Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824, USA.
Science. 2010 Oct 8;330(6001):226-8. doi: 10.1126/science.1191803. Epub 2010 Aug 26.
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.
植物表现出复杂的适应冻结的特性，以防止细胞脱水导致的细胞损伤。细胞膜在脱水过程中的脂质重排是一种关键机制，可以防止膜完整性丧失和细胞死亡。SENSITIVE TO FREEZING 2 (SFR2) 是拟南芥中抗冻所必需的基因，它编码质体外部包膜膜的半乳糖脂重塑酶。SFR2 连续地将半乳糖残基从丰富的单半乳糖脂转移到不同的半乳糖脂受体上，形成寡半乳糖脂和二酰基甘油，进一步转化为三酰基甘油。SFR2 和三酰基甘油生物合成酶的联合活性导致单半乳糖脂从包膜膜中去除，改变双层形成膜脂质和非双层形成膜脂质的比例。这种基于 SFR2 的机制补偿了细胞器体积的变化，并在冻结过程中稳定了膜。
