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Sex-linked deubiquitinase establishes uniparental transmission of chloroplast DNA. Nat Commun 2022; 13:1133. [PMID: 35241655 PMCID: PMC8894339 DOI: 10.1038/s41467-022-28807-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2021] [Accepted: 02/09/2022] [Indexed: 12/26/2022] Open
Abstract
Most sexual organisms inherit organelles from one parent, commonly by excluding organelles from the smaller gametes. However, post-mating elimination of organelles derived from one gamete ensures uniparental inheritance, where the underlying mechanisms to distinguish organelles by their origin remain obscure. Mating in Chlamydomonas reinhardtii combines isomorphic plus and minus gametes, but chloroplast DNA from minus gametes is selectively degraded in zygotes. Here, we identify OTU2p (otubain protein 2), encoded in the plus mating-type locus MT+, as the protector of plus chloroplast. Otu2p is an otubain-like deubiquitinase, which prevents proteasome-mediated degradation of the preprotein translocase of the outer chloroplast membrane (TOC) during gametogenesis. Using OTU2p-knockouts and proteasome inhibitor treatment, we successfully redirect selective DNA degradation in chloroplasts with reduced TOC levels regardless of mating type, demonstrating that plus-specific Otu2p establishes uniparental chloroplast DNA inheritance. Our work documents that a sex-linked organelle quality control mechanism drives the uniparental organelle inheritance without dimorphic gametes. Most sexual organisms ensure that organelles are inherited from a single parent. Here, the authors describe OTU2p, a Chlamydomonas deubiquitinase that drives uniparental organelle inheritance without gametic dimorphism by preventing proteasome-mediated degradation exclusively in gametes of the plus mating type.
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Shen Y, Iwao T, Motomura T, Nagasato C. Cytoplasmic inheritance of mitochondria and chloroplasts in the anisogamous brown alga Mutimo cylindricus (Phaeophyceae). PROTOPLASMA 2021; 258:19-32. [PMID: 32862312 DOI: 10.1007/s00709-020-01540-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/11/2020] [Accepted: 07/28/2020] [Indexed: 06/11/2023]
Abstract
Based on the morphology of gametes, sexual reproduction in brown algae is usually classified into three types: isogamy, anisogamy, and oogamy. In isogamy, chloroplasts and chloroplast DNA (chlDNA) in the sporophyte cells are inherited biparentally, while mitochondria (or mitochondrial DNA, mtDNA) is inherited maternally. In oogamy, chloroplasts and mitochondria are inherited maternally. However, the patterns of mitochondrial and chloroplast inheritance in anisogamy have not been clarified. Here, we examined derivation of mtDNA and chlDNA in the zygotes through strain-specific PCR analysis using primers based on single nucleotide polymorphism in the anisogamous brown alga Mutimo cylindricus. In 20-day-old sporophytes after fertilization, mtDNA and chlDNA derived from female gametes were detected, thus confirming the maternal inheritance of both organelles. Additionally, the behavior of mitochondria and chloroplasts in the zygotes was analyzed by examining the consecutive serial sections using transmission electron microscopy. Male mitochondria were isolated or compartmentalized by a double-membrane and then completely digested into a multivesicular structure 2 h after fertilization. Meanwhile, male chloroplasts with eyespots were observed even in 4-day-old, seven-celled sporophytes. The final fate of male chloroplasts could not be traced. Organelle DNA copy number was also examined in female and male gametes. The DNA copy number per chloroplast and mitochondria in male gametes was lower compared with female organelles. The degree of difference is bigger in mtDNA. Thus, changes in different morphology and DNA amount indicate that maternal inheritance of mitochondria and chloroplasts in this species may be based on different processes and timing after fertilization.
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Affiliation(s)
- Yuan Shen
- Graduate School of Environmental Science, Hokkaido University, Sapporo, 060-0810, Japan
| | - Toyoki Iwao
- Toba Fisheries Science Center, Toba, 517-0005, Japan
| | - Taizo Motomura
- Muroran Marine Station, Field Science Center for Northern Biosphere, Hokkaido University, Muroran, 051-0013, Japan
| | - Chikako Nagasato
- Muroran Marine Station, Field Science Center for Northern Biosphere, Hokkaido University, Muroran, 051-0013, Japan.
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Kariyawasam T, Joo S, Lee J, Toor D, Gao AF, Noh KC, Lee JH. TALE homeobox heterodimer GSM1/GSP1 is a molecular switch that prevents unwarranted genetic recombination in Chlamydomonas. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2019; 100:938-953. [PMID: 31368133 DOI: 10.1111/tpj.14486] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/10/2019] [Revised: 07/23/2019] [Accepted: 07/24/2019] [Indexed: 06/10/2023]
Abstract
Eukaryotic sexual life cycles alternate between haploid and diploid stages, the transitions between which are delineated by cell fusion and meiotic division. Transcription factors in the TALE-class homeobox family, GSM1 and GSP1, predominantly control gene expression for the haploid-to-diploid transition during sexual reproduction in the unicellular green alga, Chlamydomonas reinhardtii. To understand the roles that GSM1 and GSP1 play in zygote development, we used gsm1 and gsp1 mutants and examined fused gametes that normally undergo the multiple organellar fusions required for the genetic unity of the zygotes. In gsm1 and gsp1 zygotes, no fusion was observed for the nucleus and chloroplast. Surprisingly, mitochondria and endoplasmic reticulum, which undergo dynamic autologous fusion/fission, did not undergo heterologous fusions in gsm1 or gsp1 zygotes. Furthermore, the mutants failed to resorb their flagella, an event that normally renders the zygotes immotile. When gsm1 and gsp1 zygotes resumed the mitotic cycle, their two nuclei fused prior to mitosis, but neither chloroplastic nor mitochondrial fusion took place, suggesting that these fusions are specifically turned on by GSM1/GSP1. Taken together, this study shows that organellar restructuring during zygotic diploidization does not occur by default but is triggered by a combinatorial switch, the GSM1/GSP1 dyad. This switch may represent an ancient mechanism that evolved to restrict genetic recombination during sexual development.
