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

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 mitochondr ial metabolism studied, suggesting that the role of calcium in fruit ripeni ng is not related to respiration. it transient increase in mitochondrial ox idative capacity occurred during storage around day 80 after harvest. This climacteric burst was associated with an enhanced capacity of the alternati ve pathway, but not of the cytochrome pathway. The major factor determining this rise in alternative pathway capacity at the climacteric was the trans ient increase in the amount of alternative oxidase (AOX) protein. Antibodie s raised against the Sauromatum guttatum enzyme recognized a reduced form p roduct of approximately 37 kDa and a 67-kDa band corresponding to the oxidi zed form of the protein. During cold storage of the apple fruit, alternativ e pathway capacity correlated with the levels of the AOX and was apparently 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 induct ion of AOX are tightly and temporally linked.