Generation and properties of ascorbic acid-overproducing transgenic tobacco cells expressing sense RNA for l-galactono-1,4-lactone dehydrogenase

Abstract

L-Galactono-1,4-lactone dehydrogenase (GalLDH; EC 1.3.2.3) is the last enzyme in the putative L-ascorbic acid (AsA) biosynthetic pathway of plants. Here, we show for the first time that the overexpression of GalLDH can increase AsA content in tobacco (Nicotiana tabacum L.) BY-2 cells. To see the effect, we analyzed the properties of these AsA-overproducing transgenic cell lines, especially in relation to AsA content of cells, cell division, senescence and resistance to oxidative stress. The mitotic index in AsA-overproducing cells was higher than in wild-type cells. Moreover, the browning of these cells was markedly restrained, and the proportion of dead cells was reduced, especially in the later period of culture. These AsA-overproducing cells also acquired resistance to paraquat (methyl viologen), which produces active oxygen species. These results contribute to the previous insights about AsA and raise the possibility of the generation of plants that have resistance to environmental stresses by increasing their AsA content.

Effect of 1-Methylcyclopropene on the Expression of Genes for Ascorbate Metabolism in Postharvest Cauliflower

“…The enzymes in the ascorbate-glutathione cycle, such as APX, MDAR, DHAR, and glutathione reductase, exist as isoenzymes encoded by discrete genes and are distributed in distinct cellular compartments, and it is difficult to assay the activity of each isoenzyme separately. In recent years, the gene expression of each isoenzyme, which might give a more precise estimate of antioxidant gene activation, has been studied extensively (Nishikawa et al, 2003b;Tokunaga et al, 2005). In plants, APX is the key enzyme in the H 2 O 2 -detoxification system in cytosol, chloroplasts, mitochondria, and peroxisome, constituting an important component of the ascorbate-glutathione cycle.…”

Analysis of Ascorbic Acid Biosynthesis Using a Simple Transient Gene Expression System in Tomato Fruit Protoplasts

“…In higher plants, various AsA biosynthetic pathways and related genes have been proposed. [1][2][3][4] Overexpression of AsA biosynthetic genes has contributed to a significant increase in AsA contents in plants, 2,3,5,6) suggesting that gene modification of AsA biosynthetic enzymes is an effective approach for the generation of AsA-enrich plants. Hence, the rapid and simple methods of analysis are required to identify the limiting enzymes in AsA biosynthesis.…”

Molecular Cloning and Characterization of <small>L</small>-Galactose-1-phosphate Phosphatase from Tobacco (<i>Nicotiana tabacum</i>)

“…It also plays roles in plant growth, cell division, flowering and senescence. [1][2][3][4] Several AsA biosynthetic pathways have been proposed for higher plants. The D-mannose and Lgalactose pathway (D-Man/L-Gal pathway) appears to be a primary AsA biosynthetic pathway, producing AsA from D-fructose-6-phosphate through L-galactono-1,4-lactone.…”