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William C. Plaxton PhD
 William C. Plaxton
Contact Info
613-533-6000 x6150

Faculty Bio

William Plaxton received a BSc in Biochemistry in 1980 from Carleton University (Ottawa, Ontario) and a PhD in Biology in 1984 from the same institution. His doctorate work under the supervision of Ken Storey focused on the metabolic adaptations of intertidal marine molluscs to environmental anoxia stress. He then carried out post-doctoral research on plant starch metabolism with Jack Preiss at the Dept. of Biochemistry of Michigan State University. William began his independent career in 1986 when appointed to the faculty in the Dept. of Biology at Queen’s University, and is now a Full Professor in their Plant Science Research Group. He also holds a cross-appointment in the Biochemistry Division of the Dept. of Biomedical and Molecular Sciences at Queen’s. Research in the Plaxton lab has been continuously and well-funded by a series of NSERC Discovery and Equipment grants.

Lab website:

Editorial Board: The Biochemical Journal: 2007-present (

Honours & Awards:

 Queen’s Research Chair in Plant Biochemistry – Awarded in 2004 for 'Outstanding Research Contributions by a Senior Faculty Member’.  

 Queen's Junior Research Fellowship - Awarded in 1995 by Fac. Arts & Science, Queen's Univ., for 'Research Excellence by a Junior Faculty member'.

 C.D. Nelson Award - Awarded in 1993 by the Canadian Society of Plant Biologists to a scientist <40 years of age for 'Outstanding Research Contributions to Plant Biology'.

Natural Sciences and Engineering Research Council of Canada (NSERC) -

            i) University Research Fellowship: awarded in 1986 for tenure at Queen's Univ., Dept. of Biology

            ii) Postdoctorate Fellowship:   1984‑1986

            iii) Postgraduate Scholarship:   1982‑1984 

Research Interests


My research program focuses on understanding the organization and control of plant carbohydrate metabolism, and the biochemical and molecular adaptations of phosphorus-starved plants. This work integrates a variety of biochemical, proteomic, molecular biology, cell biology, and functional genomic tools to characterize the molecular and functional properties, and protein:protein interactions of key enzyme proteins.  We are particularly interested in post-translational protein modifications by phosphorylation, monoubiquitination, and glycosylation since these PTMs can play pivotal roles in controlling an enzyme’s activity, subcellular location, protein:protein interactions and/or turnover in response to various extra- or intracellular signals. Systems that we are studying include developing and germinating oilseeds, and cell cultures and seedlings of the model plant Arabidopsis thaliana. Our research has important long-term agronomic applications including the: (1) targeted modification of storage oil versus protein levels in oilseeds such as canola or soybean, and  (2) metabolic engineering of phosphorus-efficient crops, urgently needed to reduce mankind’s rampant but inefficient use of non-renewable, unsustainable, and polluting phosphorus-containing fertilizers in agricultural production.

Selected Publications

Note: In publication lists the names of undergrad and grad students are underlined, with undergrads in italics font style.


