Interaction of abscisic acid with phospholipid membranes

The plant hormone abscisic acid (ABA) is shown, under certain conditions, to greatly enhance the permeability of phospholipid bilayer membranes to the nonelectrolyte erythritol (followed spectrophotometrically by osmotic swelling) and the anion carboxyfluorescein (followed by fluorescence). The horm...

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Bibliographic Details
Published in:	Biochemistry (Easton) 1989-04, Vol.28 (7), p.2798-2804
Main Authors:	Stillwell, William, Brengle, Blair, Hester, Paul, Wassall, Stephen R
Format:	Article
Language:	eng
Subjects:	550601 - Medicine- Unsealed Radionuclides in Diagnostics ABSCISIC ACID AUXINS BIOLOGICAL EFFECTS CARBON 13 CARBON ISOTOPES CARBOXYLIC ACIDS CHEMICAL REACTIONS CROSS-LINKING ESTERS EVEN-ODD NUCLEI ISOTOPES LIGHT NUCLEI LIPIDS MAGNETIC RESONANCE MEMBRANES MONOCARBOXYLIC ACIDS NMR SPECTRA NUCLEAR MAGNETIC RESONANCE NUCLEI ODD-EVEN NUCLEI ORGANIC ACIDS ORGANIC COMPOUNDS ORGANIC PHOSPHORUS COMPOUNDS PERMEABILITY PHOSPHOLIPIDS PHOSPHORUS 31 PHOSPHORUS ISOTOPES PLANT GROWTH REGULATORS POLYMERIZATION RADIOLOGY AND NUCLEAR MEDICINE RESONANCE SPECTRA STABLE ISOTOPES
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Summary:	The plant hormone abscisic acid (ABA) is shown, under certain conditions, to greatly enhance the permeability of phospholipid bilayer membranes to the nonelectrolyte erythritol (followed spectrophotometrically by osmotic swelling) and the anion carboxyfluorescein (followed by fluorescence). The hormone is ineffective with single- and mixed-component phosphatidylcholine membranes in the liquid-crystalline or gel states. In contrast, substantial ABA-induced permeability is measured for two-component membranes containing lipids with different polar head groups or containing phosphatidylcholines with different acyl chains at temperatures where gel and liquid-crystalline phases coexist. Despite the large ABA-induced enhancement in bilayer permeability, no evidence for a substantial change at the molecular level was seen in the membranes by magnetic resonance techniques. {sup 13}C NMR spin-lattice relaxation times, T{sub 1}, in sonicated unilamellar vesicles and ESR of spin-labeled fatty acids intercalated into membranes showed negligible effect on acyl chain order and dynamics within the bilayer, while {sup 31}P NMR of sonicated unilamellar vesicles indicated negligible effect on molecular motion and conformation in the head-group region. The authors propose that, instead of causing a general nonspecific perturbation to the membrane, the hormone acts at membrane defects formed due to mismatch in molecular packing where two different head groups or acyl chain states interface. Increased membrane disruption by ABA at these points of membrane instability could then produce an enhancement in permeability.
ISSN:	0006-2960 1520-4995