William Plaxton Prof. William Plaxton
Queen's Research Chair in Plant Biochemistry
Dept. of Biology, cross-appointed to Dept.of Biomedical and Molecular Sciences
Biosciences Complex.
Queen's University.
Kingston, Ontario. Canada. K7L 3N6
Phone: 613-533-6150 | plaxton@queensu.ca
William Plaxton received a BSc in Biochemistry in 1980 from Carleton University (Ottawa, Canada) and a PhD in Biochemistry in 1984 from the same institution. His PhD research under the supervision of Ken Storey focused on the metabolic adaptations of intertidal marine molluscs  to environmental anoxia stress. He was awarded an NSERC Post-doctoral Fellowship to conduct research on plant starch metabolism with Jack Preiss (Dept. of Biochem., Michigan State Univ.). His independent career began in 1986 when appointed as a NSERC University Research Fellow and Assist. Prof. to the faculty in the Dept. of Biology at Queen’s Univ. (Kingston, Canada).

Undergraduate & Graduate Student Positions Available

No fully funded MSc or PhD student positions are currently available. However, space is available for highly qualified students who have been awarded a major external scholarship (e.g. NSERC-PGS). (Jan. 2015).

Potential Projects: There is a wide assortment of potential projects available, with the final choice depending upon the student's background and specific interests, and starting date.  Projects range from native ENZ purification and characterization, to metabolite extraction and quantification, to the use of proteomics, 2-dimensional gel electrophoresis, mass spectrometry, ENZ activity assays, immunological techniques (western blotting &/or co-immunoprecipitation using monospecific antibodies), molecular biology techniques (transcript profiling via RT-PCR, recombinant enzyme expression, etc) to assess the influence of seed development and germination, or environmental stressors such as phosphate starvation on ENZ control, expression, protein:protein interactions and in vivo subcellular targeting. Possible projects also include using our Dept's state of the art confocal fluorescence laser scanning microscope for imaging fluorescent protein tagged enzymes in living cells, and screening and analyzing transgenic plants in which several of the ENZs that we have been studying have been 'knocked out' (loss-of-function) or over-expressed.

