Segregation and transmission of mitochondrial markers in fusion products of the asporogenous yeast Torulopsis glabrata

Summary Using a protoplast fusion technique we have been able to locate to the mitochondrial genome of the asporogenous yeast Torulopsis glabrata mutations conferring resistance to oligomycin, antimycin and diuron. When two strains differing in the size of their mtDNAs were fused the mitochondrial markers from the parent with the larger mtDNA (71–91) were transmitted predominantly among the fusion products. Both genetical and physical evidence support the occurrence of recombination in T. glabrata mitochondrial genome. Segregation of the mitochondrial genome appears to take place before the separation of the first bud from the fusion product.     

Conserved tRNA gene cluster in starfish mitochondrial DNA

Summary Partial sequencing of mtDNA from four long-diverged species of starfish reveals the existence of a conserved cluster of 13 tRNA genes, organized in a manner similar to that of the tRNA cluster of sea urchin mtDNA, but located at a position distant from the presumed replication origin. These findings suggest that a clustered organization of tRNA genes may have been present in the ancestral mitochondrial genome, and raise the possibility that tRNAs may have catalyzed the dispersal rather than the accumulation of the genes which encode them.     

rRNA genes are located far away from the D-loop region in Peking duck mitochondrial DNA

Summary Peking duck mitochondrial DNA was isolated, digested with restriction endonucleases, electrophoresed and blotted with ³²P-labeled mitochondrial ribosomal RNAs. The genes for these RNAs were thereby shown to lie within a 3.23 kb Bgll fragment approximately 9.5 kb from the D-loop.     

Electrophoretic karyotypes of Torulopsis glabrata.

Chromosome-sized DNA molecules of clinical isolates of Torulopsis glabrata were resolved by a pulsed-field electrophoretic method, contour-clamped homogeneous electric fields. With the conditions established in this study, 8 to 12 bands (ranging from 445 to 3,000 kilobases) were observed. There were differences in the intensities and migrations of bands, consistent with T. glabrata being either haploid or diploid. A total of 22 distinctive electrophoretic patterns were noted among single isolates of T. glabrata recovered from 33 patients. When strains were delineated by an electrophoretic pattern, individuals usually harbored only one strain.     

Temperature-sensitive nuclear mutants of Neurospora crassa deficient in mitochondrial ribosomes

Summary We have isolated two non-allelic nuclear mutants of Neurospora crassa that are temperature-sensitive for the production of cytochromes aa ₃ and b. When grown at 23 °C the mutants are virtually indistinguishable from the parent wild-type strains. When grown at 41 °C the mutants have large amounts of KCN-insensitive respiration and lack cytochromes aa ₃ and b. Further examination of the mutants revealed that they were extremely deficient in their capacity for mitochondrial protein synthesis when grown at 41 °C. This protein synthesis deficiency appears to be related to a virtual absence of both small and large mitochondrial ribosomal subunits following growth at 41 °C. Examination of the mitochondrial RNAs of the mutants suggests that mitochondrial rRNAs are synthesized in greatly reduced amounts or that they are misprocessed when these mutants are grown at the non-permissive temperature.Abbreviations mt mitochondrial - SDS sodium dodecylsulfate - EDTA ethylenediaminetetraacetic acid - CAP chloramphenicol - TCA trichloroacetic acid - SHAM salicylhydroxamic acid     

A mitochondrial frameshift-suppressor (+) of the yeast S. cerevisiae maps in the mitochondrial 15S rRNA locus

Summary The first case of a +1 extrageneic frameshift suppressor (MF1), mapping in the yeast mitochondrial 15S rRNA gene is reported. The suppressor was identified by genetic analyses in a leaky mitochondrial oxi1 frameshift mutant and the respective wild-type strain 777-3A of the yeast S. cerevisiae. This is in accordance with the finding that all mitochondrial frameshift mutants isolated from this strain tend to be leaky to a variable degree. MF1 does not suppress known nonsense mutations created by a direct basepair exchange in strain 777-3A. These mutants exhibit a non-leaky phenotype (Weiss-Brummer et al. 1984).     

