Analysis of the mycotoxin levels and expression pattern of SWN genes at different time points in the fungus Slafractonia leguminicola

Authors: DAS, SUMANJARI - New Mexico State University; GARDNER, DALE - Retired ARS Employee; Cook, Daniel; CREAMER, REBECCA - New Mexico State University

Submitted to: Microorganisms
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/15/2024
Publication Date: 3/27/2024
Citation: Das, S., Gardner, D.R., Cook, D., Creamer, R. 2024. Analysis of the mycotoxin levels and expression pattern of SWN genes at different time points in the fungus Slafractonia leguminicola. Microorganisms. 12(4). Article 670. https://doi.org/10.3390/microorganisms12040670.
DOI: https://doi.org/10.3390/microorganisms12040670

Interpretive Summary: The fungal plant pathogen Slafractonia leguminicola produces two mycotoxins that affect animals: slaframine and swainsonine. The indolizidine alkaloid swainsonine causes locoism to grazing animals, while slaframine causes slobbers syndrome. Many swainsonine-producing fungi, including S. leguminicola share orthologous gene clusters, “SWN,” which include: a multifunctional swnK gene (NRPS-PKS hybrid), swnH1 and swnH2 (nonheme iron dioxygenase genes), swnN and swnR (reductase genes), and swnT (transmembrane trans-porter). In addition to these genes, two paralogs of swnK, swnK1 (paralog1) and swnk2 (paralog2) are found in S. leguminicola. This study investigated the mRNA levels of all the genes of SWN clusters and level of toxin production in S. leguminicola at different time points. cDNAs from total mRNA were isolated from the S. leguminicola mycelia grown in the culture plates as well as from leaves inoculated with the fungal mycelia at different time points and expression pattern of the SWN genes were analyzed using RT-qPCR. The con-centrations of swainsonine and slaframine production from this fungus at different time points were also examined using liquid chromatography–mass spectrometry. The timing of gene expression was similar in cultured fungus and inoculated leaves. Substantially more swainsonine was produced than slaframine during time course studies.

Technical Abstract: The fungal plant pathogen Slafractonia leguminicola produces two mycotoxins that affect animals: slaframine and swainsonine. The indolizidine alkaloid swainsonine causes locoism to grazing animals, while slaframine causes slobbers syndrome. Many swainsonine-producing fungi, including S. leguminicola share orthologous gene clusters, “SWN,” which include: a multifunctional swnK gene (NRPS-PKS hybrid), swnH1 and swnH2 (nonheme iron dioxygenase genes), swnN and swnR (reductase genes), and swnT (transmembrane trans-porter). In addition to these genes, two paralogs of swnK, swnK1 (paralog1) and swnk2 (paralog2) are found in S. leguminicola. This study investigated the mRNA levels of all the genes of SWN clusters and level of toxin production in S. leguminicola at different time points. cDNAs from total mRNA were isolated from the S. leguminicola mycelia grown in the culture plates as well as from leaves inoculated with the fungal mycelia at different time points and expression pattern of the SWN genes were analyzed using RT-qPCR. The con-centrations of swainsonine and slaframine production from this fungus at different time points were also examined using liquid chromatography–mass spectrometry. The timing of gene expression was similar in cultured fungus and inoculated leaves. Substantially more swainsonine was produced than slaframine during time course studies.