Post-Doctoral Research: No fully funded post-doctoral positions are currently available. Interested post-doctoral candidates who have been awarded a major fellowship (that provides their salary stipend) are requested to contact Prof. Plaxton.
TRAINING ENVIRONMENT FOR HIGHLY QUALIFIED PERSONNEL (HQP)(the following section was directly copied from Plaxton's NSERC Discovery Grant Application - submitted to NSERC on Oct. 30, 2012): Owing to their training in enzymology, protein purification, and metabolic biochemistry many of my former HQP have enjoyed rewarding careers in biotech and molecular biology-oriented academic, government, or industry labs. Over the past decade I have been contacted at regular intervals by metabolic engineering departments of ag-biotech companies (e.g. BASF, Monsanto, Pioneer) struggling to fill gene discovery positions requiring HQP trained in native ENZ purification/characterization, ENZ kinetics, and metabolic biochemistry. However, my HQP recruitment and training has been considerably augmented by the ongoing integration of innovative proteomic and mass spectrometry tools, along with advanced molecular biology, functional genomic, and cell biology/imaging techniques into my research program.
  • Over the 5 years of the current proposal, I anticipate training 2 post-doctoral fellows (PDFs), 4 PhD students, 5 MSc students, ≥10 BSc thesis students, 5-10 summer undergrad research assistants, and 10-15 volunteers. Key to successful HQP training is matching a project with their interests and abilities. I initially identify clear objectives for each thesis student or PDF, and enjoy working with them to design projects that align with their interests, while nurturing their career development. As my HQP gain experience they are progressively encouraged to develop their own ideas and innovative approaches to their research, while developing solid oral and written communication skills. Thus, most HQP leave my lab as effective communicators while having a clear understanding of the ‘big picture’. They also gain important insights into the cost of research, lab budget management, and especially the need to maximize the return on every single Canadian taxpayer $ that has been invested in our research via NSERC grants.
  • My individual HQP projects often bridge multiple disciplines, including plant ecophysiology, biochemistry, protein structure-function, molecular genetics, and cell biology. I foster this integrative approach while broadening the scope for individual projects by encouraging students and PDFs to contribute to each other’s research. BSc thesis students are another important component of my HQP training as they typically work under direct supervision of a senior grad student or PDF to help complete a specific component of their research. The continual challenge of training ‘raw rookies’ is more than compensated for by their youthful enthusiasm and motivation to master theoretical and practical aspects of techniques we use, while helping us to discover how plants work. I work hard to ensure my lab retains accumulated experience (PDFs and senior grad students enjoy serving as mentors for junior students), and we have excellent relationships with other labs within our department and at Queen’s which allows us to tap into local expertise to enhance our research abilities.
  • Facilitating international collaborations and interactions has been another significant component of HQP training as all of my PDFs, and a number of grad students, have come from other countries while bringing new ideas and technical skills. Recent PDFs (Rao, Park, & Ying) have played an important role in the integration of molecular biology, functional genomics, and cell biology/imaging into my research program and student training. We have also enjoyed hosting a number of visiting international Profs. and PhD students:  most recently Mike Shane (W. Australia), Isabel Ballesta (Seville), and Alex Valentine (Stellenbosch) who have each enriched my lab and HQP with their wisdom and collaborative approach to plant sciences, while themselves becoming well qualified with key methods and equipment instrumental to my research program.
  • Regular participation in national (and occasional international) plant science or biochem conferences has also made an important contribution to my HQP training as it provides them with: i) invaluable feedback (& perspectives) about their own research, ii) an opportunity to network and establish contacts and interactions with their peers, as well as established PIs (while enhancing their communication skills), and iii) inspiration and education by other conference participants. 
  • Tangible Evidence of HQP Training Success: One of the most rewarding aspects of my faculty career has been having the privilege of observing and participating in the evolution of raw, untapped talent into mature, innovative, and creative research scientists (while sharing in their ‘joy of discovery’). With few exceptions my grad students finish ‘on time’, and 100% of the 25 MSc or PhD students that I have graduated to date (and 12 of 13 PDFs) have obtained at least one first authorship refereed publication in a high impact biochemistry or plant science journal.  Many of my BSc thesis students (at least 50%) have coauthored our publications. I am also gratified that a high proportion of my HQP have continued in research. Perhaps most compelling is that fifteen of my previous grad students or PDFs are now academic faculty members (9), or senior staff scientists (6) in government institutes or biotech companies like Monsanto or Oncolytics Biotech.


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    • December 2014. PhD student Eric Fedosjevs wins 'Director's Award' for best student oral presentation at Eastern Regional Meeting of Can Soc Plant Biol (Guelph, ON). Eric's presentation was entitled: The Ca2+-dependent protein kinase RcCDPK2 in vivo phosphorylates the sucrose synthase isozyme RcSUS1 at serine-11 in developing castor oil seeds. Congratulations Eric! (as well as for your extensive paper on castor bean sucrose synthase that was recently published in J Biol Chem). 
    • November - December 2014. Plaxton enjoys a productive two-week visit with PEP carboxylase collaborator Prof. Cristina Echevarria and other colleagues at Univ. de Sevilla in this beautiful and historic city of S-W Spain, while presenting a pair of research seminars concerning our recent PEP carboxylase and purple acid phosphatase research. 
    • November 2014. Plaxton visits our long -time mass spec collaborator Dr. Yi-Min She (Director of Mass Spec Facility, Shanghai Centre for Plant Stress Biology) and other colleagues at highly impressive Chinese Academy of Sciences labs in Shanghai and Beijing, and also gives a pair of seminars entitled "Purple Enzymes Feed Hungry Plants". 
    • September 2014. Plaxton visits calcium signaling and cell wall proteomics colleagues Jean-Phillipe Gallaud and Elisabeth Jamet at Univ. of Toulouse, prior to embarking on a 'Pyrenees Traverse', a week long cycling adventure across the Pyrenees from the Atlantic Ocean (Hendaye) to the Mediterranean (Perpignan)
    • September 2014. The Plaxton lab is delighted to welcome 3 new graduate students, Kyla Stigter (MSc), Mike Ting (MSc), and Mina Ghahremani (PhD). Congratulations to Kyla and Mina for being awarded a presigious Ontario Graduate Scholarship and Ontario Trillium Scholarship, respectively . 
    • July 2014. Post-doc Sheng Ying attends Annual General Meeting of American & Canadian Societies of Plant Biologists (Portland, OR) and presents his research on: "In vivo seryl phosphorylation of bacterial-type phosphoenolpyruvate carboxylase by RcCDPK1 suggests a link between calcium-signaling and the control of anaplerotic photosynthate-partitioning in developing castor beans".
    • March 2014. Plaxton visits Max Planck Instit for Molecular Plant Physiology (Potsdam, Germany) and present a pair of research seminars concerning his lab's recent PEP carboxylase and purple acid phosphatase research. 
    • December 2013Plaxton presents a Plenary Lecture entitled: Feeding hungry plants: Purple acid phosphatases play a pivotal role in phosphorus nutrition, at the “Applying Genomics to Canola Improvement Workshop”, Saskatoon, SK 
    • September-December 2013. We were delighted to host the return 3 month visit of Snrta. Isabel Ballesta, outstanding PhD student of Prof. Cristina Echevarria (Universidad de Sevilla, Espana). Isabel is continuing to collaborate with us on biochemical studies of PEP carboxylase and its in vivo post-translational modifications (phosphorylation vs. monoubiquitination) in developing vs. germinating sorghum seeds. She recently had a nice paper accepted in Journal of Experimental Botany (concerning in vivo monoubiquitination of Sorghum PEPC) largely based upon research she performed during her 2012 visit to our lab. 
    • August 2013. Congratulations to Allyson Hill who successfully defended her MSc thesis entitled: "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". A manuscript based upon her thesis research has been accepted for publication in the Biochemical Journal (November 2013) . Allyson has enrolled in a Masters of Policy Studies program at Queen's. We wish her all possible successes with this new endeavor.