  1. Fedosejevs ET, Ying S, Park J, Anderson EM, Mullen RT, She Y-M, Plaxton WC (2014) Biochemical and molecular characterization of RcSUS1, a cytosolic sucrose synthase isozyme phosphorylated in vivo at serine-11 in developing castor oil seeds. Journal of Biological Chemistry 289: 33412-33424
  2. Hill AT, Ying S, Plaxton WC (2014) Phosphorylation of bacterial-type phosphoenolpyruvate carboxylase by a Ca2+-dependent protein kinase suggests a link between Ca2+-signaling and anaplerotic pathway control in developing castor oil seeds. Biochemical Journal 458: 109-118
  3. Del Vecchio HA, Ying S, Park J, Knowles VL,  Kanno S,  Tanoi K, She Y-M, Plaxton WC (2014) The cell-wall targeted purple acid phosphatase AtPAP25 is critical for acclimation ofArabidopsis thaliana to nutritional phosphorus-deprivation. The Plant Journal 80: 569-581
  4. Shane MW, Stigter K, Fedosejevs ET, Plaxton WC (2014) Senescence-inducible cell-wall and intracellular purple acid phosphatases: implications for phosphorus remobilization in Hakea prostrata (Proteaceae) and Arabidopsis thaliana (Brassicaceae). Journal of Experimental Botany  65: 6097-6106
  5. Dahal K, Knowles VL, Plaxton WC, Hüner NPA (2014) Enhancement of photosynthetic performance, water use efficiency and grain yield during long-term growth under elevated CO2 in wheat and rye is growth temperature and cultivar dependent. Environmental and Experimental Botany 106:  207-220
  6. Ruiz-Ballesta I, Feria A-B, Hong N, She Y-M, Plaxton WC, Echevarria C (2014) In vivo monoubiquitination of anaplerotic phosphoenolpyruvate carboxylase occurs at lysine-624 in germinating sorghum seeds. Journal of Experimental Botany 65: 443-451
  7. Dahal K, Sarathi MW, Kane K, Rauf SA, Leonardos ED, Gadapati W, Savitch L, Singh J, Marillia E-F, Taylor DC, Micallef MC, Knowles VL, Plaxton WC, Barron J, Sarhan F, Huner N, Grodzinski B, Micallef BJ (2014) Enhancing biomass production and yield by maintaining enhanced capacity for CO2 uptake in response to elevated CO2. Canadian Journal of Plant Science 94: 1075-1083
  8. Shane MW, Fedosejevs ET, Plaxton WC (2013) Reciprocal control of anaplerotic phosphoenolpyruvate carboxylase by in vivo monoubiquitination and phosphorylation in developing proteoid roots of phosphate deficient Hakea prostrataPlant Physiology 161:1634–1644 
  9. Robinson WD, Park J, Tran HT, Del Vecchio HA, Ying S, Patel K, McKnight TD, Plaxton WC (2012) The secreted purple acid phosphatase isozymes AtPAP12 and AtPAP26 play a pivotal role in extracellular phosphate scavenging by Arabidopsis thalianaJournal of Experimental Botany 63: 6531–6542
  10. Robinson WD, Carson I, Ying S, Ellis K, Plaxton WC (2012) Eliminating the purple acid phosphatase AtPAP26 in Arabidopsis thaliana delays leaf senescence and impairs phosphorus remobilization. New Phytologist 196: 1024–1029
  11. Park J, Khuu N, Howard AS, Mullen RT, Plaxton WC (2012) Bacterial- and plant-type phosphoenolpyruvate carboxylase isozymes from developing castor oil seeds interact in vivo and associate with the surface of mitochondria. The Plant Journal 71: 251-262
  12. Dalziel KJ, O'Leary B, Brikis C, Rao SK, She Y-M, Cyr T, Plaxton WC (2012) The bacterial-type phosphoenolpyruvate carboxylase isozyme from developing castor oil seeds is subject to in vivo regulatory phosphorylation at serine-451. FEBS Letters 586: 1049-1054
  13. O'Leary B, Fedosejevs ET, Hill AT, Bettridge J, Park J, Rao SK, Leach CA, Plaxton WC (2011) Tissue-specific expression and post-translational modifications of plant- and bacterial-type phosphoenolpyruvate carboxylase isozymes of the castor oil plant, Ricinus communis L. Journal of Experimental Botany 62: 5485-5495
  14. O'Leary B, Rao S, Plaxton WC (2011) Phosphorylation of a bacterial-type phosphoenolpyruvate carboxylase at serine-425 provides a further tier of enzyme control in developing castor oil seeds. Biochemical Journal 433: 65-74
  15. Tran HT, Qian W, Hurley BA, She Y-M, Wang D, Plaxton WC (2010) Biochemical and molecular characterization of AtPAP12 and AtPAP26: the predominant purple acid phosphatases isozymes secreted by phosphate-starved Arabidopsis thalianaPlant, Cell & Environment 33: 1789-1803
  16. Hurley BA, Tran HT, Murty N, Park J, Snedden WA, Mullen RT, Plaxton WC (2010) The dual-targeted purple acid phosphatase isozyme AtPAP26 is essential for efficient acclimation of Arabidopsis thaliana to nutritional phosphate deprivation. Plant Physiology 153:1112–1122
  17. O'Leary B, Rao S, Kim J, Plaxton WC (2009) Bacterial-type phosphoenolpyruvate carboxylase (PEPC) functions as a catalytic and regulatory subunit of the novel class-2 PEPC complex of vascular plants. Journal of Biological Chemistry 284: 24797-243805
  18. Gregory AL, Hurley BA, Tran HT, Valentine AJ, She Y-M, Knowles VL, Plaxton WC (2009) In vivo regulatory phosphorylation of the phosphoenolpyruvate carboxylase AtPPC1 in phosphate-starved Arabidopsis thalianaBiochemical Journal 420: 57-65
  19. Uhrig RG, She Y-M, Leach CA, Plaxton WC (2008) Regulatory monoubiquitination of phosphoenolpyruvate carboxylase in germinating castor oil seeds. Journal of Biological Chemistry 283: 29650-29657 (selected as a JBC 'Paper of the Week').
  20. Tran HT, Plaxton WC (2008) Proteomic analysis of alterations in the secretome of Arabidopsis thaliana suspension cells subjected to nutritional phosphate deficiency. Proteomics 8: 4317-4326
  21. Uhrig RG, O’Leary B, Spang HE, MacDonald JA, She Y-M, Plaxton WC (2008) Co-immunopurification of phosphorylated bacterial- and plant-type phosphoenolpyruvate carboxylases with the plastidial pyruvate dehydrogenase complex from developing castor oil seeds. Plant Physiology 146: 1346-1357
  22. Gennidakis S, Rao S, Greenham K, Uhrig RG, O’Leary B, Snedden WA, Lu C, Plaxton WC (2007) Bacterial- and plant-type phosphoenolpyruvate carboxylase polypeptides interact in the hetero-oligomeric Class-2 PEPC complex of developing castor oil seeds. The Plant Journal 52: 839–849


