Functional conservatism in mitochondrial evolution: insight from hybridization of arctic and brook charrs.
To assess the potential adaptive value of mtDNA, we evaluated functional properties and thermal sensitivity of key mitochondrial enzymes in two species that have originally evolved in different thermal environments (arctic charr, Salvelinus alpinus, and brook charr, S. fontinalis), as well as in their hybrids. We measured the activity of two enzymes of the electron transport system (cytochrome c oxidase and NADH-ubiquinone oxidoreductase), one enzyme of the mitochondrial matrix (citrate synthase), and one enzyme of the anaerobic glycolysis (lactate dehydrogenase) in the red muscle at three temperatures (6 degrees C, 12 degrees C and 18 degrees C). Surprisingly, the species presented no significant differences in enzyme activity, thermal sensitivity or thermostability of key metabolic enzymes even though they evolved in different thermal environments and present important differences in amino acid sequences. It seems that amino acid substitutions between those species have minor impact on the functional properties of mitochondrial enzymes studied. The thermal sensitivity results (Q(10)) obtained for inner-membrane mitochondrial enzymes differed somewhat from those of mitochondrial matrix or cytosolic enzymes. This result indicates the modulation of thermal sensitivity of all mitochondrial inner-membrane processes by a common parameter, which could be the structural and functional properties of membrane phospholipids.
Blier
Pierre U
PU
Laboratoire de Biologie Evolutive, Université du Québec à Rimouski, 300 Allée des Ursulines, Rimouski, Que., Canada G5L 3A1. pierre_blier@uqar.qc.ca
Breton
Sophie
S
Desrosiers
Véronique
V
Lemieux
Hélène
H
D000222:Adaptation, Physiological; D000818:Animals; D001110:Arctic Regions; D005075:Biological Evolution; D002678:Chimera / Q000235:genetics*; D004272:DNA, Mitochondrial / Q000502:physiology*; D042967:Electron Transport Complex I / Q000378:metabolism; D003576:Electron Transport Complex IV / Q000378:metabolism; D004795:Enzyme Stability; D005260:Female; D008297:Male; D008928:Mitochondria / Q000201:enzymology / Q000235:genetics*; D051336:Mitochondrial Membranes / Q000201:enzymology; D018656:Muscle Fibers, Fast-Twitch / Q000201:enzymology; D018482:Muscle, Skeletal / Q000201:enzymology; D013696:Temperature; D014337:Trout / Q000145:classification / Q000235:genetics* / Q000254:growth & development
D004272:DNA, Mitochondrial; D003576:Electron Transport Complex IV; D042967:Electron Transport Complex I