    • May 2013. Mike Shane returns from School of Plant Biology, Univ. of Western Australia, for another visit to study the metabolic adaptations of Harsh Hakea to nutritional phosphate deprivation. Harsh Hakea is a native 'extremophile' plant that thrives in the ancient, nutrient impoverished soils of Western Australia. Mike
    • April 2013. Plaxton's NSERC Discovery Grant was successfully renewed for another 5 years. The grant application received an 'Outstanding' rating for each of the 3 major criteria (Training of Highly Qualified Personnel, Quality of Proposed Research, Past Research Contributions) used to determine one's funding level (from NSERC's Biological Systems & Processes Grant Selection Panel #1502)
    • August 2012. Hernan Del Vecchio & Whitney Robinson successfully defended their MSc Theses respectively entitled: "Biochemical and molecular characterization of AtPAPX, a novel cell wall-localized purple acid phosphatase isozyme upregulated by phosphate-starved Arabidopsis thaliana" & "The secreted purple acid phosphatase isozymes AtPAP12 and AtPAP26 play a pivotal role in extracellular phosphate scavenging by Arabidopsis thaliana" . Whitney is entering Queen's law school this Sept. and will do a great job integrating her solid plant biochemistry/science background with a legal career. Hernan will continue working in our lab for next few months prior to returning to his hometown of Rosario, Argentina - (also hometown of another exceptional Argentine known as Lionel Messi) ... adios amigo! Best wishes for continued success Whitney & Hernan! We will all miss both of you very much but hope you stay in touch and that our paths cross again 'down the road.

    • July 2012. We are very happy to welcome Dr. Sheng Ying from the Chinese Academy of Science (Beijing) who is initiating post-doctoral research in plant molecular biology and metabolic engineering. Sheng is following in the footsteps of our former post-doc Joonho Park, who is now back home running his own lab as an Assist. Prof. at Seoul National University (Korea)
    • July 2012. Plaxton presents invited seminars at the: (i) President's Symposium of the Annual Meeting of the American Society of Plant Biologists (Austin TX) entitled: "Regulatory phosphorylation and monoubiquitination of novel phosphoenolpyruvate carboxylase isoforms in castor oil seeds", and (ii) Noble Foundation (Ardmore OK) entitled: "FEEDING HUNGRY PLANTS: The purple acid phosphatase AtPAP26 plays a pivotal role in Arabidopsis phosphate nutrition".
    • May - July 2012. We were very pleased to host a 3 month visit of Snrta. Isabel Ballesta, an outstanding PhD student of Prof. Cristina Echevarria (Universidad de Sevilla, Espana). Isabel collaborated with us on her biochemical studies of PEP carboxylase and its in vivo post-translational modifications (phosphorylation vs. monoubiquitination) in developing vs. germinating sorghum seeds. We all wish you could have stayed here longer, but thanks for enriching our lab and lives, and Canada with your visit!
    Dec 2011. Prof. Mike Shane arrives from School of Plant Biology, Univ. of Western Australia, for a 6 month sabbatical visit to study the metabolic adaptations of Harsh Hakea cluster (proteoid) roots to nutritional Pi deprivation. Harsh Hakea is a native 'extremophile' plant that thrives in the ancient, nutrient impoverished soils of Western Australia.

