Submitted to: International Symposium on Poisonous Plants
Publication Type: Proceedings
Publication Acceptance Date: 5/30/2015
Publication Date: 6/5/2015
Citation: Cook, D., Gardner, D.R., Grum, D.S., Pfister, J.A. 2015. Isolation of endosymbionts from Ipomoea carnea and Swainsona canescens that produce swainsonine. International Symposium on Poisonous Plants. 9:201-206.
Interpretive Summary: Endosymbionts that produce swainsonine were isolated from seeds of Ipomoea carnea and Swainsona canescens, and each endosymbiont was found in plants containing swainsonine of the respective species. Given what we now know about the fungal origin of swainsonine in the Fabaceae family and Ipomoea carnea, the occurrence of swainsonine in other species of the Convolvulaceae and at least one species in the Malvaceae family could be explained by the presence of a swainsonine-producing endosymbiont but this remains to be investigated. This study provides another example of a bioactive secondary metabolite produced by a vertically-transmitted fungal symbiont.
Technical Abstract: Fungi including Metarhizium anisopliae (Clavicipitaceae), Rhizoctonia leguminicola (Ceratobasidiaceae), and Undifilum (Pleosporaceae), an endophyte found in the plant genera Astragalus and Oxytropis (Fabaceae) have been reported to be responsible for the production of swainsonine. Based upon the association of swainsonine and fungi, we hypothesized that Ipomoea carnea, a plant of pantropical distribution, and Swainsona canescens, a plant from Australia, are host to a fungal endosymbiont that produce swainsonine. We addressed the following questions: (1) do seeds of these species contain a fungal endosymbiont that produces swainsonine, and if so, (2) do plants of these species contain the same fungal endosymbiont? In summary, endosymbionts that produce swainsonine were isolated from seeds of Ipomoea carnea and Swainsona canescens, and each endosymbiont was found in plants containing swainsonine of the respective species.