Phylogenetic patterns of bioactive secondary metabolites produced by fungal endosymbionts in morning glories (Ipomoeaee, Convolvulaceae)

Authors: QUACH, QUYNH - Tulane University; CLAY, KEITH - Tulane University; Lee, Stephen; Gardner, Dale; Cook, Daniel

Submitted to: New Phytologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/27/2023
Publication Date: 2/2/2023
Citation: Quach, Q.N., Clay, K., Lee, S.T., Gardner, D.R., Cook, D. 2023. Phylogenetic patterns of bioactive secondary metabolites produced by fungal endosymbionts in morning glories (Ipomoeaee, Convolvulaceae). New Phytologist. 238(4):1351-1361. https://doi.org/10.1111/nph.18785.
DOI: https://doi.org/10.1111/nph.18785

Interpretive Summary: Heritable fungal endosymbiosis is an under-investigated area in plant biology where it has been documented in only three plant families (Convolvulaceae, Fabaceae, Poaceae). An estimated 40% of all morning glory species in the largest tribe Ipomoeaee (Convolvulaceae, morning glory family) have associations with one of two distinct heritable, endosymbiotic fungi (Periglandula and Chaetothyriales) which produce bioactive metabolites such as ergot alkaloids, indole diterpene alkaloids, and swainsonine. These alkaloids have long been of interest for their toxic effects on animals and potential medical applications. Here, we report the occurrence of ergot alkaloids, indole diterpene alkaloids, swainsonine, and the fungi that produce them, based on new data and a synthesis of previous studies in the Convolvulaceae in a phylogenetic, geographic and life-history context. We find that individual morning glory species do not host more than one metabolite-producing fungal endosymbiont (with one possible exception) due to possible costs to the host and overlapping functions of the diverse alkaloids. The symbiotic morning glory lineages occur in distinct phylogenetic clades and host species have significantly larger seed size than non-symbiotic species. The distinct and widely distributed endosymbiotic relationships in the morning glory family are unprecedented in other angiosperms, and provide accessible study systems for understanding heritable plant-fungal symbiosis evolution and their potential functions for host plants.

Technical Abstract: Heritable fungal endosymbiosis is an under-investigated area in plant biology where it has been documented in only three plant families (Convolvulaceae, Fabaceae, Poaceae). An estimated 40% of all morning glory species in the largest tribe Ipomoeaee (Convolvulaceae, morning glory family) have associations with one of two distinct heritable, endosymbiotic fungi (Periglandula and Chaetothyriales) which produce bioactive metabolites such as ergot alkaloids, indole diterpene alkaloids, and swainsonine. These alkaloids have long been of interest for their toxic effects on animals and potential medical applications. Here, we report the occurrence of ergot alkaloids, indole diterpene alkaloids, swainsonine, and the fungi that produce them, based on new data and a synthesis of previous studies in the Convolvulaceae in a phylogenetic, geographic and life-history context. We find that individual morning glory species do not host more than one metabolite-producing fungal endosymbiont (with one possible exception) due to possible costs to the host and overlapping functions of the diverse alkaloids. The symbiotic morning glory lineages occur in distinct phylogenetic clades and host species have significantly larger seed size than non-symbiotic species. The distinct and widely distributed endosymbiotic relationships in the morning glory family are unprecedented in other angiosperms, and provide accessible study systems for understanding heritable plant-fungal symbiosis evolution and their potential functions for host plants.