    Sept 2011. MSc student Eric Fedosejevs presents invited lecture on "In vivo phosphorylation of castor seed sucrose synthase", and Plaxton talks about the "Remarkable Diversity of Phosphoenolpyruvate Carboxylase" at the Plant Protein Phosphorylation Workshop (Lake Tahoe, USA).

    July 2011.MSc student Whitney Robinson won the President's award from the Canadian Society of Plant Biologists for giving the best student oral presentation at the recent Plant Canada 2011 conference in Halifax.  Her talk was entitled "Feeding hungry plants. The role of secreted purple acid phosphatases in Arabidopsis phosphate nutrition". Congratulations Whitney!

    • July 2011. Plaxton assumes the Presidency of the Canadian Society of Plant Biologists (formerly, the Can. Soc. Plant Physiologists) for the next 2 years (for more info please visit: http://www.cspp-scpv.ca/ ).
    • June 2011. MSc student Katie Dalziel successfully defended her MSc thesis on "Phosphorylation of bacterial type phosphoenolpyruvate carboxylase from developing castor oil seeds at Thr-4 and Ser-451". Katie will be entering medical school at Queen's this coming Sept. and we wish her every possible success w/ this new endeavor!
    • April 2011. PhD student Brendan O'Leary successfully defended his PhD thesis on the "In vivo regulatory phosphorylation of bacterial type phosphoenolpyruvate carboxylase from developing castor oil seeds". Brendan will soon be carrying out post-doctoral research in the U.K. with Prof. Lee Sweetlove at the Dept. of Plant Sciences, Oxford Univ. All best wishes for continued research success Brendan - you will succeed where others falter!

    • March 2011. PhD student Brendan O'Leary presents invited seminar on "Castor Seed Metabolism: Biochemical and Molecular Biology Opportunities" at a "Development of the Castor Sector in Ontario", meeting (Guelph ON) organized by the Erie Innovation and Commercialization Ctr. and Univ. of Guelph.
    • February 2011. Plaxton presents invited seminar on "Biochemical Flexibility of Hungry Plants" while participating in the "International Plant Phosphorus Workshop" organized by colleagues at the Univ. of Western Australia. While in the Perth region Plaxton also presented research seminars on "The Myth of Phosphite Fertilizers" (at UWA's School of Plant Biology's Summer Grad School on beautiful Rottnest Island) & "The Remarkable Diversity of Plant PEP Carboxylase" (at UWA's amazing Plant Energy Biology Centre, an incredibly well funded, staffed, & equipped Australian Research Council Centre of Excellence).
    • August 2010. PhD Student Brendan O'Leary was selected to give an oral presentation on "In vivo multi-site phosphorylation of bacterial-type phosphoenolpyruvate carboxylase from castor oil seeds" in the "Enzyme Regulation" minisymposium at the joint annual meeting of CSPP & ASPB in Montreal.
    • June 2010. PhD Student Brendan O'Leary received the "Best Student Oral Presentation" award at the 2nd Banff Conference on Plant Metabolism  for his talk entitled: "In vivo multi-site phosphorylation of bacterial-type phosphoenolpyruvate carboxylase from castor oil seeds".
    • June 2010. Plaxton presents plenary lecture entitled: "Post-translational control of novel PEP carboxylase isoforms in castor oil seeds" at the 2nd Banff Conference onPlant Metabolism.
    • April 2010.  Dr. Hue Tran successfully defended her PhD thesis on "The Influence of Phosphate Deprivation on the Secreted Proteome of Arabidopsis thaliana". Hue then departed for post-doc research in plant secondary metabolism and genomics with Dr. Dae-Kyun Ro (Univ of Calgary). We greatly miss Hue, and wish her every possible success for her post-doc and future scientific career.

