.8 kb in its cox2 gene. This feature—an enlarged male cox2 gene—is found in many species with DUI; the COX2 protein can be up to 420 amino acids long. Through RT-PCRs, immunoassays and comparative genetics, the evolution and functionality of this insertion in S. plana were characterized. The in-frame insertion is conserved among individuals from different populations and bears the signature of purifying selection seemingly indicating maintenance of functionality. Its transcription and translation were confirmed: this gene produces a polypeptide of 1892 amino acids, making it the largest metazoan COX2 protein known to date. We hypothesize that these extreme modifications in the COX2 protein affect the metabolism of mitochondria containing the male-transmitted mtDNA in Scrobicularia plana.
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Affiliation(s)
- Mélanie Tassé
- Département de sciences biologiques, Université de Montréal, Montréal, QC, Canada
| | - Thierry Choquette
- Département de sciences biologiques, Université de Montréal, Montréal, QC, Canada
| | - Annie Angers
- Département de sciences biologiques, Université de Montréal, Montréal, QC, Canada
| | | | - Eric Pante
- Littoral, Environnement et Sociétés (LIENSs), UMR 7266 CNRS-La Rochelle Université, 2 rue Olympe de Gouges, 17000 La Rochelle, France
| | - Sophie Breton
- Département de sciences biologiques, Université de Montréal, Montréal, QC, Canada
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Lubośny M, Śmietanka B, Arculeo M, Burzyński A. No evidence of DUI in the Mediterranean alien species Brachidontes pharaonis (P. Fisher, 1870) despite mitochondrial heteroplasmy. Sci Rep 2022; 12:8569. [PMID: 35595866 PMCID: PMC9122905 DOI: 10.1038/s41598-022-12606-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2021] [Accepted: 05/13/2022] [Indexed: 01/05/2023] Open
Abstract
Two genetically different mitochondrial haplogroups of Brachidontes pharaonis (p-distance 6.8%) have been identified in the Mediterranean Sea. This hinted at a possible presence of doubly uniparental inheritance in this species. To ascertain this possibility, we sequenced two complete mitogenomes of Brachidontes pharaonis mussels and performed a qPCR analysis to measure the relative mitogenome copy numbers of both mtDNAs. Despite the presence of two very similar regions composed entirely of repetitive sequences in the two haplogroups, no recombination between mitogenomes was detected. In heteroplasmic individuals, both mitogenomes were present in the generative tissues of both sexes, which argues against the presence of doubly uniparental inheritance in this species.
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Affiliation(s)
- Marek Lubośny
- Department of Genetics and Marine Biotechnology, Institute of Oceanology Polish Academy of Sciences, Sopot, Poland.
| | - Beata Śmietanka
- Department of Genetics and Marine Biotechnology, Institute of Oceanology Polish Academy of Sciences, Sopot, Poland
| | - Marco Arculeo
- Department of Biological, Chemical and Pharmaceutical Sciences and Technologies, University of Palermo, Palermo, Italy
| | - Artur Burzyński
- Department of Genetics and Marine Biotechnology, Institute of Oceanology Polish Academy of Sciences, Sopot, Poland
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Breton S, Stewart DT, Brémaud J, Havird JC, Smith CH, Hoeh WR. Did doubly uniparental inheritance (DUI) of mtDNA originate as a cytoplasmic male sterility (CMS) system? Bioessays 2022; 44:e2100283. [PMID: 35170770 PMCID: PMC9083018 DOI: 10.1002/bies.202100283] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2021] [Revised: 01/26/2022] [Accepted: 01/31/2022] [Indexed: 01/10/2023]
Abstract
Animal and plant species exhibit an astonishing diversity of sexual systems, including environmental and genetic determinants of sex, with the latter including genetic material in the mitochondrial genome. In several hermaphroditic plants for example, sex is determined by an interaction between mitochondrial cytoplasmic male sterility (CMS) genes and nuclear restorer genes. Specifically, CMS involves aberrant mitochondrial genes that prevent pollen development and specific nuclear genes that restore it, leading to a mixture of female (male-sterile) and hermaphroditic individuals in the population (gynodioecy). Such a mitochondrial-nuclear sex determination system is thought to be rare outside plants. Here, we present one possible case of CMS in animals. We hypothesize that the only exception to the strict maternal mtDNA inheritance in animals, the doubly uniparental inheritance (DUI) system in bivalves, might have originated as a mitochondrial-nuclear sex-determination system. We document and explore similarities that exist between DUI and CMS, and we propose various ways to test our hypothesis.
