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Gray, Michael W.; Burger, Gertraud; Lang, B. Franz

doi:10.1186/gb-2001-2-6-reviews1018

Cited by 338 publications

(104 citation statements)

References 41 publications

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“…Evidence for recombination in mtDNA has been reported for plants and fungi (53), and it has been regarded as a driving force to create subgenomic molecules that confer an extreme fluidity to the organization of plant mt genomes (54). Homologous recombination is well studied in chloroplasts, and cpDNA transformation is performed taking advantage of this activity (55,56).…”

Section: Discussionmentioning

confidence: 99%

Active digestion of sperm mitochondrial DNA in single living sperm revealed by optical tweezers

Nishimura

Yoshinari

Naruse

et al. 2006

Proc. Natl. Acad. Sci. U.S.A.

144

104

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In almost all eukaryotes, mitochondrial (mt) genes are transmitted to progeny mainly from the maternal parent. The most popular explanation for this phenomenon is simple dilution of paternal mtDNA, because the paternal gametes (sperm) are much smaller than maternal gametes (egg) and contribute a limited amount of mitochondria to the progeny. Recently, this simple explanation has been challenged in several reports that describe the active digestion of sperm mtDNA, down-regulation of mtDNA replication in sperm, and proteolysis of mitochondria triggered by ubiquitination. In this investigation, we visualized mt nucleoids in living sperm by using highly sensitive SYBR green I vital staining. The ability to visualize mt nucleoids allowed us to clarify that the elimination of sperm mtDNA upon fertilization is achieved through two steps: (i) gradual decrease of mt nucleoid numbers during spermatogenesis and (ii) rapid digestion of sperm mtDNA just after fertilization. One notable point is that the digestion of mtDNA is achieved before the complete destruction of mitochondrial structures, which may be necessary to avoid the diffusion and transmission of potentially deleterious sperm mtDNA to the progeny. maternal inheritance ͉ medaka ͉ mtDNA M itochondria and chloroplasts contain their own genomes, which are believed to be vestiges of their bacterial ancestors (1). Mitochondrial (mt) and chloroplast (cp) genes are inherited in non-Mendelian fashion. A variety of patterns and mechanisms have been observed for the transmission of these genes, but in almost all eukaryotes, they are inherited mainly from the maternal parent (2-4).Generally, the maternal inheritance of mt (cp) DNA is thought to be a result of the dilution of the paternal contribution, because the paternal gametes (sperm) are much smaller than maternal gametes (egg) and contribute only a limited amount of cytoplasm to the progeny. In animals, a mature sperm carries Ϸ100 copies of mtDNA, which might be necessary to maintain the integrity of mitochondrial activity (5). In contrast, the animal oocyte contains Ϸ10 5 to 10 8 copies of mtDNA, exceeding that of sperm by a factor of at least 10 3 (3, 6). Therefore, the paternal contribution of mtDNA or cpDNA would be diluted beyond the limits of detection by using conventional restriction enzyme analysis (7).This simple explanation, however, has been challenged by many findings (8). For example, there have been several fairly unsuccessful attempts to detect leaky transmission of paternal mtDNA by repetitive backcross experiments using lepidopteran insects (9). On the contrary, in mussels (Mtylus), paternal mtDNA can be transmitted to male progeny at a remarkably high frequency, even though paternal mtDNAs are transmitted by sperm (10-12). A more striking example was found in the unicellular alga Chlamydomonas reinhardtii. In C. reinhardtii, despite the fact that mtϩ (female) and mtϪ (male) gametes contribute equal amounts of cytoplasm to the progeny, cpDNA is transmitted only from the mtϩ parent. One biochemical stud...

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Section: Discussionmentioning

confidence: 99%

Active digestion of sperm mitochondrial DNA in single living sperm revealed by optical tweezers

Nishimura

Yoshinari

Naruse

et al. 2006

Proc. Natl. Acad. Sci. U.S.A.

