title: 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.
authors.affiliation: Graduate School of Biosphere Sciences, Hiroshima University, Kagamiyama, 739-8528, Higashi-Hiroshima, Japan.
authors.forename: Takaaki
authors.initials: T
authors.lastname: Tokunaga
authors.forename: Katsunori
authors.initials: K
authors.lastname: Miyahara
authors.forename: Kazufumi
authors.initials: K
authors.lastname: Tabata
authors.forename: Muneharu
authors.initials: M
authors.lastname: Esaka
mesh_terms: D001205:Ascorbic Acid / Q000378:metabolism*; D002455:Cell Division / Q000187:drug effects / Q000235:genetics; D002460:Cell Line; D004351:Drug Resistance / Q000235:genetics; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D005822:Genetic Vectors / Q000235:genetics; D006540:Herbicides / Q000633:toxicity; D015151:Immunoblotting; D008940:Mitotic Index; D044925:Oxidoreductases Acting on CH-CH Group Donors / Q000235:genetics* / Q000378:metabolism; D010269:Paraquat / Q000633:toxicity; D030821:Plants, Genetically Modified; D018749:RNA, Plant / Q000235:genetics / Q000378:metabolism*; D014026:Nicotiana / Q000166:cytology / Q000235:genetics* / Q000378:metabolism
chemical_list: D006540:Herbicides; D018749:RNA, Plant; D044925:Oxidoreductases Acting on CH-CH Group Donors; C093910:galactonolactone dehydrogenase; D010269:Paraquat; D001205:Ascorbic Acid