Unfolded protein response in the model species Arabidopsis thaliana

描述（由申请人提供）：不利的环境条件以及需要增强分泌性蛋白质合成的生理状况可能导致内质网（ER）蛋白质合成需求和能力之间的不平衡。内质网可以感知压力并通过调用被称为未折叠蛋白反应（UPR）的保护性信号通路来恢复体内平衡。为了启动UPR，酵母在很大程度上依赖于基于保守传感器Ire1p作用的线性臂。在进化过程中，这套普遍定期审议臂利用了额外的传感器，以适应多细胞环境中更具体的反应。目前，普遍定期审议研究的一个主要挑战是了解各种普遍定期审议臂在完整生物体中的生物学作用，以确定普遍定期审议信号网络如何在发育和对生物和非生物应激的反应中指导各种细胞命运决定。植物和后生动物UPR的保护以及强大的基因组学和分子工具的可用性使得模式植物拟南芥成为解决这些问题的一个有吸引力的系统。在植物中，普遍定期审议被认为在各种胁迫情况下发挥重要作用，但对植物普遍定期审议机制的了解仍然有限。在拟南芥中，两个膜系的突变转录因子bZIP28和bZIP60，以及一个保守的异三聚体G蛋白复合物AGB1的亚基，已被证明是植物UPR的调节因子，但对这些介质控制的UPR分支的分子成分知之甚少。我们最近确定了AtIRE1直接参与内质网应激反应和生长。这些发现将使我们能够探索IRE1与植物UPR的其他关键参与者的作用，以建立一个多细胞环境下将逆境反应中的UPR信号与体内生长发育联系起来的模型。因此，本提案的直接目标是：1)阐明AtIRE1控制的信号转导途径中的保守和植物特异性特征；2)确定普遍定期审议各部分在生长、发育和各种应激条件中的作用；3)确定每个UPR臂对应的靶基因，以确定下游效应物，并阐明UPR信号臂如何相互交叉。将植物作为一种进化上独特且易于处理的模型来研究多细胞生物的UPR是很重要的，因为它将允许比较和对比植物、酵母和动物的UPR，从而将为这些系统提供重要的见解，增加我们对真核细胞生物学的基本理解。为了实现我们的目标，我们将功能基因组学与体外分析和转录组学相结合。我们将能够确定植物在生长发育过程中如何依赖UPR信号网络，以及在需要增强分泌性蛋白质合成的胁迫条件下如何做出反应。我们的研究结果不仅将增强我们对人类生长和疾病的理解，还将允许在可处理的多细胞模型中开发普遍定期审议药物，并有助于我们了解旨在维持地球粮食安全的农业过程和植物生物技术中的限制因素。

DESCRIPTION (provided by applicant): Adverse environmental conditions as well as physiological situations requiring enhanced secretory protein synthesis can cause an imbalance between demand and capacity of protein synthesis at the endoplasmic reticulum (ER). The ER can sense stress and restore homeostasis by invoking a protective signaling pathway known as the unfolded protein response (UPR). To initiate UPR, yeast largely relies on a linear arm based on the action of a conserved sensor, Ire1p. During the course of evolution, the suite of UPR arms harnessed additional sensors to accommodate more specific responses in a multicellular context. A major challenge in UPR studies is now to understand the biological role of the various UPR arms in intact organisms to define how the UPR signaling network functions to direct diverse cell-fate decisions in development and response to biotic and abiotic stress. The conservation of plant and metazoan UPR and the availability of powerful genomics and molecular tools render the model plant Arabidopsis thaliana an appealing system in which to address these questions. In plants, the UPR is thought to play a major role in various stress situations, but the understanding of plant UPR mechanisms is still limited. In Arabidopsis, two membrane-tethered blip transcription factors, bZIP28 and bZIP60, and a subunit of the conserved heterotrimeric G protein complex, AGB1, have been shown to function as regulators of plant UPR, but little is known about the molecular components of the UPR arms controlled by these mediators. We have recently established a direct involvement of AtIRE1 in ER stress response and in growth. These findings will enable us to explore the role of IRE1 in combination with other key players of plant UPR to develop a model that links UPR signaling during stress responses with growth and development in vivo in a multicellular context. The immediate goals of this proposal therefore are 1) to elucidate conserved and plant-specific features in the signal transduction pathway controlled by AtIRE1; 2) to define the role of the UPR arms in growth, development, and various conditions of stress; and 3) to identify the target genes corresponding to each UPR arm to define downstream effectors and to elucidate how the UPR signaling arms intersect with each other. Adding plants as an evolutionarily distinct and tractable model for the study of the UPR in multicellular organisms is important because it will allow comparing and contrasting plant, yeast, and animal UPRs, and thus will provide significant insights into these systems, adding to our fundamental understanding of eukaryotic cell biology at large. To achieve our goals we will integrate functional genomics with in vitro assays and transcriptomics. We will be able to establish how plants depend on the UPR signaling network during growth and development and in response to stress conditions that require enhanced secretory protein synthesis. Our results will not only enhance our understanding of human growth and disease, they will also permit the development of UPR drugs in a tractable multicellular model, and contribute to our understanding of limiting factors in agricultural processes and plant biotechnology designed to sustain food security on earth.