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Affiliation(s)
| | - Sunjoo Joo
- Department of Botany, University of British Columbia, Vancouver, Canada
| | - Jenny Lee
- Department of Botany, University of British Columbia, Vancouver, Canada
| | - Deepak Toor
- Department of Botany, University of British Columbia, Vancouver, Canada
| | - Ally F Gao
- Department of Botany, University of British Columbia, Vancouver, Canada
| | - Kyung-Chul Noh
- Department of Biology, Washington University, St. Louis, MO, USA
| | - Jae-Hyeok Lee
- Department of Botany, University of British Columbia, Vancouver, Canada
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Takeuchi T, Benning C. Nitrogen-dependent coordination of cell cycle, quiescence and TAG accumulation in Chlamydomonas. BIOTECHNOLOGY FOR BIOFUELS 2019; 12:292. [PMID: 31890020 PMCID: PMC6927116 DOI: 10.1186/s13068-019-1635-0] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/15/2019] [Accepted: 12/12/2019] [Indexed: 05/07/2023]
Abstract
Microalgae hold great promises as sustainable cellular factories for the production of alternative fuels, feeds, and biopharmaceuticals for human health. While the biorefinery approach for fuels along with the coproduction of high-value compounds with industrial, therapeutic, or nutraceutical applications have the potential to make algal biofuels more economically viable, a number of challenges continue to hamper algal production systems at all levels. One such hurdle includes the metabolic trade-off often observed between the increased yields of desired products, such as triacylglycerols (TAG), and the growth of an organism. Initial genetic engineering strategies to improve lipid productivity in microalgae, which focused on overproducing the enzymes involved in fatty acid and TAG biosynthesis or inactivating competing carbon (C) metabolism, have seen some successes albeit at the cost of often greatly reduced biomass. Emergent approaches that aim at modifying the dynamics of entire metabolic pathways by engineering of pertinent transcription factors or signaling networks appear to have successfully achieved a balance between growth and neutral lipid accumulation. However, the biological knowledge of key signaling networks and molecular components linking these two processes is still incomplete in photosynthetic eukaryotes, making it difficult to optimize metabolic engineering strategies for microalgae. Here, we focus on nitrogen (N) starvation of the model green microalga, Chlamydomonas reinhardtii, to present the current understanding of the nutrient-dependent switch between proliferation and quiescence, and the drastic reprogramming of metabolism that results in the storage of C compounds following N starvation. We discuss the potential components mediating the transcriptional repression of cell cycle genes and the establishment of quiescence in Chlamydomonas, and highlight the importance of signaling pathways such as those governed by the target of rapamycin (TOR) and sucrose nonfermenting-related (SnRK) kinases in the coordination of metabolic status with cellular growth. A better understanding of how the cell division cycle is regulated in response to nutrient scarcity and of the signaling pathways linking cellular growth to energy and lipid homeostasis, is essential to improve the prospects of biofuels and biomass production in microalgae.
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Affiliation(s)
- Tomomi Takeuchi
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824 USA
- Department of Energy-Plant Research Laboratory, Michigan State University, East Lansing, MI 48824 USA
| | - Christoph Benning
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824 USA
- Department of Energy-Plant Research Laboratory, Michigan State University, East Lansing, MI 48824 USA
- Department of Plant Biology, Michigan State University, East Lansing, MI 48824 USA
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5
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Heimerl N, Hommel E, Westermann M, Meichsner D, Lohr M, Hertweck C, Grossman AR, Mittag M, Sasso S. A giant type I polyketide synthase participates in zygospore maturation in Chlamydomonas reinhardtii. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2018; 95:268-281. [PMID: 29729034 DOI: 10.1111/tpj.13948] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/28/2017] [Revised: 04/14/2018] [Accepted: 04/23/2018] [Indexed: 06/08/2023]
Abstract
Polyketide synthases (PKSs) occur in many bacteria, fungi and plants. They are highly versatile enzymes involved in the biosynthesis of a large variety of compounds including antimicrobial agents, polymers associated with bacterial cell walls and plant pigments. While harmful algae are known to produce polyketide toxins, sequences of the genomes of non-toxic algae, including those of many green algal species, have surprisingly revealed the presence of genes encoding type I PKSs. The genome of the model alga Chlamydomonas reinhardtii (Chlorophyta) contains a single type I PKS gene, designated PKS1 (Cre10.g449750), which encodes a giant PKS with a predicted mass of 2.3 MDa. Here, we show that PKS1 is induced in 2-day-old zygotes and is required for their development into zygospores, the dormant stage of the zygote. Wild-type zygospores contain knob-like structures (~50 nm diameter) that form at the cell surface and develop a central cell wall layer; both of these structures are absent from homozygous pks1 mutants. Additionally, in contrast to wild-type zygotes, chlorophyll degradation is delayed in homozygous pks1 mutant zygotes, indicating a disruption in zygospore development. In agreement with the role of the PKS in the formation of the highly resistant zygospore wall, mutant zygotes have lost the formidable desiccation tolerance of wild-type zygotes. Together, our results represent functional analyses of a PKS mutant in a photosynthetic eukaryotic microorganism, revealing a central function for polyketides in the sexual cycle and survival under stressful environmental conditions.
