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  • 1
    ISSN: 1432-203X
    Keywords: glyphosate ; gene expression ; gene amplification ; cell culture ; resistance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The stability and expression of amplified 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) genes was examined in glyphosate resistant tobacco cells grown in glyphosate-free medium, and in plantlets regenerated from resistant cells. Amplified DNA was maintained in resistant cells grown in the absence of glyphosate for three years. Amplified EPSPS genes were retained in regenerated plantlets at levels comparable to those observed in the resistant cells, and EPSPS mRNA was overexpressed (compared to unselected plantlets). However, glyphosate resistance in cell lines grown in glyphosate-free medium declined 7-fold, and in regenerated plantlets approximately 20-fold, compared to resistant cells maintained under glyphosate selection. In plantlets, reduced resistance correlated with lower levels of EPSPS mRNA. Plantlets regenerated from resistant cells exhibited morphological variation, and had an approximate doubling of their nuclear genome size.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-203X
    Keywords: Key words Peppermint ; Transformation ; Agrobacterium ; GUS ; Transgenic
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The first transgenic peppermint (Mentha×piperita L. cultivar Black Mitcham) plants have been obtained by Agrobacterium-mediated transformation by cocultivation with morphogenically responsive leaf explants. Basal leaf explants with petioles, from leaves closest to the apex of in-vitro-culture-maintained shoots (5 cm), exhibited optimal shoot organogenetic responsiveness on medium supplemented with thidiazuron (8.4 µm). Shoot formation occurred at sites of excision on the leaf blade and petiole either directly from cells of the explant or via a primary callus. Analyses of transient GUS activity data indicated that DNA delivery by microprojectile bombardment was more effective than Agrobacterium infection. However, no transgenic plants were obtained from over 22,000 leaf explants after particle bombardment. Cocultivation of leaf explants with Agrobacterium strain EHA 105 and kanamycin selection produced transgenic plants. Greater transient and stable -glucuronidase (GUS) activities were detected in explants or propagules transformed with the construct where gusA was driven by the pBISN1 promoter rather than a CaMV 35S promoter. Eight plants were subsequently regenerated and verified as transgenic based on detection of the nptII transgene by PCR and Southern blot analyses. The Southern analyses indicated that the plants were derived from eight unique transformation events. All transgenic plants appeared morphologically normal. Analyses of GUS activities in leaves sampled from different portions of these transgenic plants, 10 months after transfer to the greenhouse, indicated that six out of the eight original regenerants were uniformly transformed, i.e., did not exhibit chimeric sectors.
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  • 3
    Publication Date: 1997-04-01
    Print ISSN: 0021-8561
    Electronic ISSN: 1520-5118
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
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