Venkateshwari Varadarajan, Vijayakumar Anitha, Vijayakumar Arun Kumar, Reddy L Prasanna Anjaneya, Srinivasan Malathi, Rajasekharan Ram
Department of Lipid Science, Central Food Technological Research Institute, Mysore, 570020, Karnataka, India.
Academy of Scientific and Innovative Research, New Delhi, India.
Planta. 2018 Aug;248(2):347-367. doi: 10.1007/s00425-018-2908-8. Epub 2018 May 7.
Portulaca leaves serve as an alternative bioresource for edible PUFAs. Transcriptome data provide information to explore Portulaca as a model system for galactolipids, leaf lipid metabolism, and PUFA-rich designer lipids. Poly-unsaturated fatty acids (PUFAs) are gaining importance due to their innumerable health benefits, and hence, understanding their biosynthesis in plants has attained prominence in recent years. The most common source of PUFAs is of marine origin. Although reports have identified Portulaca oleracea (purslane) as a leaf source of omega-3 fatty acids in the form of alpha-linolenic acid (ALA), the mechanism of ALA accumulation and its distribution into various lipids has not been elucidated. Here, we present the lipid profiles of leaves and seeds of several accessions of P. oleracea. Among the nineteen distinct accessions, the RR04 accession has the highest amount of ALA and is primarily associated with galactolipids. In addition, we report the transcriptome of RR04, and we have mapped the potential genes involved in lipid metabolism. Phosphatidylcholine (PC) is the major site of acyl editing, which is catalyzed by lysophosphatidylcholine acyltransferase (LPCAT), an integral membrane protein that plays a major role in supplying oleate to the PC pool for further unsaturation. Our investigations using mass spectrometric analysis of leaf microsomal fractions identified LPCAT as part of a membrane protein complex. Both native and recombinant LPCAT showed strong acyltransferase activity with various acyl-CoA substrates. Altogether, the results suggest that ALA-rich glycerolipid biosynthetic machinery is highly active in nutritionally important Portulaca leaves. Furthermore, lipidome, transcriptome, and mass spectrometric analyses of RR04 provide novel information for exploring Portulaca as a potential resource and a model system for studying leaf lipid metabolism.
马齿苋叶是食用多不饱和脂肪酸的另一种生物资源。转录组数据为探索马齿苋作为半乳糖脂、叶片脂质代谢和富含多不饱和脂肪酸的设计脂质的模型系统提供了信息。多不饱和脂肪酸（PUFAs）因其无数的健康益处而变得越来越重要，因此，近年来了解它们在植物中的生物合成已变得十分突出。PUFAs最常见的来源是海洋。尽管有报道称马齿苋是α-亚麻酸（ALA）形式的ω-3脂肪酸的叶片来源，但ALA积累的机制及其在各种脂质中的分布尚未阐明。在此，我们展示了几种马齿苋种质叶片和种子的脂质谱。在19个不同的种质中，RR04种质的ALA含量最高，且主要与半乳糖脂相关。此外，我们报告了RR04的转录组，并绘制了参与脂质代谢的潜在基因。磷脂酰胆碱（PC）是酰基编辑的主要位点，由溶血磷脂酰胆碱酰基转移酶（LPCAT）催化，LPCAT是一种整合膜蛋白，在为PC库提供油酸以进一步去饱和方面起主要作用。我们使用叶片微粒体组分的质谱分析进行的研究确定LPCAT是膜蛋白复合物的一部分。天然和重组LPCAT对各种酰基辅酶A底物均表现出强大的酰基转移酶活性。总之，结果表明富含ALA的甘油脂生物合成机制在营养重要的马齿苋叶中高度活跃。此外，RR04的脂质组、转录组和质谱分析为探索马齿苋作为潜在资源和研究叶片脂质代谢的模型系统提供了新信息。
