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  • 1
    ISSN: 1432-0983
    Keywords: Nicotiana plumbaginifolia ; Chloroplast 16s ribosomal RNA ; Streptomycin resistance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In a previous paper we reported the isolation of streptomycin-resistant mutants from Nicotiana plumbaginifolia and presented evidence for chloroplast control of the resistance trait. To understand the molecular basis of the resistance in these mutants, we sequenced three regions in the chloroplast 16s rRNA gene, which correspond to the 5′ terminus, the 530 loop, and the 900 stem/loop of Escherichia coli 16s rRNA, and compared them with the sequences of the wild-type. Our results show that: (1) nine mutants have a C to T change at position 912, (2) one mutant (SR1021) has a G to A change at position 885, (3) one mutant has a C to T change at position 526, based on E. coli numbering; and (4) three mutants do not have any change in the regions analyzed. The point mutation detected in SR1021 has not been reported previously. In E. coli 16s rRNA, position 885 is protected from chemical probing by ribosomal protein S12 and is closely juxtaposed with the streptomycin-binding region (positions 912–915) in the predicted secondary structure. It is likely that the G to A transition at this position is a novel mutation for streptomycin resistance.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical and applied genetics 78 (1989), S. 81-86 
    ISSN: 1432-2242
    Keywords: Nicotiana plumbaginifolia ; Streptomycin resistance ; Maternal inheritance ; Chloroplast ultrastructure ; In organello protein synthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Streptomycin-resistant colonies were isolated from protoplast cultures of haploid Nicotiana plumbaginifolia based on their ability to green in medium containing 1 mg/ml streptomycin sulfate. The frequency of resistant colonies was 0.9×10−5 in nonmutagenized culture, and increased ten-fold following treatment of culture with 10 μg/ml N-methyl-N′-nitro-N-nitrosoguanidine. Of a total of 52 resistant clones isolated, 2 gave rise to haploid, 15 to diploid, and 3 to tetraploid plants upon transfer of calli to differentiation medium. Leaf-segment and protoplast assays showed that all diploid regenerates were resistant to streptomycin but sensitive to chloramphenicol, kanamycin, lincomycin, neomycin, and spectinomycin. Plants in most diploid clones were fertile and able to set seeds when self-fertilized and crossed reciprocally to wild-type plants. Inheritance of streptomycin resistance was studied in the diploid clones and, without exception, the resistance was transmitted maternally. Comparative studies of the ultrastructure of organelles and protein synthesis in isolated chloroplasts between wild-type and resistant clones in the presence of streptomycin suggest that streptomycin resistance is controlled by chloroplasts.
    Type of Medium: Electronic Resource
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