Protonophores as inducers of energy-dependent changes of ultrastructure of mitochondria in wheat root cells

Abstract

The membrane potential of plasmalemma, the release of K+ ions into incubation medium, respiratory gas exchange, the ATP content, and changes in the ultrastructure in cells of excised roots of wheat seedlings have been studied under the effect of protonophores 2,4-DNP (2,4-dinitrophenol) and CCCP (carbonyl cyanide m-chlorophenylhydrazone). After 1–4 h, a drop occurred in the plasmalemma membrane potential, as well as the release of K+ ions into incubation solution and the suppression of the intensity of oxygen absorption by cells. Mitochondria were of ovoid shape and had numerous and clearly outlined, slightly swollen cristae, which corresponds to the condensed type of the organelles. Additionally, a peculiar spatial arrangement of cristae in mitochondria has been revealed (as piles parallel to each other, as well as in the form of fans and of propellers) under the effects of protonophores. After 5 h of the action of protonophores against a background of the significant stimulation of oxygen consumption, low membrane potential, and a decrease in the functional activity of mitochondria, the destruction of the cell ultrastructure began. It is suggested that the revealed conformational transitions of mitochondria reflect gradual changes in their functional activity and the functional state of the cells under the long action of protonophores.