    • September 2008. Mr. Brenden Hurley successfully defended his MSc thesis on "Making Sure Hungry Plants Get Fed: The Dual-targeted Purple Acid Phosphatase Isozyme AtPAP26 is Essential for Efficient Acclimation of Arabidopsis thaliana to Nutritional Phosphate Deprivation". Brenden  has since initiated PhD thesis research on the genomics of plant pathogen defense responses with Dr. Darrell Desveaux at Univ. of Toronto. Gone but not forgotten! Good luck Brenden... !

    • September 2009.  'Queen's news centre' releases a Press Release entitled Queen’s research inspires national guidelines for phosphite 'fertilizers' that pertains to an interesting practical outcome of NSERC funded research in the Plaxton laboratory. Owing to our research documenting the very harmful effects of the important agricultural commodity, phosphite (HPO3-), on the growth of phosphate starved plants, The Fertilizer Section of the Canadian Food Inspection Agency (CFIA) recently banned (June 2009) sales of so-called ‘phosphite fertilizer’ products in Canada (described in CFIA trade memorandum T-4-12 on "Requirements for Phosphite and Phosphorous Acid Materials Represented for Use as Fertilizers" at http://www.inspection.gc.ca/english/plaveg/fereng/tmemo/t-4-121e.shtml)
    • July 2009. Dr. Joonho Park was awarded a 2 year postdoctoral fellowship from Queen's University-Province of Ontario, Ministry of Research & Innovation. Total value of the fellowship is $50,000 per year (includes $20 K per year from supervisor's grant).  These funds will be used to help offset cost of Dr. Park's salary, as well as materials & supplies etc needed for his research in the Plaxton lab.
    • June 2009. Plaxton presents plenary lecture entitled "Metabolic biochemistry helps to close the gap in plant functional genomics" at the Annual Meeting of the Canadian Society of Plant Physiologists (Simon Fraser Univ., Burnaby, BC)
    • June 2009. Plaxton presents lecture entitled "Metabolic biochemistry helps to close the gap in functional genomics" at Monsanto Company (St. Louis, MO, USA).
    • June 2009. Plaxton presents symposium lecture: "Regulatory monoubiquitination of PEP carboxylase in germinating castor seeds" at the 2nd Annual Plant Proteomics Symposium, University of Missouri, Columbia MO, USA
    • Oct. 2008: Dr. Joonho Park begins post-doctoral research in the Plaxton lab. Joonho recently completed his PhD under supervision of Prof. Gerry Edwards (Washington State Univ.) where he integrated numerous genetic, biochemical, and cell biology/imaging tools to study single celled C4 photosynthesis in a desert plant that is native to the middle east.
    • August 2008: Former MSc student Glen Uhrig's paper on the "Regulatory monoubiquitination of PEP carboxylase in germinating castor seeds" was selected as a J. Biol. Chem. 'paper of the week' and was highlighted on the cover of the JBC issue that his article appeared in.
    • July 2008: Plaxton's Queen's Research Chair in "Plant Biochemistry" was successfully renewed for a second 5 year term.
    • Sam GennidakisJune 2008: Former MSc student Sam Gennidakis received the prestigious "Ragai Ibrahim Award" from the Canadian Society of Plant Physiologists (CSPP) for the "Best paper published by a student member of the CSPP in 2007" (see Plant Journal 52: 839-849)
    • Brenden HurleyJune 2008: MSc Student Brenden Hurley received the "Best Student Oral Presentation" award at Annual Meeting of CSPP (Ottawa) for his talk entitled: "The purple acid phosphatase AtPAP26 is required for efficient acclimation of Arabidopsis thaliana to nutritional phosphate starvation".
    • Allison Gregory
    • June 2008: BSc Student Allison Gregory received runner-up award for "Best Student Poster Presentation" at Annual Meeting of CSPP (Ottawa) for her poster entitled: "In vivo regulatory phosphorylation of the PEP carboxylase AtPPC1 in phosphate starved Arabidopsis".
    • June 2008: Plaxton presented a plenary lecture entitled: "Metabolic biochemistry helps to close the gap in functional genomics" at the Annual Meeting of the North American Phytochemical Society (Washington State Univ.).
    • Sept 2007: Mr. Glen Uhrig defended his impressive MSc Thesis on "Co-immunoprecipitation Analysis of the Phosphoenolpyruvate Carboxylase Interactome of Developing Castor Oil Seeds". Glen then worked in our lab as a research assistant until May 2008 (leading to discovery of PEP carboxylase regulatory monoubiquitination in germinated castor seeds), after which he departed to initiate PhD thesis research on plant protein phosphatases in Dr. Greg Moorhead's lab at Univ of Calgary. Good luck Glen!