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Affiliation(s)
- Natalie Heimerl
- Matthias Schleiden Institute of Genetics, Bioinformatics and Molecular Botany, Friedrich Schiller University, Jena, Germany
| | - Elisabeth Hommel
- Matthias Schleiden Institute of Genetics, Bioinformatics and Molecular Botany, Friedrich Schiller University, Jena, Germany
| | | | - Doreen Meichsner
- Matthias Schleiden Institute of Genetics, Bioinformatics and Molecular Botany, Friedrich Schiller University, Jena, Germany
| | - Martin Lohr
- Institute of Molecular Physiology, Plant Biochemistry, Johannes Gutenberg University, Mainz, Germany
| | - Christian Hertweck
- Department of Biomolecular Chemistry, Leibniz Institute for Natural Product Research and Infection Biology (HKI), Jena, Germany
- Friedrich Schiller University, Jena, Germany
| | | | - Maria Mittag
- Matthias Schleiden Institute of Genetics, Bioinformatics and Molecular Botany, Friedrich Schiller University, Jena, Germany
| | - Severin Sasso
- Matthias Schleiden Institute of Genetics, Bioinformatics and Molecular Botany, Friedrich Schiller University, Jena, Germany
- Department of Biomolecular Chemistry, Leibniz Institute for Natural Product Research and Infection Biology (HKI), Jena, Germany
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Raven JA. Implications of mutation of organelle genomes for organelle function and evolution. JOURNAL OF EXPERIMENTAL BOTANY 2015; 66:5639-50. [PMID: 26077836 DOI: 10.1093/jxb/erv298] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Organelle genomes undergo more variation, including that resulting from damage, than eukaryotic nuclear genomes, or bacterial genomes, under the same conditions. Recent advances in characterizing the changes to genomes of chloroplasts and mitochondria of Zea mays should, when applied more widely, help our understanding of how damage to organelle genomes relates to how organelle function is maintained through the life of individuals and in succeeding generations. Understanding of the degree of variation in the changes to organelle DNA and its repair among photosynthetic organisms might help to explain the variations in the rate of nucleotide substitution among organelle genomes. Further studies of organelle DNA variation, including that due to damage and its repair might also help us to understand why the extent of DNA turnover in the organelles is so much greater than that in their bacterial (cyanobacteria for chloroplasts, proteobacteria for mitochondria) relatives with similar rates of production of DNA-damaging reactive oxygen species. Finally, from the available data, even the longest-lived organelle-encoded proteins, and the RNAs needed for their synthesis, are unlikely to maintain organelle function for much more than a week after the complete loss of organelle DNA.
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Affiliation(s)
- John A Raven
- Division of Plant Sciences, University of Dundee at the James Hutton Institute, Invergowrie, Dundee DD2 5DA, UK †School of Plant Biology, University of Western Australia, M048, 35 Stirling Highway, Crawley, WA 6009, Australia
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Mets L. Uniparental inheritance of chloroplast DNA sequences in interspecific hybrids of Chlamydomonas. Curr Genet 2013; 2:131-8. [PMID: 24189804 DOI: 10.1007/bf00420625] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/1980] [Indexed: 11/29/2022]
Abstract
The meiotic transmission of chloroplast DNA (cpDNA) was studied in crosses between two species of Chlamydomonas (C. moewusii and C. eugametos) which have substantial differences in cpDNA restriction patterns. The results provide a direct demonstration that cpDNA can be inherited in a uniparental pattern, paralleling the transmission of a uniparentally inherited antibiotic resistance marker. Thus, cpDNA could carry the uniparental genes of these species, but other extrachromosomal DNAs are not excluded as possible carriers. For example, C. moewusii was found to contain a set of low molecular weight (LMW) DNA species which cannot be detected in C. eugametos. These LMW DNA species are also transmitted uniparentally in the tetrads studied. Uniparentai transmission may not be an exclusive property of cpDNA in Chlamydomonas species.
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Affiliation(s)
- L Mets
- Department of Biology, Case Western Reserve University, 44106, Cleveland, Ohio, USA
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8
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Matagne RF, Mathieu D. Transmission of chloroplast genes in triploid and tetraploid zygospores of Chlamydomonas reinhardtii: Roles of mating-type gene dosage and gametic chloroplast DNA content. Proc Natl Acad Sci U S A 2010; 80:4780-3. [PMID: 16593351 PMCID: PMC384128 DOI: 10.1073/pnas.80.15.4780] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Diploid clones homozygous (mt(+)/mt(+) or mt(-)/mt(-)) or heterozygous (mt(+)/mt(-); phenotypically mt(-)) for the mating-type locus and homoplasmic for a chloroplast marker conferring resistance to an antibiotic were isolated by artificially induced cell fusion or sexual mating. These diploids were crossed with haploid or diploid strains of opposite mating type and carrying another chloroplast marker. The transmission of the chloroplast genes was analyzed in the triploid and tetraploid zygospores in comparison with diploid zygospores used as controls. The transmission was almost exclusively maternal (mt(+)) (>94%) in the crosses mt(+) x mt(-), mt(+)/mt(+) x mt(-), and mt(+)/mt(+) x mt(-)/mt(-). The transmission was preferentially maternal (>76%) in the crosses mt(+) x mt(-)/mt(-) whereas in the crosses mt(+) x mt(+)/mt(-), <50% of the zygospores transmitted the chloroplast allele of maternal (mt(+)) origin. The zygospores produced in crosses mt(+)/mt(+) x mt(+)/mt(-) transmitted the alleles from both parents in >60% of cases. The results show that (i) the presence of one mt(+) allele in the mt(+)/mt(-) (phenotypically mt(-)) diploid gametes and (ii) the higher amount of chloroplast DNA molecules (input) present in the diploid gametes versus the haploid ones favor the transmission of the chloroplast allele contributed by these gametes. Moreover, because the zygospores issued from crosses mt(+)/mt(+) x mt(-) and mt(+) x mt(+)/mt(-) were genotypically identical mt(+)/mt(+)/mt(-)) but behaved very differently in their chloroplast gene transmission, it was concluded that the molecular events leading to preferential elimination of paternal DNA copies must occur before the fusion of nuclei or chloroplasts in the newly formed zygotes.
