Molecular mechanisms of oxidative stress tolerance in plants

加拿大每年因不同的环境压力造成的作物产量损失数亿美元。氧化应激是对热、冷、强光、干旱、渗透性休克、创伤、UV-B辐射、臭氧、铝和病原体等不同应激反应的共同反应。我们对铝胁迫和耐性的研究使我们能够确定几个基因，这些基因可能在调节植物对氧化胁迫的反应中发挥重要作用。提高对这种逆境的耐受性可能会通过增加对各种逆境的交叉耐受性来增强植物的适合性。为达致这个目标，我们会： I)描述参与氧化应激反应的调节因素及其在提高对活性氧物种(ROS)耐受性方面的潜在功能。我们最近发现了两个锌指转录因子家族成员，它们在近等基因小麦品系中的表达与耐铝性显著相关。这些转录因子也对不同来源的氧化应激做出反应，如过氧化氢和羟基自由基。鉴定这些小麦转录因子及其上游因子将有助于理解它们的调控机制。这些因子在转基因株系中的过度表达将证实它们是否能够提高根或叶对铝和其他ROS的耐受性。 Ii)确定参与ROS解毒的关键能量途径调控基因的功能。在这些基因中，一些编码酶(如果糖-1，6-二磷酸酶和葡萄糖-6-磷酸脱氢酶)参与了抗氧化剂分子再生所涉及的关键能量途径的调节。调控这些基因的效果将通过转基因植物模型来研究，以评估它们产生抗氧化剂分子和耐受氧化应激的能力。 了解氧化胁迫耐受性的调控机制将有助于开发适当的作物改良策略，使植物能够抵御各种胁迫。这将提高植物的适合性和生产率。

Each year Canada loses hundreds of millions of dollars from loss in crop productivity caused by different environmental stresses. Oxidative stress is a common response to different stresses such as heat, cold, high-light, drought, osmotic shock, wounding, UV-B radiation, ozone, aluminum and pathogens. Our studies on aluminum stress and tolerance allowed us to identify several genes that could play an important role in regulating plant responses to oxidative stress. Improving tolerance to this stress will likely enhance plant fitness by increasing cross-tolerance to a variety of stresses. To achieve this goal, we will: I) Characterize the regulatory factors involved in oxidative stress responses and their potential function in improving tolerance to reactive oxygen species (ROS). We have recently identified two Zinc finger transcription factor family members which expression is significantly associated with Al tolerance in near-isogenic wheat lines. These transcription factors are also responsive to different sources of oxidative stress such as H2O2 and hydroxyl radicals. Characterization of these wheat transcription factors and their upstream factors will help to understand their mechanisms of regulation. Over-expression of these factors in transgenic lines will confirm whether they can improve tolerance to aluminum and other ROS in either roots or leaves. II) Determine the function of key energy pathway regulatory genes involved in ROS detoxification. Among these genes, some encode enzymes (e.g. fructose-1,6-bisphosphatase and glucose-6-phosphate dehydrogenase) involved in the regulation of key energy pathways involved in the regeneration of antioxidant molecules. The effect of regulating these genes will be studied using transgenic plant models to evaluate their ability to produce antioxidant molecules and to tolerate oxidative stress. Understanding the regulatory mechanisms involved in oxidative stress tolerance will lead to the development of appropriate strategies for crop improvement allowing plants to withstand a variety of stresses. This will result in improved plant fitness and productivity.