The gas ozone (O3) functions as a protector against ultra-violet radiation in the stratosphere. However, in the troposphere it is toxic to plants and causes significant reductions in crop yields. Ozone is a reactive oxygen species (ROS) and can cause oxidative damage directly by entering stomata and interacting with cell wall and membrane components. Ozone can also form other ROS such as hydrogen peroxide and hydroxyl radicals that can cross the plasma membrane and cause further damage, leading to reduced transpiration, accelerated senescence and decreased photosynthesis. A plant-derived oxidative burst also occurs after plants have been exposed to ozone. This closely resembles the hypersensitive response (HR) displayed when plants are challenged by a pathogen. Plants react to oxidative stress by increasing their antioxidant defences in an attempt to neutralise harmful ROS. The individual roles of several antioxidants have been extensively studied, however their regulation and interaction in planta have yet to be fully elucidated. The specificity of antioxidants and other stress-related molecules to each unique stress is also poorly understood. In this work a functional genomics approach has been used to identify novel genes in Arabidopsis thaliana, that are regulated by ozone. A DNA microarray has been utilised to determine gene regulation at the transcriptional level and NMR spectroscopy has been employed to investigate ozone-induced changes to the metabolite profile of Arabidopsis. Twenty genes, which are significantly up-regulated and one gene that is down-regulated by ozone treatment have been identified. The expression of these genes in response to a range of ozone concentrations and time points has been further investigated