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Affiliation(s)
- R F Matagne
- Genetics of Microorganisms, Department of Botany, University of Liège, Sart Tilman B-4000 Liège, Belgium
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Miyamura S. Cytoplasmic inheritance in green algae: patterns, mechanisms and relation to sex type. JOURNAL OF PLANT RESEARCH 2010; 123:171-184. [PMID: 20112126 DOI: 10.1007/s10265-010-0309-6] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/14/2009] [Accepted: 12/21/2009] [Indexed: 05/28/2023]
Abstract
Cytological and genetic investigations of two major groups of green algae, chlorophyte and streptophyte green algae, show a predominance of uniparental inheritance of the plastid and mitochondrial genomes in most species. However, in some crosses of isogamous species of Ulva compressa, these genomes are transmitted from mt+, mt(-), and both parents. In species with uniparental organelle inheritance, various mechanisms can eliminate organelles and their DNA during male gametogenesis or after fertilization. Concerning plastid inheritance, two major mechanisms are widespread in green algae: (1) digestion of plastid DNA during male gametogenesis, during fertilization, or after fertilization; and (2) disintegration or fusion of the plastid in the zygote. The first mechanism also eliminates the mitochondrial DNA in anisogamous and oogamous species. These mechanisms would ensure the predominantly uniparental inheritance of organelle genomes in green algae. To trace the evolutionary history of cytoplasmic inheritance in green algae, the relations between uniparental inheritance and sex type were considered in isogamous, anisogamous, and oogamous species using sex-specific features that might be nearly universal among Chlorophyta.
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Affiliation(s)
- Shinichi Miyamura
- Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8572, Japan.
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10
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Cavalier-Smith T. Origin of the cell nucleus, mitosis and sex: roles of intracellular coevolution. Biol Direct 2010; 5:7. [PMID: 20132544 PMCID: PMC2837639 DOI: 10.1186/1745-6150-5-7] [Citation(s) in RCA: 139] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2009] [Accepted: 02/04/2010] [Indexed: 12/18/2022] Open
Abstract
BACKGROUND The transition from prokaryotes to eukaryotes was the most radical change in cell organisation since life began, with the largest ever burst of gene duplication and novelty. According to the coevolutionary theory of eukaryote origins, the fundamental innovations were the concerted origins of the endomembrane system and cytoskeleton, subsequently recruited to form the cell nucleus and coevolving mitotic apparatus, with numerous genetic eukaryotic novelties inevitable consequences of this compartmentation and novel DNA segregation mechanism. Physical and mutational mechanisms of origin of the nucleus are seldom considered beyond the long-standing assumption that it involved wrapping pre-existing endomembranes around chromatin. Discussions on the origin of sex typically overlook its association with protozoan entry into dormant walled cysts and the likely simultaneous coevolutionary, not sequential, origin of mitosis and meiosis. RESULTS I elucidate nuclear and mitotic coevolution, explaining the origins of dicer and small centromeric RNAs for positionally controlling centromeric heterochromatin, and how 27 major features of the cell nucleus evolved in four logical stages, making both mechanisms and selective advantages explicit: two initial stages (origin of 30 nm chromatin fibres, enabling DNA compaction; and firmer attachment of endomembranes to heterochromatin) protected DNA and nascent RNA from shearing by novel molecular motors mediating vesicle transport, division, and cytoplasmic motility. Then octagonal nuclear pore complexes (NPCs) arguably evolved from COPII coated vesicle proteins trapped in clumps by Ran GTPase-mediated cisternal fusion that generated the fenestrated nuclear envelope, preventing lethal complete cisternal fusion, and allowing passive protein and RNA exchange. Finally, plugging NPC lumens by an FG-nucleoporin meshwork and adopting karyopherins for nucleocytoplasmic exchange conferred compartmentation advantages. These successive changes took place in naked growing cells, probably as indirect consequences of the origin of phagotrophy. The first eukaryote had 1-2 cilia and also walled resting cysts; I outline how encystation may have promoted the origin of meiotic sex. I also explain why many alternative ideas are inadequate. CONCLUSION Nuclear pore complexes are evolutionary chimaeras of endomembrane- and mitosis-related chromatin-associated proteins. The keys to understanding eukaryogenesis are a proper phylogenetic context and understanding organelle coevolution: how innovations in one cell component caused repercussions on others.
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Guo GQGQ, Zheng GCGC. Hypotheses for the functions of intercellular bridges in male germ cell development and its cellular mechanisms. J Theor Biol 2004; 229:139-46. [PMID: 15178192 DOI: 10.1016/j.jtbi.2004.03.010] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2003] [Revised: 03/12/2004] [Accepted: 03/12/2004] [Indexed: 11/30/2022]
Abstract
In oogamous reproduction of multicellular organisms, a striking phenomenon is the prevailing synchronous development of male germ cells connected by wide intercellular bridges (IBs, 0.1-2 microm), which is well conserved in both animal and plant species ranging from algae to human. In the literature, IBs are believed either to allow genetically segregated haploid spermatids to share diploid gene products after meiosis, or to mediate rapid transfer of some vital signals or nutrients. Although intercellular sharing of gene transcripts has experimental evidences, these hypotheses are still not satisfactory. To explore the unknown roles of IB, we assume that developing male germ cells may be especially sensitive to stochastic gene expression to become heterogeneous. To achieve best gamete quality, such heterogeneity must be eliminated so that relatively uniform gametes with normal functions can be produced. Development within a common syncytium may be the only way for this purpose. The process may require not only the intercellular exchange of a few molecular signals but also the mixing of protoplasm between the connected cells so that they have similar levels/states of mRNAs, proteins and organelles, which can be achieved only through wide IBs. This hypothesis can explain some quite intriguing aspects of male gametogenesis and provide unique predictions that can be tested experimentally.
