NaCl-stimulated ATP synthesis in mitochondria of a halophyte Mesembryanthemum crystallinum L

Salinity adaptive responses in halophytes include energy-requiring processes, but the mechanism supplying ATP to meet the increased ATP demand remains unclear. In the present study, we examined the effects of NaCl on ATP synthesis in mitochondria isolated from a halophyte, the common ice plant (Mesembryanthemum crystallinum L.). The ATP synthesis rate was maintained or enhanced with increasing osmotic pressures ranged from 0.2 to 2.0 MPa in the assay mixtures containing NaCl, whereas it was decreased in the mixtures with the equivalent osmotic pressures generated by sorbitol only. Also, the ATP synthesis rate was enhanced with increasing NaCl concentrations ranged from 50 to 350 mM in the assay mixtures with fixed (2.0 MPa) osmotic pressure. These results suggested a mechanism of enhanced ATP synthesis in the mitochondria by the ionic effects of NaCl, which might play an important role in the adaptation of the ice plant under salinity.