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- Student Stories
Professor Nick Kruger
Fellow and Tutor in Biological Sciences, Associate Professor of Plant Sciences
- Biological Sciences
General biological chemistry (enzymology, enzyme kinetics and metabolism)
Plant and microbial biology (photosynthesis, carbohydrate metabolism and metabolic regulation).
- Molecular & Cellular Biochemistry
Plant metabolism (plant genetic manipulation, plant carbon metabolism, metabolic modelling)
George Ratcliffe and I recently organised a symposium on “Pathways and fluxes: analysis of the plant metabolic network” for SEB Glasgow in July 2011. A special issue of the Journal of Experimental Botany based on this symposium will be published in 2012, but in the meantime the abstracts of the presentations from the meeting are available.
A collaborative study on the role of the small chloroplast protein CP12 on growth and metabolism in tobacco plants is due to be published in Plant Physiology. Beyond my main focus on plant biology, metabolic flux analysis of Mycobacterium tuberculosis has revealed an unexpected function for the enzyme isocitrate lyase which provides a potential drug target for treatment of TB.
Committee member of the Biochemical Society Theme Panel III: Bioenergetics and Metabolism. The theme panel meets about three times each year to consider sponsorship of meeting proposals. If you have any suggestions for novel and exciting meetings in the area of metabolic biology, I would love to hear from you. In autumn 2010 I again attended the Biochemical Society jamboree in London - a two-day event that seeks to bring together the members of all the specialist themes to coordinate our diverse activities and explore areas and topics of common interest.
Member of the Editorial Board of Phytochemistry, and the Faculty of 1000 Biology Plant Biology (Plant Biochemistry and Physiology section).
- Biochemical Society
- American Society of Plant Biology
Sugars and starch are the major respiratory substrate in most plants, providing both the energy and metabolic precursors needed for growth. I am interested in understanding how the synthesis and degradation of these carbohydrates are regulated to meet the varying requirements of the plant (and humans) in response to changing environmental and developmental demands.
This work involves a combination of metabolic physiology, enzymology and molecular biology. We are exploiting mutant lines in which the function of particular genes has been completely disrupted to examine the requirements for specific enzymes, and applying metabolic control analysis to quantify the contribution of individual steps to flux through the major pathways of carbohydrate metabolism. These approaches rely on the ability to alter the activities of individual enzymes specifically and independently, and 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. Where appropriate, metabolic flux analysis is used to measure the rates of a wide range of individual reactions throughout the metabolic network and, in particular, to discriminate between the same reactions occurring in different parts of the cell (a common feature of plant metabolism). This work, performed in collaboration with Prof. R.G. Ratcliffe, involves determining the specific abundance of 13C in individual carbon atoms of a range of metabolic end-products by nuclear magnetic resonance (NMR) spectroscopy and gas chromatography-mass spectrometry (GC-MS) after labelling cells with [13C]glucose, and using this approach we are able to construct flux maps that define the behaviour of the network of central carbon metabolism in plant cells.
The techniques described above are being used to establish the metabolic response of plants to environmental stress. Currently we are examining the extent to which plants adjust carbohydrate metabolism in response to limitations in supply of mineral nutrients, 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 for the development and sustainable production of food, feedstock and biofuels.