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Affiliation(s)
- G-Q Guanq-Qin Guo
- Laboratory of cell biology, Lanzhou University, Lanzhou 730000, PR China. ,
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12
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Abstract
Mutation plays the primary role in evolution that Weismann mistakenly attributed to sex. Homologous recombination, as in sex, is important for population genetics--shuffling of minor variants, but relatively insignificant for large-scale evolution. Major evolutionary innovations depend much more on illegitimate recombination, which makes novel genes by gene duplication and by gene chimaerisation--essentially mutational forces. The machinery of recombination and sex evolved in two distinct bouts of quantum evolution separated by nearly 3 Gy of stasis; I discuss their nature and causes. The dominant selective force in the evolution of recombination and sex has been selection for replicational fidelity and viability; without the recombination machinery, accurate reproduction, stasis, resistance to radical deleterious evolutionary change and preservation of evolutionary innovations would be impossible. Recombination proteins betray in their phylogeny and domain structure a key role for gene duplication and chimaerisation in their own origin. They arose about 3.8 Gy ago to enable faithful replication and segregation of the first circular DNA genomes in precellular ancestors of Gram-negative eubacteria. Then they were recruited and modified by selfish genetic parasites (viruses; transposons) to help them spread from host to host. Bacteria differ fundamentally from eukaryotes in that gene transfer between cells, whether incidental to their absorptive feeding on DNA and virus infection or directly by plasmids, involves only genomic fragments. This was radically changed by the neomuran revolution about 850 million years ago when a posibacterium evolved into the thermophilic cenancestor of eukaryotes and archaebacteria (jointly called neomurans), radically modifying or substituting its DNA-handling enzymes (those responsible for transcription as well as for replication, repair and recombination) as a coadaptive consequence of the origin of core histones to stabilise its chromosome. Substitution of glycoprotein for peptidoglycan walls in the neomuran ancestor and the evolution of an endoskeleton and endomembrane system in eukaryotes alone required the origin of nuclei, mitosis and novel cell cycle controls and enabled them to evolve cell fusion and thereby the combination of whole genomes from different cells. Meiosis evolved because of resulting selection for periodic ploidy reduction, with incidental consequences for intrapopulation genetic exchange. Little modification was needed to recombination enzymes or to the ancient bacterial catalysts of homology search by spontaneous base pairing to mediate chromosome pairing. The key innovation was the origin of meiotic cohesins delaying centromere splitting to allow two successive divisions before reversion to vegetative growth and replication, necessarily yielding two-step meiosis. Also significant was the evolution of synaptonemal complexes to stabilise bivalents and of monopolins to orient sister centromeres to one spindle pole. The primary significance of sex was not to promote evolutionary change but to limit it by facilitating ploidy cycles to balance the conflicting selective forces acting on rapidly growing phagotrophic protozoa and starved dormant cysts subject to radiation and other damage.
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Affiliation(s)
- T Cavalier-Smith
- Department of Zoology, University of Oxford, South Parks Road, Oxford, OX1 3PS, UK.
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Kavanagh TA, Thanh ND, Lao NT, McGrath N, Peter SO, Horváth EM, Dix PJ, Medgyesy P. Homeologous plastid DNA transformation in tobacco is mediated by multiple recombination events. Genetics 1999; 152:1111-22. [PMID: 10388829 PMCID: PMC1460644 DOI: 10.1093/genetics/152.3.1111] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Efficient plastid transformation has been achieved in Nicotiana tabacum using cloned plastid DNA of Solanum nigrum carrying mutations conferring spectinomycin and streptomycin resistance. The use of the incompletely homologous (homeologous) Solanum plastid DNA as donor resulted in a Nicotiana plastid transformation frequency comparable with that of other experiments where completely homologous plastid DNA was introduced. Physical mapping and nucleotide sequence analysis of the targeted plastid DNA region in the transformants demonstrated efficient site-specific integration of the 7.8-kb Solanum plastid DNA and the exclusion of the vector DNA. The integration of the cloned Solanum plastid DNA into the Nicotiana plastid genome involved multiple recombination events as revealed by the presence of discontinuous tracts of Solanum-specific sequences that were interspersed between Nicotiana-specific markers. Marked position effects resulted in very frequent cointegration of the nonselected peripheral donor markers located adjacent to the vector DNA. Data presented here on the efficiency and features of homeologous plastid DNA recombination are consistent with the existence of an active RecA-mediated, but a diminished mismatch, recombination/repair system in higher-plant plastids.
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Affiliation(s)
- T A Kavanagh
- Department of Genetics, Trinity College, University of Dublin, Dublin 2, Ireland
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Kuriyama H, Takano H, Suzuki L, Uchida H, Kawano S, Kuroiwa H, Kuroiwa T. Characterization of Chlamydomonas reinhardtii zygote-specific cDNAs that encode novel proteins containing ankyrin repeats and WW domains. PLANT PHYSIOLOGY 1999; 119:873-84. [PMID: 10069826 PMCID: PMC32102 DOI: 10.1104/pp.119.3.873] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/21/1998] [Accepted: 12/02/1998] [Indexed: 05/18/2023]
Abstract
Genes that are expressed only in the young zygote are considered to be of great importance in the development of an isogamous green alga, Chlamydomonas reinhardtii. Clones representing the Zys3 gene were isolated from a cDNA library prepared using zygotes at 10 min after fertilization. Sequencing of Zys3 cDNA clones resulted in the isolation of two related molecular species. One of them encoded a protein that contained two kinds of protein-to-protein interaction motifs known as ankyrin repeats and WW domains. The other clone lacked the ankyrin repeats but was otherwise identical. These mRNA species began to accumulate simultaneously in cells beginning 10 min after fertilization, and reached maximum levels at about 4 h, after which time levels decreased markedly. Genomic DNA gel-blot analysis indicated that Zys3 was a single-copy gene. The Zys3 proteins exhibited parallel expression to the Zys3 mRNAs at first, appearing 2 h after mating, and reached maximum levels at more than 6 h, but persisted to at least 1 d. Immunocytochemical analysis revealed their localization in the endoplasmic reticulum, which suggests a role in the morphological changes of the endoplasmic reticulum or in the synthesis and transport of proteins to the Golgi apparatus or related vesicles.
