Metabolically Distinct Pools of Phosphatidylcholine Are Involved in Trafficking of Fatty Acids out of and into the Chloroplast for Membrane Production
Metabolically Distinct Pools of Phosphatidylcholine Are Involved in Trafficking of Fatty Acids out of and into the Chloroplast for Membrane Production
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DOI：
10.1105/tpc.19.00121
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发表时间：
2019-11-01
期刊：
影响因子：
11.6
通讯作者：
Bates, Philip D.
中科院分区：
文献类型：
--
作者：
Karki, Nischal;Johnson, Brandon S.;Bates, Philip D.
半乳糖脂合成的真核途径涉及叶绿体中的脂肪酸合成，随后是磷脂酰胆碱（PC）在内质网（ER）中的组装，然后PC周转以提供叶绿体半乳糖脂合成的底物。然而，在叶绿体和内质网之间转运的脂质的机制和类别尚不清楚。PC、PC衍生的二酰基甘油、磷脂酸和溶血磷脂酰胆碱（LPC）都参与了内质网向叶绿体的脂质转移。LPC转运需要叶绿体中的溶血磷脂酰胆碱酰基转移酶（LPCAT）活性，以在转化为半乳糖脂之前形成PC。然而，LPCAT还涉及通过PC酰基编辑的新合成的脂肪酸的相反的叶绿体至ER运输。为了了解LPC和LPCAT在酰基运输中的作用，我们制备并分析了拟南芥（Arabidopsis thaliana）act 1 lpcat 1 lpcat 2三重突变体。LPCAT 1和LPCAT 2编码叶绿体的主要溶血磷脂酰基转移酶活性，并且其主要用于通过酰基编辑将从叶绿体输出的新生脂肪酸并入PC中。在体内酰基通量分析显示，真核生物半乳糖脂的合成是不受损害的act 1 lpcat 1 lpcat 2和使用的PC池不同的PC酰基编辑。我们提出了一个模型的真核生物途径与代谢不同池的PC，这表明一个潜在的空间组织的PC代谢的一部分，ER-叶绿体代谢相互作用。
The eukaryotic pathway of galactolipid synthesis involves fatty acid synthesis in the chloroplast, followed by assembly of phosphatidylcholine (PC) in the endoplasmic reticulum (ER), and then turnover of PC to provide a substrate for chloroplast galactolipid synthesis. However, the mechanisms and classes of lipids transported between the chloroplast and the ER are unclear. PC, PC-derived diacylglycerol, phosphatidic acid, and lyso-phosphatidylcholine (LPC) have all been implicated in ER-to-chloroplast lipid transfer. LPC transport requires lysophosphatidylcholine acyltransferase (LPCAT) activity at the chloroplast to form PC before conversion to galactolipids. However, LPCAT has also been implicated in the opposite chloroplast-to-ER trafficking of newly synthesized fatty acids through PC acyl editing. To understand the role of LPC and LPCAT in acyl trafficking we produced and analyzed the Arabidopsis (Arabidopsis thaliana) act1 lpcat1 lpcat2 triple mutant. LPCAT1 and LPCAT2 encode the major lysophospholipid acyltransferase activity of the chloroplast, and it is predominantly for incorporation of nascent fatty acids exported form the chloroplast into PC by acyl editing. In vivo acyl flux analysis revealed eukaryotic galactolipid synthesis is not impaired in act1 lpcat1 lpcat2 and uses a PC pool distinct from that of PC acyl editing. We present a model for the eukaryotic pathway with metabolically distinct pools of PC, suggesting an underlying spatial organization of PC metabolism as part of the ER-chloroplast metabolic interactions.