title: Freezing tolerance in plants requires lipid remodeling at the outer chloroplast membrane.
abstract: Plants show complex adaptations to freezing that prevent cell damage caused by 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 non-bilayer-forming membrane lipids. This SFR2-based mechanism compensates for changes in organelle volume and stabilizes membranes during freezing.
authors.affiliation: Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824, USA.
authors.forename: Eric R
authors.initials: ER
authors.lastname: Moellering
authors.forename: Bagyalakshmi
authors.initials: B
authors.lastname: Muthan
authors.forename: Christoph
authors.initials: C
authors.lastname: Benning
mesh_terms: D000064:Acclimatization; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002736:Chloroplasts / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D004075:Diglycerides / Q000378:metabolism; D005615:Freezing; D038983:Galactolipids / Q000737:chemistry / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D007425:Intracellular Membranes / Q000737:chemistry / Q000378:metabolism*; D008051:Lipid Bilayers / Q000737:chemistry / Q000378:metabolism*; D008563:Membrane Lipids / Q000737:chemistry / Q000378:metabolism*; D009154:Mutation; D014280:Triglycerides / Q000378:metabolism; D001617:beta-Glucosidase / Q000235:genetics / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; D004075:Diglycerides; D038983:Galactolipids; D008051:Lipid Bilayers; D008563:Membrane Lipids; D014280:Triglycerides; C009909:monogalactosyldiacylglycerol; C492903:SFR2 protein, Arabidopsis; D001617:beta-Glucosidase