DGD2, an Arabidopsis gene encoding a UDP-galactose-dependent digalactosyldiacylglycerol synthase is expressed during growth under phosphate-limiting conditions
DGD2, an Arabidopsis gene encoding a UDP-galactose-dependent digalactosyldiacylglycerol synthase is expressed during growth under phosphate-limiting conditions
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DOI：
10.1074/jbc.m110066200
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发表时间：
2002-01-11
影响因子：
4.8
通讯作者：
Dörmann, P
中科院分区：
文献类型：
--
作者：
Kelly, AA;Dörmann, P
半乳糖脂二半乳糖基二酰基甘油（DGDG）是高等植物中主要的叶绿体脂质之一，被认为是由半乳糖脂：半乳糖脂半乳糖基转移酶合成的，其将半乳糖部分从一个单半乳糖基二酰基甘油（MGDG）分子转移到另一个分子。在这里，我们报告，拟南芥以及其他植物物种含有两个基因，DGD 1和DGD 2，编码酶与DGDG合酶活性。使用MGDG和UDP-半乳糖作为底物在体外测定与DGD 2，我们可以为第一次测量DGDG合成酶活性的异源表达的植物cDNA。UDP-半乳糖，而不是MGDG，作为半乳糖供体的DGD 2催化的DGDG合成，提供了明确的证据，在高等植物中存在UDP-半乳糖依赖的DGDG合成酶。在体外试验中，DGD 2能够将DGDG半乳糖基化，导致合成一种寡聚半乳糖脂，初步鉴定为三半乳糖基甘油二酯。DGD 2 mRNA在叶片中的表达是非常低的，但强烈诱导生长在磷限制条件下。这种诱导与先前描述的磷酸盐剥夺过程中DGDG的增加相关。因此，与DGD 1相反，DGD 1负责叶绿体中发现的大量DGDG的合成，DGD 2显然在特定生长条件下参与DGDG的合成。
The galactolipid digalactosyldiacylglycerol (DGDG), one of the main chloroplast lipids in higher plants, is believed to be synthesized by the galactolipid:galactolipid galactosyltransferase, which transfers a galactose moiety from one molecule of monogalactosyldiacylglycerol (MGDG) to another. Here, we report that Arabidopsis as well as other plant species contain two genes, DGD1 and DGD2, encoding enzymes with DGDG synthase activity. Using MGDG and UDP-galactose as substrates for in vitro assays with DGD2 we could for the first time measure DGDG synthase activity of a heterologously expressed plant cDNA. UDP-galactose, but not MGDG, serves as the galactose donor for DGDG synthesis catalyzed by DGD2, providing clear evidence for the existence of a UDP-galactose-dependent DGDG synthase in higher plants. In in vitro assays, DGD2 was capable of galactosylating DGDG, resulting in the synthesis of an oligogalactolipid tentatively identified as trigalactosyldiacylglycerol. DGD2 mRNA expression in leaves was very low but was strongly induced during growth under phosphate-limiting conditions. This induction correlates with the previously described increase in DGDG during phosphate deprivation. Therefore, in contrast to DGD1, which is responsible for the synthesis of the bulk of DGDG found in chloroplasts, DGD2 apparently is involved in the synthesis of DGDG under specific growth conditions.