Page 65 - PC2019 Program & Proceedings

PLANT CANADA 2019

PS12. Wednesday, July 10, afternoon session at 3:40 pm

Dr. William Plaxton

Queen’s University, Kingston, ON

CSPB Gold Medal Address:
Feeding hungry plants: Purple acid phosphatases play a
pivotal role in phosphorous nutrition
Abstract: Phosphorus is an environmentally-limiting macronutrient that roots can only assimilate from soil as
-
soluble inorganic phosphate (Pi, H2PO4 ). The most abundant P fraction of many soils exists as organic Pi-
monoesters (derived from decomposing biomaterial) unavailable for root uptake until hydrolyzed by secretory
purple acid phosphatases (PAPs). Plant PAPs belong to a relatively large multigene family whose specific
functions in P-metabolism are poorly understood. Purification, characterization, and identification via LC-MS/MS
(peptide sequencing) of intracellular (vacuolar) and secreted (cell wall) PAP isozymes upregulated by Pi-starved
suspension cell cultures of the model plant Arabidopsis thaliana have been complemented by studies of the
corresponding loss-of-function mutants. This has allowed us to pinpoint the predominant Pi-starvation-inducible
PAP isozymes (i.e., AtPAP12, AtPAP17, AtPAP25, and AtPAP26) that facilitate Arabidopsis P-acquisition efficiency.
AtPAP26 is of particular interest since it is: (i) the predominant PAP isozyme upregulated by Pi-deprived
Arabidopsis, and (ii) also markedly upregulated during leaf senescence to remobilize Pi to developing seeds.
Kinetic studies with purified vacuolar and secreted AtPAP26 glycoforms demonstrated that it effectively
hydrolyzes Pi from a wide range of substrates with high catalytic efficiency. Furthermore, a Pi starvation- and
senescence-inducible, tyrosine-phosphorylated and dual-targeted (i.e., cell wall & vacuole) GNA-apple domain
lectin (AtGAL1) interacts with, stabilizes, and activates a high-mannose glycoform of AtPAP26. AtPAP26 is
emerging as a promising candidate for enhancing the P-acquisition and P-use efficiency of engineered crop
plants. Achieving this goal is urgently required to reduce the massive overuse of non-renewable, inefficient, and
polluting Pi-containing fertilizers in agricultural production.

Bio:

William Plaxton received BSc (in 1980) and PhD (in 1984) degrees in Biochemistry from Carleton University
(Ottawa). His PhD dissertation was under the supervision of Ken Storey and focussed on the metabolic
adaptations of intertidal marine molluscs to anoxia stress. Plaxton was awarded an NSERC Post-doctoral
Fellowship to conduct research on plant starch metabolism with Jack Preiss at the Dept. of Biochemistry,
Michigan State University. In 1986 he was appointed to the faculty in the Dept. of Biology at Queen’s University
(Kingston). Plaxton’s research program has been funded by NSERC and the Queen's Research Chair Program to
conduct studies of the organization and control of plant (especially oilseed) glycolysis and respiratory
metabolism, and the metabolic adaptations of phosphorus-starved plants. This research has integrated various
biochemical, proteomic, genetic, and cell biology tools to characterize the molecular and functional properties
of key enzyme proteins (with a particular interest in the crucial post-translational enzyme modifications such as
phosphorylation and glycosylation). He has served as the President of the CSPB, and he is the recipient of both
the CSPB C.D. Nelson Award and The Society Medal. Plaxton also enjoys Canada’s magnificent outdoors and
natural beauty, keeping fit, and playing upright and electric bass.
https://biology.queensu.ca/people/department/professors/plaxton/

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