Biology has been a lifelong fascination that started by watching amoebae through my first microscope at age 10. As an undergraduate and a graduate student at McMaster University, I was introduced to the intricacies of cell and sub-cellular structure revealed by the transmission electron microscope. I combined light and electron microscopy with biochemistry during my Ph.D. program at the University of Calgary to better understand metabolic processes occurring in plant cells during seed development. I added some molecular-based tools to study how proteins are moved and precisely deposited within plant cells when I was a Postdoctoral Fellow at the University of California (San Diego) and a visiting scientist at the University of Florida (Gainesville) and more recently at the Technical University of Munich. As a faculty member in the Botany Department at the University of Guelph, I use these tools and techniques to better understand whole plant development by studying the relationship between plant structure and function at the cellular level.
I am a member of the Canadian Society of Plant Physiologists and the American Society of Plant Physiologists, and I serve on the Editorial Board of Seed Science Research.
BSc, MSc - McMaster University
PhD - University of Calgary
Post-doctoral Fellow - University of California (San Diego)
My research goal is to understand, at a cellular level, how plants develop, survive stress or prepare for periods of inactivity. I personally maintain an active research interest in seed development and germination, Right now, though, my Cell Biology Lab is focusing on processes that control the suicide of cells. Programmed cell death is necessary for the proper development of plants. It is involved in seed development and germination, and in the formation of water conducting tissues. It allows plants to form protective layers such as bark, to shed leaves in autumn and to resist infection. Understanding how programmed cell death is controlled also has direct application to agriculture in the areas of fruit harvesting and controlling over-ripening. Some of the research being addressed in my lab are as follows:
- Protein digesting enzymes involved in programmed cell death (Chris Trobacher, Adriano Senatore, M.Sc. candidates)
Chris is using recombinant DNA technology (tagging proteins with green, yellow and cyan fluorescent protein markers) plus immunocytochemical techniques to localize one of the enzymes that is apparently involved in both developmental and experimentally induced programmed cell death in our first model system, faba bean. He is using a variety of molecular genetic and microscopic approaches to investigate the timing and location of expression of the cell death enzyme and pinpoint its cellular location. Adriano recently entered the lab, and is investigating the potential role of an enzyme homologous to the faba bean programmed cell death related proteinase, but found in tomato. Tomato is a much more amenable species to work on because so much is known about its genetic makeup, and there are a wide variety of mutants available to us. Adriano has also found that there are a number of other protein digesting enzymes related to our target enzyme that appear to function in sequence during the initial, mid and final stages of programmed cell death.
- Do plant cells undergoing programmed cell death display characteristics typical of those in other organisms? (NSERC Post-doctoral Fellow Arunika Gunawardena and Allan DeBono, M.Sc. Candidate)
These researchers are using light and transmission electron microscopy, as well as molecular markers of programmed cell death, to compare the cell death processes seen in various plants. Arunika, in conjunction with my collaborator Dr. Nancy Dengler of the University of Toronto, is investigating an excellent model system in Aponogeton madagascariensis or Lace plant, where programmed cell death is involved in removing a majority of the mesophyll tissue lying between the veins of the leaf during development. She is also following the same process in Monstera, the split leaf philodendron. Allan is using similar tools in his investigation of programmed cell death of the endosperm of tomato seeds following germination, and the influence of the embryo on the process. Seed development in Castor Bean (Ricinus communis) is a past favourite research subject of mine, and in the past few years I was able to look at programmed cell death of the nucellar tissues in developing Castor bean seeds, and the involvement of a fairly novel organelle, the ricinosome, in the process. This research was done in collaboration with Dr. Christine Gietl, Institute for Botany, Technical University of Munich, Freising, Germany.
-on Programmed Cell Death and the Cysteine Proteinases
John S. Greenwood, Michael Helm, and Christine Gietl. 2005. Ricinosomes and endosperm transfer cell structure in programmed cell death of the nucellus during Ricinus seed development. PNAS USA 102: 2238-2243.
Arunika H. L. A. N. Gunawardena, John S. Greenwood, and Nancy G. Dengler. 2004. Programmed Cell Death Remodels Lace Plant Leaf Shape during Development. Plant Cell 16: 60-73.
"A very nice paper on Arunika's model system, the lace plant. One of Arunika's images was selected for the cover art of the January edition of this volume of the journal."
Wenjin Yu and John S.Greenwood. 1996. A cDNA encoding a cysteine proteinase (Accession No. U59465) from Germinated Vicia faba L. (PGR96-080). Plant Physiol. 112: 862
"This paper characterizes the cDNA encoding one of the cysteine proteinases in which we are interested."
Wenjin Yu and John S. Greenwood. 1994. Purification and characterization of a cysteine proteinase involved in globulin hydrolysation in germinated Vicia faba L. J. Exp. Bot. 271: 261-268
This is the first of our research that suggests that this enzyme not only digests seed nutrient proteins but it has other functions as well.
Wen-Jin Yu, Amanda C. Rogers, Lori Ann Korol, Chris Trobacher and John S. Greenwood. A cysteine proteinase from Vicia faba L. involved in programmed cell death. (In final stages of preparation for submission to Can. J. Bot.)
"The paper that establishes our hypothesis that the cysteine proteinase is involved in many, if not all aspects of PCD in this species. It draws on a large amount of research carried out over the last few years and includes a detailed characterization of the gene encoding the cysteine proteinase and comparisons with those from other species."