Functional characterization of two families of lipid droplet-associated proteins

脂滴（LD，也称为油体或油质体）是亚细胞结构，其由附着或嵌入磷脂单层的蛋白质组成，所述磷脂单层围绕主要为三酰甘油的疏水核心。在植物中，LD不仅存在于种子和花粉中，而且存在于营养组织中，在胁迫下它们在营养组织中积累。近年来的研究也强调了LDs在非生物和生物胁迫响应中的重要作用。以前只有少数蛋白质家族与脂滴相关，但我们可以在过去几年中增加这个数字。现在，我们的目标是了解这些蛋白质的亚细胞和生理功能，包括来自拟南芥的两个蛋白质家族：种子脂滴蛋白1和2（SLDP 1/2）及其结合伴侣脂滴质膜锚（利帕）是以前未知功能的蛋白质，形成LD与质膜（PM）结合所需的复合物。我们现在想进一步研究这个复合物，以表明SLDP 1，SLDP 2和利帕共定位于形成接触位点的LD和PM子域，并以相互依赖的方式进行。我们还想研究这些接触部位在压力下的重要性，以及它们是否在膜稳态中发挥作用。此外，我们还希望进一步鉴定与该复合物相关的蛋白质。在酵母双杂交筛选中鉴定了SLDP 1的一个潜在相互作用伴侣。这种蛋白质，SYNAPTOTAGMIN 1，与PM相关，可以作为脂质转移蛋白。此外，它还参与冷冻胁迫耐受性。我们想知道这种蛋白质是否也与这种复合物相关，并有助于其功能。我们还想研究LD相关的脂滴甲基转移酶1/2（LIME 1/2）及其在植物代谢和胁迫生理中的功能。这些蛋白质被注释为N-甲基转移酶，并参与次级代谢，但迄今尚未进行任何详细研究。我们不仅在幼苗中检测到这些蛋白，而且在干旱胁迫的叶片中也检测到这些蛋白。我们希望确定这种假定的酶催化的反应的底物和产物以及它们参与的代谢途径。此外，我们想研究这些酶在非生物和生物胁迫中的潜在作用。通过这个项目，我们的目标是扩大对营养组织中LD的认识。

Lipid droplets (LDs, also referred to as oil bodies or oleosomes) are subcellular structures that consist of proteins attached to or embedded in a phospholipid monolayer surrounding a hydrophobic core of mostly triacylglycerol. In plants, LDs occur not only in seeds and pollen but also in vegetative tissues, where they accumulate under stress. Studies in recent years also underlined important functions of LDs in abiotic and biotic stress responses. Previously only few protein families were known that are associated with lipid droplets but we could increase this number in the last years. Now, we aim to understand the subcellular and physiological function of these proteins including two families of proteins from Arabidopsis:SEED LIPID DROPLET PROTEIN 1 and 2 (SLDP1/2) and their binding partner LIPID DROPLET PLASMA MEMBRANE ANCHOR (LIPA) are proteins of previously unknown function that form a complex needed for the association of LDs with the plasma membrane (PM). We now want to study this complex further to show that SLDP1, SLDP2 and LIPA colocalize at LD and PM subdomains that form contact sites and do so in a co-dependent manner. We also want to study the importance of these contact sites under stress and if they play a role in membrane homeostasis. In addition, we want to identify further proteins associated with this complex. One potential interaction partner of SLDP1 was identified in a yeast-2-hybrid screen. This protein, SYNAPTOTAGMIN1, is associated with the PM and could act as a lipid transfer protein. It is furthermore involved in freezing stress tolerance. We want to find out if this protein is also associated with this complex and contributes to its function.We additionally want to study the LD-associated LIPID DROPLET METHYL TRANSFERASEs 1/2 (LIME1/2) and their function in plant metabolism and stress physiology. These proteins are annotated as N-methyltransferases and to be involved in secondary metabolism, but has so far not been studied in any detail. We detected these proteins not only in seedlings but also drought-stressed leaves. We want to identify the substrate and product of the reaction(s) catalyzed by this putative enzymes and the metabolic pathway they are involved in. Furthermore, we want to study the potential role of these enzymes in abiotic and biotic stress. With this project, we aim to broaden the knowledge on LDs in vegetative tissues.