Silencing of the transmembrane transporter (swnT) gene of the fungus Slafractonia leguminicola results in a reduction of mycotoxin transport

Authors: DAS, SUMANJARI - New Mexico State University; Gardner, Dale; NEYAZ, MARWA - New Mexico State University; CHARLESTON III, A - New Mexico State University; Cook, Daniel; CREAMER, REBECCA - New Mexico State University

Submitted to: Fungi
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/16/2023
Publication Date: 3/18/2023
Citation: Das, S., Gardner, D.R., Neyaz, M., Charleston III, A.B., Cook, D., Creamer, R. 2023. Silencing of the transmembrane transporter (swnT) gene of the fungus Slafractonia leguminicola results in a reduction of mycotoxin transport. Fungi. 9(3). Article 370. https://doi.org/10.3390/jof9030370.
DOI: https://doi.org/10.3390/jof9030370

Interpretive Summary: Slafractonia leguminicola infects red clover and other legumes causing black-patch disease. This pathogenic fungus also produces two toxins: slaframine and swainsonine, that are toxic to live-stock grazing on clover hay or pasture infested with the fungus. Swainsonine toxicosis causes loco-ism while slaframine causes the slobbers syndrome. The mechanism of toxin secretion by this fun-gus is poorly understood. The aim of this research was to investigate the role of a putative trans-membrane transporter, swnT, in mycotoxin transport. swnT was silenced by RNA interference using the silencing vector Psilent1 which included inverted repeat transgenes of swnT. This resulted in significant reduction in swnT transcript levels compared to the controls. Silencing caused a decline in active efflux of toxins from the mycelia to the media as shown by LC-MS analysis. Transformants in which SwnT was silenced showed higher concentrations of both toxins in the mycelia compared to the concentrations in the media. These transformants exhibited a visibly distinct phenotype with much thicker and shorter mycelia compared to the wild type. These transformants were also unable to infect detached clover leaves, unlike the controls, suggesting that swnT function might play an important role in pathogenesis in addition to toxin transportation. This research demonstrates the importance of this transporter to secretion of mycotoxins for this phytopathogenic fungus.

Technical Abstract: Slafractonia leguminicola infects red clover and other legumes causing black-patch disease. This pathogenic fungus also produces two toxins: slaframine and swainsonine, that are toxic to live-stock grazing on clover hay or pasture infested with the fungus. Swainsonine toxicosis causes loco-ism while slaframine causes the slobbers syndrome. The mechanism of toxin secretion by this fun-gus is poorly understood. The aim of this research was to investigate the role of a putative trans-membrane transporter, swnT, in mycotoxin transport. swnT was silenced by RNA interference using the silencing vector Psilent1 which included inverted repeat transgenes of swnT. This resulted in significant reduction in swnT transcript levels compared to the controls. Silencing caused a decline in active efflux of toxins from the mycelia to the media as shown by LC-MS analysis. Transformants in which SwnT was silenced showed higher concentrations of both toxins in the mycelia compared to the concentrations in the media. These transformants exhibited a visibly distinct phenotype with much thicker and shorter mycelia compared to the wild type. These transformants were also unable to infect detached clover leaves, unlike the controls, suggesting that swnT function might play an important role in pathogenesis in addition to toxin transportation. This research demonstrates the importance of this transporter to secretion of mycotoxins for this phytopathogenic fungus.