144

104

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“…However, mitochondrial proteins are encoded by both the mitochondrial genome and the nuclear genome (32). The nuclear-encoded mitochondrial genes seem to be of both bacterial and eukaryotic ancestry (32,35). In yeast, approximately one-half of such genes seem to be of bacterial origin, whereas only one-third is predicted to be of eukaryotic origin (32,35).…”

Section: Discussionmentioning

confidence: 99%

“…The nuclear-encoded mitochondrial genes seem to be of both bacterial and eukaryotic ancestry (32,35). In yeast, approximately one-half of such genes seem to be of bacterial origin, whereas only one-third is predicted to be of eukaryotic origin (32,35). During mitochondrial evolution, numerous genes may have been transferred from an ancestral mitochondrial genome to the nuclear genome (36,37).…”

Section: Discussionmentioning

confidence: 99%

A mitochondrial-like aconitase in the bacterium Bacteroides fragilis : Implications for the evolution of the mitochondrial Krebs cycle

Baughn

Malamy

2002

Proc. Natl. Acad. Sci. U.S.A.

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Aconitase and isocitrate dehydrogenase (IDH) enzyme activities were detected in anaerobically prepared cell extracts of the obligate anaerobe Bacteroides fragilis. The aconitase gene was located upstream of the genes encoding the other two components of the oxidative branch of the Krebs cycle, IDH and citrate synthase. Mutational analysis indicates that these genes are cotranscribed. A nonpolar in-frame deletion of the acnA gene that encodes the aconitase prevented growth in glucose minimal medium unless heme or succinate was added to the medium. These results imply that B. fragilis has two pathways for ␣-ketoglutarate biosynthesis-one from isocitrate and the other from succinate. Homology searches indicated that the B. fragilis aconitase is most closely related to aconitases of two other Cytophaga-FlavobacteriumBacteroides (CFB) group bacteria, Cytophaga hutchinsonii and Fibrobacter succinogenes. Phylogenetic analysis indicates that the CFB group aconitases are most closely related to mitochondrial aconitases. In addition, the IDH of C. hutchinsonii was found to be most closely related to the mitochondrial͞cytosolic IDH-2 group of eukaryotic organisms. These data suggest a common origin for these Krebs cycle enzymes in mitochondria and CFB group bacteria.

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“…That is, they contain genes that encode proteins that in aerobes typically function in mitochondria and, when the proteins are subjected to phylogenetic analysis, they form a monophyletic group with the alpha-proteobacteria. This is the group of bacteria from which the mitochondrial endosymbiont is held to have originated based upon analyses of genes that are encoded by mitochondrial genomes (Yang et al 1985;Gray et al 2001). One criticism of using the genes in table 1 to reject the Archezoa hypothesis is that none of them have ever been found on a mitochondrial genome (Gray et al 2004;Gray 2005).…”

Section: The Demise Of Archezoamentioning

confidence: 99%

Multiple secondary origins of the anaerobic lifestyle in eukaryotes

Embley

2006

Phil. Trans. R. Soc. B

111

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Classical ideas for early eukaryotic evolution often posited a period of anaerobic evolution producing a nucleated phagocytic cell to engulf the mitochondrial endosymbiont, whose presence allowed the host to colonize emerging aerobic environments. This idea was given credence by the existence of contemporary anaerobic eukaryotes that were thought to primitively lack mitochondria, thus providing examples of the type of host cell needed. However, the groups key to this hypothesis have now been shown to contain previously overlooked mitochondrial homologues called hydrogenosomes or mitosomes; organelles that share common ancestry with mitochondria but which do not carry out aerobic respiration. Mapping these data on the unfolding eukaryotic tree reveals that secondary adaptation to anaerobic habitats is a reoccurring theme among eukaryotes. The apparent ubiquity of mitochondrial homologues bears testament to the importance of the mitochondrial endosymbiosis, perhaps as a founding event, in eukaryotic evolution. Comparative study of different mitochondrial homologues is needed to determine their fundamental importance for contemporary eukaryotic cells.

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Untitled

Cited by 338 publications

References 41 publications

Active digestion of sperm mitochondrial DNA in single living sperm revealed by optical tweezers

Active digestion of sperm mitochondrial DNA in single living sperm revealed by optical tweezers

A mitochondrial-like aconitase in the bacterium Bacteroides fragilis : Implications for the evolution of the mitochondrial Krebs cycle

Multiple secondary origins of the anaerobic lifestyle in eukaryotes

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