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  • Nicotiana sylvestris  (3)
  • 1
    ISSN: 1617-4623
    Keywords: Nicotiana sylvestris ; Cytoplasmic male sterility ; Mitochondrial DNA deletion ; Substoichiometric sequences ; Mitochondrialnad7 gene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract InNicotiana sylvestris, two cytoplasmic male sterile (CMS) mutants obtained by protoplast culture show abnormal developmental features of both vegetative and reproductive organs, and mitochondrial gene reorganization following homologous recombination between 65 bp repeated sequences. A mitochondrial region of 16.2 kb deleted from both CMS mutants was found to contain the last two exons of thenad7 gene coding for a subunit of the mitochondrial respiratory chain complex I, which is encoded in the nucleus in fungi and animals but was recently found to be encoded by the mitochondrial genome in wheat. Although theN. sylvestris nad7 gene shows strong homology with its wheat counterpart, it contains only three introns instead of four. Polymerase chain reaction (PCR) experiments indicated that the parental gene organization, including the completenad7 gene, is probably maintained at a substoichiometric level in the CMS mutants, but this proportion is too low to have a significant physiological role, as confirmed by expression studies showing the lack of detectable amounts of the NAD7 polypeptide. Consequently, absence of NAD7 is not lethal to plant cells but a deficiency of complex I could be involved in the abnormal CMS phenotype.
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  • 2
    ISSN: 1617-4623
    Keywords: Protoplast culture ; Nuclear male sterility ; Mitochondrial DNA recombination ; Substoichiometric molecules ; Nicotiana sylvestris
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary ANicotiana sylvestris plant regenerated from protoplast culture was found to be mutated in both the mitochondrial (mt) and nuclear genomes. The novel mt DNA organization, called U, is due to the amplification of recombinant substoichiometric DNA sequences that preexist in the parent line. The recombination event involves two 404 by repeats, which hybridize to a 2.1 kb transcript. Although the sequence of both repeats was not altered by the recombination, an additional transcript of 2.5 kb was detected in U mitochondria. In addition to this mitochondrial reorganization, the protoclone carried a recessive nuclear mutation conferring male sterility (ms4). A possible role ofms4 in the appearance of the U mt DNA organization was investigated by introducing this gene into normalN. sylvestris cytoplasm. No mt DNA change could be found in homozygousms4/ms4 plants of the F2 generation.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1617-4623
    Keywords: Protoplast culture ; Nuclear and cytoplasmic male sterility ; Mitochondrial DNA and proteins ; Nicotiana sylvestris
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Male sterile plants appeared in the progeny of three fertile plants obtained after one cycle of protoplast culture from a fertile botanical line and two androgenetic lines ofNicotiana sylvestris. These plants showed the same foliar and floral abnormalities as the cytoplasmic male sterile (cms) mitochondrial variants obtained after two cycles of culture. We show that male sterility in these plants is controlled by three independent nuclear genes,ms1, ms2 andms3, while no changes can be seen in the mitochondrial genome. However, differences were found between thein organello mitochondrial protein synthesis patterns of male sterile and parent plants. Two reproducible changes were observed: the presence of a new 20 kDa polypeptide and the absence of a 40 kDa one. Such variations were described previously in mitochondrial protein synthesis patterns of the cms lines. Fertile hybrids of male sterile plants showed normal synthesis patterns. The male sterile plants are thus mutated in nuclear genes involved in changes observed in mitochondrial protein synthesis patterns.
    Type of Medium: Electronic Resource
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