Analysis of ergot alkaloid gene expression and ergine levels in different parts of Ipomoea asarifolia

Abstract

Background: Ergot alkaloids are renowned for their pharmacological significance and were historically attributed to fungal symbioses with cereal crops and grasses. Recent research uncovered a symbiotic relationship between the fungus Periglandula ipomoea and Ipomoea asarifolia (Convolvulaceae), revealing a new source for ergot alkaloid synthesis. While past studies have emphasized the storage of both the fungus and alkaloids in leaves and seeds, recent work has found they also occur in other plant parts. This study aimed to examine expression of the dmaW gene, which plays a crucial role in ergot alkaloid biosynthesis, and to quantify ergot alkaloid levels across various organs and growth stages of I. asarifolia. Results: Our findings revealed the highest levels of dmaW gene expression in young seeds and young leaves, whereas the highest ergine concentrations were found in mature leaves followed by young leaves. In light of previous studies, we propose three hypotheses to reconcile these conflicting results: the possibility of an inefficient ergot alkaloid biosynthesis pathway, the possibility that different types of ergot alkaloids are produced, and the existence of an ergot alkaloid translocation system within the plant. Furthermore, ergine concentration and ergot alkaloid biosynthesis gene expression were detected in stems, roots, and flowers, indicating that ergot alkaloids are produced and accumulated in all studied parts of I. asarifolia, rather than being solely confined to the leaves and seeds, as previously reported. Conclusions: Overall, our study reveals that ergot alkaloids are produced and accumulated in most parts of I. asarifolia, suggesting a plant-wide biosynthesis and potential transport system, challenging the previous belief that biosynthesis was confined to glandular trichomes on leaves.