Acyl Editing and Headgroup Exchange Are the Major Mechanisms That Direct Polyunsaturated Fatty Acid Flux into Triacylglycerols
Acyl Editing and Headgroup Exchange Are the Major Mechanisms That Direct Polyunsaturated Fatty Acid Flux into Triacylglycerols
复制标题
DOI：
10.1104/pp.112.204438
复制
发表时间：
2012-11-01
期刊：
影响因子：
7.4
通讯作者：
Lu, Chaofu
中科院分区：
文献类型：
--
作者：
Bates, Philip D.;Fatihi, Abdelhak;Lu, Chaofu
拟南芥和许多植物种子中的三酰甘油（TAG）含有大量的多不饱和脂肪酸（PUFA）。这些PUFA在膜脂质磷脂酰胆碱（PC）上合成。然而，脂肪酸如何进入PC以及它们在被修饰以参与TAG组装后如何从PC中去除的确切机制尚不清楚，控制这些通量的关键酶/基因的身份也不清楚。通过反向遗传学和代谢标记实验，我们证明了拟南芥中编码溶血磷脂酰胆碱酰基转移酶LPCAT 1和LPCAT 2的两个基因控制先前确定的“酰基编辑”过程，脂肪酸进入PC的主要入口。lpcat 1/lpcat 2突变体表现出非常长链脂肪酸的含量增加，减少PUFA的TAG和积累的少量溶血磷脂酰胆碱在发展中的种子[C-14]乙酸标记实验揭示。我们还表明，在减少油酸去饱和1（rod 1）/lpcat 1/lpcat 2突变体中的LPCAT和PC二酰基甘油胆碱磷酸转移酶的突变导致种子TAG中PUFA含量急剧减少，积累只有野生型水平的三分之一。这些结果表明PC酰基编辑和PC与二酰基甘油之间的磷酸胆碱头基交换控制了通过PC的大部分酰基通量，以提供用于TAG合成的PUFA。
Triacylglycerols (TAG) in seeds of Arabidopsis (Arabidopsis thaliana) and many plant species contain large amounts of polyunsaturated fatty acids (PUFA). These PUFA are synthesized on the membrane lipid phosphatidylcholine (PC). However, the exact mechanisms of how fatty acids enter PC and how they are removed from PC after being modified to participate in the TAG assembly are unclear, nor are the identities of the key enzymes/genes that control these fluxes known. By reverse genetics and metabolic labeling experiments, we demonstrate that two genes encoding the lysophosphatidylcholine acyltransferases LPCAT1 and LPCAT2 in Arabidopsis control the previously identified "acyl-editing" process, the main entry of fatty acids into PC. The lpcat1/lpcat2 mutant showed increased contents of very-long-chain fatty acids and decreased PUFA in TAG and the accumulation of small amounts of lysophosphatidylcholine in developing seeds revealed by [C-14] acetate-labeling experiments. We also showed that mutations in LPCATs and the PC diacylglycerol cholinephosphotransferase in the reduced oleate desaturation1 (rod1)/lpcat1/lpcat2 mutant resulted in a drastic reduction of PUFA content in seed TAG, accumulating only one-third of the wild-type level. These results indicate that PC acyl editing and phosphocholine headgroup exchange between PC and diacylglycerols control the majority of acyl fluxes through PC to provide PUFA for TAG synthesis.