线粒体基因组A1555G突变在中国非综合征性聋患者中的流行病学分析

目的检测线粒体基因组12SrRNA、基因A1555G突变在中国非综合征性聋患者中的携带频率,探讨中国非综合征性聋的分子病因的流行病学意义。方法提取中国人群中22例氨基糖甙类药物致聋患者、158例散发的非综合征性聋患者以及60例非综合征性聋家系先证者的DNA,以聚合酶链反应结合限制性内切酶酶解分析法检测线粒体基因组A1555G突变的发生情况。结果线粒体基因组A1555G阳性患者占所有耳聋患者的4.2%,散发病例组中A1555G阳性率为1.3%,非综合征性聋家系组中A1555G阳性率为13.3%,22例氨基糖甙类药物致聋患者中未发现A1555G突变。结论线粒体基因组A1555G的突变发生率略高于以往报道,是非综合征性聋家系中致聋的主要病因之一,这对于中国人群耳聋的病因学研究有积极意义。     

Recombination of yeast mitochondrial DNA does not require mitochondrial protein synthesis

Summary Mitochondrial genes recombine extensively in yeast zygotes. In heteropolar crosses (⁺ × ^–) in which the ^– allele consists of an insertion, there is preferential recovery of ⁺ and markers closely linked to it. This polarity has been postulated to be a consequence of one-way gene conversion beginning at the locus (- to ⁺). We have shown that most or all mitochondrial recombination in homopolar and heteropolar crosses, and the phenomenon of polarity itself, does not require products of protein synthesis on mitochondrial ribosomes. (i) Yeast strains were grown and mated, and the zygotes plated and grown, on glucose medium with erythromycin to inhibit and dilute out the products of mitochondrial protein synthesis. Recombination frequencies and polarity at the cap1 and oli1 loci were normal compared to controls in some homopolar (⁺ × ^–) and heteropolar crosses. Apparent changes in recombination frequencies and polarity were seen in other crosses but are attributable to locus-specific petite induction by erythromycin. (ii) Homopolar (⁺ × ⁺) and heteropolar crosses between pairs of petite mutants retaining the cap1, ery1, and oli1 loci also showed nearly normal recombination at the cap1 and oli1 loci, as determined by test-crossing the petite progeny. The petite mutants and zygotes cannot do mitochondria) protein synthesis. These results support the recombinational model of polarity.     

Genetic imprint of the Mongol: signal from phylogeographic analysis of mitochondrial DNA

Mitochondrial deoxyribonucleic acid (DNA) from 201 unrelated Mongolian individuals in the three different regions was analyzed. The Mongolians took the dominant East Asian-specific haplogroups, and some European-prevalent haplogroups were detected. The East Asians-specific haplogroups distributed from east to west in decreasing frequencies, and the European-specific haplogroups distributed conversely. These genetic data suggest that the Mongolian empire played an important role in the maternal genetic admixture across Mongolians and even Central Asian populations, whereas the Silk Road might have contributed little in the admixture between the East Asians and the Europeans. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Partial mitochondrial DNA sequence of the crustaceanDaphnia pulex

A 3667-base pair (bp) fragment of the mitochondrial genome of the crustaceanDaphnia pulex has been sequenced and found to contain the complete genes for the small subunit ribosomal RNA, ND2, seven tRNAs and the control region. This organization is identical to that found inDrosophila yakuba mtDNA yetD. pulex mtDNA exhibits several unique features when compared to other mitochondrial sequences. The sequenced fragment is only 62.6% A+T which is much lower than that of any other arthropod mtDNA sequenced to date.D. pulex mtDNA also exhibits length conservation having shorter coding and non-coding regions. The putative control region is 689 bp in length and includes a sequence that has the potential to fold into a hairpin structure with a perfect 20-bp pair stem and a 22-base loop.     

Molecular analysis of mitochondrial DNA and its inheritance in Epilobium

Summary The mitochondrial genome of four Epilobium species has been characterized by restriction analysis and hybridizations with gene probes from Oenothera. Mitochondrial DNA of Epilobium has a complex restriction fragment pattern and an estimated size of about 320 kb. All species exhibit specific restriction patterns. Plasmid-like DNA molecules of 0.3 kb to 1.2 kb are found in preparations of undigested nucleic acids of mitochondria from E. montanum, E. watsonii, and E. lanceolatum. In contrast, the mitochondria of E. hirsutum contain double-stranded RNAs of 2.7 kb. The location of the genes for cytochrome c oxidase subunits I and III on the mitochondrial DNA seems to be conserved in those species analyzed. However, the genes for subunit II of this complex, and for the alpha subunit of ATPase, are located on different restriction fragments in the mitochondrial genomes of certain species. The location of the COX II gene on different BamHI fragments in E. watsonii and E. lanceolatum has been used for the analysis of mitochondrial inheritance in reciprocal hybrids. Like the plastids, mitochondria are inherited maternally in Epilobium.Abbreviations kb kilobase pairs - mtDNA mitochondrial DNA     

