Changes in functional properties of mitochondria during growth cycle of Arabidopsis thaliana cell suspension cultures

Composition and properties of Percoll-purified mitochondria isolated from Arabidopsis thaliana cell suspension cultures were studied at various stages of the growth cycle. During the lag phase (2 days) mitochondria exhibited high lipid/ protein ratio, high double bound index and very low oxidative rate. After day 2 and up to day 4 for NADH (exponential phase), or to day 7 (beginning of the senescence) for succinate as substrates, the oxidation rate in state 3 increased while oxidation rate in state 4 remained low. Consequently, mitochondria appeared more and more coupled over the whole time of the growth cycle. Along with the constant oxidation rate in state 4, characteristics of membranes remained similar in terms of polypeptide pattern, proton conductance or fluorescence anisotropy although unsaturation of membranous fatty acids increased significantly during the growth cycle. All these results indicated that oxidation rate in state 3 increased continuously while basic properties of mitochondrial membranes remained similar during the growth.