Sensitivities of the alternative respiratory components of potato tuber mitochondria to thiol reagents and Ca2

• Published in: Plant physiology and biochemistry Vol. 43; no. 1; pp. 61 - 67
• Main Authors: MARIANO, André B, VALENTE, Caroline, CADENA, Silvia M. S. C, ROCHA, Maria E. M, DE OLIVEIRA, Maria B. M, CARNIERI, Eva G. S
• Format: Journal Article
• Language: English
• Published: Paris Elsevier 2005
• Subjects: Agronomy. Soil science and plant productions; Biological and medical sciences; Calcium - pharmacology; Cell Membrane - enzymology; Cell Membrane - physiology; Diamide - toxicity; Economic plant physiology; Fundamental and applied biological sciences. Psychology; Membrane Potentials - physiology; Mersalyl - toxicity; Mitochondria - enzymology; Mitochondria - physiology; Mitochondrial Proteins; NADH Dehydrogenase - metabolism; Net assimilation, photosynthesis, carbon metabolism. Photorespiration, respiration, fermentation (anoxia, hypoxia); Nutrition. Photosynthesis. Respiration. Metabolism; Oxidation-Reduction - drug effects; Oxidoreductases - metabolism; Oxygen - metabolism; Plant Proteins; Solanum tuberosum - enzymology; Solanum tuberosum - physiology; Succinic Acid - metabolism; Sulfhydryl Reagents - pharmacology; Ubiquinone - analogs & derivatives; Ubiquinone - metabolism; SH active reagents; Mitochondria; Plant mitochondria; Potato tubers; Enzyme; Ca2; Oxidase; SHAM; Tuber; Cold-stress; Oxidoreductases
• ISSN: 0981-9428; 1873-2690
• DOI: 10.1016/j.plaphy.2004.12.008

Plant mitochondria differ from those of mammals, since they incorporate an alternative electron transport pathway, which branches at ubiquinol to an alternative oxidase (AOX), characteristically inhibited by salicylhydroxamic acid (SHAM). Another feature of plant mitochondria is that besides complex I (EC 1.6.5.3) they possess alternative NAD(P)H-dehydrogenases insensitive to rotenone. Many stress conditions are known to alter the expression of the alternative electron transport pathway in plant mitochondria. In the present study we investigated the effects of some thiol reagents and Ca(2+) on potato mitochondrial respiratory chain presenting different activities of the alternative respiratory components AOX and external NADH dehydrogenase, a condition induced by previous treatment of potato tubers (Solanum tuberosum L., cv. Bintje) to cold stress. The results showed that Ca(2+) presented an inhibitory effect on AOX pathway in potato mitochondria energized with NADH or succinate, which was only now observed when the cytochrome pathway was inhibited by cyanide. When the cytochrome pathway was functional, Ca(2+) stimulated the external NADH dehydrogenase. Diamide was a potent AOX inhibitor and this effect was only now observed when the cytochrome pathway was inactive, as was the case for the calcium ion. Mersalyl inhibited the externally located NADH dehydrogenase and had no effect on AOX activity. The results may represent an important function of Ca(2+) on the alternative mitochondrial enzymes NADH-DH(ext) and AOX.