Office: SCIE 4471
Lab: SCIE 4409-10
My early interest in biology grew during my time at high school in Manchester, England, and also made me realize the importance of applied aspects of the biological sciences. My undergraduate degree was in Plant Science in the Faculty of Agriculture at the University of Newcastle-upon-Tyne (England). During my third (final) year at Newcastle I became interested in carbon metabolism in plants (through a combination of undergraduate project work and interesting biochemistry lectures). I pursued my interest in plant carbon metabolism during my Ph.D. studies at University College of North Wales (Bangor), studying the physiological and biochemical aspects of plants infected by biotrophic fungal pathogens under the supervision of Dr. John F. Farrar. I moved back to my native city of Manchester to do post-doctoral work with Dr. Michael Emes, studying starch synthesis in plants, an area of research that I have continued with to this day. At Manchester, I developed methods for isolating the fragile organelles (amyloplasts) responsible for starch synthesis in storage tissues such as cereal endosperms and tubers. I also worked on characterizing plastidial metabolite transporters using liposome-based systems, with the help of Dr. Malcolm Jones (University of Manchester, retired). Following post-doctoral studies, I was awarded a Leverhulme Special Research Fellowship, and studied the role of protein phosphorylation in the regulation of starch biosynthesis. At this stage, no role for this mode of regulation had been demonstrated for this pathway, and I was the first to demonstrate the regulation of key enzymes in the starch biosynthetic pathway by protein phosphorylation. In 2002 I moved to the University of Guelph (Department of Botany/ Molecular Biology and Genetics, now MCB). During the transition period from Manchester to Guelph my research work led to the important discovery that many of the enzymes of starch biosynthesis are also regulated by protein-protein interactions and much of my current research interest remains focused in this area.
B.Sc. University of Newcastle-upon-Tyne
Ph.D. University College of North Wales (Bangor)
An underlying aim throughout my research career has been to understand how plant metabolism is regulated; and in particular, how carbohydrate metabolism in plastids is regulated. One of the unique aspects of plant cell biology is the compartmentalization of certain metabolic pathways within specialized sub-cellular organelles termed plastids. The origin of plastids is thought to be traced back in time to the ingestion of a photosynthetic cyanobacterial cell by an ancient plastid-less protist, and its eventual transformation into a plastid. Many of the world’s most important agricultural products (e.g. starches and oils) are made inside plastids, and the central theme of my research interests has been the study of these important organelles. The major research topics currently being pursued in my laboratory are summarized below.
1. Regulation of Starch Biosynthesis in Higher Plants
Broadly, this involves examining the control mechanisms underpinning starch biosynthesis in leaf chloroplasts (which make starch during the daytime, and degrade it at night) and non-photosynthetic amyloplasts of cereal endosperms such as maize, wheat, barley and rice which make storage starches. More specifically, we are interested in the biochemical control mechanisms governing the many enzymes and enzyme classes which make up the core pathway of starch biosynthesis. This involves investigating the role of protein-protein interactions and protein phosphorylation in coordinating the proteins involved in starch synthesis and degradation within the plastid to produce the highly ordered and complex structure of the starch granule.
Addressing these fundamental scientific questions has potentially important applied benefits, enabling us to make more rational attempts at yield improvement in crops, and design starch structures which are suited to particular end-users, e.g. starches for the food industry with improved human health benefits, or starches for the non-food sector (e.g. paints and coatings). Consequently, this research has led to a number of collaborations with scientists in the food and non-food industries.
Related projects include work on human glycogen storage diseases in collaboration with Dr. Berge Minassian (Hospital for Sick Children, University of Toronto), and I am a member of the BioCar project, a multidisciplinary team involved in delivering biomaterials for the automotive industry.
The various projects related to understanding starch metabolism are part of a close, long-standing collaboration with Dr. Michael Emes (Dean of CBS, and faculty member of MCB) and Dr. Matthew Morell (Theme Leader, Food Futures Flagship, CSIRO Plant Industry, Canberra). My research in starch metabolism is currently funded by OMAFRA, NSERC, CFI and ABIP grants.
2. Regulation of Tocopherol (Vitamin E) Biosynthesis in Plants
Tocopherols and tocotrienols are an important group of lipid-soluble antioxidants synthesized exclusively in photosynthetic tissues, with many beneficial properties, both with respect to human health (e.g. vitamin E activity), and within the food industry. We are taking a multi-disciplinary approach to understanding the regulation and organization of tocopherol and tocotrienol biosynthesis both in leaf chloroplasts of Arabidopsis (a model plant system) and photo-heterotrophic plastids of developing oilseeds such as soybean. In particular, the sub-organellar organization of the pathway is being examined, and its relationship to other metabolic pathways and factors or elements of signal transduction cascades and intra-plastidial trafficking systems. This research will provide important insights into the mechanisms governing the control and regulation of important metabolic pathways in the plastids of higher plants, and contribute to engineering crops with improved nutritional value and enhanced high-value bioproducts. This research is funded by NSERC and ABIP grants.
