ISSN 1021-4437, Russian Journal of Plant Physiology, 2006, Vol. 53, No. 1, pp. 39–47. © MAIK “Nauka /Interperiodica” (Russia), 2006.
Original Russian Text © S.S. Medvedev, O.V. Tankelyun, A.Yu. Batov, O.V. Voronina, J. Martinec, I. Machá ková, 2006, published in Fiziologiya Rastenii, 2006, Vol. 53, No. 1,
Phosphatidic acid (PA) accounts for 1–2% of the
total amount of membrane phospholipids in plant cells
and plays a key role in lipid metabolism, as it is
involved in the biosynthesis of structural phospho- and
glycolipids [1, 2]. Moreover, current visions consider
PA as a lipid secondary messenger that transmits sig-
nals concerning wounding, water deﬁcit, salinity, and
oxidative stresses and is involved in polar growth and in
osmotic volume changes of stomatal guard cells [3–7].
The PA level in targeted cells can be transiently ele-
vated under the action of pathogens, elicitors, ABA,
and ethylene [4, 8–11].
Nevertheless, the mechanisms of PA-mediated sig-
nal transduction in plant cells are poorly investigated to
date. Phosphatidic acid is thought to promote binding
of some enzymes to the plasma membrane, thereby ele-
vating the activities of NADPH oxidase, MAPK-cas-
cade kinases engaged in ethylene signaling, and of cal-
cium-dependent protein kinases (CDPK) [12, 13].
Changes in the PA level affect physical properties of
cell membranes and their capacity of vesicle formation.
Thus, PA may affect vesicle trafﬁcking associated with
exo- and endocytosis .
There is evidence that PA is able to transport Ca
across muscle and nerve cell membranes [14–16].
Experiments with guard cells of plant stomata
revealed that changes in phospholipase D (PLD)
activity during transduction of ABA signal are accom-
panied by the increase in cytosolic Ca
However, it remains to be established whether
changes in PLD activity and the increase in the cyto-
concentration are sequential events in an
integrated signaling pathway or whether they repre-
sent independent processes.
The goal of this study was to investigate iono-
phorous functions of PA in membrane vesicles using
Ionophorous Functions of Phosphatidic Acid
in the Plant Cell
S. S. Medvedev*, O. V. Tankelyun*, A. Yu. Batov*,
O. V. Voronina*, J. Martinec**, and I. Machá ková**
*Department of Plant Physiology and Biochemistry, St. Petersburg State University,
Universitetskaya nab. 7/9, St. Petersburg, 199034 Russia;
fax: 7 (812) 328-9703; e-mail: firstname.lastname@example.org
**Institute of Experimental Botany, Czech Academy of Sciences,
Praha, 16500 Czech Republic
Received June 3, 2005
—Effects of phosphatidic acid (PA), a product of phospholipase D activity, on Ca
were investigated in membrane vesicles obtained from roots and coleoptiles of maize (
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
M) was found to induce downhill ﬂow of
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
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
M 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
across plant cell membranes along concentration gradients of these ions. The role of PA in mech-
anisms of intracellular signaling in plants is discussed.
Key words: Zea mays - phosphatidic acid - membrane vesicles - ﬂuorescent probes - membrane transport of
- ionophores - signal transduction
: CDPK—calcium-dependent protein kinase;
CTC—chlorotetracycline; DTT—dithiothreitol; FCCP—carbo-
nyl cyanide p-(triﬂuoromethoxy)phenylhydrazone; MAPK—
mitogen-activated protein kinase; PA—phosphatidic acid; PIP
phosphatidylinositol 4,5-diphosphate; PLD—phospholipase D;