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Affiliation(s)
- Sophie Breton
- Département des sciences biologiques, Université de Montréal, Montréal, Québec, Canada
| | - Donald T Stewart
- Department of Biology, Acadia University, Wolfville, Nova Scotia, Canada
| | - Julie Brémaud
- Département des sciences biologiques, Université de Montréal, Montréal, Québec, Canada
| | - Justin C Havird
- Department of Integrative Biology, The University of Texas at Austin, Austin, Texas, USA
| | - Chase H Smith
- Department of Integrative Biology, The University of Texas at Austin, Austin, Texas, USA
| | - Walter R Hoeh
- Department of Biological Sciences, Kent State University, Kent, Ohio, USA
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Bettinazzi S, Milani L, Blier PU, Breton S. Bioenergetic consequences of sex-specific mitochondrial DNA evolution. Proc Biol Sci 2021; 288:20211585. [PMID: 34403637 PMCID: PMC8370797 DOI: 10.1098/rspb.2021.1585] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2021] [Accepted: 07/27/2021] [Indexed: 12/16/2022] Open
Abstract
Doubly uniparental inheritance (DUI) represents a notable exception to the general rule of strict maternal inheritance (SMI) of mitochondria in metazoans. This system entails the coexistence of two mitochondrial lineages (F- and M-type) transmitted separately through oocytes and sperm, thence providing an unprecedented opportunity for the mitochondrial genome to evolve adaptively for male functions. In this study, we explored the impact of a sex-specific mitochondrial evolution upon gamete bioenergetics of DUI and SMI bivalve species, comparing the activity of key enzymes of glycolysis, fermentation, fatty acid metabolism, tricarboxylic acid cycle, oxidative phosphorylation and antioxidant metabolism. Our findings suggest reorganized bioenergetic pathways in DUI gametes compared to SMI gametes. This generally results in a decreased enzymatic capacity in DUI sperm with respect to DUI oocytes, a limitation especially prominent at the terminus of the electron transport system. This bioenergetic remodelling fits a reproductive strategy that does not require high energy input and could potentially link with the preservation of the paternally transmitted mitochondrial genome in DUI species. Whether this phenotype may derive from positive or relaxed selection acting on DUI sperm is still uncertain.
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Affiliation(s)
- Stefano Bettinazzi
- Département de sciences biologiques, Université de Montréal, Montréal, Quebec, Canada H2V 2S9
| | - Liliana Milani
- Dipartimento di Scienze Biologiche, Geologiche e Ambientali, Università di Bologna, Bologna 40126, Italia
| | - Pierre U. Blier
- Département de biologie, Université du Québec à Rimouski, Rimouski, Quebec, Canada G5 L 3A1
| | - Sophie Breton
- Département de sciences biologiques, Université de Montréal, Montréal, Quebec, Canada H2V 2S9
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Pereira CV, Gitschlag BL, Patel MR. Cellular mechanisms of mtDNA heteroplasmy dynamics. Crit Rev Biochem Mol Biol 2021; 56:510-525. [PMID: 34120542 DOI: 10.1080/10409238.2021.1934812] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Heteroplasmy refers to the coexistence of more than one variant of the mitochondrial genome (mtDNA). Mutated or partially deleted mtDNAs can induce chronic metabolic impairment and cause mitochondrial diseases when their heteroplasmy levels exceed a critical threshold. These mutant mtDNAs can be maternally inherited or can arise de novo. Compelling evidence has emerged showing that mutant mtDNA levels can vary and change in a nonrandom fashion across generations and amongst tissues of an individual. However, our lack of understanding of the basic cellular and molecular mechanisms of mtDNA heteroplasmy dynamics has made it difficult to predict who will inherit or develop mtDNA-associated diseases. More recently, with the advances in technology and the establishment of tractable model systems, insights into the mechanisms underlying the selection forces that modulate heteroplasmy dynamics are beginning to emerge. In this review, we summarize evidence from different organisms, showing that mutant mtDNA can experience both positive and negative selection. We also review the recently identified mechanisms that modulate heteroplasmy dynamics. Taken together, this is an opportune time to survey the literature and to identify key cellular pathways that can be targeted to develop therapies for diseases caused by heteroplasmic mtDNA mutations.