Chapters and Reviews
Tetlow, I. J. (2006). Understanding storage starch biosynthesis in plants: a means to quality improvement. Can. J. Bot. 84, 1167-1185.
Tetlow, I.J., Morell, M.K., Emes, M.J. (2004). Recent developments in understanding the regulation of starch metabolism in higher plants. J.Exp. Bot. 55, 2131-2145.
Tetlow, I.J., Rawsthorne, S., Raines, C, Emes, M.J. (2004). Plastid Metabolic Pathways. Annual Plant Reviews 13, Chapter 3, 60-125.
Liu, F., Makhmoudova, A., Lee, E.A., Wait, R., Emes, M.J., and Tetlow, I.J. (2009). The amylose extender mutant of maize conditions novel protein-protein interactions between starch biosynthetic enzymes in amyloplasts. Journal of Experimental Botany 60 (15): 4423-4440.
Bowsher, C.G., Tickle, P., Burrell, M., Coates, S., Emes, M., and Tetlow, I. (2009). Characterization of plastidial starch phosphorylase in Triticum aestivum L. endosperm. Journal of Plant Physiology 166, 1465-1478.
Tetlow, I.J., Beisel, K.G., Cameron, S., Makhmoudova, A., Liu, F., Bresolin,
N. S., Wait, R., Morell, M.K., and Emes, M.J. (2008). Analysis of Protein Complexes in Amyloplasts Reveals Functional Interactions among Starch Biosynthetic Enzymes. Plant Physiology 146, 1878-1891.
Hennen-Bierwagen, T. A., Liu, F., Marsh, R., Kim, S., Gan, Q., Tetlow, I.J., Emes, M.J., James, M.G., and Myers, A.M. (2008). Multiple Starch Biosynthetic Enzymes from Developing Zea mays Endosperm Associate in Multisubunit Complexes. Plant Physiology 146, 1892-1908.
Ahmed, N., Maekawa, M., and Tetlow, I.J. (2008). Effects of low temperature on grain filling, amylose content and activity of starch biosynthesis enzymes in endosperm of basmati rice. Australian Journal of Agricultural Research 59, (7) 599-604.
Bowsher, C.G., Scrase-Field, E. F.A.L., Esposito, S., Emes, M.J., and Tetlow, I.J. (2007). Characterization of ADP-glucose Transport across the Cereal Endosperm Amyloplast Envelope. Journal of Experimental Botany 58, 1321-1332.
Liu, Q., Gu, Z., Donner, E., Tetlow, I.J. and Emes, M.J. (2007). Investigation of digestibility in vitro and physicochemical properties of A- and B-type starch from soft and hard wheat flour. Cereal Chemistry 84, 15-21.
Bresolin, N.S., Li, Z., Kosar-Hashemi, B., Tetlow, I.J., Chaterjee, M., Rahman, S., Morell, M.K., and Howitt, C.A. (2006). Characterisation of disproportionating enzyme from wheat endosperm. Planta 224, 20-31.
Tetlow, I.J., Wait, R., Lu, Z., Akkasaeng, R., Bowsher, C.G., Esposito, S., Kosar-Hashemi, B., Morell, M.K., Emes, M.J. (2004). Protein phosphorylation in amyloplasts regulates starch branching enzyme activity and protein-protein interactions. Plant Cell 16, 694-708.
Tetlow, I.J., Bowsher, C.G., Emes, M.J. (2003) Biochemical properties and enzymic capacities of chromoplasts isolated from wild buttercup (Ranunculus acris L.). Plant Science 165, 383-394.
Tetlow, IJ, Bowsher, CG, Scrase-Field, ESF, Davies, EJ, Emes, MJ. (2003). The synthesis and transport of ADPglucose in cereal endosperms. J. Appl. Glycoscience 50, 231-236.
Emes, MJ, Bowsher, CG, Hedley, C, Burrell, MM, Scrase-Field, ESF, Tetlow, IJ. (2003). Starch synthesis and carbon partitioning in developing endosperm. Journal of Experimental Botany 54, 569-575.
Tetlow, I.J., Davies, E.J., Vardy, K.A., Bowsher, C.G., Burrell, M.M. and Emes, M.J. (2003). Sub-cellular localization of ADPglucose pyrophosphorylase in developing wheat endosperm and analysis of the properties of a plastidial isoform. Journal of Experimental Botany 54, 715-725.
Davies, EJ, Tetlow, IJ, Bowsher, CG, Emes, MJ. (2003). Molecular and biochemical characterisation of cytosolic phosphoglucomutase in wheat endosperm (Triticum aestivum L. cv. Axona). Journal of Experimental Botany 54, 1351-1360.
BOT2100 Life Strategies of Plants
BOT4380/6438 Plant Metabolism
MCB*6350 Advanced Topics in Plant Biology
Renuka Subasinghe (Ph.D.)
Liliya Nasanovsky (M.Sc.)
John Hollingshead (M.Sc.)*
Zaheer Ahmed (Ph.D.)*
Usha Rayirath (Ph.D.)*
Amina Makhmoudova (laboratory technician) *
*Co-supervised with Dr. Michael Emes