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Queen's University

William Plaxton - Professor

Plaxton.jpg Research:  Our research integrates modern biochemical/proteomic, molecular biological, and functional genomic tools to assess the organization and control of plant carbohydrate metabolism and the biochemical and molecular adaptations of phosphorus-starved plants. We are particularly interested in the occurrence, functions, and mechanisms of post-translational protein modification by phosphorylation, monoubiquitination, and glycosylation since these PTMs can play pivotal roles in controlling enzyme activity, subcellular location, and protein:protein interactions 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 results are integrated with a wide range of information on genomics, the control of gene expression, protein structure-function, metabolomics, and whole plant physiology into a framework that leads to a deeper understanding of how plants work in their natural environment. This research has important 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 phosphate-containing fertilizers.

»» Lab Website »« email: »« telephone: 613-533-6150 ««

Some Recent Publications (undergrad and grad students indicated by asterisks*):

    • Hill AT*, Ying S, Plaxton WC (2013) Phosphorylation of a bacterial-type phosphoenolpyruvate carboxylase by a calcium-dependent protein kinase suggests a link between Ca2+-signalling and anaplerotic pathway control in developing castor oil seeds. Biochemical Journal (in press)
    • Ruiz-Ballesta I*, Feria A-B, Hong N, She Y-M, Plaxton WC, Echevarria C (2013) In vivo monoubiquitination of anaplerotic phosphoenolpyruvate carboxylase occurs at lysine-624 in germinating sorghum seeds. Journal of Experimental Botany (in press)
    • 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 prostrata. Plant Physiology 161:1634–1644
    • 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 thaliana. Journal of Experimental Botany 63: 6531–6542
    • 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
    • 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
    • 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
    • Plaxton WC, Tran HT* (2011) Metabolic adaptations of phosphate-starved plants. Plant Physiology 156: 1006-1015
    • 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
    • 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
    • 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
    • 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
    • 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 thaliana. Plant, Cell & Environment 33: 1789-1803
    • 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
    • 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 thaliana. Biochemical Journal 420: 57-65
    • 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

      Kingston, Ontario, Canada. K7L 3N6. 613.533.2000