Manipulation of the Rice L-Galactose Pathway: Evaluation of the Effects of Transgene Overexpression on Ascorbate Accumulation and Abiotic Stress Tolerance

• Published in: PloS one Vol. 10; no. 5; p. e0125870
• Main Authors: Zhang, Gui-Yun, Liu, Ru-Ru, Zhang, Chang-Quan, Tang, Ke-Xuan, Sun, Ming-Fa, Yan, Guo-Hong, Liu, Qiao-Quan
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 04.05.2015; Public Library of Science (PLoS)
• Subjects: Abiotic stress; Accumulation; Acids; Analysis; Antioxidants; Arabidopsis; Ascorbic acid; Ascorbic Acid - metabolism; Biosynthesis; Brassica napus; Caprolactone; Cloning; Coding; Corn; Crops; Cultivars; Dehydrogenase; Dehydrogenases; Enzymes; Epimerase; Galactose; Galactose - metabolism; GDP-mannose; GDP-mannose pyrophosphorylase; Gene Expression; Genes; Genetic engineering; Homozygote; Influence; Laboratories; Leaves; Mannose; Metabolic Networks and Pathways; Metabolism; Oryza; Oryza - genetics; Oryza - growth & development; Oryza - metabolism; Oxidation-Reduction; Phosphates; Phosphorylase; Physiological aspects; Physiology; Plant growth; Plant Leaves - metabolism; Plants (botany); Plants, Genetically Modified; Rapeseed; Reactive oxygen species; Redox properties; Rice; Salinity; Salinity tolerance; Salt tolerance; Salt-Tolerance - genetics; Salts; Seedlings; Stress; Stress, Physiological; Stresses; Transgenes; Transgenic plants; Vitamin C
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0125870

Ascorbic acid (AsA) is the most abundant water-soluble antioxidant in plants, and it plays a crucial role in plant growth, development and abiotic stress tolerance. In the present study, six key Arabidopsis or rapeseed genes involved in AsA biosynthesis were constitutively overexpressed in an elite Japonica rice cultivar. These genes encoded the GDP-mannose pyrophosphorylase (GMP), GDP-mannose-3',5'-epimerase (GME), GDP-L-galactose phosphorylase (GGP), L-galactose-1-phosphate phosphatase (GPP), L-galactose dehydrogenase (GDH), and L-galactono-1,4-lactone dehydrogenase (GalLDH). The effects of transgene expression on rice leaf AsA accumulation were carefully evaluated. In homozygous transgenic seedlings, AtGGP transgenic lines had the highest AsA contents (2.55-fold greater than the empty vector transgenic control), followed by the AtGME and AtGDH transgenic lines. Moreover, with the exception of the AtGPP lines, the increased AsA content also provoked an increase in the redox state (AsA/DHA ratio). To evaluate salt tolerance, AtGGP and AtGME transgenic seedlings were exposed to salt stress for one week. The relative plant height, root length and fresh weight growth rates were significantly higher for the transgenic lines compared with the control plants. Altogether, our results suggest that GGP may be a key rate-limiting step in rice AsA biosynthesis, and the plants with elevated AsA contents demonstrated enhanced tolerance for salt stress.