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  • 1
    Electronic Resource
    Electronic Resource
    Genetic analysis of nitrate reductase deficient mutants of Nicotiana plumbaginifolia: Evidence for six complementation groups among 70 classified molybdenum cofactor deficient mutants (1988)
    Springer
    Molecular genetics and genomics 213 (1988), S. 206-213 
    Details
    ISSN: 1617-4623
    Keywords: Nicotiana plumbaginifolia ; Nitrate reductase ; Genetics ; Molybdenum cofactor biosynthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A total of 70 cnx mutants have been characterized from a collection of 211 nitrate reductase deficient (NR-) mutants isolated from mutagenized Nicotiana plumbaginifolia protoplast cultures after chlorate selection and regeneration into plants. They are presumed to be affected in the biosynthesis of the molybdenum cofactor since they are also deficient for xanthine dehydrogenase activity but contain NR apoenzyme. The remaining clones were classified as nia mutants. Sexual crosses performed between cnx mutants allowed them to be classified into six independent complementation groups. Mutants representative of these complementation groups were used for somatic hybridization experiments with the already characterized N. plumbaginifolia mutants NX1, NX24, NX23 and CNX103 belonging to the complementation groups cnxA, B, C and D respectively. On the basis of genetic analysis and somatic hybridization experiments, two new complementation groups, cnxE and F, not previously described in higher plants, were characterized. Unphysiologically high levels of molybdate can restore the NR activity of cnxA mutant seedlings in vivo, but cannot restore NR activity to any mutant from the other cnx complementation groups.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00339583
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  • 2
    Electronic Resource
    Electronic Resource
    Isolation and characterization of Nicotiana plumbaginifolia nitrate reductase-deficient mutants: genetic and biochemical analysis of the NIA complementation group (1987)
    Springer
    Molecular genetics and genomics 209 (1987), S. 596-606 
    Details
    ISSN: 1617-4623
    Keywords: Mutagenized protoplast cultures ; Nicotiana plumbaginifolia ; Nitrate-deficient mutants
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Two hundred and eleven nitrate reductase-deficient mutants (NR−) were isolated from mutagenized Nicotiana plumbaginifolia protoplast cultures by chlorate selection and regenerated into plant. More than 40% of these clones were classified as cnx and presumed to be affected in the biosynthesis of the molybdenum cofactor, the remaining clones being classified as nia mutants. A genetic analysis of the regenerated plants confirmed this proportion of nia and cnx clones. All mutants regenerated were found to carry monogenic recessive mutations that impaired growth on nitrate as sole nitrogen source. Mutants propagated by grafting on N. tabacum systematically displayed a chlorotic leaf phenotype. This chlorosis was therefore related to the NR deficiency. The observation of leaves with NR− chlorotic sectors surrounded by NR+ wild-type tissues suggeests that an NR deficiency is not corrected by diffusible factors. Periclinal chimeras between wild-type tobacco and the NR− graft were also observed. In this type of chimeric tissue chlorosis was no longer detectable when NR+ cells were in the secondmost (L2) layer, but was still detectable when NR− cells were in the secondmost layer. The genetic analysis of nia mutants revealed that they belong to a single complementation group. However three nia mutants were found to complement some of the other nia mutants. The apoenzyme of nitrate reductase was immunologically detected in several nia mutants but not in other members of this complementation group. Some of the nia mutants, although they were NR−, still displayed methylviologenitrate reductase activity at a high level. These data show that the nia complementation group corresponds to the structural gene of nitrate reductase. Some of the mutations affecting this structural gene result in the overproduction of an inactive nitrate reductase, suggesting a feedback regulation of the level of the apoenzyme in the wild type.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00331169
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    Paper (German National Licenses)
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