Welcome to the Metabolic Physiology Group based in the Tom ap Rees Laboratory, Department of Plant Sciences, University of Oxford. The principal focus of this group is the regulation of carbohydrate metabolism in higher plants.

Carbohydrates are the major respiratory substrate in most plants, providing both the energy and metabolic precursors for growth. We are interested in understanding how the pathways of carbohydrate metabolism are regulated to meet the requirements of the plant in response to changing environmental and developmental demands.

Our work involves a combination of metabolic physiology, enzymology and molecular biology. We are applying metabolic control analysis to quantify the contribution of individual steps to flux through the major pathways of carbohydrate metabolism; these include glycolysis, the oxidative pentose phosphate pathway and sucrose production during photosynthesis and seed germination. Our approach relies on the ability to alter the activities of individual enzymes specifically and independently. This is achieved through exploitation of naturally occurring mutants, application of specific inhibitors, and generation of transgenic plants. The effects of these manipulations are determined by measuring the extent to which metabolism is perturbed. We are developing techniques based on metabolic network analysis to discriminate between fluxes through pathways of carbohydrate oxidation that are duplicated between the cytosol and plastids in plant cells. This work, performed in collaboration with Dr R.G. Ratcliffe, involves determining the specific abundance of ¹³C in individual carbon atoms of a range of metabolic end-products by NMR spectroscopy after feeding with ¹³C-glucose. Using this approach we are able to measure flux through different sections of the oxidatitve pentose phosphate pathway(s).

The techniques described above are being used to establish the metabolic response of plants to environmental stress. In particular we are examining the extent to which plants adjust carbohydrate metabolism in response to anoxia and to oxidative stress, the mechanisms by which these changes occur, and the contribution of the responses to the capacity of the plants to survive in a changing environment. Such information is essential for any rational manipulation of carbohydrate metabolism in crop species.