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Affiliation(s)
- Claudia V Pereira
- Department of Biological Sciences, Vanderbilt University, Nashville, TN, USA
| | - Bryan L Gitschlag
- Department of Biological Sciences, Vanderbilt University, Nashville, TN, USA
| | - Maulik R Patel
- Department of Biological Sciences, Vanderbilt University, Nashville, TN, USA.,Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN, USA.,Diabetes Research and Training Center, Vanderbilt University School of Medicine, Nashville, TN, USA
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9
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McGrath C. Highlight: Reconciling Differences between Germline and Soma. Genome Biol Evol 2021. [PMCID: PMC8245196 DOI: 10.1093/gbe/evab102] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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Suh A, Dion-Côté AM. New Perspectives on the Evolution of Within-Individual Genome Variation and Germline/Soma Distinction. Genome Biol Evol 2021; 13:evab095. [PMID: 33963843 PMCID: PMC8245192 DOI: 10.1093/gbe/evab095] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/07/2021] [Indexed: 12/19/2022] Open
Abstract
Genomes can vary significantly even within the same individual. The underlying mechanisms are manifold, ranging from somatic mutation and recombination, development-associated ploidy changes and genetic bottlenecks, over to programmed DNA elimination during germline/soma differentiation. In this perspective piece, we briefly review recent developments in the study of within-individual genome variation in eukaryotes and prokaryotes. We highlight a Society for Molecular Biology and Evolution 2020 virtual symposium entitled "Within-individual genome variation and germline/soma distinction" and the present Special Section of the same name in Genome Biology and Evolution, together fostering cross-taxon synergies in the field to identify and tackle key open questions in the understanding of within-individual genome variation.
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Affiliation(s)
- Alexander Suh
- School of Biological Sciences—Organisms and the Environment, University of East Anglia, Norwich, United Kingdom
- Department of Organismal Biology—Systematic Biology, Evolutionary Biology Centre (EBC), Science for Life Laboratory, Uppsala University, Sweden
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Ghiselli F, Iannello M, Piccinini G, Milani L. Bivalve molluscs as model systems for studying mitochondrial biology. Integr Comp Biol 2021; 61:1699-1714. [PMID: 33944910 DOI: 10.1093/icb/icab057] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
The class Bivalvia is a highly successful and ancient taxon including ∼25,000 living species. During their long evolutionary history bivalves adapted to a wide range of physicochemical conditions, habitats, biological interactions, and feeding habits. Bivalves can have strikingly different size, and despite their apparently simple body plan, they evolved very different shell shapes, and complex anatomic structures. One of the most striking features of this class of animals is their peculiar mitochondrial biology: some bivalves have facultatively anaerobic mitochondria that allow them to survive prolonged periods of anoxia/hypoxia. Moreover, more than 100 species have now been reported showing the only known evolutionarily stable exception to the strictly maternal inheritance of mitochondria in animals, named doubly uniparental inheritance. Mitochondrial activity is fundamental to eukaryotic life, and thanks to their diversity and uncommon features, bivalves represent a great model system to expand our knowledge about mitochondrial biology, so far limited to a few species. We highlight recent works studying mitochondrial biology in bivalves at either genomic or physiological level. A link between these two approaches is still missing, and we believe that an integrated approach and collaborative relationships are the only possible ways to be successful in such endeavour.
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Affiliation(s)
- Fabrizio Ghiselli
- Department of Biological, Geological, and Environmental Sciences, University of Bologna, Italy
| | - Mariangela Iannello
- Department of Biological, Geological, and Environmental Sciences, University of Bologna, Italy
| | - Giovanni Piccinini
- Department of Biological, Geological, and Environmental Sciences, University of Bologna, Italy
| | - Liliana Milani
- Department of Biological, Geological, and Environmental Sciences, University of Bologna, Italy
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