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  • 1
    ISSN: 1432-0983
    Keywords: Plant mitochondria ; RNA editing ; Apocytochrome b ; Solanum tuberosum, Triticum aestivum, Triticum timopheevi
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Editing of the complete coding region of cob transcripts from two genera of plants has been studied by cDNA sequence analysis. Eighteen and nine C residues are edited into U in the mitochondrial transcripts from wheat and potato respectively. Both systems share eight common editing sites; ten codons edited in wheat are “pre-edited” at the genomic level in potato, and one codon edited in potato is “pre-edited” in wheat. Most amino-acid modifications lead to hydrophobic residues and increase the homology between the COB polypeptides and the corresponding protein of other species. In two out of the nine potato cDNA clones, an additional C-to-T modification, which also leads to a change in the encoded amino acid, was identified. Heterogeneity observed at the carboxy-terminus of the COB open reading frame in Triticum aestivum and Triticum timopheevi is not corrected by editing.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-0983
    Keywords: Key words RNA editing ; Plant mitochondria ; Maturase ; Reverse transcriptase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The intronic mat-r ORF encodes a protein with significant homology to retroviral reverse transcriptases. Here, we describe the nucleotide sequence of potato mat-r and study the editing status of mat-r transcripts in two systems, potato and wheat, where the mat-r ORF is part of the trans-introns but in two different configurations relative to nad1 exons d and e. In potato and wheat, 13 and 15 C-to-U transitions respectively were observed. Most transcripts were partially edited, but potato transcripts were edited more efficiently than wheat transcripts. As in functional mitochondrial genes, RNA editing increased the similarity between plant mat-r proteins and their homologous non-plant counterparts. Interestingly, editing of mat-r was clustered in the reverse-transcriptase (RT) and the maturase (X) domains, two well defined regions having known functions in other systems. These results, together with the integrity and sequence conservation of mat-r, strongly suggest that the encoded protein plays a functional role in plant mitochondria.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1573-4919
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Summary An adenylate cyclase activity was identified and characterized in preparations from Xenopus laevis ovarian tissue and follicles. The enzyme is more active in the presence of Mn2+ than of Mg2+, and it is highly activated by fluoride, guanyl-5′-yl-imidodiphosphate [Gpp(NH)p] and cholera toxin. During the last stages of oogenesis, as the oocytes grow in volume, the total adenylate cyclase activity increases more than tenfold, maintaining a constant relationship to the surface area of the follicle.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Plant molecular biology 17 (1991), S. 527-530 
    ISSN: 1573-5028
    Keywords: apocytochrome b gene ; nucleotide sequence ; plant mitochondria ; potato ; Solanum tuberosum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Plant molecular biology 31 (1996), S. 365-372 
    ISSN: 1573-5028
    Keywords: DNA polymerase ; plant mitochondria ; potato (Solanum tuberosum) ; reverse transcriptase ; reverse transcriptase inhibitors
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A reverse transcriptase activity has been detected in potato mitochondria using special RNAs as templates: a bacterial RNA coding for neomycin phosphotransferase (neo pa RNA) and a Neurospora crassa mitochondrial RNA (184 nt RNA). Surprisingly, no exogenous primer addition was required. These RNA templates share a primary and secondary structure similar to the TψCG loop of tRNAs that could constitute the recognition site for the enzyme. Reverse transcriptase activity was inhibited by ddTTP, ethidium bromide and aphidicolin, while potato mitochondrial DNA polymerase was not inhibited by aphidicolin indicating that these activities correspond to distinct enzymes. A conserved sequence of reverse transcriptases was detected in potato mitochondrial DNA suggesting that this enzyme could be mitochondrially encoded.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1573-5028
    Keywords: apocytochrome b pseudogene ; pea cox1 ; plant mitochondria ; potato ; S10 ribosomal protein ; wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The S10 ribosomal protein gene (rps10), which has not been previously reported in any angiosperm mitochondrial genome, was identified by sequence analysis in the potato mitochondrial DNA. This gene is found downstream of a truncated non-functional apocytochrome b (cob) pseudogene, and is expressed as multiple transcripts ranging in size from 0.8 to 5.0 kb. Southern hybridization analysis indicates that rps10-homologous sequences are not present in the wheat mitochondrial genome. Sequence analysis of a single-copy region of the pea mitochondrial genome located upstream of cox1 [11] shows that a non-functional rps10 pseudogene is present in this species. These results suggest that the functional genes coding for wheat and pea mitochondrial RPS10 polypeptides have been translocated to the nucleus.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1573-5028
    Keywords: apocytochrome b gene ; plant mitochondria ; potato ; RNA editing ; rpl5 gene ; rpsl4 pseudogene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The L5 ribosomal protein gene (rpl5) and a S14 ribosomal protein pseudogene were identified by sequence analysis in the potato mitochondrial genome. The two genes are separated by one nucleotide and are found upstream of the apocytochrome b gene (cob), an arrangement conserved also in Arabidopsis and Brassica. The rpl5 gene has an intact open reading frame while the rpsl4 locus is disrupted by a five nucleotide duplication that introduces a frameshift in the reading frame. Editing of rpl5 and pseudorps14 cotranscripts has been studied by cDNA sequence analysis. Eight C residues are edited into U in the rpl5 coding region, resulting in eight amino acid changes that increase the homology between potato and other RPL5 polypeptides. Interestingly, the rps14 pseudogene sequence is not edited at any nucleotide position.
    Type of Medium: Electronic Resource
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