DGD1-independent biosynthesis of extraplastidic galactolipids after phosphate deprivation in Arabidopsis
DGD1-independent biosynthesis of extraplastidic galactolipids after phosphate deprivation in Arabidopsis
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DOI：
10.1073/pnas.180320497
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发表时间：
2000-09-12
影响因子：
11.1
通讯作者：
Benning, C
中科院分区：
文献类型：
--
作者：
Härtel, H;Dörmann, P;Benning, C
半乳糖脂。单-和二半乳糖基二酰基甘油（DGDG）是生物圈中最常见的非磷脂质，占绿色植物组织中发现的膜脂质的80%。这些脂质是光合膜（类囊体）的主要成分，大量证据表明，半乳糖脂主要与种子植物的质体膜。拟南芥属的无效突变体（dgd 1）缺乏DGDG合酶（DGD 1），导致在正常生长条件下DGDG的量减少90%，在磷酸盐剥夺后积累的DGDG高达野生型中存在的量的60%。这一观察结果表明，存在一个DGD 1非依赖性途径的半乳糖脂生物合成。新形成的DGDG的脂肪酸组成是不同的，显示在DGDG的甘油主链的C-1位置中富集16-碳脂肪酸。缺磷后，根及其退化质体积累了大量的DGDG。提示这种半乳糖脂可能位于质体外膜中。这一假说的确证证据是直接获得的亚细胞膜从叶组织和间接的磷剥夺fad 3突变体主要缺乏质外脂肪酸去饱和的脂质分析分馏。缺磷诱导的DGDG生物合成的发现揭示了植物保存磷的生化机制。显然，植物用非磷半乳糖脂取代磷脂，如果环境条件如磷酸盐匮乏需要这种生存。
The galactolipids. mono- and digalactosyldiacylglycerol (DGDG), are the most common nonphosphorous lipids in the biosphere and account for 80% of the membrane lipids found in green plant tissues. These lipids are major constituents of photosynthetic membranes (thylakoids), and a large body of evidence suggests that galactolipids are associated primarily with plastid membranes in seed plants. A null-mutant of Arabidopsis (dgd1), which lacks the DGDG synthase (DGD1) resulting in a 90% reduction in the amount of DGDG under normal growth conditions, accumulated DGDG after phosphate deprivation up to 60% of the amount present in the wild type. This observation suggests the existence of a DGD1-independent pathway of galactolipid biosynthesis. The fatty acid composition of the newly formed DGDG was distinct, showing an enrichment of 16-carbon fatty acids in the C-1 position of the glycerol backbone of DGDG. Roots with their rudimentary plastids accumulated large amounts of DGDG after phosphate deprivation. suggesting that this galactolipid may be located in extraplastidic membranes. Corroborating evidence for this hypothesis was obtained directly by fractionation of subcellular membranes from leaf tissue and indirectly by lipid analysis of the phosphate-deprived fad3 mutant primarily deficient in extraplastidic fatty acid desaturation. The discovery of extraplastidic DGDG biosynthesis induced by phosphate deprivation has revealed a biochemical mechanism for plants to conserve phosphate. Apparently, plants replace phospholipids with nonphosphorous galactolipids if environmental conditions such as phosphate deprivation require this for survival.