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，几乎涉及真核生物生物学的各个方面。它涉及到泛素（一种小的、高度保守的蛋白质）附着在选定的底物上。泛素化的结果取决于修饰的性质，可以包括降解、再定位和底物的激活。泛素分子的多功能性是由于它可以作为单个分子附着（单泛素化），也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26S蛋白酶体复合物进行降解。泛素蛋白酶体系统（UPS）控制许多酶，结构和调节蛋白的丰度，确保适当的细胞功能。植物，作为无根生物，利用UPS来促进细胞的变化，以应对和忍受不利的生长条件。水资源短缺、温度升高、营养来源和病原体感染等环境压力会对作物生长发育产生负面影响，从而限制作物产量。最近的进展扩大了我们对UPS功能的理解，但是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。本研究计划的目标是深入了解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铁吸收，并增强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时发生适当的反应，以改善损伤。我们还将通过研究钙活化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中的作用。这项研究将深入了解UPS如何可能被操纵，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在高等植物中的作用，并更好地了解对加拿大经济具有商业意义的作物的类似过程。

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.