# Analysis of the Mycotoxin Levels and Expression Pattern of SWN Genes at Different Time Points in the Fungus Slafractonia leguminicola

## TL;DR

This study examines the production of mycotoxins and gene expression patterns in the fungus Slafractonia leguminicola over time.

## Contribution

The study identifies and compares SWN gene expression and mycotoxin production in cultured fungus and infected plant leaves.

## Key findings

- Gene expression timing in cultured fungus and inoculated leaves aligns with the proposed biosynthetic pathway.
- Swainsonine is produced in significantly higher amounts than slaframine during time course studies.

## Abstract

The fungal plant pathogen Slafractonia leguminicola produces two mycotoxins that affect animals: slaframine, which causes slobbers, and swainsonine, which causes locoism. Slafractonia leguminicola contains the swainsonine-associated 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 transporter). In addition to these genes, two paralogs of swnK, swnK1 (paralog1) and swnk2 (paralog2), are found in S. leguminicola. 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 concentrations 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 and agreed with our proposed biosynthetic pathway. Substantially more swainsonine was produced than slaframine during time course studies.