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MESH Headings
- Amino Acid Sequence
- Animals
- Ankyrins/chemistry
- Ankyrins/genetics
- Base Sequence
- Chlamydomonas reinhardtii/genetics
- Chlamydomonas reinhardtii/growth & development
- Chlamydomonas reinhardtii/metabolism
- DNA, Complementary/genetics
- DNA, Plant/genetics
- DNA, Protozoan/genetics
- Genes, Plant
- Genes, Protozoan
- Molecular Sequence Data
- Plant Proteins/chemistry
- Plant Proteins/genetics
- Plant Proteins/metabolism
- Protozoan Proteins/chemistry
- Protozoan Proteins/genetics
- Protozoan Proteins/metabolism
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- RNA, Plant/genetics
- RNA, Plant/metabolism
- RNA, Protozoan/genetics
- RNA, Protozoan/metabolism
- Repetitive Sequences, Amino Acid
- Sequence Homology, Amino Acid
- Zygote/metabolism
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Affiliation(s)
- H Kuriyama
- Department of Biological Sciences, Graduate School of Science, University of Tokyo, Hongo, Tokyo 113, Japan.
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15
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16
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Armbrust EV, Ferris PJ, Goodenough UW. A mating type-linked gene cluster expressed in Chlamydomonas zygotes participates in the uniparental inheritance of the chloroplast genome. Cell 1993; 74:801-11. [PMID: 8374951 DOI: 10.1016/0092-8674(93)90460-8] [Citation(s) in RCA: 57] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
A characteristic feature of early zygote development in Chlamydomonas is the selective degradation of chloroplast DNA from the mating type minus parent. The zygote-specific gene cluster ezy-1 is linked to the mating type locus and is transcribed almost immediately upon zygote formation. We show here that the acidic Ezy-1 polypeptide is rapidly transported to both the plus and minus chloroplasts, where it interacts with each chloroplast nucleoid. Expression of ezy-1 is selectively inhibited when plus, but not minus, gametes are briefly ultraviolet irradiated just prior to mating, a treatment known to disrupt the uniparental inheritance of chloroplast traits. We propose that the Ezy-1 polypeptide participates in the destruction of the minus chloroplast DNA in zygotes and thus the uniparental inheritance of chloroplast traits. The ezy-1 gene represents a valuable molecular probe for dissecting mechanisms underlying organelle inheritance.
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Affiliation(s)
- E V Armbrust
- Department of Biology, Washington University, St. Louis, Missouri 63130
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17
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Baldan B, Girard-Bascou J, Wollman FA, Olive J. Evidence for thylakoid membrane fusion during zygote formation in Chlamydomonas reinhardtii. J Cell Biol 1991; 114:905-15. [PMID: 1874788 PMCID: PMC2289111 DOI: 10.1083/jcb.114.5.905] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
To understand whether fusions of thylakoid membranes from the parental chloroplasts occurred during zygote formation in Chlamydomonas reinhardtii, we performed an ultrastructural analysis of the zygotes produced by crossing mutants lacking photosystem I or II protein complexes, in the absence of de novo chloroplast protein synthesis. Thylakoid membranes from each parent could be distinguished on thin sections due to their organization in "supergrana" in mutants lacking photosystem I centers, by freeze-fracturing due to the absence of most of the exoplasmic-face (EF) particles in mutants lacking photosystem II centers, by immunocytochemistry using antibodies directed against photosystem II subunits. We demonstrate that a fusion of the thylakoid membranes occurred during zygote formation approximately 15 h after mating. These fusions allowed a lateral redistribution of the thylakoid membrane proteins. These observations provide the structural basis for the restoration of photosynthetic electron flow in the mature zygote that we observed in fluorescence induction experiments.
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Affiliation(s)
- B Baldan
- Dipartimento Biologia, Università di Padova, Italy
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18
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Abstract
After conjugation between Chlamydomonas gametes of opposite mating type, a transient dikaryon is formed. The two nuclei fuse within 4-6 hr after mating. The young diploid zygote differentiates into dormant zygospore competent to complete meiosis, or more rarely (2-10% of cases) it undergoes mitosis to produce a stable diploid progeny. We here bring genetical, biochemical, and cytological evidence that among the mitotic zygotes, a large proportion of them undergo cytokinesis without fusion of the nuclei-a process that has been termed "cytoduction." By using appropriate genetic markers, haploid cytoductants that possess the nuclear genotype of one parent and the chloroplast marker of the other parent can easily be isolated. Genetical analysis and hybridization experiments moreover show that many haploid cytoductants transmit the chloroplast DNA molecules of both parents and that, as in diploids, these DNA copies occasionally recombine. This process of cytoduction extends the life cycle of Chlamydomonas and provides new tools for its genetic analysis.
