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  • 1
    Electronic Resource
    Electronic Resource
    GBSS T-DNA inserts giving partial complementation of the amylose-free potato mutant can also cause co-suppression of the endogenous GBSS gene in a wild-type background (1996)
    Springer
    Plant molecular biology 31 (1996), S. 731-739 
    Details
    ISSN: 1573-5028
    Keywords: complementation ; expression ; co-suppression ; granule-bound starch synthase ; Solanum tubersoum L. ; transgenic inheritance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The wild-type gene encoding granule-bound starch synthase (GBSS) is capable of both complementing the amylosefree (amf) potato mutant and inhibiting the endogenous GBSS gene expression in wild-type potato. Co-suppression of the endogenous GBSS gene, easily visualised by staining the starch with iodine, occurred when the full-size GBSS sequence (genomic), GBSS cDNA or even the mutant amf allele were introduced into the wild-type potato. Conversely, introduction of the GBSS promoter sequence alone, did not result in co-suppression in the 80 analysed transformants. Neither the orientation of the GBSS gene with respect to kanamycin resistance nor the presence of an enhancer influenced the frequency of plants showing a co-suppression phenotype. After crossing a partially complemented amf mutant with a homozygous wild-type plant, the F1 offspring segregated into plant phenotypes with normal and decreased expression of the GBSS gene. This decreased expression correlated with the presence of a linked block of five T-DNA inserts which was previously shown to be correlated with partial complementation of the amf mutant. This crossing experiment indicates that co-suppression can cause inhibition of gene expression of both inserted and endogenous wild-type GBSS genes. The frequency of partially complemented amf plants was equal to the frequency of co-suppressed wild types when a construct, with an enhancer in front of the GBSS promoter, was used (pWAM 101E). This might suggest that partial complementation of the amf genotype caused by unstable expression of the transgene can be overcome by inserting an enhancer in front of the GBSS promoter.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00019461
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  • 2
    Electronic Resource
    Electronic Resource
    Expression of wild-type GBSS transgenes in the off-spring of partially and fully complementedamylose-free transformants of potato (1996)
    Springer
    Molecular breeding 2 (1996), S. 211-218 
    Details
    ISSN: 1572-9788
    Keywords: complementation ; granule-bound starch synthase ; Solanum tuberosum L. ; expression ; transgenic inheritance ; ploidy level
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Theamylose-free (amf) potato mutant can easily be complemented through introduction of the wild-type gene coding for granule-bound starch synthase (GBSS). After iodine staining the starch of theamf mutant is red whereas that of the wild type and the complementedamf mutant is blue. The level of complementation of selected transformants and their sexual off-spring after backcrossing withamf was investigated using sporophytic tuber cells and gametophytic microspore cells. Two diploid and two tetraploid transformants with full complementation demonstrated the expected segregation patterns of 1:1 (one active insert) or 3:1 (two independently segregating active inserts) in the microspores and in the F1 offspring based on staining of tubers. All expected genotypes in the F1 generation were found, based on microspore segregation patterns of the individual F1 plants. Two transformants with partial complementation (mixed phenotypes) were investigated. One of them, B1, was tetraploid and duplex for the GBSS insert, which had originated through mitotic doubling of the transformed diploid cells. In the F1 generation three phenotypic classes were found:amf, fully complemented and partially complemented. The latter two classes exist independently of a simplex or duplex gene status. The second transformant with partial complementation, B10, appeared to have a complex molecular composition. One cluster of five transgenes caused the partial complementation. Fully and partially complemented phenotypic classes were found after crossing B10 with theamf mutant. Indications were found that the ploidy level of the tissue in which the genes were introduced and expressed played an important role. Firstly, partial complementation was found after transformation of the diploid and not of the tetraploidamf genotypes. Secondly, the level of complementation was higher in tissue with lower ploidy levels, as illustrated by the colour of the starch inin vitro tubers (2x–4x cells) versus field-grown tubers (16x–64x).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00564198
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