Laurie Johnson | Xiaohui Bao | Yang (Lilia) Li | Catherine Peters | Xanthe Walker | Fakhra Shahid | Nathan Allen
Laurie Johnson (): Endophyte fungi from extreme environments
Terrestrial plants use symbioses with endophyte and mycorrhizal fungi to enhance survival. One group of endophyte fungi helps plants to survive in harsh environments, for example, being specialized for cold or dry or low-nutrient conditions. My project studied endophytes from the Canadian High Arctic and from local deserts like the Great Sand Hills of southwestern Saskatchewan. Wheat that had been colonized by specific endophyte germinated faster and grew significantly larger within the first week after seeding. These isolates may help agriculture without added chemicals.
Xiaohui Bao (): Mycorrhizae in the Athabaska Tar Sands
Arbuscular mycorrhizae (AM) are associated with ~80% of terrestrial plant species, where they contribute to plant survival and competitiveness by supplying minerals in exchange for sugars produced by photosynthesis. Our lab has shown that AM and other fungal root associates are common even in extreme environments. I am studying root fungi associated with plants like dandelions that are able to grow on tar sands following extraction, a process that intuitively seems likely to have removed all possible soil microbes. Plants that can colonize this extreme environment may be useful for re-establishing soil micro-ecology in a relatively natural and cost-effective manner.
The Athabasca Tar Sands are a vast hydrocarbon reserve in western Canada that are a natural model system to understanding how mycorrhizal fungi respond to petrochemicals. The hydrocarbons are extracted using solvents and hot water, after which the sand is remediated to permit revegetation. I am studying mycorrhizal fungi associated with Taraxacum officinale (common dandelion) collected from unextracted, extracted, and remediated sites. This photo shows that, following extraction of bituminous tar, clean mineral sand has become colonized by dandelions and sowthistle. Surprisingly, although the extraction process was expected to severely deplete the soil microflora, preliminary studies showed that the dandelion roots have abundant AM typical of unextracted sites.
Yang (Lilia) Li: Mycorrhiza diversity
Taraxacum officinale (dandelion) lateral roots form arbuscular mycorrhizae (AM) as well as other root-fungal endophyte associations. I am examining roots containing multiple types of fungi using light, confocal epifluorescence and electron microscopy (EM).
Image to the right: confocal fluorescence microscopy of dandelion roots stained with lactofuchsin shows an aseptate AM hypha (arrow) that has produced arbuscules (A) near the vascular cylinder (V) that forms the core of the root. In addition, septate endophytic hyphae (arrowheads indicate septa) can be found throughout the root cortex. AM and septate fungi often occur close together. In future these species will be identified using molecular methods. This is the first ultrastructural study of dandelion lateral roots. These have closely packed cells in the peripheral cortex, and gaps between cells near the vascular cylinder, consistent with variations in AM morphology. EM will be used to characterize interactions between plant and fungal cells.
Catherine Peters: Endorhizal fungi on Devon Island
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Truelove Lowland, on Devon Island in the Canadian High Arctic archipelago, has been studied since the 1970s as a model for tundra ecology. However, despite intensive study in the late 1980s (Bledsoe et al. 1990 Can J Bot 68: 1848-1856) no plants were found to host endorhizal fungal associations. Recent work in our lab (Ormbsy et al. 2007 Can J Bot, in press) showed that endorhizal fungi were more common in 2004 and 2006 than in previous years, at least for Asteraceae collected on Axel Heiberg Island. Using plant and soil samples collected at Truelove in 2005 from about 20 species, and sensitive confocal fluorescent microscopy methods for visualizing endorhizal fungi, I will be revisiting whether endorhizal fungi are indeed absent from Truelove. |
Xanthe Walker: Endorhizal fungi in Ranunculus
Ranunculus (buttercups) are small herbaceous plants found from the Prairies to the High Arctic, where they are common in moist to marshy sites. Mycorrhizal fungi have seldom been reported from plants growing on wet soils, however our lab showed (Allen et al. 2006 Can J Bot 84: 1094-1100) these fungi are abundant in High Arctic Ranunculus. My project is to characterize endorhizal fungi in Ranunculus from diverse Arctic and Prairie sites.
The image shows Ranunculus nivalis from Axel Heiberg Island, 80ºN, growing by a stream with a temperature of 2.9ºC.
Fakhra Shahid: Mycorrhizae in Equisetum
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Equisetum (horsetails) is the sole remaining genus from a group of primitive plants that were abundant in the Carboniferous period. Today Equisetum is a dominant understory plant in boreal and mixed forests, although the inset shows it can also colonize disturbed sites. I am continuing work to characterize fungi associated with Equisetum roots, in order to better understand their role(s) in forest soil microbial ecology. |
Nathan Allen: Arbuscular mycorrhizae Taraxacum spp; ectomycorrhizae of Dryas octopetala
Arctic plants endure harsh conditions but relatively little is known about their mycorrhizae, due to difficulty of access to remote regions. My current project is to compare arbuscular mycorrhizae (AM) of temperate (Taraxacum officinale) and arctic (T. arcticum and T. hyparcticum) dandelion, imaged with confocal laser scanning microscopy (CLSM).
This CLSM fluorescence image shows a Taraxacum officinale arbuscular mycorrhiza stained with lactofuchsin. Click the  above the still to play the movie (22 MB). (Larger, crisper still)
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