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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Plant molecular biology 20 (1992), S. 809-819 
    ISSN: 1573-5028
    Keywords: Branching enzyme ; cassava ; cDNA ; expression pattern ; Manihot esculenta Crantz ; sequence homology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Branching enzyme is involved in the synthesis of amylopectin in plant reserve starch. A cDNA coding for cassava (Manihot esculenta Crantz) branching enzyme was cloned from a λgt11 cDNA library using a potato cDNA probe. The cloned cDNA was partially sequenced. The sequence data confirmed the identity of the clone when compared to that of potato, the homology being ca. 80% at the nucleotide level and 85% at the amino acid level. Furthermore, the cloned cassava cDNA was able to restore branching enzyme activity in a branching enzyme deficient Escherichia coli mutant. Results of the Southern analysis suggested that there is a single gene for this particular branching enzyme in the cassava genome. Study of expression patterns by northern hybridization showed that the gene is highly expressed in tubers. The transcript is detectable in stem and petiole, but not in leaves. In roots, the mRNA is hardly present. The expression levels at different stages of tuber growth are similar with exception of very young tubers in which it is relatively low. It is also shown that there is a difference in the level of branching enzyme expression between different cassava genotypes.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-5028
    Keywords: antisense effect ; granule-bound starch synthase ; cassava ; cDNA ; heterologous gene ; potato
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A tuber-specific cDNA library of cassava (Manihot esculenta Crantz) was constructed and a full-length cDNA for granule-bound starch synthase (GBSS, also known as waxy protein), the enzyme responsible for the synthesis of amylose in reserve starch, was cloned. Sequencing of the cloned cDNA showed that it has 74% identity with potato GBSS and 60–72% identity with GBSS from other plant species. The cDNA encodes a 608 amino acid protein of which 78 amino acids form a chloroplast/amyloplast transit peptide of 8.37 kDa. The mature protein has a predicted molecular mass of 58.61 kDa (530 amino acids). Comparison of the GBSS proteins of various plant species and glycogen synthase of bacteria showed extensive identity among the mature form of plant GBSS proteins, in which the monocots and dicots form two separate branches in the evolutionary tree. From analysis of the genomic DNA of allotetraploid cassava, it is shown that GBSS is a low-copy-number gene. GBSS transcript is synthesized in a number of different organs, but most abundantly in tubers. Potato plants were transformed with the cassava GBSS cDNA in antisense orientation fused between the potato GBSS promoter and the nopaline synthase terminator. The expression of the endogenous GBSS gene in these transgenic potato plants was partially or completely inhibited. Complete inhibition of GBSS activity by the cassava antisense gene resulted in absence of GBSS protein and amylose giving rise to almost complete amylose-free potato starch. This shows that also heterologous genes can be used to achieve antisense effects in other plant species.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1573-5028
    Keywords: Agrobacterium tumefaciens ; adventitious shoot regeneration ; transformation ; homozygous potato
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Transformed potato (Solanum tuberosum) plants were obtained from homozygous diploid potato by using a transformation procedure in combination with an adventitious shoot regeneration method. Leaf and stem explants were inoculated with an Agrobacterium tumefaciens strain which contained a binary vector (pVU 1011) carrying the neomycin phosphotransferase gene. Shoot regeneration most effectively on stem explants, occurred within six weeks directly from the explants without introducing a callus phase. A strong seasonal influence on transformation efficiencies was observed. Analysis of a number of randomly selected regenerated shoots for their ability to root and form shoots on kanamycin-containing medium shows that over 90% of the regenerated shoots obtained are transformed. In a number of shoots transformation was confirmed by a test for the presence and expression of the NPT-II gene.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1573-5060
    Keywords: Agrobacterium rhizogenes ; antisense RNA ; granule-bound starch synthase ; Solanum tuberosum ; starch composition ; transformation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Granule-bound starch synthase (GBSS) catalyses the synthesis of amylose in starch granules. Analysis of antisense RNA mediated inhibition of GBSS gene expression in large numbers of tubers from in vitro grown, greenhouse grown and field grown transgenic potato plants revealed stable and total inhibition of GBSS gene expression in one clone. In three other transgenic genotypes partial and unstable inhibition was found. In these genotypes both GBSS activity and amylose content were remarkably reduced compared with the non-transformed control genotype. No relationship was found between the level of inhibition of GBSS gene expression and yield and dry matter content.
    Type of Medium: Electronic Resource
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