Functional characterization of Arabidopsis ER-PM contact sites as non-vesicular lipid transfer platforms

植物是固着生物，在其生命周期中经常暴露于不断变化的环境条件。因此，植物细胞已经进化出复杂的调节机制，使细胞外信号的转导和促进特定的适应性反应的环境线索。植物细胞通过质膜（PM）与环境分离。这种外部脂质膜包围细胞的内容物，并促进离子和有机化合物与周围环境的受控交换。PM也是一个关键的信号中枢，PM处的脂质充当激活对生物（例如细菌、真菌）和非生物（例如盐度、干旱、寒冷）胁迫的细胞应答的主要传感器。虽然表面上看起来是均匀的，PM脂质分布的微小变化严重影响下游细胞对应力的反应。在大多数情况下，这些变化的生物学意义尚不清楚，但许多研究植物胁迫超敏反应和PM脂质不平衡强调需要稳态调节机制，以控制PM脂质组成的空间和时间。 在哺乳动物细胞中，PM脂质稳态由内质网（ER）-PM接触位点（EPCS）网络调节，EPCS促进脂质在ER合成位点和PM作用位点之间的非囊泡交换。在植物中，我们最近的研究已经推进了我们对植物EPCS的结构和分子组织的理解，并建立了EPCS组分在调节脂质介导的应激反应中的关键作用;然而，植物EPCS作为非囊泡脂质交换平台的作用仅得到间接证据的支持。在这里，我将使用模式植物拟南芥了解是否，如何以及为什么植物EPCS调节非囊泡脂质转移响应环境压力。拟议的研究将使用生物信息学和细胞生物学方法，以获得一个库存的蛋白质调节EPCS组织和脂质转移，生化方法来建立其分子功能，和遗传方法来揭示的监管网络，翻译的EPCS功能到压力反应在生物体水平。 在压力过程中控制EPCS功能的机制的解剖代表了理解细胞过程的重要一步，包括脂质转移，离子转运和细胞内信号传导，被认为是在植物EPCS调节。从长远来看，我们的研究计划致力于为未来耐逆作物的发展提供坚实的理论基础和遗传靶点。由于气候变化带来的严重环境压力，我们预计这些作物将在市场上具有竞争优势，并将在加拿大和国外实现更可持续的农业实践。

Plants are sessile organisms frequently exposed to changing environmental conditions during their life cycle. Consequently, plant cells have evolved complex regulatory mechanisms that enable the transduction of extracellular signals and promote specific adaptive responses to environmental cues. Plant cells are separated from the environment by the plasma membrane (PM). This external lipid membrane encloses the cells' content and facilitates the controlled exchange of ions and organic compounds with their surroundings. The PM is also a crucial signaling hub and lipids at the PM act as a primary sensor for the activation of cellular responses to biotic (e.g. bacteria, fungi) and abiotic (e.g. salinity, drought, cold) stresses. Although seemingly uniform in appearance, minor changes on the PM lipid distribution heavily affect downstream cellular responses to stresses. In most cases, the biological significance of these changes remains unclear, but numerous studies linking plant stress hypersensitivity and PM lipid disequilibrium underscores the need for homeostatic regulatory mechanisms to control the PM lipid composition in space and time.    In mammalian cells, PM lipid homeostasis is regulated by a network of endoplasmic reticulum (ER)-PM Contact Sites (EPCS) that facilitate the non-vesicular exchange of lipids between their synthesis site at the ER and their action site at the PM. In plants, our recent research has advanced our understanding of the structure and molecular organization of the plant EPCS, and has established critical roles for EPCS components in the regulation of lipid-mediated responses to stress; however, the role of plant EPCS as platforms for non-vesicular lipid exchange is only supported by indirect evidence. Here, I will use the model plant Arabidopsis thaliana to understand whether, how, and why plant EPCS regulate non-vesicular lipid transfer in response to environmental stresses. The proposed research will use bioinformatics and cell biology approaches to obtain an inventory of proteins regulating EPCS organization and lipid transfer, biochemical approaches to establish their molecular function, and genetic approaches to uncover the regulatory networks that translate the EPCS function into stress responses at the organism level.    The dissection of mechanisms controlling EPCS function during stress represents an important step towards understanding cellular processes, including lipid transfer, ionic transport, and intracellular signaling, believed to be regulated at plant EPCS. In the long-term, our research program strives to provide a solid theoretical foundation and a collection of genetic targets for the future development of stress tolerant crops. Due to the severe environmental stresses associated with climate change, we envision that these crops will have a competitive edge in the market, and will enable more sustainable agricultural practices in Canada and abroad.