Unravelling mechanisms of wood decay fungal community change in the post-genomic era

About a third of the carbon in the biosphere is in forest ecosystems, mostly in woody plant tissues. Photosynthesis continually adds to this, but in balanced systems a similar amount is broken down to CO2 and H2O, and nutrients are released. The organisms responsible for this decay and cycling are almost exclusively a narrow range of fungi - basidiomycetes and a few ascomycetes. Fungi do not grow in isolation in wood, but form a 3-D mosaic of individuals of the same and different species, which compete with neighbours. Competition leads to community change. Decay rate depends on fungal community composition, climate and the competitive interactions themselves. It is not known how predicted climatic change might influence these interactions and the balance of carbon and nutrient cycling in forests.
Since wood is a solid organic substance, competition for resources is effectively competition for space/territory. Fungi defend and obtain new territory by combative, antagonistic interactions. The overall outcomes are deadlock, where neither species gains headway, or replacement where one species wrests territory from the other, but sometimes partial replacement or mutual replacement. With the complexity of multiple species and environmental conditions, many different antagonistic mechanisms operate. Responses to antagonists include rapid cell division and death, production of pigments, volatile (VOCs) and diffusible organic compounds, and other antimicrobial agents. These responses determine the outcome of interactions, but we do not understand the underlying mechanisms which is crucial for understanding wood decomposition.
Ultimately we want to know how wood decay communities function in natural ecosystems. We will investigate the physiological changes during interactions between species of decay fungi in wood representing the succession from primary coloniser to secondary and tertiary decomposers, under differing environmental conditions. New post-genomic tools allow us to get a complete picture of the genes that are switched on and off during interactions. We will focus on a secondary coloniser Trametes versicolor, and its interaction with another secondary coloniser with which it deadlocks, a primary coloniser that it replaces, and a tertiary coloniser that it is replaced by.
There are 5 main things we want to understand: Firstly, what are the responses of fungal cells during antagonistic confrontation with other mycelia in wood? We will analyse the full complement of transcribed genes, extracellular proteins, VOCs and selected enzymes in the laboratory. Secondly, how are competitive outcomes influenced by environment - temperature, water availability and amount of decay? We will vary conditions and focus on a subset of important genes. Thirdly, are these interaction responses common to wood decay fungi in general? We will interact Trametes versicolor with 15 wood decay species representative of different fungal families and different decay abilities, focusing on a subset of important genes. Fourthly, do responses in the lab reflect the real world? Some of the combinations of fungi paired in wood will be placed on the forest floor, and then changes in expression of important genes measured. Finally, what happens in more complex situations, commonly found in nature, where several wood decay fungi interact with each other simultaneously? We will measure expression of important genes in wood discs colonised with T. versicolor left on the forest floor for 6, 12, 18 and 24 months, allowing natural colonisation from many spores and mycelium in the soil.
This ambitious project uses a logical progression from controlled lab-based experiments to the natural environment using state-of-the-art molecular technologies. It will provide solid foundations for the investigation of complex community-based decay processes, and knowledge to aid the control of timber decay and source novel antimicrobial compounds and other chemicals.

The core academic findings of the project will have a direct impact on academic researchers into fungal biology and ecology, forestry science, climate change scientists, practitioners in the timber industry, pharmaceutical and chemical industry, woodland managers, and the general public:

Academic beneficiaries: Detailed data on mechanisms of interspecific mycelial interactions, gene expression, metabolic costs and relation between community structure and decay will be important for fungal biologists, fungal ecologists, decomposition ecologists, systems ecologists and modellers. The effects of changing environmental conditions on interactions and decay will also be of relevance to research predicting the impact of climate change on biogeochemical cycling, particularly of carbon.

The timber industry: Loss of stored timber and timber in service through wood decay is a major source of financial loss. Understanding the underlying mechanisms, will be helpful in the long term in developing new diagnostic approaches and perhaps control measures for timber decay.

The pharmaceutical and chemical industry: This project will investigate biochemical processes in under exploited fungi. Fungi generate a wide range of novel chemicals through metabolic processes or the modification of extracellular substrates. Some compounds are produced in pure cultures, while others are produced in response to competition from other microbes or during decomposition. These compounds include major pharmaceuticals e.g. antibiotics such as penicillin, statins for cholesterol control, and cylosporines to prevent transplant tissue rejection, industrially valuable chemicals, e.g. citric acid, and new technologies, such as lignocellulosic breakdown products for biofuels and phenolics.

Woodland management: Tree pathogens are a major cause of financial loss, therefore their control is important. Understanding antagonistic interactions will give insights into ways of controlling pathogens. In forestry there is also a need to understand the rate of wood decay and hence nutrient release for continued tree growth.

General public: Though most people do not realize it, fungi are central to our lives. As well as being crucial to ecosystem function they have considerable amenity value as part of the woodland biota, some have yielded major pharmaceuticals and others are food sources or used in production of food. Knowledge of basic fungal biology and ecology of wood decay fungi will underpin future uses of the fungi.