Plant sterol inhibition of abscisic acid-induced perturbations in phospholipid bilayers.
Abscisic acid (ABA)-induced phospholipid bilayer perturbations (permeability and lipid vesicle aggregation) are shown to be reversed by incorporation of a commercially available mixture of plant sterols (60% beta-sitosterol, 27% campesterol and 13% dihydrobrassicasterol) into the membranes. As little and 5 membrane mol% plant sterol inhibits ABA-stimulated permeability of both saturated and unsaturated mixed phosphatidylcholine/phosphatidylethanolamine bilayers to the fluorescent anion carboxyfluorescein by more than 50%. The same conclusion was reached by an osmotic swelling technique for the uncharged permeant solute erythritol. Hormone-induced carboxyfluorescein permeability to mixed acyl chain phosphatidylcholine bilayers was similarly inhibited by the sterols, but only if the membranes were tested at a temperature where liquid crystal and gel states coexist. The plant sterols were also shown to prevent the ABA-induced fusion of mixed phosphatidylcholine/phosphatidylethanolamine bilayers. The ABA effect on membranes is inhibited equally by plant sterols as well as cholesterol. From these experiments a possible role is suggested for plant sterols in controlling the mode of action of ABA.
Stillwell
W
W
Department of Biology, Indiana University-Purdue University, Indianapolis 46205.
Cheng
Y F
YF
Wassall
S R
SR
D000040:Abscisic Acid / Q000494:pharmacology*; D002463:Cell Membrane Permeability / Q000187:drug effects*; D002784:Cholesterol / Q000494:pharmacology; D003509:Cyclohexanecarboxylic Acids / Q000494:pharmacology*; D008051:Lipid Bilayers / Q000378:metabolism*; D010743:Phospholipids / Q000378:metabolism*; D010840:Phytosterols / Q000494:pharmacology*
D003509:Cyclohexanecarboxylic Acids; D008051:Lipid Bilayers; D010743:Phospholipids; D010840:Phytosterols; D000040:Abscisic Acid; D002784:Cholesterol