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Jennifer L. LaBundy

Project Topic / Abstract:

“An Ultrastructural Study of the Endophyte-Host Relationship of Epichloè typhina and Elymus vrginicus

A symbiotic relationship exists between the endophytic fungus Epichloe‘ typhina and its host grass Elymus virginicus. Infected grass individuals experience less herbivory, due to fungally produced alkaloids, and tolerate drought stress better than uninfected conspecifics. Occasionally the fungus produces an epiphytic sexual phase, known as a stroma, on the culm of some host tillers. Once fertilized, a layer of perithecia forms over the “primary” stroma. This study examined the ultrastructural aspects of the Elymus-Epichloe’ system using light, scanning electron, and transmission electron microscopy. First, the research evaluated how the presence of the endophyte anatomically affects its host, and tested the hypothesis that there are structural differences (indicating possible physiological differences) between leaves growing above the fungal stroma and those growing below it. Several features were morphologically compared, including gross leaf thickness, cuticle thickness, epidermal cell wall thickness, stomatal density, bulliform cell size, and chloroplast ultrastructure. Secondly, the epiphytic fungal phase was critically examined. Each perithecium, resembling a flask-shaped chamber, has a two-zoned wall, an opercular cap delimited by a distinct histological layer, and contains filiform asci. This study is the first to morphologically investigate the Elymus-Epichloe‘ symbiosis, and is the first to document the ultrastructural nature of the “primary” and perithecial stromal stages for any stroma-bearing endophyte.

Presentations:

1995

  • National Conference of Undergraduate Research (Schenectady, NY)
  • Truman Undergraduate Research Symposium (Kirksville, MO)
  • Sigma Xi Research Symposium (Kirksville, MO)