An international research team from Cornell University, The University
of Western Australia, and The Australian National University have
identified thegenetic mechanismsbehind the production of Victorin, a
deadly toxin that causes Victoria blight of oats, a disease that wiped
out oat crops in the U.S. in the 1940s. The researchers found that
Victorin is encoded by a smallgenethat exists as multiple copies buried
in highly repetitive and rapidly evolving regions of the genome.
Victoria blight is caused by the fungus/Cochliobolus victoriae/, which
produces the Victorin toxin, but until now no one has uncovered the
genes and mechanisms involved. According to Gillian Turgeon, professor
and chair of the Plant Pathology and Plant-Microbe Biology Section of
the School of Integrative Plant Science, in the College of Agriculture
and Life Sciences (CALS), the oat varieties favored by farmers in the
1940s were resistant to Crown Rust disease, which scientists later
discovered was the very trait that made these oat varieties susceptible
to Victoria blight because the Victorin toxin was targeting that
specific plant protein.
Most fungal toxins are synthesized by large, multi-functional 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,
discovered the Victorin toxin is actually synthesized directly in the
ribosome, a cell organelle that makes most proteins. These small
molecules produced in ribosomes are known as ribosomally synthesized and
post-translationally modified peptides, or RiPPs.
First author Simon Kessler from the University of Western Australia
confirmed the enzymatic function of several Victorin genes, including a
novel enzyme that converts the Victorin peptide to its active form. The
research team found that the Victorin genes encoding these enzymes are
scattered across repetitive regions in the pathogen genome â?? a stark
contrast to genes for most known small molecules which are typically
found in compact clusters on the fungal chromosomes.
Researchers identify genetics behind deadly oat blight | Cornell