Abstract
Aspergillus carbonarius is the principal fungal species responsible for ochratoxin A (OTA) contamination of grapes and derived products in the main viticultural regions worldwide. In recent years, co-expressed genes representing a putative-OTA gene cluster were identified, and the deletion of a few of them allowed the partial elucidation of the biosynthetic pathway in the fungus. In the putative OTA-gene cluster is additionally present a bZIP transcription factor (AcOTAbZIP), and with this work, A. carbonarius ΔAcOTAbZIP strains were generated to study its functional role. According to phylogenetic analysis, the gene is conserved in the OTA-producing fungi. A Saccharomyces cerevisiae transcription factor binding motif (TFBM) homolog, associated with bZIP transcription factors was present in the A. carbonarius OTA-gene cluster no-coding regions. AcOTAbZIP deletion results in the loss of OTA and the intermediates OTB and OTβ. Additionally, in ΔAcOTAbZIP strains, a down-regulation of AcOTApks, AcOTAnrps, AcOTAp450, and AcOTAhal genes was observed compared to wild type (WT). These results provide evidence of the direct involvement of the AcOTAbZIP gene in the OTA biosynthetic pathway by regulating the involved genes. The loss of OTA biosynthesis ability does not affect fungal development as demonstrated by the comparison of ΔAcOTAbZIP strains and WT strains in terms of vegetative growth and asexual sporulation on three different media. Finally, no statistically significant differences in virulence were observed among ΔAcOTAbZIP strains and WT strains on artificially inoculated grape berries, demonstrating that OTA is not required by A. carbonarius for the pathogenicity process.
Highlights
Ochratoxin A (OTA) is a mycotoxin with nephrotoxic, carcinogenic, hepatotoxic, neurotoxic, immunosuppressive, and teratogenic effects, classified as a possible carcinogen in humans by the International Agency for Research in Cancer [1].The fungi responsible for OTA contamination in agricultural products belong mainly to the genus Aspergillus, sections Nigri (e.g., Aspergillus carbonarius and Aspergillus niger), Circumdati (e.g., Aspergillus steynii, Aspergillus westerdijkiae), and Flavi (A. albertensis andA. alliaceus), and the genus Penicillium (e.g., Penicillium nordicum and Penicillium verrucosum) [2,3,4,5,6,7]
The cluster included a polyketide synthase (AcOTApks), a nonribosomal peptide synthase (AcOTAnrps), and halogenase (AcOTAhal) genes, proved to be directly involved in OTA biosynthesis [10,11,12], and a hypothetical protein recently annotated as cyclase [13], a cytochrome P450 monooxygenase (AcOTAp450) and a bZIP transcription factor (AcOTAbZIP) [14]
A consensus OTA biosynthetic pathway was identified in A. ochraceus fc-1 by gene deletion approach demonstrating that the AcOTApks, AcOTAnrps, AcOTAP450, AcOTAbZIP, and AcOTAhal orthologue genes of A. carbonarius were directly involved in OTA biosynthesis [18]
Summary
Ochratoxin A (OTA) is a mycotoxin with nephrotoxic, carcinogenic, hepatotoxic, neurotoxic, immunosuppressive, and teratogenic effects, classified as a possible carcinogen in humans (group 2B) by the International Agency for Research in Cancer [1].The fungi responsible for OTA contamination in agricultural products belong mainly to the genus Aspergillus, sections Nigri (e.g., Aspergillus carbonarius and Aspergillus niger), Circumdati (e.g., Aspergillus steynii, Aspergillus westerdijkiae), and Flavi (A. albertensis andA. alliaceus), and the genus Penicillium (e.g., Penicillium nordicum and Penicillium verrucosum) [2,3,4,5,6,7]. The fungi responsible for OTA contamination in agricultural products belong mainly to the genus Aspergillus, sections Nigri (e.g., Aspergillus carbonarius and Aspergillus niger), Circumdati (e.g., Aspergillus steynii, Aspergillus westerdijkiae), and Flavi The cluster included a polyketide synthase (AcOTApks), a nonribosomal peptide synthase (AcOTAnrps), and halogenase (AcOTAhal) genes, proved to be directly involved in OTA biosynthesis [10,11,12], and a hypothetical protein recently annotated as cyclase [13], a cytochrome P450 monooxygenase (AcOTAp450) and a bZIP transcription factor (AcOTAbZIP) [14]. A consensus OTA biosynthetic pathway was identified in A. ochraceus fc-1 (recently re-classified as A. westerdijkiae [17]) by gene deletion approach demonstrating that the AcOTApks, AcOTAnrps, AcOTAP450, AcOTAbZIP, and AcOTAhal orthologue genes of A. carbonarius were directly involved in OTA biosynthesis [18]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
