A genetic approach to elucidate the pathway of patulin degradation by a biocontrol yeast
R. Castoria, D.V. De Felice, S. D’Alonges, G. Ianiri, J. Heitman, A. Idnurm and S.A.I. Wright.
Journal of Plant Pathology Volume 90 (2, Supplement) August 2008, Book of Abstract, 9th International Congress of Plant Pathology, August 24-29, 2008 Torino,Italy,. 507 pages.
2008
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A genetic approach to elucidate the pathway of patulin degradation by a biocontrol yeast
The basidiomycetous yeastRhodotorula glutinis(teleomorphRhodosporidiumspp.)can be isolated from diverse environments.R. glutinisstrain LS11 was isolated from apple, and was subsequently found to protect apples from postharvest rots caused byPenicillium expansumandBotrytis cinerea. It is also able to degrade and detoxify the mycotoxin patulin, which is formed in apples infected withP. expansum. Patulin is a very potent toxin and only minute concentrations are permitted in commercial apple juice. The extreme sensitivity ofEscherichia colito patulin and its insensitivity to the degradation products was utilized to develop an assay for screening of mutants defective in patulin degradation.In order to find the genes responsible for enzymatic degradation, we generatedAgrobacterium-mediated insertion mutants and are in the process of constructing a genomic library. The genes of mutants that do not degrade patulin are being identified. The genome library is being constructed inCryptococcus neoformansstrain JEC43, a basidiomycetous yeast strain that is sensitive to patulin and is unable to degrade it. To have additional genetic tools forR. glutinisLS11 uracil auxotrophs were selected on minimal medium supplemented with 5-FoA (5-fluoro-orotic acid).This approach yielded mutants in genes for enzymes involved in uracil biosynthesis,URA3(orotidine-5’-phosphate decarboxylase) orURA5(orotate phosphoribosyltransferase). In order to identify the gene mutated, each auxotroph was complemented with theURA3andURA5genes ofC. neoformans. Of eight auxotrophs analysed, two were auxotrophs for URA3 and six for URA5. The transformants were confirmed phenotypically and genotypically.