Dataset Information

Functional Role of Aspergillus carbonarius AcOTAbZIP Gene, a bZIP Transcription Factor within the OTA Gene Cluster.

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 ?AcOTAbZIP 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 OT?. Additionally, in ?AcOTAbZIP 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 ?AcOTAbZIP 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 ?AcOTAbZIP strains and WT strains on artificially inoculated grape berries, demonstrating that OTA is not required by A. carbonarius for the pathogenicity process.

SUBMITTER: Gerin D

PROVIDER: S-EPMC7913050 | biostudies-literature | 2021 Feb

REPOSITORIES: biostudies-literature

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Functional Role of Aspergillus carbonariusAcOTAbZIP Gene, a bZIP Transcription Factor within the OTA Gene Cluster.

Gerin Donato D Garrapa Federica F Ballester Ana-Rosa AR González-Candelas Luis L De Miccolis Angelini Rita Milvia RM Faretra Francesco F Pollastro Stefania S

Toxins 20210202 2

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 w ...[more]

PMID: 33540740

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Project description:Transcription factors (TFs) with the basic leucin zipper domain are key elements of the stress response pathways in filamentous fungi. In this study, we functionally characterized the two bZIP type TFs AtfA and AtfB by deletion (Δ) and overexpression (OE) of their encoding genes in all combination: ΔatfA, ΔatfB, ΔatfAΔatfB, ΔatfAatfBOE, ΔatfBatfAOE, atfAOE, atfBOE and atfAOEatfBOE in Aspergillus nidulans. Based on our previous studies, ΔatfA increased the sensitivity of the fungus to oxidative stress mediated by menadione sodium bisulfite (MSB) and tert-butylhydroperoxide (tBOOH), while ΔatfB was not sensitive to any oxidative stress generating agents, namely MSB, tBOOH and diamide at all. Contrarily, the ΔatfB mutant was sensitive to NaCl, but tolerant to sorbitol. Overexpression of atfB was able to compensate the MSB sensitivity of the ΔatfA mutant. Heavy metal stress elicited by CdCl2 reduced diameter of the atfBOE and atfAOEatfBOE mutant colonies to about 50% of control colony, while the cell wall stress generating agent CongoRed increased the tolerance of the ΔatfA mutant. When we tested the heat stress sensitivity of the asexual spores (conidiospores) of the mutants, we found that conidiospores of ΔatfAatfBOE and ΔatfBatfAOE showed nearly 100% tolerance to heat stress. Asexual development was negatively affected by ΔatfA, while atfAOE and atfAOE coupled with ΔatfB increased the number of conidiospores of the fungus approximately 150% compared to the control. Overexpression of atfB led to a 25% reduction in the number of conidiospores, but increased levels of abaA mRNA and size of conidiospores. Sexual fruiting body (cleistothecium) formation was diminished in the ΔatfA and the ΔatfAΔatfB mutants, while relatively elevated in the ΔatfB and the ΔatfBatfAOE mutants. Production of the mycotoxin sterigmatocystin (ST) was decreased to undetectable levels in the ΔatfA mutant, yet ST production was restored in the ΔatfAΔatfB mutant, suggesting that ΔatfB can suppress ST production defect caused by ΔatfA. Levels of ST were also significantly decreased in the ΔatfAatfBOE, ΔatfBatfAOE and atfAOEatfBOE mutants.

Dataset Information

Functional Role of Aspergillus carbonarius AcOTAbZIP Gene, a bZIP Transcription Factor within the OTA Gene Cluster.

Publications

Functional Role of <i>Aspergillus carbonarius</i><i>AcOTAbZIP</i> Gene, a bZIP Transcription Factor within the OTA Gene Cluster.

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