    Sports, Music, & the Great Outdoors

    The Great Outdoors
      • Being a firm believer in the "healthy body = heathy mind" concept, I am an avid cyclist, sea kayaker / canoeist, and skier (downhill / nordic). Apart from paddling all around the remarkably diverse waterways of the Kingston region, I look forward to annual wilderness canoe/kayak camping trips with my family, particularly in La Verendrye Park, a vast natural paradise in Quebec with amazing and unspoiled nature. 
      • Plaxton Summer
      • Plaxton Winter
      • I enjoy playing an upright  bass in "The Whiskey River Band" an all acoustic band (featuring guitars, dobro, harmonica, piano, accordion, & percussion) that rehearses each week and performs in local clubs once or twice amonth, as well as at the Limestone City Bluesfest.
      •  The Whiskey River Band - July 2013


    My research program focuses on understanding the organization and control of plant carbohydrate metabolism and the biochemical adaptations of phosphate-starved plants. This work integrates a variety of biochemical, proteomic, molecular biology, and genomic tools to characterize the molecular and functional properties, and protein:protein interactions of key enzyme proteins.  We are particularly interested in post-translational enzyme modification by phosphorylation, monoubiquitination, and glycosylation since these can play pivotal roles in regulating an enzyme's activity, subcellular location, protein:protein interactions &/or turnover in response to various extra- or intracellular signals.
    Castor Beans

    Systems that we are currently studying include developing and germinating castor oilseeds, and suspension cell cultures and seedlings of the model plant Arabidopsis thaliana. Our research has significant applications to problems in Canadian agriculture including the: (1) targeted modification of storage oil versus protein levels in oilseeds such as canola or soybean, (2) optimizing plant-based conversion of atmospheric CO2 into renewable energy sources such as biodiesel and ethanol, and (3) development of phosphate-efficient crops, urgently needed to reduce mankind’s rampant but inefficient use of non-renewable, unsustainable, and polluting phosphate fertilizers.

    Queens UniversityNSERCCIHR
    Generous funding of our research by NSERC and the Queen's Research Chairs Program is gratefully acknowledged. We are also indebted to the CIHR for their support of the Queen's Protein Function Discovery Research and Training Program.


    Traditional undergraduate courses in biochemistry tend to focus on the conserved aspects of metabolic pathways: those established through studying relatively few "model" organisms, typically mammalian. In contrast, BIOL-334 is intended to give students an appreciation of biochemical adaptation. We survey the myriad of strategies by which diverse organisms alter the basic biochemical plan to meet the challenges of living in a wide range of environments. Thus, this course compares and contrasts various aspects of bioenergetics, metabolism and its control with an emphasis on: (i) fundamental similarities and distinctions between animal, plant and microbial metabolism, and (ii) examples of how the survival of various species in 'extreme' environments is highly dependent upon key adaptations at the biochemical/metabolic level of biological organization. We also discuss the importance of proteomic and enzyme research in functional genomics and biotechnology. BIOL334 course info
    Life on earth has radiated to exploit virtually every conceivable habitat and lifestyle. Biochemical adaptation is a fundamental aspect of biological diversity for it integrates molecular structure, with metabolic function and control. The purpose of the seminar course is to survey the impressive array of mechanisms whereby animal, plant, & microbial 'extremophiles' acclimate at the biochemical level to  environmental stresses such as extremes of temperature or pressure, lack of oxygen, salt stress, oxidative stress, and desiccation.
    This graduate course explores contemporary research ideas and techniques used to elucidate plant metabolism and its control. Topics include plant signal transduction, plant metabolic adaptations to abiotic and biotic stress, as well as the application of proteomics, genomics, and molecular biology for comprehending plant metabolism and the production of 'improved' transgenic crops via metabolic engineering.