Manipulation of L-ascorbic acid biosynthesis pathways in Solanum lycopersicum: elevated GDP-mannose pyrophosphorylase activity enhances L-ascorbate levels in red fruit

• Published in: Planta 2012-03, Vol.235 (3), p.553-564
• Main Authors: Cronje, Christelle, George, Gavin M., Fernie, Alisdair R., Bekker, Jan, Kossmann, Jens, Bauer, Rolene
• Format: Article
• Language: English
• Subjects: Agriculture; Arabidopsis - genetics; Arabidopsis - metabolism; Ascorbic Acid - biosynthesis; Biological and medical sciences; Biomedical and Life Sciences; Biosynthesis; Biotechnology; Cell walls; Ecology; Enzymes; Forestry; Fruit - genetics; Fruit - metabolism; Fruits; Fundamental and applied biological sciences. Psychology; Gene Expression Regulation, Plant; Genes; Inositol Oxygenase - genetics; Inositol Oxygenase - metabolism; Leaves; Life Sciences; Lycopersicon esculentum - genetics; Lycopersicon esculentum - metabolism; Models, Biological; Nucleotidyltransferases - genetics; Nucleotidyltransferases - metabolism; Original Article; Oxidases; Plant Sciences; Plants; Plants, Genetically Modified - genetics; Plants, Genetically Modified - metabolism; Tomatoes; Transgenic plants; Uronic acids; Vitamin C; Yeasts
• ISSN: 0032-0935; 1432-2048
• DOI: 10.1007/s00425-011-1525-6

Ascorbate (AsA) plays a fundamental role in redox homeostasis in plants and animals, primarily by scavenging reactive oxygen species. Three genes, representing diverse steps putatively involved in plant AsA biosynthesis pathways, were cloned and independently expressed in Solarium lycopersicum (tomato) under the control of the CaMV 35S promoter. Yeast-derived GDPmannose pyrophosphorylase (GMPase) and arabinono-1,4-lactone oxidase (ALO), as well as myo-inositol oxygenase 2 (MI0X2) from Arabidopsis thaliana, were targeted. Increases in GMPase activity were concomitant with increased AsA levels of up to 70% in leaves, 50% in green fruit, and 35% in red fruit. Expression of ALO significantly pulled biosynthetic flux towards AsA in leaves and green fruit by up to 54 and 25%, respectively. Changes in AsA content in plants transcribing the MI0X2 gene were inconsistent in different tissue. On the other hand, MIOX activity was strongly correlated with cell wall uronic acid levels, suggesting that MIOX may be a useful tool for the manipulation of cell wall composition. In conclusion, the Smirnoff-Wheeler pathway showed great promise as a target for biotechnological manipulation of ascorbate levels in tomato.