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  • Cell & Developmental Biology  (2)
  • Ribosomal RNA genes  (2)
  • 1
    ISSN: 1432-0983
    Keywords: Mitochondrial genome size ; Repeated sequences ; Ribosomal RNA genes ; Nonflowering plants
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We report the first estimates of genome size and complexity for mitochondrial DNAs (mtDNAs) from nonflowering land plants. The mtDNA of Onoclea sensibilis (sensitive fern) is approximately 300 kb in size, while that of Equisetum arvense (common horsetail) is at least 200 kb. Sufficient mtDNA of Onoclea was available to permit an estimation of the copy number and a linkage analysis of nine mitochondrial genes. Six of these genes appear to be present in only one or two copies in the Onoclea genome, whereas three other genes are present in multiple copies. Five of the approximately ten genes encoding 26S rRNA are located on a large, 〉10kb, dispersed repeat that also contains closely linked genes for 18S rRNA and the alpha subunit of ATPase (atpA). The other 26S genes belong to a second dispersed repeat family of 〉8 kb whose elements do not contain any other identified genes. Because flowering plant mtDNAs are also large and contain dispersed, gene-containing, repeats, it appears that these features arose early in the evolution of land plants, or perhaps even in their green algal ancestors.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1432
    Keywords: Southern blots ; Restriction maps ; Ribosomal RNA genes ; Introns ; Phylogenetic trees ; Boletaceae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Mapping studies were performed with 18 cloned probes on mitochondrial DNA (mtDNA) from 15 species ofSuillus and four species from three related genera of fleshy pore mushrooms (Boletaceae). WithinSuillus, mtDNAs vary in size from 36 to 121 kb, differ in gene order by only one major rearrangement, and have diverged in nucleotide sequence within the large subunit ribosomal RNA gene region by up to 2.9%. Three additional gene orders exist in related genera. Two of the three can be transformed into the predominantSuillus order by either one or two rearrangements. The fourth requires two to three rearrangements to be converted to any of the others. The minimum estimates of nucleotide divergence within the large subunit ribosomal RNA gene region vary from 8.3% to 11% in comparisons betweenSuillus and these related species. Trees based on restriction-site and size differences within the mitochondrial ribosomal RNA genes were consistent with the hypothesized sequence of genome rearrangements and provide suggestive evidence for a major expansion of the mitochondrial genome withinSuillus. Structural and sequence changes in mtDNA provided information about phylogenetic relationships within the Boletaceae.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    BioEssays 17 (1995), S. 1005-1008 
    ISSN: 0265-9247
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The most common form of the CO2-fixing enzyme rubisco is a form I enzyme, heretofore found universally in oxygenic phototrophs (cyanobacteria and plastids) and widely in proteobacteria. Two groups(1-4), however, now report that in dinoflagellate plastids the usual form I rubisco has been replaced by the distantly related form II enzyme, known previously only from anaerobic proteobacteria. This raises the important question of how such an oxygensensitive rubisco could function in an aerobic organism. Moreover, the dinoflagellate rubisco has unusual molecular properties: it is encoded as a polyprotein, by nuclear (rather than plastid) genes, and these genes contain noncanonical spliceosomal introns. The nuclear location and alphaproteobacterial affinity of dinoflagellate rubisco genes hint at a possible mitochondrial origin and highlight the extraordinary richness of lateral gene transfers, both between and within organisms, that have occurred during rubisco evolution.
    Additional Material: 1 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    BioEssays 2 (1985), S. 263-267 
    ISSN: 0265-9247
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The small, relatively constant size and conservative evolution of chloroplast DNA (cpDNA) make it an ideal molecule for tracing the evolutionary history of plant species. At lower taxonomic levels, cpDNA variation is easily and conveniently assayed by comparing restriction patterns and maps, while at higher taxonomic levels, DNA sequencing and inversion analysis are the methods of choice for comparing chloroplast genomes. The study of cpDNA variation has already yielded important new insights into the origin and evolution of many agriculturally important crop plants, and promises to significantly enhance our phylogenetic understanding of the major lines of descent among land plants and algae.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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