Role of oxidative stress responses in aluminum and freezing tolerant wheat

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Oxidative stress is a common response to many abiotic and biotic stresses and is a pivotal signalling event that is central to stress survival. Our hypothesis is that key genes involved in the control of oxidative stress are required for tolerance to abiotic stresses such as aluminum (Al) and low temperature (LT).I) Al tolerance is characterized by the ability to maintain root growth under high Al concentrations. Of the 9 genes shown to be strongly associated with Al tolerance in wheat, at least four are proposed to directly reduce the impact of oxidative stress; one gene encodes a key enzyme controlling glucose supply, an important precursor needed to maintain the level of antioxidants such as glutathione and ascorbate; and the other 4 genes encode proteins of unknown function. To understand the role of these genes in stress tolerance, we will pursue their functional characterization by: 1) Performing function studies in Arabidopsis, yeast and wheat to demonstrate their role in stress tolerance; 2) Developing simple markers of Al tolerance for breeders; 3) Analysing the mechanisms responsible for the differential regulation of Al-tolerance genes.II) LT tolerance is associated with the higher capacity of tolerant plants to resist to oxidative and high light stress at low temperature (photoinhibition). A survey of Expressed Sequence Tags (EST) present in cold acclimated wheat plants has identified at least 4 genes that could improve resistance to photoinhibition. Three of these genes encode proteins that could protect the chloroplast machinery by improving energy flow and by reducing oxidative damages. The functional characterization of these genes will be pursued by: 1) Analysis of gene expression to identify those that are closely associated with tolerance; and 2) Performing function studies in Arabidopsis and wheat.Some of these genes may have important applications to improve resistance to oxidative stress and increase plant productivity under a variety of stresses.