Department of Plant Sciences and Plant Pathology, Montana State University, Bozeman, Montana 59717-3150, USA.
Plant Physiol. 2012 Apr;158(4):1944-54. doi: 10.1104/pp.111.192153. Epub 2012 Feb 27.
We previously identified an enzyme, phosphatidylcholine diacylglycerol cholinephosphotransferase (PDCT), that plays an important role in directing fatty acyl fluxes during triacylglycerol (TAG) biosynthesis. The PDCT mediates a symmetrical interconversion between phosphatidylcholine (PC) and diacylglycerol (DAG), thus enriching PC-modified fatty acids in the DAG pool prior to forming TAG. We show here that PDCT is required for the efficient metabolism of engineered hydroxy fatty acids in Arabidopsis (Arabidopsis thaliana) seeds. When a fatty acid hydroxylase (FAH12) from castor (Ricinus communis) was expressed in Arabidopsis seeds, the PDCT-deficient mutant accumulated only about half the amount of hydroxy fatty acids compared with that in the wild-type seeds. We also isolated a PDCT from castor encoded by the RcROD1 (Reduced Oleate Desaturation1) gene. Seed-specific coexpression of this enzyme significantly increased hydroxy fatty acid accumulation in wild type-FAH12 and in a previously produced transgenic Arabidopsis line coexpressing a castor diacylglycerol acyltransferase 2. Analyzing the TAG molecular species and regiochemistry, along with analysis of fatty acid composition in TAG and PC during seed development, indicate that PDCT acts in planta to enhance the fluxes of fatty acids through PC and enrich the hydroxy fatty acids in DAG, and thus in TAG. In addition, PDCT partially restores the oil content that is decreased in FAH12-expressing seeds. Our results add a new gene in the genetic toolbox for efficiently engineering unusual fatty acids in transgenic oilseeds.
我们先前鉴定出一种酶，即磷酸甘油二酯胆碱磷酸转移酶（PDCT），它在三酰基甘油（TAG）生物合成过程中脂肪酸通量的定向中起着重要作用。PDCT介导了磷酸胆碱（PC）和二酰基甘油（DAG）之间的对称相互转化，从而在形成TAG 之前使 PC 修饰的脂肪酸在 DAG 池中富集。我们在这里表明，PDCT是拟南芥（Arabidopsis thaliana）种子中工程化羟基脂肪酸有效代谢所必需的。当蓖麻（Ricinus communis）中的脂肪酸羟化酶（FAH12）在拟南芥种子中表达时，与野生型种子相比，PDCT 缺陷突变体积累的羟基脂肪酸量仅约为其一半。我们还从蓖麻中分离出编码 RcROD1（Reduced Oleate Desaturation1）基因的 PDCT。该酶在种子中的特异性共表达显著增加了野生型-FAH12 和先前生产的共表达蓖麻二酰基甘油酰基转移酶 2 的转基因拟南芥系中羟基脂肪酸的积累。对 TAG 分子种类和区域化学的分析，以及对种子发育过程中 TAG 和 PC 中脂肪酸组成的分析表明，PDCT 在植物体内作用是增强脂肪酸通过 PC 的通量，并使 DAG 中的羟基脂肪酸富集，从而使 TAG 中的羟基脂肪酸富集。此外，PDCT部分恢复了在表达 FAH12 的种子中降低的油含量。我们的结果为在转基因油料作物中有效地工程化不寻常脂肪酸添加了一个新的基因工具箱。
