Molecular mechanisms of oxidative stress tolerance in plants

在植物中，氧化胁迫是对热、冷、强光、干旱、渗透休克、伤害、UV-B辐射、臭氧、铝和病原体等不同胁迫的共同反应。这些压力加在一起，给加拿大的几种作物造成了重大损失。我们鉴定了一个小麦转录因子亚家族(Tf)，它至少包含53个成员(命名为TaZFP)，可能在调节植物对氧化胁迫的反应中发挥重要作用。我们的结果表明，该家族的大多数成员(52/53)都受到不同非生物胁迫的上调，其中两个与铝耐受性有关。在水稻和拟南芥等其他物种中，该基因亚家族特定成员的过表达被证明提高了对氧化胁迫和其他非生物胁迫(如盐和干旱胁迫)的耐受性。然而，该基因亚家族中最重要的成员仍然在小麦中被鉴定。 我们的长期目标是开发有效的策略来提高对氧化应激的耐受性，氧化应激是各种非生物和生物应激的主要组成部分。我们的工作假设是，TaZFP亚家族的特定小麦成员可以提高对氧化应激的耐受性，并增强对各种其他逆境的交叉耐受性。 我们的第一个短期目标是通过小麦的功能研究“确定选定的TaZFP家族成员与氧化胁迫相关的功能”。我们最近证明了大麦条纹花叶病毒(BSMV)可以用来快速而均匀地过表达小基因。我们将鉴定这两个与铝耐受性相关的TaZFP基因，并利用改进的BSMV方法对受不同非生物胁迫强烈上调的TaZFP基因进行鉴定。这种方法避免了生产转基因植物的需要，并允许快速评估它们提高对铝和其他非生物胁迫的耐受性的能力。 我们的第二个目标是“确定调节TaZFP的上游转录因子(Tf)”。在我们的第一个目标中确定的最重要的TaZFP的启动子将用于在酵母中通过单杂交筛选来分离上游TF。这些因素可能调节不止一个TaZFP，并为提高氧化应激耐受性提供更有效的策略。 我们的第三个目标是“确定选定的miRNAs在铝/氧化应激耐受中的功能”。我们已经确定了几个与铝耐受性相关的miRNAs，并可以靶向与氧化应激耐受性相关的基因。我们将利用BSMV系统验证这些miRNAs在体内影响预测靶标表达和提高应激耐受性的能力。 总体而言，这些知识将有助于设计适当的分子标记，以提高对不同非生物胁迫的耐受性。这将有助于支持育种人员在不利条件下生产生产率更高的小麦品种。

In plants, 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. Together, these stresses cause major losses to several crops in Canada. We identified a subfamily of wheat transcription factors (TF) containing at least 53 members (named TaZFPs) that could play an important role in regulating plant responses to oxidative stress. Our results showed that most (52/53) members of this family are up-regulated by different abiotic stresses and two of them are associated to Al tolerance. In other species such as rice and Arabidopsis, the overexpression of specific members of this gene subfamily was shown to improve tolerance to oxidative stress and other abiotic stresses such as salt and drought stresses. However, the most important members of this gene subfamily remain to be identified in wheat. Our long term goal is to develop efficient strategies to improve tolerance to oxidative stress, a major component of various abiotic and biotic stresses. Our working hypothesis is that specific wheat members of the TaZFP subfamily can improve tolerance to oxidative stress and enhance cross-tolerance to a variety of other stresses. Our first short term objective is to “determine the function of selected TaZFP family members that are associated to oxidative stress” by function studies in wheat. We have recently demonstrated that the Barley Stripe Mosaic Virus (BSMV) can be used to rapidly and uniformly overexpress small genes. We will characterize the two TaZFPs associated to Al tolerance and initiate the characterization of TaZFPs genes that are strongly up-regulated by different abiotic stresses using the improved BSMV protocol. This approach avoids the need to produce transgenic plants and allows a rapid asessment of their ability to increase tolerance to Al and other abiotic stresses. Our second objective is to “identify upstream transcription factors (TF) that regulate TaZFPs”. The promoters of the most important TaZFPs as determined in our first objective will be used to isolate upstream TFs using one-hybrid screening in yeast. These factors may regulate more than one TaZFPs and provide more efficient strategies to improve oxidative stress tolerance. Our third objective is to “determine the function of selected miRNAs in Al/oxidative stress tolerance”. We have identified several miRNAs that are associated to Al tolerance and can target genes of potential interest for oxidative stress tolerance. We will validate the ability of these miRNAs to affect the expression of the predicted targets in vivo and to improve stress tolerance by using the BSMV system. Overall, this knowledge will help design appropriate molecular markers to improve tolerance to different abiotic stresses. This will help support breeders in producing wheat varieties with improved productivity under adverse conditions.