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Affiliation(s)
- R F Matagne
- Department of Botany, University of Liege, Sart Tilman, Belgium
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19
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Lemieux B, Turmel M, Lemieux C. Recombination of Chlamydomonas chloroplast DNA occurs more frequently in the large inverted repeat sequence than in the single-copy regions. TAG. THEORETICAL AND APPLIED GENETICS. THEORETISCHE UND ANGEWANDTE GENETIK 1990; 79:17-27. [PMID: 24226114 DOI: 10.1007/bf00223781] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/01/1989] [Accepted: 08/30/1989] [Indexed: 06/02/2023]
Abstract
It is well documented that chloroplast DNA (cpDNA) recombination occurs at a relatively high frequency during sexual reproduction of unicellular green algae from the Chlamydomonas genus. Like the cpDNAs of most land plants, those of Chlamydomonas species are divided into two single-copy regions by a large inverted repeat sequence, part of which encodes the chloroplast rRNA genes. In the present study, we scored the inheritance of polymorphic loci spanning the entire chloroplast genome in hybrids recovered from reciprocal interspecific and F1 crosses between Chlamydomonas eugametes and C. moewusii, and from these data, estimated the density of recombination junctions within each region of recombinant cpDNAs. Our results indicate that recombination junctions occur at highly variable frequencies across the three main domains of the chloroplast genome. The large inverted repeat sequence was found to exhibit at least a five-fold higher density of recombination junctions compared to one of the singlecopy regions, whereas junctions in the latter region were five-fold more abundant relative to those in the other single-copy region. This marked difference in the densities of recombination junctions implies that the extent of genetic linkage between two given chloroplast loci will depend not only on their physical distance, but also on their locations within the genome.
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Affiliation(s)
- B Lemieux
- Département de Biochimie, Faculté des Sciences et de Génie, Université Laval, G1K 7P4, Québec, Québec, Canada
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20
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Unidirectional gene conversions in the chloroplast of Chlamydomonas interspecific hybrids. ACTA ACUST UNITED AC 1988. [DOI: 10.1007/bf00322443] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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21
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Matagne RF. Chloroplast gene transmission in Chlamydomonas reinhardtii. A model for its control by the mating-type locus. Curr Genet 1987. [DOI: 10.1007/bf00435286] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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22
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Boynton JE, Harris EH, Burkhart BD, Lamerson PM, Gillham NW. Transmission of mitochondrial and chloroplast genomes in crosses of Chlamydomonas. Proc Natl Acad Sci U S A 1987; 84:2391-5. [PMID: 3031682 PMCID: PMC304657 DOI: 10.1073/pnas.84.8.2391] [Citation(s) in RCA: 114] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Physical differences between organelle genomes of the interfertile species Chlamydomonas reinhardtii and Chlamydomonas smithii have been used to demonstrate that sexual zygotes transmit chloroplast and mitochondrial DNA from opposite mating types. Processes responsible can be separated functionally and genetically, although both are controlled by mating type. In vegetative diploids, chloroplast and mitochondrial genomes are transmitted biparentally, but a 1-kilobase insert present in the C. smithii mitochondrial genome spreads unidirectionally to all C. reinhardtii genomes in a manner reminiscent of the intron found in the mitochondrial 21S rRNA gene of omega + strains of yeast.
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23
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Chiu WL, Sears BB. Recombination between chloroplast DNAs does not occur in sexual crosses of Oenothera. MOLECULAR & GENERAL GENETICS : MGG 1985; 198:525-8. [PMID: 3859732 DOI: 10.1007/bf00332951] [Citation(s) in RCA: 50] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Crosses of Oenothera result in the transmission of chloroplasts from both parents to their offspring. In spite of this biparental inheritance, no wild-type recombinants were recovered from crosses between different chloroplast mutants. Since more than 7500 progeny were examined, the results indicate that recombination between the chloroplast DNAs of higher plants must be a very rare event.
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24
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Coleman AW. The fate of chloroplast DNA during cell fusion, zygote maturation and zygote germination in Chlamydomonas reinhardi as revealed by DAPI staining. Exp Cell Res 1984; 152:528-40. [PMID: 6539223 DOI: 10.1016/0014-4827(84)90655-4] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Chlamydomonas reinhardi, a haploid isogamous green alga, presents a classic case of uniparental inheritance of chloroplast genes. Since the molecular basis of this phenomenon is poorly understood, an examination of the cytology of the C. reinhardi plastid DNA was made in gametes, newly formed zygotes, maturing zygotes, and at zygote germination. The single plastid per cell of Chlamydomonas contains a small number of DNA aggregates ('nucleoids') which can be seen after staining with DNA-binding fluorochromes. In zygotes formed by pre-stained gametes, the fluorescing nucleoids disappear from the plastid of mating type minus (male) gamete plastids but not from the plastid of mating type plus (female) gamete plastids about 1 h after zygote formation. Subsequently, nucleoids aggregate slowly to a final average of two or three in the single plastid of the mature zygote. Quantitative microspectrofluorimetry indicates that gametes of both mating types have equal amounts of plastid DNA, and that zoospores arising from zygotes have 3.5 X as much as gametes. Assuming degradation of male plastid DNA, there must be a very major synthesis of plastid DNA between zygote formation and zoospore release when zygotes produce the typical 8-16 zoospores. That synthesis appears to occur at germination, where there is a massive increase in plastid DNA and nucleoid number beginning just prior to meiosis. The results support the theory that uniparental inheritance results from degradation of plastid DNA entering the zygote via the male gamete and suggest further studies, using mutants and altered conditions, which might explain how male plastid DNA sometimes survives.
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25
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Disintegration of chloroplasts during zygote formation inSpirogyra verruculosa. ACTA ACUST UNITED AC 1982. [DOI: 10.1007/bf02488537] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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27
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Kuroiwa T, Kawano S, Nishibayashi S, Sato C. Epifluorescent microscopic evidence for maternal inheritance of chloroplast DNA. Nature 1982; 298:481-3. [PMID: 7088193 DOI: 10.1038/298481a0] [Citation(s) in RCA: 149] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Maternal inheritance of chloroplast genes occurs in the isogamous green alga Chlamydomonas reinhardii. It has been shown using biochemical techniques that the chloroplast DNA of male origin is preferentially lost by 6 h after mating. DNAs in the chloroplast are organized by proteins into about 10 chloroplast nucleoids. Therefore, if chloroplast DNA in zygotes is preferentially destroyed, the disappearance of chloroplast nucleoids from male gametes should be observable during zygote formation by high resolution epifluorescent microscopy. Here we present the first fluorescent microscopic evidence that in C. reinhardii, about eight chloroplast nucleoids from the male parent disappear during the first 40-50 min after mating, while those from the female parent persist and finally fuse together to form one large chloroplast nucleoid.
