RNA-Seq Reveals OTA-Related Gene Transcriptional Changes in Aspergillus carbonarius
Donato Gerin1, Rita M De Miccolis Angelini1, Stefania Pollastro1
1Department of Soil, Plant and Food Sciences, Section of Plant Pathology, University of Bari Aldo Moro, Bari, Italy.
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.
Insights
This study reveals how Ochratoxin A (OTA) production in Aspergillus carbonarius is regulated at the gene expression level. Identifying key genes provides insights into controlling this harmful mycotoxin in food products.
Area of Science:
- Mycology and Food Safety
- Genomics and Transcriptomics
- Secondary Metabolite Biosynthesis
Background:
- Ochratoxin A (OTA) is a potent mycotoxin produced by Aspergillus species, posing risks to human and animal health.
- Aspergillus carbonarius is a primary source of OTA contamination in grapes and derived products, necessitating a deeper understanding of its biosynthesis.
- Transcriptional regulation plays a crucial role in controlling the production of mycotoxins like OTA.
Purpose of the Study:
- To investigate the global gene expression changes in Aspergillus carbonarius associated with Ochratoxin A production.
- To identify key genes and pathways involved in OTA biosynthesis under different cultural conditions.
- To validate the differential expression of candidate genes related to OTA production.
Main Methods:
- RNA-Sequencing (RNA-Seq) was employed to profile gene transcription in four A. carbonarius strains.
- Comparative analysis of gene expression under OTA-inducing (OTAI) versus non-inducing (OTAN) conditions.
- Quantitative real-time PCR (RT-qPCR) was used to validate the expression patterns of selected genes.
Main Results:
- A total of 3,705 differentially expressed genes (DEGs) were identified between OTAI and OTAN conditions.
- Genes involved in primary metabolism, secondary metabolism, transport, stress response, and sporulation were significantly upregulated under OTAI conditions.
- A putative OTA-gene cluster, containing polyketide synthase (pks) and non-ribosomal peptide synthetase (nrps) genes, was identified in the A. carbonarius genome.
Conclusions:
- Gene expression profiling provides valuable insights into the complex regulatory network governing OTA biosynthesis in A. carbonarius.
- The identified DEGs, particularly those in secondary metabolic pathways and transcription factors, are potential targets for controlling OTA contamination.
- The discovery of a putative OTA-gene cluster offers a significant advancement in understanding and potentially manipulating OTA production.
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