The water permeability of Arabidopsis thaliana plasma membrane is regulated by divalent cations and pH

PATRICIA GERBEAU; GABRIELA AMODEO; TOBIAS HENZLER; PIERRE RIPOCHE; CHRISTOPHE MAUREL

PLANT JOURNAL

Blackwell Science Ltd

Lugar: London; Año: 2002 p. 71 - 81

0960-7412

Mechanisms that regulate water channels in the plant plasma membrane (PM) were investigated in Arabidopsis suspension cells. Cell hydraulic conductivity was measured with a cell pressure probe and was reduced 4-fold as compared to control values when calcium was added in the pipette and in bathing solution. To assess the signiÆcance of these effects in vitro, PM vesicles were isolated by aqueous twophase partitioning and their water transport properties were characterized by stopped-Øow spectrophotometry. Membrane vesicles isolated in standard conditions exhibited reduced water permeability (Pf) together with a lack of active water channels. In contrast, when prepared in the presence of chelators of divalent cations, PM vesicles showed a 2.3-fold higher Pf and active water channels. Furthermore, equilibration of puriÆed PM vesicles with divalent cations reduced their Pf and water channel activity down to the basal level of membranes isolated in standard conditions. Ca2+ was the most efÆcient with a half-inhibition of Pf at 50±100 mM free Ca2+. Water transport in puriÆed PM vesicles was also reversibly blocked by H+, with a half-inhibition of Pf at pH 7.2±7.5. Thus, both Ca2+ and H+ contribute to a membrane-delimited switch from active to inactive water channels that may allow coupling of water transport to cell signalling and metabolism.