|Kistler, H - Corby|
Submitted to: Molecular Plant-Microbe Interactions
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/26/2012
Publication Date: 11/1/2012
Citation: Kistler, H.C., Menke, J., Dong, Y. 2012. Fusarium graminearum Tri12p influences virulence to wheat and trichothecene accumulation. Molecular Plant-Microbe Interactions. 25:1408-1418. Interpretive Summary: The fungus Fusarium graminearum contaminates harvested grain with a compound known as DON or vomitoxin, whose levels in the food supply are strictly regulated. Previous studies have shown that the fungus is remarkably adapted for producing vomitoxin, by precisely regulating the genes unique to toxin synthesis in order to promote toxin accumulation. We have now found, by labeling proteins for toxin synthesis with fluorescent proteins, that some of the previously uncharacterized genes result in the production of "toxin factories;" subcellular vesicles that appear to serve as the staging area for the toxin biosynthetic assembly line. Alterations in components the cellular factory can reduce levels of vomitoxin in grain. These alterations point out potential targets for control strategies designed to reduce toxin concentrations in the food supply. This information will be helpful to plant improvement specialists who are working to develop plants resistant to these pathogens and the toxins they produce.
Technical Abstract: The gene Tri12 encodes a predicted Major Facilitator Superfamily protein suggested to play a role in export of trichothecene mycotoxins produced by Fusarium species. However it is currently unclear how the Tri12 protein (Tri12p) may influence trichothecene sensitivity and virulence of the wheat pathogen Fusarium graminearum. In this study we establish a role for Tri12 in toxin accumulation and sensitivity as well as in pathogenicity toward wheat. A tri12 deletion mutant is reduced in symptom severity and trichothecene accumulation when inoculated on wheat compared to the wild type strain or the mutant complemented with wild type Tri12. Mutants also show reduced radial growth on trichothecene biosynthesis induction medium compared to wild type and the complement strains. In contrast to toxin levels during infection, tri12 mutants accumulate higher levels of trichothecene in liquid medium than the wild type strain. Wild type fungal cells grown in liquid TBI medium develop a distinct subapical swelling and form large vacuoles. A strain having Tri12p linked to green fluorescent protein shows localization of the protein consistent with the plasma membrane. Our results indicate Tri12 plays a role in self-protection and influences toxin production and virulence of the fungus in planta.