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H D Osiewacz

Publications and source records attributed to H D Osiewacz.

45 records · Page 3Linked to original sources
PubMed1992

The role of mitochondrial DNA rearrangements in aging and human diseases.

Instabilities and point mutations of the high molecular weight mitochondrial DNA (mtDNA) were shown to be correlated with various degenerative processes in both lower eukaryotes as well as in mammals. In filamentous fungi, circular and linear plasmids were demonstrated to be involved in mtDNA rearrangements and in the genetic control of senescence. In addition, in these eukaryotic microorganisms, which have proved to be ideal model systems in experimental gerontology, a number of nuclear genes were identified controlling the stability of the mitochondrial genome. Although the mitochondrial genome of mammals, including humans, appears to be quite stable in comparison to other species, mtDNA instabilities of the type described in fungi were observed in mitochondria of patients with different mitochondrial degenerative disorders (CPEO, KSS, Pearson syndrome, LHON, MERRF, MELAS). It was later demonstrated that such mtDNA rearrangements appear to accumulate progressively during aging in human subjects. These data suggest that instabilities of the mitochondrial genome may play an important role in the control of life span not only in lower eukaryotes, but also in humans.

Aging↗
PubMed1991

Integrative transformation of the ascomycete Podospora anserina: identification of the mating-type locus on chromosome VII of electrophoretically separated chromosomes.

Protoplasts of wild-type strain s and a long-lived extrachromosomal mutant (AL2) of the ascomycete Podospora anserina were transformed using a plasmid (pAN7-1) which contains the hygromycin B phosphotransferase gene (hph) of Escherichia coli under the control of Aspergillus nidulans regulatory sequences. After optimizing the transformation procedure, transformation efficiencies of 15-21 transformants/micrograms plasmid DNA were obtained. Using a second selectable vector (pBT3), which contains the beta-tubuline gene of a benomyl-resistant Neurospora crassa mutant, the co-transformation rate was determined. Southern blot hybridization experiments revealed that the transforming plasmid became integrated into the genome of the recipient either as a single copy or as multiple copies. In addition, the data from molecular as well as from classical genetic analyses indicated that in independent transformants vector integration occurred at different positions. The mitotic and meiotic stability of transformants proved to be dependent on the number of integrated plasmid copies. Genetic analyses revealed a transformant in which the integrated vector is closely linked to the mating-type locus. Fractionation of whole chromosomes by pulsed field gel electrophoresis and subsequent hybridization of the immobilized DNAs against radiolabelled vector sequences indicated the largest of seven chromosomes as the chromosome containing the integrated vector and thus the mating-type locus.

Ascomycota↗
PubMed1991

Genome analysis of imperfect fungi: electrophoretic karyotyping and characterization of the nuclear gene coding for glyceraldehyde-3-phosphate dehydrogenase (gpd) of Curvularia lunata.

The gene coding for glyceraldehyde-3-phosphate dehydrogenase (gpd) has been isolated from a genomic library of the filamentous fungus Curvularia lunata. The coding region of this gene consists of 1014 nucleotides and is interrupted by four introns. The gpd gene product shows a high degree of sequence identity with the corresponding proteins of various species belonging to both taxonomically related (e.g., Aspergillus nidulans), as well as more divergent, taxa. Using contour-clamped homogeneous electric field (CHEF) gel electrophoresis eight distinct chromosomal bands have been resolved, with two bands migrating as doublets and one as a triplet. Thus, the total number of chromosomes of C. lunata appears to be 12. The size of the chromosomes ranges from about 1.4 Mb to 4.0 Mb allowing an estimation of the genome to be approximately 29.7 Mb. By hybridization of fractionated chromosomes the gpd gene and the rDNA locus have been localized on individual chromosomes.

Amino Acid Sequence↗
PubMed1991

Sequence of the nuclear ATP synthase subunit 9 gene of Podospora anserina: lack of similarity to the mitochondrial genome.

The nuclear gene coding for the mitochondrial subunit 9 of the F0F1-ATP synthase complex was isolated from a genomic library of Podospora anserina. Nucleotide sequencing revealed an open reading frame capable to code for 144 amino acids including an amino-terminal pre-sequence of 63 amino acid residues for mitochondrial import of the pre-proteolipid. The P. anserina proteolipid shows extensive sequence identity with the corresponding gene products of the related filamentous fungi Neurospora crassa, Aspergillus nidulans and Aspergillus niger. In contrast to the situation in Saccharomyces cerevisiae, N. crassa and A. nidulans, no sequence similarity of the ATP synthase subunit 9 gene to the mitochondrial genome of P. anserina could be detected. Thus, in P. anserina this gene appears to be exclusively encoded by the nuclear genome.

Amino Acid Sequence↗
PubMed1989

Mitochondrial DNA rearrangements are correlated with a delayed amplification of the mobile intron (plDNA) in a long-lived mutant of Podospora anserina.

A new long-lived mutant of Podospora anserina has been isolated and characterized. Its longevity is maternally inherited as revealed by reciprocal crosses. A molecular analysis resulted in the identification of an amplified DNA species (designated pAL2-1) with homology to mitochondrial DNA (mtDNA). The presence of this DNA species is correlated with mtDNA rearrangements and a delayed amplification of the mobile intron (plDNA).

Aging↗
PubMed1987

Construction of an Obligate Photoheterotrophic Mutant of the Cyanobacterium Synechocystis 6803 : Inactivation of the psbA Gene Family.

psbA in Synechocystis 6803 was found to belong to a small multigene family with three copies. The psbA gene family was inactivated in vitro by insertation of bacterial drug resistance markers. Inactivation of all three genes resulted in a transformant that is unable to grow photosynthetically but can be cultured photoheterotrophically. This mutant lacks oxygen evolving capacity but retains photosystem I activity. Room temperature measurements of chlorophyll a fluorescence induction demonstrated that the transformant exhibits a high fluorescence yield with little or no variable fluorescence. Immunoblot analyses showed complete loss of the psbA gene product (the DI polypeptide) from thylakoid membranes in the transformant. However, the extrinsic 33 kilodalton polypeptide of the water-splitting complex of photosystem II, is still present. The results indicate that assembly of a partial photosystem II complex may occur even in the absence of the intrinsic D1 polypeptide, a protein implicated as a crucial component of the photosystem II reaction center.

Journal Article↗
PubMed1985

The onset of senescence is affected by DNA rearrangements of a discontinuous mitochondrial gene in Podospora anserina.

Mapping and transcription studies have revealed that in Podospora anserina the causative agent of senescence, a mitochondrial plasmid (plDNA), is identical with intron 1 of the discontinuous gene for cytochrome-c-oxidase subunit 1 (COI), which is 2 kpb from the discontinuous gene for cytochrome b (Cytb). A mitochondrial mutant (ex1) devoid of the COI, but not of the Cytb gene provides longevity. A molecular model for the onset of senescence is presented.

Amino Acid Sequence↗