Metabolic engineering of isoflavonoid biosynthesis in alfalfa

• Published in: Plant physiology (Bethesda) Vol. 138; no. 4; pp. 2245 - 2259
• Main Authors: Deavours, B.E, Dixon, R.A
• Format: Journal Article
• Language: English
• Published: Rockville, MD American Society of Plant Biologists 01.08.2005; American Society of Plant Physiologists
• Subjects: Agronomy. Soil science and plant productions; Alfalfa; biochemical pathways; Biochemical Processes and Macromolecular Structures; Biological and medical sciences; biosynthesis; Complementary DNA; Directional control; Economic plant physiology; Flavones; Flavonoids; Fundamental and applied biological sciences. Psychology; fungal diseases of plants; Fungi - physiology; Gene expression; Gene Expression Profiling; gene expression regulation; Genetic Engineering - methods; isoflavone synthase; Isoflavones; Isoflavones - biosynthesis; Isoflavones - chemistry; isoflavonoids; leaf spotting; Leaves; Medicago truncatula; Medicago truncatula - genetics; Medicago truncatula - metabolism; Medicago truncatula - microbiology; metabolic engineering; microarray technology; Molecular Sequence Data; Molecular Structure; Nitrogen metabolism and other ones (excepting carbon metabolism); nucleotide sequences; Nutrition. Photosynthesis. Respiration. Metabolism; oxygenases; Phoma medicaginis; plant biochemistry; Plant Diseases; plant metabolism; plant pathogenic fungi; plant physiology; Plant Proteins - genetics; Plant Proteins - metabolism; Plants; Plants, Genetically Modified; Transgenic plants; ultraviolet radiation; Ultraviolet Rays; Medicago truncatula; Enzyme; UVB radiation; Glucoside; Medicago sativa; Environmental factor; Biosynthesis; Plant leaf; Synthase; Gene expression; Isoflavone derivatives; Chalcone; Flavanone derivatives; Fungi; Leguminosae; Phytoalexin; Dicotyledones; Angiospermae; Phoma medicaginis; Spermatophyta; Fungi Imperfecti; Thallophyta
• ISSN: 0032-0889; 1532-2548
• DOI: 10.1104/pp.105.062539

The potential health benefits of dietary isoflavones have generated considerable interest in engineering the synthesis of these phytoestrogens into plants. Genistein glucoside production (up to 50 nmol g(-1) fresh weight) was engineered in alfalfa (Medicago sativa) leaves by constitutive expression of isoflavone synthase from Medicago truncatula (MtIFS1). Glucosides of biochanin A (4'-O-methylgenistein) and pratensein (3'-hydroxybiochanin A) also accumulated. Although MtIFS1 was highly expressed in all organs examined, genistein accumulation was limited to leaves. MtIFS1-expressing lines accumulated several additional isoflavones, including formononetin and daidzein, in response to UV-B or Phoma medicaginis, whereas the chalcone and flavanone precursors of these compounds accumulated in control lines. Enhanced accumulation of the phytoalexin medicarpin was observed in P. medicaginis-infected leaves of MtIFS1-expressing plants. Microarray profiling indicated that MtIFS1 expression does not significantly alter global gene expression in the leaves. Our results highlight some of the challenges associated with metabolic engineering of plant natural products, including tissue-specific accumulation, potential for further modification by endogenous enzyme activities (hydroxylation, methylation, and glycosylation), and the differential response of engineered plants to environmental factors.