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In A. niger, the genome sequencing of strain CBS 513.88 revealed the presence of a pks gene An15g07920 that has a strong similarity to the pks gene of A. ochraceus involved in OTA biosynthesis ( Pel et al., 2007). In our laboratory, we showed that a fragment of this gene was specific for ochratoxigenic strains of A. niger ( Castellá & Cabañes, 2011), being present only in the strains of A. niger that were able to produce OTA. Interestingly, genome sequencing of A. niger strain ATCC 1015, which does not produce OTA, showed that this strain has a 21-kb deletion in this predicted biosynthetic cluster ( Andersen et al., 2011) and include this pks gene. However, no functional genetic studies have been performed to confirm its role in OTA biosynthesis in A. niger.
The aim of this study is to demonstrate that pks gene expression appears to correlate with OTA production in the fungus indicating a possible role for the product of this gene in OTA biosynthesis in A. niger. We also evaluated the influence of substrate composition and incubation time on pks gene expression and OTA production in A. niger.