Adaptation and evolution of mitochondria: osmotic and ionic considerations

Abstract

Mitochondrial evolution has been examined on the basis of properties of mitochondria from representatives of key adaptive stages. The major step in the evolution of mitochondria was the transfer of mitochondrial genes to the nucleus to take advantage of recombination during meiosis. The ensuing increase in variability facilitated adaptation to environmental stress. The role of environmental factors such as atmospheric oxygen levels in the evolution of mitochondria is discussed on the basis of evidence obtained from mitochondria of living representatives of important groups and the fossil record. Rate enhancement has been a central theme in the evolution of animal mitochondria. Optimization of mitochondrial oxidation rates occurred through adjustments in intracellular solute systems. This took place in several stages, including (i) a reduction of intracellular inorganic ion levels by substitution of a variety of compatible solutes, (ii) a counteracting solute system (urea and methylamines), and (iii) osmoregulation.