Changes in message amount of V-ATPase subunits during salt-stress induced C3-CAM transition in Mesembryanthemum crystallinum

Total RNA was isolated from control plants and salt-treated plants of Mesembryanthemum crystallinum L. at the beginning and at the end of the light phase. The amounts of mRNA for V-ATPase (EC 3.6.1.34) subunits A, B and c were quantified by northern blot analyses with homologous cDNA probes. In leaves harvested at the beginning of the light phase, mRNA and protein amounts of subunits B and c showed a much higher increase, compared to subunit-A mRNA, correlated with the extent of salt accumulation in the leaves and the expression of CAM. In leaves collected at the end of the light phase, message amounts of subunits B and c were high and similar in controls and salt-treated plants. Possible correlation of diurnal changes of V-ATPase subunit transcript amounts to structural changes of the V-ATPase holoenzyme occurring during salt stress CAM induction are discussed.