Molecular analysis of fatty acid export from plastids of oilseed plants and green microalgae - towards developing tools to improve plant biofuel production

油籽植物和绿色微藻质体脂肪酸输出的分子分析 - 旨在开发提高植物生物燃料生产的工具

• 批准号: 270310439
• 负责人: Professorin Dr. Katrin Philippar
• 金额: --
• 依托单位: Professur für Pflanzenbiologie
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2015
• 资助国家: 德国
• 起止时间: 2014-12-31 至 2020-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/270310439?language=en
• 关键词: Molecular; analysis; fatty; acid; export

Fatty acids (FAs) build the majority of cellular lipids, which are essential not only for membrane function, but also for growth and development of organisms. For example, triacylglycerol lipids (TAGs) in seeds of oilseed plants represent the major form of carbon energy storage, or waxes on the plant surface restrict loss of water and provide pathogen protection. Since in plants de novo FA synthesis occurs in plastids, transport to the endoplasmic reticulum for further lipid assembly is required. Although it is generally agreed that free FAs are shuttled across plastid envelope membranes, the mode of plastid FA-export, however, still remains enigmatic. We isolated FAX1 (fatty acid export 1), a novel membrane protein in the plastid inner envelope, which in Arabidopsis thaliana is crucial for biomass production, male fertility, and synthesis of FA-derived compounds such as lipids, ketone waxes or pollen cell walls. Whereas ER-derived lipids decrease when FAX1 is missing, levels of plastid-produced lipids increase. FAX1 over-expressing lines show the opposite, including a TAG increase in leaves and flowers. Since in yeast, FAX1 can complement for FA-transport, we conclude that FAX1 mediates FA-export across the plastid inner envelope. In Arabidopsis, FAX1 belongs to a family of seven proteins. Four are predicted to be in plastids, three most likely integrate into membranes of the secretory pathway. The green microalga Chlamydomonas reinhardtii contains one member of each of these subgroups. In vertebrates, FAX relatives are mitochondrial membrane 'TMEM14' proteins, linked to heme metabolism and apoptosis. However, their biological function is unknown. Thus, this protein family represents a powerful tool not only to increase lipid/biofuel production in the green lineage, but also to explore novel transport systems with impact on mitochondrial dynamics and/or apoptosis in vertebrates.The project aims to characterise FAX proteins in Arabidopsis and Chlamydomonas. Research should clarify their impact on cellular metabolism, in particular on FAs, lipids and FA/lipid-derived compounds (waxes, cutin or oxilipin hormones) as well as on carbon energy metabolites. A spotlight will be on synthesis of storage oils in seeds, i.e. the significance of FAX in TAG production. In Chlamydomonas, over-production of FAX proteins (FA-transport) in combination with enhanced expression of FA/lipid biosynthesis enzymes will lead to development of strategies for biofuel production. The structure/function correlation of FAX1 is completely novel and not related to 'classical' FA or lipid transporters. Thus, research will enable us to study plant-specific but also general aspects of a new intracellular FA-transport pathway. Evaluation of FAX topology, structure, and FA/lipid binding, functional characteristics in a heterologous yeast system as well as identification of interaction partners will help to describe the plastid FA-export pathway.

脂肪酸（FAs）构成了大部分细胞脂质，不仅对膜功能至关重要，而且对生物体的生长和发育也至关重要。例如，油籽植物种子中的三酰甘油脂质（TAG）代表碳能量储存的主要形式，或者植物表面上的蜡限制水分损失并提供病原体保护。由于在植物中FA的从头合成发生在质体中，因此需要转运到内质网进行进一步的脂质组装。虽然人们普遍认为游离脂肪酸穿梭在质体被膜，模式的质体脂肪酸输出，然而，仍然是谜。我们分离了FAX 1（脂肪酸输出1），一种新的膜蛋白质的质体内被膜，这在拟南芥是至关重要的生物量生产，雄性育性，和合成FA衍生的化合物，如脂质，酮蜡或花粉细胞壁。当FAX 1缺失时，ER衍生的脂质减少，而质体产生的脂质水平增加。FAX 1过表达株系显示相反的情况，包括叶和花中的TAG增加。由于在酵母中，FAX 1可以补充FA-运输，我们得出结论，FAX 1介导的FA-出口的质体内被膜。在拟南芥中，FAX 1属于七种蛋白质的家族。四个被预测在质体中，三个最有可能整合到分泌途径的膜中。绿色的微小衣藻莱茵衣藻包含这些亚群中的每一个成员。在脊椎动物中，FAX亲属是线粒体膜'TMEM 14'蛋白，与血红素代谢和细胞凋亡有关。但其生物学功能尚不清楚。因此，这个蛋白质家族代表了一个强大的工具，不仅可以增加绿色谱系中的脂质/生物燃料的生产，而且还可以探索新的运输系统，影响线粒体动力学和/或脊椎动物的凋亡。研究应阐明它们对细胞代谢的影响，特别是对脂肪酸、脂质和脂肪酸/脂质衍生化合物（蜡、角质或oxilipin激素）以及碳能代谢物的影响。重点将放在种子中储存油的合成上，即FAX在TAG生产中的重要性。在衣原体中，与FA/脂质生物合成酶的表达增强相结合的FAX蛋白（FA-转运）的过度生产将导致生物燃料生产策略的发展。FAX 1的结构/功能相关性是全新的，与“经典”FA或脂质转运蛋白无关。因此，研究将使我们能够研究植物特异性，但也是一个新的细胞内FA-运输途径的一般方面。FAX的拓扑结构，结构，FA/脂质结合，在异源酵母系统中的功能特性，以及相互作用的合作伙伴的识别评估将有助于描述质体FA-出口途径。