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Department of Biological Sciences
Confrontation between fungal cells of the same species or different species leads to one of a variety of events including no apparent interaction, avoidance, growth inhibition, death of one or both fungi, or cell fusion (parasitic, vegetative or sexual fusion). Early cellular recognition events are mediated by production and reception of diffusible signals or through direct cell to cell contact mediated by surface ligands and receptors. My research is devoted to two systems chosen for the elucidation of these early events. Longer term goals include definition of the genetic control of signal production, reception and transduction and determination of the universality of these mechanisms within other fungus-fungus interactions. Work of this nature will give insight into diverse areas such as recognition, attachment and disease progression in plant and animal tissues by parasitic fungi and the use of fungi as biocontrol agents of other fungi.
Trichoderma harzianum and Agaricus bisporus
Green molds, including species in the genus Trichoderma, are common contaminants of spawn and compost on commercial mushroom farms. Very severe mushroom crop damage by T. harzianum was noted in Ireland in the mid 1980s and in North America in the early 1990s. Reasons for this change are largely unknown although it has been suggested that problematic strains of T. harzianum have been selected through the narrow range of environmental conditions used to produce mushrooms. Current research goals are: (a) to determine if the production of hydrolytic enzymes (chitinases and glucanases) and toxins by T. harzianum is altered during growth with A. bisporus; (b) to determine the nature of the signal produced by A. bisporus which leads to these altered metabolic functions in T. harzianum; (c) to determine if there are differences in parasitism associated with genetic variation in T. harzianum or between strains of the commercial mushroom and (d) to determine if differences in parasitism are associated with differential signal production and reception between T. harzianum and A. bisporus. A long term goal is to develop procedures which will prevent or disrupt the relationship and thereby result in disease control.
Most fungal hyphae or cells have the ability to grow towards and fuse with other cells. The mechanisms of recognition that there is another cell in the vicinity and directed growth towards that cell are poorly understood processes. In my lab, we are investigating the potential roles of surface fibrils termed "fimbriae" in these processes. This work involves characterization of the proteins and the genes coding for the proteins of fimbriae of the fungal species Microbotryum violaceum, Schizophyllum commune and Coprinus cinereus.
Drs. Paul A Horgen, Ullrich Krull and Chad Gubala, University of Toronto at Mississauga. Development of technologies for monitoring pathogenic microbes in water supplies.
Dr. Dan Rinker, University of Guelph, Vineland Station. Green mould and post harvest spotting diseases of the commercial mushroom.
Dr. Antonet Svircev, AAFC, Vineland Station. Biological control of Erwinia amylovora, the causative gent of apple fire blight and incidence of benomyl resistance in the apple scab pathogen, Venturia inaequalis.
Horgen, P. A. and A. Castle. 2002. The application and potential of molecular approaches to mushrooms. The Mycota (in press).
Svircev, A. M., J. Gill, T. Zhou, A. Castle and M. Chiba. 2000. A comparison of techniques for assessing benzimidazole resistance in Venturia inaequalis. J. Phytopathol. 148: 205-210.
Horgen, P. A. and A. J. Castle. 1999. Genetically engineered mushrooms, are they a blessing or bad news? Mushroom News.
Castle, A. J., D. Speranzini, N. Rghei., G. Alm, D. Rinker and J. Bissett. 1998. Molecular and morphological identification of Trichoderma isolates causing losses on North American mushroom farms. Appl. Environ. Microbiol. 64:133-137.
CURRENT GRADUATE STUDENT RESEARCH
Jennifer Guthrie (MSc 2000-2002) Changes in chitinase activities during interaction between Trichoderma harzianum and Agaricus bisporus.
Durga Sivanesan (MSc 2001-2002) Variation in Pseudomonas tolaasii isolated from spotted mushrooms.