Regulation of the plant metabolic network during stress

In the field, plants have to cope with environmental fluctuations which at their extremes cause stress to the plant. Under such stress conditions, the growth and development of the plant can be severely retarded. In an agricultural context, such sub-optimal growth conditions cause significant lowering of yields and are a major cause of variations in agricultural productivity from year to year. Furthermore, global climate changes are likely to dramatically exacerbate this problem. There is thus a pressing need to develop new varieties of staple crops that are more tolerant of abiotic stress conditions. Many modern crop species are the product of extensive breeding designed to maximise the biomass of the harvested organs. However, traits such as stress tolerance that are present in the wild progenitor species are often lost during the breeding process. Successful reintroduction of such traits will be dependent upon a detailed understanding of their molecular basis. One fo the key components of the response of plants to stress conditions is adaptive change in their metabolism. Understanding the nature of these metabolic reconfigurations is vital if we are to successfully generate new stress-resistant varieties of crops. Accordingly, the aim of the proposed work is to dissect the regulation of the metabolic network during oxidative stress in the model plant, Arabidopsis thaliana. Particular attention will be paid to discriminating between changes that occur at the level of gene expression and those that operate directly on proteins (so-called post-translational changes).

Metabolic change is a key component of the response of plants to abiotic stresses and yet the metabolic response of plants to stress has been poorly characterised and largely overlooked in the decades of research on abiotic stress. Although the accumulation of specific metabolites during stress is well known (e.g. accumulation of compatible solutes during drought), the metabolic reconfigurations that support such flux shifts are not well understood. In particular, the way in which metabolic change is brought about is not known in any detail, despite the fact that this knowledge can be considered to be a prerequisite for the generation of plants with improved stress tolerance. Accordingly, this proposal aims to dissect the regulation of the Arabidopsis metabolic network during oxidative stress, quantifying the extent to which metabolic fluxes change and identifying transcriptional and post-translational levels of control. This will involve a global analysis of metabolite abundances and labelling to quantify change in the metabolic network and a comparison with transcriptomic change to divide enzymes into two classes - those that are transcriptionally regulated and those that are post-translationally regulated. A small group of the latter will be characterised in more detail to assess the various levels and mechanisms by which this post-translational change is brought about.