Recent Research Papers
T.P. Howard, M.J. Fryer, P. Singh, M.Metodiev, A. Lytovchenko, T. Obata, A.R. Fernie, N.J. Kruger, W.P. Quick, J.C. Lloyd, C.A. Raines (2011) Antisense suppression of the small chloroplast protein CP12 in tobacco alters carbon partitioning and severely restricts growth. Plant Physiology doi:10.1104/pp.111.183806. Link
Beste, D.J.V, Bonde, B, Hawkins, N, Ward, J.L, Beale, M.H, Noack, S, Noh, K, Kruger, N.J, Ratcliffe, R.G, McFadden, J. (2011) 13C metabolic flux analysis identifies an unusual route for pyruvate dissimilation in mycobacteria which requires isocitrate lyase and carbon dioxide fixation. PLoS Pathogens. 7: e1002091. Link
Andriotis VME, Kruger NJ, Pike MJ, Smith AM (2010) Plastidial glycolysis in developing Arabidopsis embryos. New Phytologist 185: 649-662. Link
Masakapalli SK, Le Lay P, Huddleston JE, Pollock NL, Kruger NJ, Ratcliffe RG (2010) Subcellular flux analysis of central metabolism in a heterotrophic Arabidopsis cell suspension using steady-state stable isotope labelling. Plant Physiology 152: 602-619. Link
Couldwell DL, Dunford R, Kruger NJ, Lloyd DC, Ratcliffe RG, Smith AMO (2009) Response of cytoplasmic pH to anoxia in plant tissues with altered activities of fermentation enzymes: Application of methyl phosphonate as an NMR pH probe. Annals of Botany 103: 249-258. Link
Kruger NJ, Ratcliffe RG (2009) Insights into plant metabolic networks from steady-state metabolic flux analysis. Biochimie 91: 697-702. Link
Troncoso-Ponce MA, Kruger NJ, Ratcliffe RG, Garces R, Martinez-Force E (2009) Characterization of glycolytic initial metabolites and enzyme activities in developing sunflower (Helianthus annuus L.) seeds. Phytochemistry 70: 1117-1122. Link
Harrison PW, Kruger NJ (2008) Validation of the design of feeding experiments involving [14C]substrates used to monitor metabolic flux in higher plants. Phytochemistry 69: 2920-2927. Link
Kruger NJ, Troncoso-Ponce MA, Ratcliffe RG (2008) 1H NMR metabolite fingerprinting and metabolomic analysis of perchloric acid extracts from plant tissues Nature Protocols 3: 1001-1012. Link
Williams TCR, Miguet L, Masakapalli SK, Kruger NJ, Sweetlove LJ, Ratcliffe RG (2008) Metabolic network fluxes in heterotrophic Arabidopsis cells: Stability of the flux distribution under different oxygenation conditions. Plant Physiology 148: 704-718. Link
Bieniawska Z, Barratt DHP, Garlick AP, Thole V, Kruger NJ, Martin C, Zrenner R, Smith AM (2007) Analysis of the sucrose synthase gene family in Arabidopsis. Plant Journal 49: 810-828. Link
Kruger NJ, Ratcliffe RG (2007) Dynamic metabolic networks: Going with the flow. Phytochemistry 68: 2136-2138. Link
Kruger NJ, Huddleston JE, Le Lay P, Brown ND, Ratcliffe RG (2007) Network flux analysis: Impact of 13C-substrates on metabolism in Arabidopsis thaliana cell suspension cultures. Phytochemistry 68: 2176-2188. Link
Kruger NJ, Le Lay P, Ratcliffe RG (2007) Vacuolar compartmentation complicates the steady-state analysis of glucose metabolism and forces reappraisal of sucrose cycling in plants. Phytochemistry 68: 2189-2196. Link
Kruger NJ (2009) The Bradford method for protein quantitation. The Protein Protocols Handbook (3rd edition) Walker JM, ed. pp 17-24.
Kruger NJ (2009) Detection of proteins on western blots using colorimetric and radiometric visualization of secondary ligands. The Protein Protocols Handbook (3rd edition) Walker JM, ed. pp 737-753.
Kruger NJ, Ratcliffe RG (2008) Metabolic organization in plants: a challenge for the metabolic engineer. Advances in Plant Biochemistry and Molecular Biology : Bioengineering and Molecular Biology of Plant Pathways, vol 1, pp 1-27. Link
Pembroke's tutors are engaged in research across the breadth of the field. Professor Alex Kacelnik is an expert in animal behaviour; with a particular speciality in the study of the tool-making behaviour of crows and cockatoos. Professor Nick Kruger's research explores the metabolic networks of plants.