Freezing Tolerance in Plants Requires Lipid Remodeling at the Outer Chloroplast Membrane

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Science  26 Aug 2010:
DOI: 10.1126/science.1191803


Plants show complex adaptations to freezing that prevent cell damage due to cellular dehydration. Lipid remodeling of cell membranes during dehydration is one critical mechanism countering loss of membrane integrity and cell death. SENSITIVE TO FREEZING 2 (SFR2), a gene essential for freezing tolerance in Arabidopsis , encodes a galactolipid remodeling enzyme of the outer chloroplast envelope membrane. SFR2 processively transfers galactosyl residues from the abundant monogalactolipid to different galactolipid acceptors forming oligogalactolipids and diacylglycerol, which is further converted to triacylglycerol. The combined activity of SFR2 and triacylglycerol-biosynthetic enzymes leads to the removal of monogalactolipids from the envelope membrane, changing the ratio of bilayer to nonbilayer forming membrane lipids. This SFR2-based mechanism compensates for changes in organelle volume and stabilizes membranes during freezing.