Overexpression of a bacterial 1-deoxy-D-xylulose 5-phosphate synthase gene in potato tubers perturbs the isoprenoid metabolic network: implications for the control of the tuber life cycle

• Published in: Journal of experimental botany Vol. 57; no. 12; pp. 3007 - 3018
• Main Authors: Morris, Wayne L, Ducreux, Laurence J.M, Hedden, Peter, Millam, Steve, Taylor, Mark A
• Format: Journal Article
• Language: English
• Published: Oxford Oxford University Press 01.09.2006; Oxford Publishing Limited (England)
• Subjects: 1-deoxy-D-xylulose 5-phosphate synthase; Abscisic Acid - metabolism; Agronomy. Soil science and plant productions; Alkyl and Aryl Transferases - metabolism; Bacteria; Bacterial Proteins - metabolism; Biological and medical sciences; Biosynthesis; buds; Carotenoids; Carotenoids - metabolism; Cytokinin; Cytokinins; Cytokinins - metabolism; Dormancy; dormancy breaking; Economic plant physiology; enzyme activity; Fundamental and applied biological sciences. Psychology; gene expression; genes; Geranylgeranyl-Diphosphate Geranylgeranyltransferase; Gibberellins; Gibberellins - metabolism; isoprenoid; isoprenoids; Net assimilation, photosynthesis, carbon metabolism. Photorespiration, respiration, fermentation (anoxia, hypoxia); Nutrition. Photosynthesis. Respiration. Metabolism; Oxidoreductases - metabolism; Phenotype; Plant Growth Regulators - metabolism; Plant Proteins - metabolism; Plant Tubers - genetics; Plant Tubers - growth & development; Plant Tubers - metabolism; Plants; Plants, Genetically Modified - anatomy & histology; Plants, Genetically Modified - growth & development; Plants, Genetically Modified - metabolism; Plastids - metabolism; potato; potatoes; Research Papers; Solanum tuberosum; Solanum tuberosum - genetics; Solanum tuberosum - growth & development; Solanum tuberosum - metabolism; sprouting; Sprouts; Terpenes - metabolism; Terpenoids; Transferases - genetics; Transferases - metabolism; transgenes; Transgenic plants; transketolases and transaldolases; Tubers; Up-Regulation; zeatin; Dormancy; Life cycle; sprouting; Gene; Enzyme; potato; 1-deoxy-D-xylulose 5-phosphate synthase; Tuber; Synthase; Cytokinin; isoprenoid
• ISSN: 0022-0957; 1460-2431
• DOI: 10.1093/jxb/erl061

Potato tubers were engineered to express a bacterial gene encoding 1-deoxy-D-xylulose 5-phosphate synthase (DXS) in order to investigate the effects of perturbation of isoprenoid biosynthesis. Twenty-four independent transgenic lines out of 38 generated produced tubers with significantly elongated shape that also exhibited an early tuber sprouting phenotype. Expression analysis of nine transgenic lines (four exhibiting the phenotype and five showing a wild-type phenotype) demonstrated that the phenotype was strongly associated with dxs expression. At harvest, apical bud growth had already commenced in dxs-expressing tubers whereas in control lines no bud growth was evident until dormancy was released after 56–70 d of storage. The initial phase of bud growth in dxs tubers was followed by a lag period of ∼56 d, before further elongation of the developing sprouts could be detected. Thus dxs expression results in the separation of distinct phases in the dormancy and sprouting processes. In order to account for the sprouting phenotype, the levels of plastid-derived isoprenoid growth regulators were measured in transgenic and control tubers. The major difference measured was an increase in the level of trans-zeatin riboside in tubers at harvest expressing dxs. Additionally, compared with controls, in some dxs-expressing lines, tuber carotenoid content increased ∼2-fold, with most of the increase accounted for by a 6–7-fold increase in phytoene.