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28
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Vaughn KC. Plastid fusion as an agent to arrest sorting out. Curr Genet 1981; 3:243-5. [DOI: 10.1007/bf00429827] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/1981] [Indexed: 12/01/2022]
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29
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A model for the rapid vegetative segregation of multiple chloroplast genomes in Chlamydomonas: Assumptions and predictions of the model. Curr Genet 1980; 1:113-25. [DOI: 10.1007/bf00446957] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/1979] [Indexed: 10/26/2022]
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31
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Behavior of chloroplast genes during the early zygotic divisions of Chlamydomonas reinhardtii. Curr Genet 1980; 1:137-53. [DOI: 10.1007/bf00446960] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/1979] [Indexed: 10/26/2022]
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32
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Sears BB. Disappearance of the heteroplasmic state for chloroplast markers in zygospores of Chlamydomonas reinhardtii. Plasmid 1980; 3:18-34. [PMID: 6950439 DOI: 10.1016/s0147-619x(80)90031-1] [Citation(s) in RCA: 28] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
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33
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34
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Blank R, Grobe B, Arnold CG. Time-sequence of nuclear and chloroplast fusions in the zygote of Chlamydomonas reinhardii. PLANTA 1978; 138:63-64. [PMID: 24413943 DOI: 10.1007/bf00392916] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/12/1977] [Accepted: 09/29/1977] [Indexed: 06/03/2023]
Abstract
Contradictory data have been published concerning the time-sequence of nuclear and chloroplast fusions in the zygote of Chlamydomonas. In the present study, adjacent ultrathin sections of Chlamydomonas reinhardii zygotes of various ages were examined with the electron microscope. These sections clearly reveal that nuclear fusion precedes chloroplast fusion.
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Affiliation(s)
- R Blank
- Institut für Botanik und Pharmazeutische Biologie der Friedrich-Alexander, Universität Erlangen-Nürnberg, Schloßgarten 4, D-8520, Erlangen, Federal Republic of Germany
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35
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Forest CL, Togasaki RK. A selection procedure for obtaining conditional gametogenic mutants using a photosynthetically incompetent strain of Chlamydomonas reinhardi. MOLECULAR & GENERAL GENETICS : MGG 1977; 153:227-30. [PMID: 887072 DOI: 10.1007/bf00264740] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
A new selection procedure has beed developed for the isolation of temperature sensitive gametogenic mutants in Chlamydomonas reinhardi. This technique makes use of pet-10-1, a mutant strain incapable of photosynthetic electron transport, and the redox dye, methyl viologen. Two mutants found by this method are discussed. The first, gam-4, does not agglutinate at 35 degrees, whereas the second, gam-5, is capable of sexual agglutination, but not of zygote formation at the restrictive temperature. Both mutants appear to be inherited in a Mendelian fashion and are expressed in mating type (+) and mating type (-).
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36
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Sager R, Ramanis Z. Mutations that alter the transmission of chloroplast genes in Chlamydomonas. Proc Natl Acad Sci U S A 1974; 71:4698-702. [PMID: 4531010 PMCID: PMC433963 DOI: 10.1073/pnas.71.12.4698] [Citation(s) in RCA: 31] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Two mutations are described that alter the pattern of inheritance of chloroplast genes in Chlamydomonas. The mutant gene mat-1 linked to the mating type allele mt(-) greatly increases the frequency of exceptional zygotes, i.e., zygotes that transmit chloroplast genes from the mt(-) (male) parent. In some crosses, 80-90% of the zygotes are biparental, transmitting chloroplast genes from both parents. The mat-2 mutation, linked to mt(+), acts to decrease the frequency of exceptional zygotes below the spontaneous level. The mutant effects are discussed in terms of a DNA modification-restriction system, postulated to regulate the transmission of chloroplast DNA in zygotes.
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Allen TD, Haigh MV, Howard A. Ultrastructure of giant plastids in a radiation induced mutant of Osmunda regalis. JOURNAL OF ULTRASTRUCTURE RESEARCH 1973; 42:491-501. [PMID: 4696218 DOI: 10.1016/s0022-5320(73)80022-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
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41
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Sager R, Ramanis Z. The mechanism of maternal inheritance in Chlamydomonas: Biochemical and genetic studies. TAG. THEORETICAL AND APPLIED GENETICS. THEORETISCHE UND ANGEWANDTE GENETIK 1973; 43:101-8. [PMID: 24424970 DOI: 10.1007/bf00306558] [Citation(s) in RCA: 31] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/09/1972] [Indexed: 05/25/2023]
Abstract
The cytoplasmic linkage group of Chlamydomonas shows maternal inheritance, i.e. preferential transmission of cytogenes from the female (m t (+)) parent and loss of the corresponding male (m t (-)) genome in sexual crosses. The mechanism of this process is postulated to be enzymatic modification of chloroplast DNA of the female to protect it from a restriction enzyme which degrades the chloroplast DNA of the male parent in the zygote soon after fusion. Genetic, biochemical and physical data bearing on this hypothesis are summarized and discussed.
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Affiliation(s)
- R Sager
- Dept. of Biological Sciences, Hunter College of the City University of New York, USA
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42
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43
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44
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Arnold CG, Schimmer O, Sch�tz F, Bathelt H. Die Mitochondrien vonChlamydomonas reinhardii. Arch Microbiol 1972. [DOI: 10.1007/bf00715024] [Citation(s) in RCA: 33] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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45
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McVittie A, Davies DR. The location of the Mendelian linkage groups in Chlamydomonas reinhardii. ACTA ACUST UNITED AC 1971. [DOI: 10.1007/bf00269175] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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