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United States Department of Agriculture

Agricultural Research Service

Research Project: ASTRAGALUS AND OXYTROPIS POISONING IN LIVESTOCK Title: Detection and localization of the endophyte Undifilum oxytropis in locoweed tissues

Authors
item Reyna, Roxanna -
item Cooke, Peter -
item Grum, Daniel
item Cook, Daniel
item Creamer, Rebecca -

Submitted to: Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 6, 2012
Publication Date: December 1, 2012
Citation: Reyna, R., Cooke, P., Grum, D.S., Cook, D., Creamer, R. 2012. Detection and localization of the endophyte Undifilum oxytropis in locoweed tissues. Botany. 90(12): 1229-36.

Interpretive Summary: Poisoning of livestock due to grazing on locoweed results in significant economic losses in the western USA. Oxytropis spp. locoweeds are plants containing a seed-transmitted endophyte that produces the toxic alkaloid swainsonine. We sought to identify, localize, and characterize growth patterns of the fungus within the leaves, and petioles of Oxytropis lambertii and Oxytropis sericea plants. Using different microscopic methods the endophyte was detected in the pith tissue of petioles and the vascular bundles of leaves. Additionally, the endophyte appeared to grow between plant cells, and was found closely associated with cell walls where the hyphae did not appear to penetrate host cells. In conclusion, a combination of microscopic methods was effectively used to identify and localize the distribution of locoweed endophytes in plant tissues.

Technical Abstract: Poisoning of livestock due to grazing on locoweed results in significant economic losses in the western USA. Oxytropis spp. locoweeds are plants containing a seed-transmitted endophytic fungus, Undifilum oxytropis, that produces the toxic indolizidine alkaloid swainsonine. We sought to identify, localize, and characterize growth patterns of the fungus within the leaves, and petioles of Oxytropis lambertii and Oxytropis sericea plants. Undifilum oxytropis was transformed with an enhanced green florescent protein (pPd-EGFP), inoculated to locoweeds (Oxytropis sericea), and observed by confocal microscopy. Vegetative hyphae were observed within locoweed tissues using integrated imaging. Topographical images revealed the presence of the endophyte in the pith tissue of petioles. The fungus was identified between plant cells, where the hyphae ramified, but did not appear to penetrate host cells. High spatial resolution bright field images of thin sections revealed that hyphae were closely associated with host cell walls. Observation of Green fluorescent protein by confocal laser scanning microscopy confirmed the presence of the endophyte hyphae throughout leaves and petioles. Similar to the results found in topographical images, the fungus appeared to be obviously present only in the pith of petioles using fluorescence. In contrast, the fungus was identified in the vascular bundle throughout extracellular spaces in leaves. Therefore, a combination of microscopic methods was effectively used to identify and localize the distribution of locoweed endophytes in plant tissues.

Last Modified: 10/23/2014
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