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Impact of OTAbZIP on Ochratoxin A production, mycelium growth and pathogenicity of Aspergillus westerdijkiae under water activity stress

Summary

Researchers studied how a specific gene (OTAbZIP) in a fungus called Aspergillus westerdijkiae controls the production of ochratoxin A, a poisonous substance that can contaminate food. By removing this gene, scientists found that the fungus could no longer produce the toxin, even when exposed to different moisture levels. This discovery could help prevent food contamination with this dangerous mycotoxin and protect human health.

Background

Aspergillus westerdijkiae is a major producer of ochratoxin A (OTA), a highly toxic and carcinogenic mycotoxin found in various food and feed products. Water activity is a key environmental factor affecting mycotoxin production during food and feed storage. The OTAbZIP gene, a bZIP transcription factor, plays a crucial role in controlling mycotoxin production in response to environmental stress conditions.

Objective

This study explored the regulation of OTA biosynthesis in A. westerdijkiae fc-1, focusing on the OTAbZIP gene’s influence under water activity stress. The research aimed to understand how deletion of the OTAbZIP gene affects OTA production, mycelium growth, and pathogenicity under varying water activity conditions.

Results

The OTAbZIP mutant demonstrated improved growth tolerance under high water activity (0.96 aw) and moderate water activity (0.91 aw) compared to wild-type. The mutant strain did not produce OTA under any water activity condition, while wild-type produced OTA with downregulated biosynthetic gene expression under stress conditions. The hog1 gene expression was significantly lower in the mutant than wild-type under water activity stress.

Conclusion

Deletion of the OTAbZIP gene greatly reduces OTA production and affects the strain’s adaptability to water activity stress. The OTAbZIP gene regulates OTA biosynthesis by controlling the expression of biosynthetic genes and is involved in the HOG-MAPK pathway’s response to water activity stress, though it does not significantly affect pathogenicity.
  • Published in:Mycology,
  • Study Type:Experimental Study,
  • Source: 10.1080/21501203.2024.2355333, PMID: 39678641
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