Development of vacuoles and vacuolar H+-ATPase activity under extremely high CO2 conditions in Chlorococcum littorale cells

The number and cross-sectional area of vacuoles in Chlorococcum littorale c ells visualized with a differential interference fluorescence microscope in creased after their transfer from air to 40% CO2. An immunological observat ion indicated that the level of subunit B of vacuolar H+-ATPase also increa sed under 40 % CO2 conditions. The activity of nitrate-sensitive ATPase ass ociated with the vacuolar membrane was 2-fold higher in 40 % CO2-grown cell s than in air-grown cells. The effects of inhibitors on the ATPase activity confirmed that these activities were derived from vacuolar-type H+-ATPase. These results suggest that vacuole development associated with that of vac uolar H+-ATPase occurred during the acclimatization of C. littorale cells t o extremely high CO2 conditions.