Comparison between Aging of Slices and Ethylene Treatment of Whole White Potato Tubers

Abstract

Cyanide-resistant 02 consumption can be stimulated by either treating whole white potato tubers (Norchip) with ethylene, in the presence of 100% 02, or aging slices obtained from untreated potato tubers. A comparison of alternative pathway activity elicited by either treatment was undertaken. The proportion of electrons flowing through the alternative path in the presence of intermediate concentrations of KCN and at various concentrations of salicylhydroxamic acid was identical in both cases. However, the respiration of slices from ethylene-treated tubers was in every case stimulated by KCN, whereas the aged slices never exhibited this phenomenon.Furthermore, the metabolism of D-IU-'4Clglucose was several hundred times greater in aged slices than in fresh slices from C2H4-treated tubers.These results, along with the respiratory kinetics of aged slices from ethylene-treated tubers, suggest that aged slices and fresh slices from ethylene-treated tubers are biochemically dissimilar.was monitored using the Warburg manometric technique (8).The oxidation of exogenously applied glucose was measured as described elsewhere (7). Two g of slices were placed in 4 ml 100 mm K-phosphate, pH 5.5, with 2 ACi (0.75 x 10-'0 mol) D-[U-'4CJglucose. 14CO2 was collected by suspending plastic cups containing 10% NaOH in the flasks. These cups were removed after 15, 30, 60, 90, and 120 min and placed into Hydromix scintillation cocktail (Yorktown Research, South Hackensack, N.J.), and new cups containing NaOH were placed in the sample chambers. Rates of "CO2 evolution were determined by regression analysis of the resulting time course.Total glucose was measured as described by Bergmeyer et al. (2) based on the reduction of NADP by glucose-6-P dehydrogenase. Five g of potato slices were homogenized in 25 ml hot 80% ethanol. The homogenate was centrifuged at 20,000g for 30 min and the supernatant was reduced to dryness. The residue was redissolved in H20 and passed through Dowex H+ and Cl-to remove ionic materials. The pH of the solution of unbound material was adjusted to 7. An aliquot of this neutral fraction was used for the analysis of glucose (2). Experiments were repeated at least two times.Slices obtained from white potato tubers exhibit a respiratory rise above that of the whole tuber (11). However, this type of respiration is not cyanide-resistant (9). Upon aging, these slices develop an additional respiratory increment and also show the development of an alternative, cyanide-resistant pathway (5). Recently (3,8), it was demonstrated that fresh slices obtained from potato tubers previously treated with C2H4 in air or 100%0 02 would possess the alternate CN--insensitive respiration prior to any aging.To gain a more complete understanding of the development of CN-resistance under these two conditions (i.e. C2H4 treatment in 100%0 02 or aging), this study was undertaken. It is apparent that, although alternative pathway activity is the result of both treatments (3,5,8)

Inhibition of O2 Consumption Resistant to Cyanide and Its Development by N-Propyl Gallate and Salicylhydroxamic Acid

“…We have previously demonstrated that ethylene-induction of CN-resistant respiration is not associated with increased glucose metabolism (9). In this regard, Table IV presents evidence for an increase in the affinity of mitochondrial membranes for lipoxygenase after the development of CN resistance.…”

“…02 consumption was not inhibited by 1 mm KCN, suggesting that a cyanide-resistant alternative pathway exists in these slices. KCN, in fact, slightly stimulated 02 consumption-a phenomenon of unknown origin (possibly due to the Pasteur effect in the presence of KCN) that was reported previously (9). SHAM and PG by themselves had little effect on 02 consumption.…”

Induction and activation of the alternative oxidase of potato tuber mitochondria

“…7/3/1. v/v) or by ageing of slices (Dizengremel and Lance 1976. Janes and Wiest 1980, Bonnerot et al 1985, Hiser and Mclntosh 1990.…”

Alternative Oxidase of Potato Is an Integral Membrane Protein Synthesized de Novo during Aging of Tuber Slices

“…Fresh tissue slices from tubers demonstrate respiration that is sensitive to cyanide while aged potato tuber slices exhibit cyanide-resistant respiration (3,11,29). However, the induction of alternative pathway respiration in aged slices could be mimicked in fresh slices if the tubers were treated with ethylene, ethanol, acetaldehyde, acetate, or cyanide for 24 h before slicing (1,13,14,24,27). These results have been interpreted to mean that the alternative pathway is present constitutively in tubers (20).…”