| The close linkage of the Neotyphodium coenophialum life cycle with that of its host grass Festuca arundinacea implies that the fungus can assess the status of the host plant's life cycle. The fungus appears to exist asymptomaticlly within the host and to elicit no known host defense responses. This implies that the fungus either avoids “triggering,” or is able to evade, the known host defense response systems. Questions of how the host communicates with, or responds to, the endophytic fungus have not been addressed. The above topics are important not only for our understanding of the biology of the grass-endophyte system, but they may also shed light on the determination of pathogen-specificity and on the mechanisms of cell-to-cell communication in plants.; Three aspects of the endophyte grass symbiosis were studied. (1) The response of N. coenophialum cultures to varying concentrations and types of plant growth regulators, (2) Differences in the anatomy of endophyte-infected and endophyte-free tall fescue plants, and (3) gene expression differences between endophyte-infected and endophyte-free tall fescue plants.; Treatment of N. coenophialum cultures with 200μM indole-3-acetic acid inhibited culture growth relative to untreated control cultures. Growth characteristics of cultures treated with napthalino acetic acid, 2-4 dichlorobenzoic acid, 6-benzylamino purine, kinetin, gibberelic acid or lesser concentrations of indole-3-acetic acid were not significantly different from the untreated control cultures.; Mean vessel member diameters were smaller in endophyte-infected tall fescue plants than in endophyte-free tall fescue plants. These differences have potentially significant biological effects and could play important roles in drought tolerance and survival.; Differences in the gene expression patterns of endophyte-infected and endophyte-free tall fescue plants were identified. These differences, however, were either artifactual or fungal in origin and, therefore, no genes important to the interactions were isolated. |
