Author/Editor		Svetek, Jelka; Kirn, Borut; Vilhar, Barbara; Schara, Milan
Title		Lateral domain diversity in membranes of callus and root cells of potato as revealed by EPR spectroscopy
Type		članek
Source		Physiol Plantarum
Vol. and No.		Letnik 105
Publication year		1999
Volume		str. 499-505
Language		eng
Abstract		Lateral heterogeneity in terms of co-existing domains with a distinct molecular organization is an area of increasing interest in membrane biology. The structural and dynamic aspects of the in-plane domain organization of lipids are becoming well documented, especially for model membrane systems. Potato (Solanum tuberosum L. cv. Desiree) callus cells and roots of plantlets from stem node culture were doped with a spin-labeled analog of the methyl ester of palmitic acid bearing the paramagnetic nitroxide group at position C-5 of the acyl chain, which serves as a monitor of membrane fluidity of the region close to the polar phospholipid head groups of the bilayer. Model reconstruction of the line-shapes of the experimental spectra revealed the co-existence of two types of membrane domains with different ordering and dynamics of lipids in the membranes of both cellus and root cells. With changes in temperature, relatively small differences were detected in either type of domain in the lipid ordering of the bilayer as characterized by order parameter S. However, the relative population of domains in the bilayer exhibited stronger temperature dependence. Typically, the relative proportion of disorder domains with less molecular order (smaller S) was larger in the membranes of callus cells compared to those of root cells, indicating higher fluidity throughout themeasured temperature range (5-35 degrees C). The Arrhenius activation energies for rearrangement of lipid molecules within the bilayer were found to be higher for root tissue membranes indicating the ability of root cells to oppose actively any drastic changes of membrane structuring under temperature stress. The distinctions in organization of lateral domains between the callus and root cell membranes may be correlated with differences in growth rate and metabolic activity between these two types of tissue.
Descriptors		POTATOES CELL MEMBRANE PLANT ROOTS MEMBRANE FLUIDITY LIPID BILAYERS CALLOSITIES ELECTRON SPIN RESONANCE SPECTROSCOPY TEMPERATURE PALMITIC ACID SPIN LABELS