Regulation of respiration in rotenone-treated tobacco cell suspension cultures

Abstract

Cells of Nicotiana tabacum L. suspension cultures were treated with the respiratory inhibitor rotenone, which specifically inhibits complex I activity of mitochondria. Rotenone retarded cell growth, as shown by decreases in fresh weight, dry weight and cell numbers on a suspension-volume basis. However, rates of the coupled respiration were higher in rotenone-treated compared to control cells when expressed on a fresh-weight basis. Rates of the rotenone-insensitive respiration increased substantially on both a fresh-weight and extractable-cellular-protein basis 24 h after rotenone treatment. ATP/ADP ratios were not significantly different between control and rotenone-treated cells. Our results indicated that cells of tobacco suspension cultures were able to maintain a slow rate of growth and adequate ATP/ADP ratios without the operation of complex I.

Respiration in postharvest sugarbeet roots is not limited by respiratory capacity or adenylates

“…Adenylate concentrations were determined by modification of the protocol of Zhang et al (2001). Adenylates were extracted by vortexing 10 mg of finely ground lyophilized tissue in 1 mL of 15% trichloroacetic acid with acid-washed sand.…”

Benzothiadiazole inhibits mitochondrial NADH:ubiquinone oxidoreductase in tobacco

“…Inhibition due to SA in contrast levelled off at 45%, even at the high concentration of 500 mM. Rotenone, a toxin and well-described inhibitor of the NADH:ubiquinone oxidoreductase (Zhang et al, 2001), resulted in a near total inhibition of the enzyme at 100 nM.…”

“…Duroquinone was excluded from control assays. Rotenone, an inhibitor of complex I, was included in control assays (1 mM) to verify that the measured NADH oxidation is due to complex I activity (Estornell et al, 1993;Zhang et al, 2001). All assays were performed at room temperature.…”

Over‐reduction of cultured tobacco cells mediates changes in respiratory activities

“…This is in agreement with results found for antimycin A‐treated tobacco cells (Maxwell et al 2002). Levels of total ATP + ADP were slightly lower within 2.5 h after the treatment and but returned to levels similar to or higher than the control cells at 6 h. In contrast, in tobacco cultures treated with rotenone (25 µ M ), an inhibitor of complex I in the inner mitochondrial membrane, ATP/ADP ratios were unchanged for 6 h (Zhang et al 2001).…”

“…It has been shown that respiration rates vary during the growth curve in cultured tobacco cells; namely that the total and uncoupled respiration and the cyt pathway are usually very high between day 3 and day 4 and decrease in the latter phase of the growth curve (Zhang et al 1999, 2001). Therefore, the effect of myxothiazol or FCCP on respiration was always compared with control cultures.…”