  1. Plaxton WC, Shane MW (2015) The Essential Role of Post-translational Enzyme Modifications in the Metabolic Adaptations of Phosphorus-Deprived Plants. Chpt. 4 of "Phosphorus  Metabolism in Plants in the Post-genomic Era: From Gene to Ecosystem" (WC Plaxton & H Lambers, Eds). Annual Plant Reviews. Wiley (in press)
  2. Lambers H, Plaxton WC (2015) Phosphorus - Back to the Roots. Chpt. 1 of "Phosphorus  Metabolism in Plants in the Post-genomic Era: From Gene to Ecosystem" (WC Plaxton & H Lambers, Eds). Annual Plant Reviews. Wiley (in press)
  3. O'Leary B, Plaxton WC (2014) The Central Role of Glutamate and Aspartate in the Post-translational Control of Respiration and Nitrogen-assimilation in Plant Cells. Chpt. 17 of "Amino Acids in Higher Plants" (JPF D'Mello; Ed). CABI International. (in press)
  4. Knowles VL, Plaxton WC (2013) Protein Extraction, Acid Phosphatase Activity Assays, and Determination of Soluble Protein Concentration Bio-protocol 3(17): e889.
  5. Knowles VL, Plaxton WC (2013) Quantification of Total and Soluble Inorganic Phosphate Bio-protocol 3(17): e890.
  6. Plaxton WC, O'Leary B (2012) The Central Role of Phosphoenolpyruvate Metabolism in Developing Oil Seeds. Chpt. 15 of  SEED DEVELOPMENT. OMICS Technologies Toward Improvement of Seed Quality and Crop Yield. (GK Agrawal & R Rakwal; Eds). Springer.
  7. Veneklass EJ, Lambers H, Bragg J, Finnegan PM, Lovelock CE, Plaxton WC, Price C, Scheible W-R, Shane MW, White PJ, Raven JA (2012) Opportunities for improving phosphorus-use efficiency in crop plants (a Tansley Review). New Phytologist  195: 306-320
  8. Plaxton WC, Tran HT (2011) Metabolic adaptations of phosphate-starved plants. Plant Physiology 156: 1006-1015
  9. O'Leary B, Park J, Plaxton WC (2011) The remarkable diversity of plant phosphoenolpyruvate carboxylase (PEPC): recent insights into the physiological functions and post-translational controls of non-photosynthetic PEPCs. Biochemical Journal 436: 15-44
  10. Tran HT, Hurley BA, Plaxton WC (2010) Feeding hungry plants: The role of purple acid phosphatases in phosphate nutrition. Plant Science 179: 14-27
  11. Plaxton WC (2010) Metabolic Flexibility Helps Plants to Survive Stress. Updated Web-essay for a web-site ( that supplements the 5th Edition of “Plant Physiology” (Taiz & Zeigler). My Web-essay augments Chapter 11 ('Respiration') of this widely used undergraduate textbook.
  12.  Plaxton WC, Podestà FE (2006) The functional organization and control of plant respiration. Critical Reviews in Plant Sciences 25: 159-198
  13. Plaxton WC (2004) Principles of Metabolic Control. In: “Functional Metabolism of Cells: Control, Regulation, and Adaptation” (KB Storey, ed). John Wiley & Sons, Inc., N.Y. pp 1-24