Two transfer RNA sequences abut the large ribosomal RNA gene in Tetrahymena mitochondrial DNA: tRNAleu (anticodon UAA) and tRNAmet (anticodon CAU)

Summary The sequence of a 1,427 base pair restriction fragment, HaeIII fragment 6, of the ciliate protozoan Tetrahymena mitochondrial DNA, is presented. The first 780 nucleotide sequence aligns well with the terminal segment of the large rDNA sequence of Paramecium mitochondria. Immediately abutting this rDNA termination sequence, a tRNA sequence was found with anticodon UAA for leucine. The derived tRNA sequence is 81 bases long without the 3 CCA end, has a high G+C content of 48.1%, and can be folded into a normal cloverleaf structure with mostly conserved bases and normal stems and loops. The tRNA sequence found at an analogous position of the Paramecium mitochondrial DNA is tRNA^tyr. Following a highly A+T rich sequence of 300 base pairs, another tRNA-like sequence is present; this putative tRNA has only 67 bases with anticodon CAT (Met) and forms standard aminoacyl, anticodon and TC stems with a conventional TC loop. However, the DHU loop and stem are unusually short and irregular; the base at position 8 is G instead of T; and the base following the anticodon, which is normally a purine, is T. The significance of these tRNA structures is discussed.     

Genic rearrangements in Phytophthora mitochondrial DNA

Summary To assess evolutionary relationships among the oomycetous fungi we have constructed a physical and genic map of the mtDNA of a broad host range strain (695T) of Phytophthora megasperma. While, like other Phytophthora species, this 43.5 kb circular genome lacks the typical oomycete large inverted repeat, a short 0.5–0.9 kb inverted repeat has been identified. Comparison of the relative order of seven genic regions with host-specific Phytophthora strains reveals both a clustering of these loci within one-third of the host-specific genomes, and two genic inversion relative to the broad host range genome. The location of the short inverted repeat suggests that at least one of the inversions is a consequence of intramolecular recombination between repeat elements.Abbreviations atp6, atp9 genes for ATP synthase subunits 6 and 9 - cox1. cox2. cox3 genes for cytochrome c oxidase subunits I, II, and III - cob gene for apocytochrome b - rns, rnl genes for small and large mitochondrial rRNAs - mtDNA mitochondrial DNA - kb kilobase pairs     

Analysis of mitochondrial DNA and its inheritance in Populus

Summary The mitochondrial genome of several poplar clones has been characterized by restriction analysis and hybridization with gene probes from Oenothera. The mitochondrial (mt) DNA of Populus has a complex restriction fragment pattern and its genome size was estimated to be about 450 kilobase pairs (kb). Restriction fragment length polymorphisms (RFLPs) could be detected only between, and not within, species of Populus and were used as genetic markers to follow mitochondrial inheritance. Location of the apocytochrome b (cob) gene on different Eco RI or Hin dIII fragments in Muhle Larsen (P. trichocarpa) and Androscoggin (P. maximowiczii × P. trichocarpa) has been used for analysis of mitochondrial inheritance. All hybrids investigated exhibit a fragment pattern identical to that of the female parent. Hybridization with other gene probes (coxIII/HindIII, coxIII/SalI, coxIII/Xho I, atp6/Bgl1, atp6/Hco RI, atp6/Hin dIII, nad1/Hin dIII, nad1/Sal I, nad1/Xba I) showed the same results as given by cob hybridization. Thus, mtDNA seems to be inherited maternally in Populus.     

tRNA genes in rat liver mitochondrial DNA

Summary Continuing the analysis of rat liver mitochondria) DNA, we have determined the sequences of two segments containing several tRNA genes. One of these segments also comprises the L-strand origin of replication. The characteristics of the 15 rat liver mitochondrial tRNA structures known at present are compared with those from other mammalian mitochondria.Abbreviations mtDNA mitochondrial DNA - U.R.F. unidentified reading frame (Anderson et al. 1981) - bp and Kbp base pairs and Kilobase pairs - Pu and Py purine and pyrimidine residues