Most plants cannot grow when soil temperatures reach levels that are above 100 °F. However, in Yellowstone National Park soil temperatures can be much higher in the geothermal areas, and occasionally plants can be found growing in soils in temperatures up to 125 °F. These plants have a fungus, called Curvularia protuberata that grows in them, and they cannot grow in these soil temperatures without the fungus. The fungus itself is infected with a virus, and the virus also is required for the whole thermal tolerant system of plant, fungus and virus (called a symbiosis) to survive. However, the interactions between the virus and fungus in this system and other microbe-interacting systems in the environment are very poorly understood. A crucial key to the understanding of adaptive changes in response to environmental stress is missing. In addition, very few beneficial viruses have been described or studied.
The long-term goal of the research is to understand how plants and mutualistic microorganisms interact with one another and their surrounding environments to acquire stress tolerance. This project will study the physiology and genetics that define the mechanism of this interaction. Its goals are to:
1) Identify and characterize additional plant-fungus-virus symbionts that are thermotolerant;
2) Identify the genetic expression and metabolite changes of plants and fungi involved in the three way symbiosis during heat stress;
3) Study how the proteins from each organism interact; and
4) Test the genes discovered for their effects on tolerance to heat.
With changes in the Earth's climate and the need to produce more and more food for the increasing human population, learning how plants adapt naturally to environmental changes such as are seen in Yellowstone National Park will provide tools will potential application to agriculture.
This project focused on one of the most fundamental aspects of life on earth, symbiosis. Simply defined, symbiosis is the living together of different species, often involving a microorganism and either a plant or animal. All plants and animals are symbiotic with microorganisms that can have profound impact on the health and physiology of hosts. For example, plants growing in hot geothermal soils require a fungal endophyte (a fungus that lives inside the plant) for heat tolerance and survival in the high stress habitat. The fungal endophyte contains a virus that is also required for heat tolerance of the plants making this a 3-way symbiosis. This NSF funded project focused on defining this 3-way symbiosis and determining if it occurred elsewhere. We discovered that plants growing in geothermal soils in both north and south America contain fungal endophytes that confer heat tolerance and that the fungi also contain viruses. Although the fungi are not genetically related, the viruses are. The fungi also substantially alter plant physiology, a topic for future studies. The significance of this project encompass the basic research findings, science training and new strategies for habitat restoration and mitigating impacts of climate change in agriculture. The research findings indicate that plants growing in geothermal soils in North and South America use the same strategy to adapt; developing symbiotic associations with fungal endophytes. This means that for plants to adapt to environmental stress they must find the right fungal partner and the fungus may require a virus to confer stress tolerance to plants. This helps explain why plants distribute differently across the planet and why some plants become invasive weeds when they are moved to different habitats. The training of future scientists is critical to the economic, political and industrial strength of the US. Several undergraduates, graduates, postdocs and visiting scientists were trained during the project and educated in the ecological importance of symbiosis. More importantly, scientists were trained to think about new potential for symbioses in solving problems in habitat restoration and agriculture. The worlds climate is changing and becoming more unpredictable. The outcome been earlier drier springs leading to increased wildfires, more frequent droughts and less dependable water supplies. The results of this project have allowed us to develop new symbiotic strategies for mitigating the impacts of climate change on natural and agricultural ecosystems. By taking a symbiotic approach, we now know that plants will be able to endure much greater levels of stress allowing for increased success in habitat restoration efforts and increasing agricultural sustainability.
