Upregulation of vacuolar H(+)-translocating pyrophosphatase by phosphate starvation of Brassica napus (rapeseed) suspension cell cultures.

The influence of phosphate (Pi) deprivation on the vacuolar H(+)-translocating pyrophosphatase (PPiase) and ATPase in tonoplast vesicles from Brassica napus suspension cells was assessed. Pi starvation significantly elevated the ratios of PPi-:ATP-dependent H(+) translocation rate and H(+)-PPiase:H(+)-ATPase hydrolytic activities. These increases were reversed 36 h following resupply of 2.5 mM Pi to the Pi-starved cells. Immunoblotting indicated that Pi starvation also induced a two-fold increase in the amount of H(+)-PPiase protein, whereas the amount of H(+)-ATPase remained unchanged. It is proposed that H(+)-PPiase facilitates the conservation of limited ATP pools, and Pi recycling during Pi stress.