Effect of two Kluyveromyces thermotolerans strains, potential biocontrol agents, on polyketide synthase gene expression, ochratoxin A and B accumulation by Penicillium and Aspergillus ochratoxigenic species

PONSONE M.L.; KUHN Y.G; SCHMIDT-HEYDT, M.; GEISEN, R.; CHULZE, S.N

World Mycotoxin Journal

Wagenigen

Año: 2013

1875-0710

In a previous study it was demonstrated that Kluyveromyces thermotolerans strains can reduce both, growth and ochratoxin A accumulation by Aspergillus section Nigri strains. There is no information about the mechanisms related to this reduction; a viable hypothesis can be that the presence of the biocontrol agents can affect ochratoxin A (OTA) biosynthesis by influencing the transcriptional activity of the polyketide synthase (pks) gene, one of the key enzymes in the OTA biosynthesis pathway. The aims of this work were: to determine the effect of two selected strains of Kluyveromyces thermotolerans as potential biocontrol agents and to evaluate if their presence can affect the otapks gene expression of ochratoxigenic Aspergillus and Penicillium species. Growth, ochratoxin A, and B biosynthesis by the fungal strains at the phenotypic and molecular levels were monitored. The results obtained showed that both K. thermotolerans strains evaluated have a strong influence on the growth, ochratoxin A and B biosynthesis and the expression of the mycotoxin biosynthesis genes. However no direct correlation between the influence of the biocontrol yeast on pks gene expression and the ochratoxin A and B production could be found. These results could indicate an inhibitory mechanism by the yeasts, which apparently involve a post-transcriptional mechanism. The data obtained could imply that the production of mycotoxins can be regarded as a kind of adaptation mechanism to environmental stress conditions by these mycotoxigenic species.