%0 Journal Article
%T LysoPC acyltransferase/PC transacylase activities in plant plasma membrane and plasma membrane-associated endoplasmic reticulum
%A Karin E Larsson
%A J Magnus Kjellberg
%A Henrik Tjellstr£żm
%A Anna Sandelius
%J BMC Plant Biology
%D 2007
%I BioMed Central
%R 10.1186/1471-2229-7-64
%X The plant plasma membrane readily incorporated the acyl chain of acyl-CoA into phospholipids. Oleic acid was preferred over palmitic acid as substrate and acyl incorporation occurred predominantly into phosphatidylcholine (PC). Phospholipase A2 stimulated the reaction, as did exogenous lysoPC when administered in above critical micellar concentrations. AgNO3 was inhibitory. The lysophospholipid acylation reaction was higher in a membrane fraction that could be washed off the isolated plasma membranes after repeated freezing and thawing cycles in a medium with lowered pH. This fraction exhibited several ER-like characteristics. When plasma membranes isolated from transgenic Arabidopsis expressing green fluorescent protein in the ER lumen were observed by confocal microscopy, membranes of ER origin were associated with the isolated plasma membranes.We conclude that a lysoPC acylation activity is associated with plant plasma membranes and cannot exclude a PC transacylase activity. It is highly plausible that the enzyme(s) resides in a fraction of the ER, closely associated with the plasma membrane, or in both. We suggest that this fraction might be the equivalent of the mitochondria associated membrane of ER origin that delivers phospholipids to the mitochondria, and to the recently isolated ER-derived membrane fraction that is in close contact with chloroplasts. The in situ function of the lysoPC acylation/PC transacylase activity is unknown, but involvement in lipid delivery from the ER to the plasma membrane is suggested.The composition of the lipid phase of plant plasma membranes adjusts to the varying conditions in the plant environment. The adjustments include selective lipid degradation, increased incorporation of certain lipid classes and/or lipid molecular species and possibly re-tailoring of the lipids within the membrane as well [1-5]. In addition to their structural role, plasma membrane lipids are crucial intermediates in several signaling pathways [6].De
%U http://www.biomedcentral.com/1471-2229/7/64