title: Mitochondrial respiration in ME-CAM, PEPCK-CAM, and C₃ succulents: comparative operation of the cytochrome, alternative, and rotenone-resistant pathways.
abstract: Mitochondria are important in the function and control of Crassulacean acid metabolism (CAM) during organic acid accumulation at night and acid decarboxylation in the day. In plants of the malic enzyme-(ME) type and the phosphoenolpyruvate carboxykinase- (PEPCK) type, mitochondria may exert their role in the control of the diurnal rhythm of malic and citric acids to a differential degree. In plants of both CAM types, the oxidative capacity of mitochondria, as well as the activity of CAM-linked mitochondrial enzymes, and of the alternative and the rotenone-resistant pathways of substrate oxidation were compared. Furthermore, a C₃ succulent was included, as well as both C₃ and CAM forms of Mesembryanthemum crystallinum during a salt-induced C₃-to-CAM shift. Mitochondria of PEPCK-type CAM plants exhibited a lower activity of malate oxidation, ratio of malate to succinate oxidation, and activity of mitochondrial NAD-ME. With the exception of Kalanchoë daigremontiana, leaf mitochondria of all other CAM species were highly sensitive to cyanide (80-100%), irrespective of the oxidant used. This indicates that the alternative oxidase is not of general importance in CAM. By contrast, rotenone-insensitive substrate oxidation was very high (50-90%) in all CAM species. This is the first comparison of the rotenone-insensitive pathway of respiration in plants with different CAM-types. The results of this study confirm that mitochondria are involved in the control of CAM to different degrees in the two CAM types, and they highlight the multiple roles of mitochondria in CAM.
authors.affiliation: Institut für Ökologie der Pflanzen, Westfälische Wilhelms-Universität, Hindenburgplatz 55, D-48143 Münster, Germany.
authors.forename: Klaus
authors.initials: K
authors.lastname: Peckmann
authors.forename: Dieter J
authors.initials: DJ
authors.lastname: von Willert
authors.forename: Craig E
authors.initials: CE
authors.lastname: Martin
authors.forename: Werner B
authors.initials: WB
authors.lastname: Herppich
mesh_terms: D000105:Acetyl Coenzyme A / Q000494:pharmacology; D002264:Carboxylic Acids; D019069:Cell Respiration / Q000187:drug effects; D003486:Cyanides / Q000633:toxicity; D003580:Cytochromes / Q000378:metabolism*; D008274:Magnesium / Q000494:pharmacology; D008291:Malate Dehydrogenase / Q000378:metabolism*; D008293:Malates / Q000378:metabolism; D008345:Manganese / Q000494:pharmacology; D053858:Metabolic Networks and Pathways / Q000187:drug effects*; D008928:Mitochondria / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D009243:NAD / Q000378:metabolism; D009249:NADP / Q000378:metabolism; D009995:Osmosis / Q000187:drug effects; D010084:Oxidation-Reduction / Q000187:drug effects; D010101:Oxygen Consumption / Q000187:drug effects; D019764:Phosphoenolpyruvate Carboxykinase (ATP) / Q000378:metabolism*; D010944:Plants / Q000187:drug effects / Q000201:enzymology*; D011773:Pyruvates / Q000494:pharmacology; D012402:Rotenone / Q000494:pharmacology*; D013045:Species Specificity; D019802:Succinic Acid / Q000378:metabolism
chemical_list: D002264:Carboxylic Acids; D003486:Cyanides; D003580:Cytochromes; D008293:Malates; D011773:Pyruvates; D012402:Rotenone; D009243:NAD; D008345:Manganese; D009249:NADP; D000105:Acetyl Coenzyme A; C030298:malic acid; D019802:Succinic Acid; D008291:Malate Dehydrogenase; C030574:malate dehydrogenase (decarboxylating); D019764:Phosphoenolpyruvate Carboxykinase (ATP); D008274:Magnesium