Respiratory metabolism during cold storage of apple fruit. II. Alternative oxidase is induced at the climacteric

Abstract

Changes in mitochondrial respiration were investigated during cold storage of apple fruit (Malus domestica Borkh. cv. Reinette du Canada). Postharvest calcium treatment of the apples had no effect on the aspects of mitochondrial metabolism studied, suggesting that the role of calcium in fruit ripening is not related to respiration. A transient increase in mitochondrial oxidative capacity occurred during storage around day 80 after harvest. This climacteric burst was associated with an enhanced capacity of the alternative pathway, but not of the cytochrome pathway. The major factor determining this rise in alternative pathway capacity at the climacteric was the transient increase in the amount of alternative oxidase (AOX) protein. Antibodies raised against the Sauromatum guttatum enzyme recognized a reduced form product of ampproximately 37 kDa and a 67‐kDa band corresponding to the oxidized form of the protein. During cold storage of the apple fruit, alternative pathway capacity correlated with the levels of the AOX and was ampparently not dependent on major changes in the oxidation state of the enzyme. This is the first work to report that the respiratory climacteric and the induction of AOX are tightly and temporally linked.