Respiration and Phosphorylation of Mitochondria from Normal and Crown-Gall Tissue Cultures of Tomato

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Abstract
Oxidative and phosphorylative activities of mitochondria from normal and crown-gall tissue cultures of tomato were studied with an O2 electrode. Mitochondria from crown-gall tissue cultures oxidized reduced diphosphopyridine nucleotide (DPNH), glutamate, succinate, citrate, malate and [alpha]-ketoglutarate more slowly (about 0.9 times), but ascorbic acid more rapidly (4.5 times) than mitochondria from normal tissue cultures. The phosphorylating efficiency of crown-gall mitochondria (P/O ratio, about 0.6 with succinate) was lower than that of normal tissue mitochondria (P/O ratio, about 1.0 with succinate). The addition of a phosphate acceptor (adenosine diphosphate or glucose-hexokinase-adenosine triphosphate mixture) increased the rates of oxidation of the Krebs cycle acids tested, but not of DPNH and ascorbic acid. In succinate oxidation by normal tissue mitochondria, the enhancing effect by the phosphate acceptor was generally more than 2-fold (respiratory control ratio). With crown-gall mitochondria, on the other hand, the ratio rarely exceeded 2. The oxidation of ascorbic acid by the mitochondria from normal and crown-gall tissue cultures was compared to the oxidation by an ascorbic acid oxidase preparation; all the evidence obtained indicated that the mitochondria from both tissue cultures contained ascorbic acid oxidase. Mitochondria from both normal and crown-gall tissue cultures responded similarly to cofactors (diphosphopyridine nucleotide, cytochrome c) and inhibitors (cyanide, Antimycin A). The mitochondria from normal and crown-gall tissue cultures differed in their oxidative and phosphorylative activities in rather small quantitative rather than qualitative characteristics. Furthermore, mitochondria isolated from tomato tissue cultures, except for ascorbic acid oxidase activity, were similar in their respiratory properties to those from intact higher plants and animals.