Medvedev S.S., Tankelyun O.V., Batov A.Y., Voronina O.V., Martinec J., Machackova I.: Ionophorous functions of phosphatidic acid in the plant cell. Russian Journal of Plant Physiology 2006, 53, 39-47.

Effects of phosphatidic acid (PA), a product of phospholipase D activity, on Ca²⁺ and H⁺ transport
were investigated in membrane vesicles obtained from roots and coleoptiles of maize (Zea mays L.). Calcium
flows were measured with fluorescent probes indo-1 and chlorotetracycline loaded into the vesicles and added
to the incubation medium, respectively. Phosphatidic acid (50–500 uM) was found to induce downhill flow of
Ca²⁺ along the concentration gradient into the plasma membrane vesicles and endomembrane vesicles (tono-
plast and endoplasmic reticulum). Protonophorous functions of PA were probed with acridine orange. First, the
ionic H⁺ gradient was created on the tonoplast vesicles by means of H⁺-ATPase activation with Mg–ATP addi-
tion. Then, the vesicles were treated with 25–100 uM PA, which induced the release of protons from tonoplast
vesicles and dissipation of the proton gradient. Thus, PA could function as an ionophore and was able to transfer
Ca²⁺ and H⁺ across plant cell membranes along concentration gradients of these ions. The role of PA in mech-
anisms of intracellular signaling in plants is discussed.