Construction of Global Acyl Lipid Metabolic Map by Comparative Genomics and Subcellular Localization Analysis in the Red Alga Cyanidioschyzon merolae.
Construction of Global Acyl Lipid Metabolic Map by Comparative Genomics and Subcellular Localization Analysis in the Red Alga Cyanidioschyzon merolae.
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DOI：
10.3389/fpls.2016.00958
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发表时间：
2016
影响因子：
5.6
通讯作者：
Sato N
中科院分区：
文献类型：
--
作者：
Mori N;Moriyama T;Toyoshima M;Sato N
在拟南芥等陆生植物中已经建立了脂质代谢途径，但微藻中脂质代谢途径的确切信息仍在研究中。与目前被广泛研究的莱茵衣藻不同，红藻的途径信息还停留在用植物的知识来类比估计酶和途径的状态。本研究试图通过比较基因组学和定位分析，构建红藻蓝藻（Cyanidioschyzon merolae）中酰基脂代谢的完整途径，为今后的遗传和生化研究奠定基础。首先，利用Gclust全基因组聚类数据，鉴定了121种酰基脂相关酶。然后，利用基于gfp的技术分析了其中113个酶的定位。我们发现，现有工具对亚细胞定位的大多数预测结果都是错误的，可能是因为这些工具已经调整为植物或绿藻。本研究的实验数据以及我们实验室之前报告的数据将构成对这些工具进行调优的良好训练集。由此构建的脂质代谢图谱表明，红藻的脂质代谢途径与拟南芥的基本相似，只是催化单个反应的酶数量相当有限。然而，在质体内缺乏脂肪酸去饱和以产生油酸和亚油酸，这突出了内质网中去饱和和酰基编辑对于质体脂质以及其他细胞脂质的合成的核心重要性。此外，还发现了一些显著的脂质代谢特征。例如，磷脂酰胆碱是由酵母中磷脂酰乙醇胺的甲基化合成的。可能只有一个3-酮酰基-酰基载体蛋白合成酶参与了脂肪酸合成的缩合反应。我们还将讨论红藻特有的多余β-氧化酶。
Pathways of lipid metabolism have been established in land plants, such as Arabidopsis thaliana, but the information on exact pathways is still under study in microalgae. In contrast with Chlamydomonas reinhardtii, which is currently studied extensively, the pathway information in red algae is still in the state in which enzymes and pathways are estimated by analogy with the knowledge in plants. Here we attempt to construct the entire acyl lipid metabolic pathways in a model red alga, Cyanidioschyzon merolae, as an initial basis for future genetic and biochemical studies, by exploiting comparative genomics and localization analysis. First, the data of whole genome clustering by Gclust were used to identify 121 acyl lipid-related enzymes. Then, the localization of 113 of these enzymes was analyzed by GFP-based techniques. We found that most of the predictions on the subcellular localization by existing tools gave erroneous results, probably because these tools had been tuned for plants or green algae. The experimental data in the present study as well as the data reported before in our laboratory will constitute a good training set for tuning these tools. The lipid metabolic map thus constructed show that the lipid metabolic pathways in the red alga are essentially similar to those in A. thaliana, except that the number of enzymes catalyzing individual reactions is quite limited. The absence of fatty acid desaturation to produce oleic and linoleic acids within the plastid, however, highlights the central importance of desaturation and acyl editing in the endoplasmic reticulum, for the synthesis of plastid lipids as well as other cellular lipids. Additionally, some notable characteristics of lipid metabolism in C. merolae were found. For example, phosphatidylcholine is synthesized by the methylation of phosphatidylethanolamine as in yeasts. It is possible that a single 3-ketoacyl-acyl carrier protein synthase is involved in the condensation reactions of fatty acid synthesis in the plastid. We will also discuss on the redundant β-oxidation enzymes, which are characteristic to red algae.