Fungicide resistant Fungi

In the project Arabidopsis thaliana (A. thaliana) will be transformed such that they express double-stranded RNA (dsRNA) targeting mRNA of the Shxdr1 gene in DMI resistant Sclerotinia homoeocarpa (S. homoeocarpa) to render the fungus resistant to DMIs. S. homoeocarpa causes dollar spot in turfgrass, the most economically important disease on golf courses. Isolates of S. homoeocarpa have been identified with practical field resistance to multiple fungicide classes including demethylation inhibitors (DMIs), preventing efficient treatment of dollar spot. The practical field resistant to DMIs arose from a mutation in ATP Binding Cassette (ABC) transporters which efflux DMIs from the fungal cells. Shxdr1 is a transcription factor downstream (Sang et al., unpublished) of the ATP Binding Cassette (ABC) transporters ShPDR1 and ShatrD, which are confirmed to be involved in the detoxification of fungicides (Sang et al., 2015; Hulvey et al., 2012). Furthermore our lab has recently validated the function of Shxdr1 in S. homoeocarpa knockout mutants, which lost resistance to multiple fungicide classes (Sang et al. unpublished). Shxdr1 dsRNA molecules engineered to be produced in the A. thaliana will be taken up by S. homoeocarpa and become integrated in the fungi's innate RNAi mechanisms, silencing Shxdr1 expression. Through the elimination of Shxdr1 transcripts, ShPDR1 and ShatrD will be downregulated preventing the efflux of fungicides out of the fungal cells rendering the fungi sensitive to DMIs. The success of the project in the model A. thaliana may lead to the application of this system in turfgrass.