Over-reduction of cultured tobacco cells mediates changes in respiratory activities |
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Authors: | Qisen Zhang Catherine S Moore Kathleen L Soole Joseph T Wiskich |
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Institution: | Department of Environmental Biology, University of Adelaide, SA 5005, Australia; School of Biological Science, Flinders University of South Australia. GPO Box 2100, SA 5001, Australia; Present address: School of Agriculture and Wine, University of Adelaide, SA 5005, Australia |
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Abstract: | Regulation of respiration in Nicotiana tabacum suspension cultures was studied using the respiratory inhibitor myxothiazol and the oxidative phosphorylation uncoupler carbonylcyanide p -(trifluoromethoxy)phenylhydrazone (FCCP). Myxothiazol (2 μ M ) or FCCP (2 μ M ) almost completely inhibited cell growth for about 24 h, after which the cultures could resume a growth rate similar to that of the untreated culture. During the first 18 h of myxothiazol treatment, rates of cellular respiration were similar to control cultures. The capacity of the alternative pathway was significantly higher than control 2–3 h after myxothiazol treatment and increased further after 18 h. The capacity of the alternative pathway in FCCP-treated tobacco cells also increased but to a lesser extent. ATP/ADP ratios decreased for at least 9 h after either myxothiazol or FCCP treatments, which triggered an increase in glycolytic flux and an over-reduction of cultured tobacco cells, as demonstrated by increases in levels of reactive oxygen species and cellular ethanol. The generation of reactive oxygen species served as a signal for an induction of alternative oxidase, which in turn relieved the aerobic fermentation and over-reduction of the cells. |
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