Abstract
Ochratoxin A (OTA) is a mycotoxin harmful for animals and humans. Aspergillus carbonarius is the main responsible for OTA contamination of grapes and derived products. Gene transcriptional profiling of 4 A. carbonarius strains was carried out by RNA-Seq analysis to study transcriptome changes associated with OTA production. By comparing OTA inducing (OTAI) vs. non-inducing (OTAN) cultural conditions, a total of 3,705 differentially expressed genes (DEGs) (fold change > |2| and FDR ≤ 0.05) were identified. Several genes involved in primary metabolic processes, with particular regard to carbohydrate and amino acid metabolisms, secondary metabolic processes, transport, response to stress and sporulation were up-regulated by OTAI conditions at all the analysed sampling times (4, 6 and 8 DAI) or starting from 6 DAI. Highly up-regulated DEGs encoding enzymes involved in biosynthesis of secondary metabolites, oxidoreductases, transporters and transcription factors were examined for their potential involvement in OTA biosynthesis and related metabolic pathways. Differential expression of genes encoding polyketide synthases (pks), non-ribosomal peptide synthetases (nrps) and chloroperoxidase (cpo) was validated by RT-qPCR. Among clusters of co-regulated genes involved in SM biosynthesis, one putative OTA-gene cluster, including both pks and nrps genes, was detected in the A. carbonarius genome.
Highlights
Ochratoxin A (OTA) is a mycotoxin produced by fungal species belonging to the genera Aspergillus and Penicillium
No significant differences were observed in terms of total number of aligned reads between the tested strains (AC49, AC66, AC67 and AC70), conditions (OTAI and OTAN) or sampling times (4, 6 and 8 Days After Inoculation (DAI))
A high Person’s correlation coefficient (R2) (0.86) was observed between RPKM values of the 4 A. carbonarius strains, used as biological replicates, indicating that the approach was appropriate for further analysis (S3 Table)
Summary
Ochratoxin A (OTA) is a mycotoxin produced by fungal species belonging to the genera Aspergillus and Penicillium. It is responsible for several adverse effects on animals and humans, having neurotoxic, carcinogenic, immunotoxic, genotoxic, teratogenic properties, and is classified as possible human carcinogen (group 2B) by the International Agency for Research on Cancer [1]. OTA is a common contaminant of various foods and drinks [2,3,4,5,6], and was first reported in wine by Zimmerli and Dick [7]. Wine is the second source of daily OTA intake for humans [8]. Aspergillus carbonarius (Bainier) Thom is recognized as the main OTA-producing fungus on grapes and derived products [9,10,11].
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