Researchers identify the genetics behind deadly oat blight

A multi-institutional team co-led by a Cornell University researcher has identified the genetic mechanisms that enable the production of a deadly toxin called Victorin, the causative agent of oat blight, a disease that wiped out oat crops in the United States. United. 40s.

Victoria blight is caused by the fungus Cochliobolus victoriae, which produces the Victorin toxin, but until now no one has discovered the genes and mechanisms involved.

“Farmers’ favorite varieties of oats in the 1940s were resistant to crown blight disease, but scientists later found that this was precisely the trait that made those oat varieties susceptible to Victoria blight because the Victorin toxin was taking. targeting that specific plant protein, ”said senior author Gillian Turgeon, professor and chair of the plant pathology and plant microbe biology section of the School of Integrative Plant Science, at Cornell’s College of Agriculture and Life Sciences (CALS). “Uncovering the molecules involved in this fungus-plant interaction is critical to our understanding of how plants respond to attacks from different microbes.”

Most fungal toxins are synthesized by large multifunctional enzymes, and the small peptides created by these enzymes include both toxins and medicines, such as the antibiotic penicillin. But Turgeon and co-author Heng Chooi, a researcher at the University of Western Australia, found that the Victorin toxin is actually synthesized directly in the ribosome, which is an organelle in cells that produces most of the proteins. These small molecules produced in ribosomes are known as post-translationally modified ribosomally synthesized peptides, or RiPPs.

This alternative mechanism for producing small peptides like Victorin, coupled with the fact that fungal genomes likely contain many genes associated with RiPP, could lead to the discovery of additional small molecules, including new toxins and beneficial compounds.

Additionally, first author Simon Kessler, a doctoral student at the University of Western Australia, confirmed the enzyme function of several Victorin genes, including a new enzyme that converts the Victorin peptide to its active form. Surprisingly, the research team found that the Victorin genes encoding these enzymes are scattered in repetitive regions of the pathogen’s genome, in stark contrast to the genes for the more well-known small molecules typically found in compact clusters on fungal chromosomes.

The discovery could help researchers better understand the evolutionary origins of molecules such as Victorin peptides, what determines the virulence of emerging crop diseases, and how to better prevent them in the future.

Turgeon notes that Victorin peptides have also been shown to interact with targets in plant cells called thioredoxins, which are also found in humans, and have a potential site for cancer therapies.

“The discovery that these genes are not found in closely related fungi gives us an idea of ​​how virulence factors are acquired and passed on,” Turgeon said. “Our results from this study greatly expand the potential for small molecule discovery in fungal organisms, which will increase our repertoire of knowledge about their beneficial and harmful activities.”