Protein Ubiquitination and Plant Response to Environmental Stress

泛素化是一种普遍存在的翻译后修饰系统，涉及到真核生物学的各个方面。它涉及泛素（一种高度保守的小蛋白）与选定底物的连接。泛素化的结果取决于修饰的性质，并且可以包括底物的降解、重新定位和活化。泛素分子的多功能性是由于它可以作为单个分子连接（单泛素化）或者它可以用于在底物的内部赖氨酸残基上构建不同拓扑结构的链（多泛素化）。泛素最显著的功能是将底物蛋白靶向多蛋白水解的26 S蛋白酶体复合物进行降解。泛素蛋白酶体系统（UPS）控制着大量的酶、结构蛋白和调节蛋白，确保适当的细胞功能。植物作为固着生物体，利用UPS来促进响应和耐受不利生长条件所需的细胞变化。缺水、温度升高、养分流失和病原体感染等环境压力会对生长和发育产生负面影响，从而限制作物生产力。最近的进展扩大了我们对UPS功能的理解，但主要的知识差距仍然存在，包括底物的身份和对系统如何调节蛋白质丰度以促进应激反应的清晰理解。该研究项目的目标是深入了解UPS在植物生物学中的调节作用，特别是对环境胁迫的反应。我们将确定由UPS调节的蛋白质，以促进防御病原体攻击所需的反应，在可用性降低时增加根系铁的吸收，并提高对高温条件的耐受性。我们将定义调节E3-底物接合的分子机制，以确保在暴露于外部应激源期间发生适当的反应以改善损伤。我们还将通过研究钙激活蛋白激酶的泛素依赖性降解来研究UPS在调节钙介导的应激信号传导中的作用。这项研究将深入了解如何操纵UPS，为在不利环境条件下生长的植物提供优势。所获得的信息将有助于了解UPS在高等植物中的功能，并更好地了解对加拿大经济具有商业意义的作物中的类似过程。

Ubiquitination is a prevalent post-translation modification system that is involved in almost every aspects of eukaryotic biology. It involves the attachment of ubiquitin, a small, highly conserved protein to selected substrates. The outcome of ubiquitination varies depending on the nature of the modification and can include degradation, relocalization and activation of the substrate. The versatility of the ubiquitin molecule is due to the fact that it can be attached as a single molecule (monoubiquitination) or it can be used to build chains (polyubiquitination) of varying topology on an internal lysine residue of the substrate. The most notable function of ubiquitin is the targeting of substrate proteins to the multi-proteolytic 26S proteasome complex for degradation. The ubiquitin proteasome system (UPS) controls the abundance of numerous enzymes, structural and regulatory proteins ensuring proper cellular function. Plants, as sessile organisms, utilize the UPS to facilitate cellular changes required to respond to and tolerate adverse growth conditions. Environmental stresses such as water scarcity, increase temperature, nutrient derivation and pathogen infection can limit crop productivity by negatively impacting growth and development. Recent advances have broadened our understanding of UPS function, however major knowledge gaps remain including the identity of substrates and a clear understanding of how the system regulate protein abundance to facilitate stress responses. The goal of this research program is to gain an in-depth understanding of the regulatory role of the UPS in plant biology, particularly response to environmental stresses. We will identify proteins that are regulated by the UPS to facilitate responses required for defending against pathogen attack, increasing root iron uptake when availability is reduced, and enhancing tolerance of high temperature conditions. We will define the molecular mechanisms that regulate E3-substrate engagement to ensure that the appropriate response occurs to ameliorate damage during exposure to external stressors. We will also investigate the role of the UPS in regulating calcium-mediated stress signalling by studying the ubiquitin-dependent degradation of calcium activated protein kinases. This research will give insight into how the UPS can possibly be manipulated to provide an advantage to plants growing under unfavourable environmental conditions. Information obtained will aid in understanding UPS function in higher plants and better our understanding of similar processes in crops that are of commercial significance to the Canadian economy.