Induction of dwarfism in transgenic Solanum dulcamara by over‐expression of a gibberellin 20‐oxidase cDNA from pumpkin

• Published in: The Plant journal : for cell and molecular biology Vol. 23; no. 3; pp. 329 - 338
• Main Authors: Curtis, Ian S., Ward, Dennis A., Thomas, Stephen G., Phillips, Andrew L., Davey, Michael R., Power, J. Brian, Lowe, Kenneth C., Croker, Stephen J., Lewis, Mervyn J., Magness, Simon L., Hedden, Peter
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Science Ltd 01.08.2000; Blackwell Science
• Subjects: Adaptation to environment and cultivation conditions; Agronomy. Soil science and plant productions; Base Sequence; Biological and medical sciences; DNA Primers; DNA, Complementary; dwarfism; Fundamental and applied biological sciences. Psychology; GA 20‐oxidase; Ga20ox1 gene; Genetics and breeding of economic plants; gibberellin; gibberellin 20-oxidase; Mixed Function Oxygenases - genetics; Plants, Genetically Modified; pumpkin; Racquet Sports; Solanaceae - enzymology; Solanaceae - genetics; Solanaceae - growth & development; Solanarum dulcamara; Solanum dulcamara; transformation; Varietal selection. Specialized plant breeding, plant breeding aims; Weed; Enzyme; Induction; Solanum dulcamara; Oxidase; Tissue specificity; Gene overexpression; Gibberellin; Concentration; Dwarfism; Regulation(control); Dicotyledones; Angiospermae; Plant growth substance; Spermatophyta; Transgenic plant; Oxidoreductases; Solanaceae; Gibberellic acid; Biological accumulation; Plant height
• ISSN: 0960-7412; 1365-313X
• DOI: 10.1046/j.1365-313x.2000.00784.x

Summary The gibberellin (GA) 20‐oxidase (CmGA20ox1) from immature pumpkin seed produces predominantly inactive tricarboxylic acid GAs. We expressed CmGA20ox1 under the control of the CaMV 35S promoter in Solanum dulcamara to assess the usefulness of this gene for reducing GA content in transgenic plants. All transgenic plants obtained were semi‐dwarfs with smaller, deep‐green leaves and highly pigmented stems compared to the wild‐type. Such transformants flowered earlier than the wild‐type plants and produced more fruit and more seeds per fruit. The transgene was efficiently expressed, producing high levels of CmGA20ox1 transcript and protein. Furthermore, the concentration of GA1 was reduced in leaves of the transformants to approximately 20% or less of that in the wild‐type and to about 40% or less in stems. The concentrations of other 13‐hydroxylated GAs were also reduced, except for the tricarboxylic acid, GA17, which accumulated in the transformants due to 13‐hydroxylation of GA25. By contrast, the concentrations of non‐13‐hydroxylated GAs, GA4 and GA34, were not consistently reduced, indicating that the effect of expressing the pumpkin gene may not be predictable. Transcript abundance for a native GA 20‐oxidase gene was higher in the leaves and stems of S. dulcamara transformed with the pumpkin gene than in wild‐type, reflecting the feedback control of 20‐oxidase gene expression that serves as a homeostatic mechanism for GAs.