Dehydroascorbate influences the plant cell cycle through a glutathione-independent reduction mechanism.
Glutathione is generally accepted as the principal electron donor for dehydroascorbate (DHA) reduction. Moreover, both glutathione and DHA affect cell cycle progression in plant cells. But other mechanisms for DHA reduction have been proposed. To investigate the connection between DHA and glutathione, we have evaluated cellular ascorbate and glutathione concentrations and their redox status after addition of dehydroascorbate to medium of tobacco (Nicotiana tabacum) L. cv Bright Yellow-2 (BY-2) cells. Addition of 1 mm DHA did not change the endogenous glutathione concentration. Total glutathione depletion of BY-2 cells was achieved after 24-h incubation with 1 mm of the glutathione biosynthesis inhibitor l-buthionine sulfoximine. Even in these cells devoid of glutathione, complete uptake and internal reduction of 1 mm DHA was observed within 6 h, although the initial reduction rate was slower. Addition of DHA to a synchronized BY-2 culture, or depleting its glutathione content, had a synergistic effect on cell cycle progression. Moreover, increased intracellular glutathione concentrations did not prevent exogenous DHA from inducing a cell cycle shift. It is therefore concluded that, together with a glutathione-driven DHA reduction, a glutathione-independent pathway for DHA reduction exists in vivo, and that both compounds act independently in growth control.
Potters
Geert
G
Laboratory of Plant Physiology, Department of Biology, University of Antwerp, B-2020 Antwerp, Belgium. geert.potters@ua.ac.be
Horemans
Nele
N
Bellone
Silvia
S
Caubergs
Roland J
RJ
Trost
Paolo
P
Guisez
Yves
Y
Asard
Han
H
D017209:Apoptosis / Q000187:drug effects; D002453:Cell Cycle / Q000187:drug effects / Q000502:physiology*; D002478:Cells, Cultured; D003683:Dehydroascorbic Acid / Q000378:metabolism* / Q000494:pharmacology; D005978:Glutathione / Q000378:metabolism*; D005980:Glutathione Reductase; D009247:NADH, NADPH Oxidoreductases / Q000037:antagonists & inhibitors / Q000378:metabolism; D009607:Nitrosourea Compounds / Q000494:pharmacology; D010084:Oxidation-Reduction / Q000187:drug effects; D010944:Plants / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D013880:Thioredoxin-Disulfide Reductase
D009607:Nitrosourea Compounds; D009247:NADH, NADPH Oxidoreductases; D005980:Glutathione Reductase; D013880:Thioredoxin-Disulfide Reductase; C424443:Txnrd3 protein, mouse; D005978:Glutathione; D003683:Dehydroascorbic Acid