| Summary: | The forest products industry is the largest industry in British Columbia and one of the main
industries in Canada. Sapstain fungi cause cosmetic defects in wood and are a major
problem to the industry. Millions of dollars are spent each year to prevent the growth of
these fungi in sawn wood; however, current control methods are unsatisfactory. Modern
chemical treatments have raised environmental concerns and do not have the duration of
effectiveness desired by the industry. Kiln drying is expensive and not always practical and
the rewetting of wood during transport can allow subsequent fungal growth and stain
production. Current biological control agents are also unsatisfactory as they are unreliable
and do not grow well in many environments. In order to develop new methods for stain
control it is vital to fully understand the relationship between the stairiing fungi and the host
wood. It is likely that the best stain control strategies will integrate these new methods with
existing techniques, incorporating the strengths of each.
The nutrient content in wood affects the growth and melanin production of sapstaining
fungi, and wood extractives are a major source of nutrients for these fungi. Levels of easily
assimilated nitrogen sources in wood are extremely low and organic sources of nitrogen,
such as proteins, are vital for the growth of sapstaining fungi. Fungi produce extracellular
proteases in order to utilise these nitrogen sources, and these enzymes are likely necessary
for fungal growth on wood.
The objective of this thesis was to understand the role of subtilases in the physiology of
sapstaining fungi. To achieve this objective several steps were taken. First, a comprehensive
study of the distribution and sequence variation of subtilases in sapstaining fungi was carried
out. Using the obtained sequences three groups of fungal subtilases were delineated. This is
the Erst report of these groups. Seven full-length sequences were also obtained providing a
basis for future work on these genes. Second, the regulation of three representative
subtilase genes was detemiined, extending what is known about the regulation of fungal
subtilase genes and providing important information on the potential roles of these genes.
Finally, the targeted disruption of opill is described. This is the first targeted disruption in
any sapstaining species of Ophiostoma. The analysis of the obtained disruptants clearly
showed that Opill is involved in nutrient acquisition for exogenous protein sources during
growth in wood. This suggests that Opill could be a useful target for the development of
new control strategies. This work also demonstrates the importance of nitrogen in fungal
growth on wood, which could lead to better decisions in tree harvesting and be used to
assist in the improved application of existing control strategies.
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