Ergoline alkaloids (syn. ergot alkaloids) are constituents of clavicipitaceous fungi (Ascomycota) and of one particular dicotyledonous plant family, the Convolvulaceae. While the biology of fungal ergoline alkaloids is rather well understood, the evolutionary and biosynthetic origin of ergoline alkaloids within the family Convolvulaceae is unknown. To investigate the possible origin of ergoline alkaloids from a plant-associated fungus, 12 endophytic fungi and one epibiotic fungus were isolated from an ergoline alkaloid-containing Convolvulaceae plant, Ipomoea asarifolia Roem. & Schult. Phylogenetic trees constructed from 18S rDNA genes as well as internal transcribed spacer (ITS) revealed that the epibiotic fungus belongs to the family Clavicipitaceae (Ascomycota) whereas none of the endophytic fungi does. In vitro and in vivo cultivation on intact plants gave no evidence that the endophytic fungi are responsible for the accumulation of ergoline alkaloids in I. asarifolia whereas the epibiotic clavicipitaceous fungus very likely is equipped with the genetic material to synthesize these compounds. This fungus resisted in vitro and in vivo cultivation and is seed transmitted. Several observations strongly indicate that this plant-associated fungus and its hitherto unidentified relatives occurring on different Convolvulaceae plants are responsible for the isolated occurrence of ergoline alkaloids in Convolvulaceae. This is the first report of an ergot alkaloid producing clavicipitaceous fungus associated with a dicotyledonous plant.

Ergoline alkaloids are constituents of Clavicipitaceous fungi living on Poaceae plants. Ergoline alkaloids as well as volatile oil are also present in Ipomoea asarifolia Roem. & Schult (Convolvulaceae). Treatment of this plant with two fungicides (Folicur, Pronto Plus) eliminates the ergoline alkaloids but not the volatile oil. Elimination of ergoline alkaloids occurs concomitantly with loss of fungal hyphae associated with secretory glands on the upper leaf surface of the Ipomoea plant. Our observations suggest that accumulation of ergoline alkaloids in the Convolvulaceae may depend on the presence of a plant-associated fungus.

Clavicipitaceous fungi producing ergot alkaloids were recently discovered to be epibiotically associated with peltate glandular trichomes of Ipomoea asarifolia and Turbina corymbosa, dicotyledonous plants of the family Convolvulaceae. Mediators of the close association between fungi and trichomes may be sesquiterpenes, main components in the volatile oil of different convolvulaceous plants. Molecular biological studies and microscopic investigations led to the observation that the trichomes do not only secrete sesquiterpenes and palmitic acid but also seem to absorb ergot alkaloids from the epibiotic fungal species of the genus Periglandula. Thus, the trichomes are likely to have a dual and key function in a metabolic dialogue between fungus and host plant.

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