Siegler Heike, Valerius Oliver, Ischebeck Till, Popko Jennifer, Tourasse Nicolas J, Vallon Olivier, Khozin-Goldberg Inna, Braus Gerhard H, Feussner Ivo
University of Goettingen, Albrecht-von-Haller-Institute for Plant Sciences, Department of Plant Biochemistry, Goettingen, Germany.
University of Goettingen, Institute for Microbiology and Genetics, Department of Molecular Microbiology and Genetics, Goettingen, Germany.
BMC Plant Biol. 2017 Jun 6;17(1):98. doi: 10.1186/s12870-017-1042-2.
Lobosphaera incisa (L. incisa) is an oleaginous microalga that stores triacylglycerol (TAG) rich in arachidonic acid in lipid bodies (LBs). This organelle is gaining attention in algal research, since evidence is accumulating that proteins attached to its surface fulfill important functions in TAG storage and metabolism.
Here, the composition of the LB proteome in L incisa was investigated by comparing different cell fractions in a semiquantitative proteomics approach. After applying stringent filters to the proteomics data in order to remove contaminating proteins from the list of possible LB proteins (LBPs), heterologous expression of candidate proteins in tobacco pollen tubes, allowed us to confirm 3 true LBPs: A member of the algal Major Lipid Droplet Protein family, a small protein of unknown function and a putative lipase. In addition, a TAG lipase that belongs to the SUGAR DEPENDENT 1 family of TAG lipases known from oilseed plants was identified. Its activity was verified by functional complementation of an Arabidopsis thaliana mutant lacking the major seed TAG lipases.
Here we describe 3 LBPs as well as a TAG lipase from the oleaginous microalga L. incisa and discuss their possible involvement in LB metabolism. This study highlights the importance of filtering LB proteome datasets and verifying the subcellular localization one by one, so that contaminating proteins can be recognized as such. Our dataset can serve as a valuable resource in the identification of additional LBPs, shedding more light on the intriguing roles of LBs in microalgae.
裂壶藻是一种产油微藻，其在脂质体中储存富含花生四烯酸的三酰甘油（TAG）。由于越来越多的证据表明附着在脂质体表面的蛋白质在TAG储存和代谢中发挥重要作用，这个细胞器在藻类研究中受到了关注。
在这里，我们采用半定量蛋白质组学方法，通过比较不同细胞组分，研究了裂壶藻脂质体蛋白质组的组成。在对蛋白质组数据应用严格筛选以从可能的脂质体蛋白（LBP）列表中去除污染蛋白后，候选蛋白在烟草花粉管中的异源表达使我们确认了3种真正的LBP：藻类主要脂滴蛋白家族的一个成员、一个功能未知的小蛋白和一个假定的脂肪酶。此外，还鉴定出一种属于从油料植物中已知的TAG脂肪酶糖依赖性1家族的TAG脂肪酶。通过对缺乏主要种子TAG脂肪酶的拟南芥突变体进行功能互补验证了其活性。
在这里，我们描述了来自产油微藻裂壶藻的3种LBP以及一种TAG脂肪酶，并讨论了它们可能参与脂质体代谢的情况。这项研究强调了筛选脂质体蛋白质组数据集并逐一验证亚细胞定位的重要性，以便能够识别污染蛋白。我们的数据集可作为鉴定其他LBP的宝贵资源，为脂质体在微藻中的有趣作用提供更多线索。
