DOE Plant Research Laboratory, Michigan State University, East Lansing, MI, 48824, USA.
Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI, 48824, USA.
Plant J. 2018 Sep;95(6):1129-1139. doi: 10.1111/tpj.13999. Epub 2018 Jul 17.
In plant lipid metabolism, the synthesis of many intermediates or end products often appears overdetermined with multiple synthesis pathways acting in parallel. Lipid metabolism is also dynamic with interorganelle transport, turnover, and remodeling of lipids. To explore this complexity in vivo, we developed an in vivo lipid 'tag and track' method. Essentially, we probed the lipid metabolism in Arabidopsis thaliana by expressing a coding sequence for a fatty acid desaturase from Physcomitrella patens (Δ6D). This enzyme places a double bond after the 6th carbon from the carboxyl end of an acyl group attached to phosphatidylcholine at its sn-2 glyceryl position providing a subtle, but easily trackable modification of the glycerolipid. Phosphatidylcholine is a central intermediate in plant lipid metabolism as it is modified and converted to precursors for other lipids throughout the plant cell. Taking advantage of the exclusive location of Δ6D in the endoplasmic reticulum (ER) and its known substrate specificity for one of the two acyl groups on phosphatidylcholine, we were able to 'tag and track' the distribution of lipids within multiple compartments and their remodeling in transgenic lines of different genetic backgrounds. Key findings were the presence of ER-derived precursors in plastid phosphatidylglycerol and prevalent acyl editing of thylakoid lipids derived from multiple pathways. We expect that this 'tag and track' method will serve as a tool to address several unresolved aspects of plant lipid metabolism, such as the nature and interaction of different subcellular glycerolipid pools during plant development or in response to adverse conditions.
在植物脂质代谢中，许多中间产物或终产物的合成通常表现出过度决定，多个合成途径平行作用。脂质代谢也是动态的，涉及细胞器间的运输、周转和脂质重塑。为了在体内探索这种复杂性，我们开发了一种体内脂质“标记和追踪”方法。从本质上讲，我们通过表达来自Physcomitrella patens 的脂肪酸去饱和酶（Δ6D）的编码序列来探测拟南芥中的脂质代谢。该酶在酰基基团连接到 sn-2 甘油基位置的磷脂酰胆碱的羧基末端的第 6 个碳之后放置一个双键，为甘油磷脂提供一个微妙但易于追踪的修饰。磷脂酰胆碱是植物脂质代谢的中心中间体，因为它在整个植物细胞中被修饰并转化为其他脂质的前体。利用 Δ6D 在内质网（ER）中的特有位置及其对磷脂酰胆碱上两个酰基基团之一的已知底物特异性，我们能够“标记和追踪”不同遗传背景的转基因系中多个隔室中脂质的分布及其重塑。主要发现是质体磷脂酰甘油中存在 ER 衍生的前体以及来自多种途径的类囊体脂质的普遍酰基编辑。我们预计，这种“标记和追踪”方法将成为解决植物脂质代谢中几个未解决问题的工具，例如植物发育过程中或应对不利条件时不同亚细胞甘油脂质池的性质和相互作用。
