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The role of Aspergillus flavus veA in the production of extracellular proteins during growth on starch substrates

  • Applied genetics and molecular biotechnology
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Abstract

The aflatoxin-producer and opportunistic plant pathogenic, filamentous fungus Aspergillus flavus is responsible for the contamination of corn and other important agricultural commodities. In order to obtain nutrients from the host A. flavus produces a variety of extracellular hydrolytic enzymes. Interestingly, A. flavus amylase and protease activity are dependent on the global regulator veA, a gene known to regulate morphogenesis and secondary metabolism in numerous fungi. Analysis of starch degradation by fungal enzymes secreted into broths of starch- or corn kernel-based media showed a notable accumulation of glucose in samples of the A. flavus control strain while the deletion veA sample accumulated high levels of maltose and maltotriose and only a small amount of glucose. Furthermore, SDS-PAGE and proteomics analysis of culture broths from starch- or corn kernel-based media demonstrated differential production of a number of proteins that included a reduction in the amount of a glucoamylase protein in the veA mutant compared to the control strain, while an alpha-amylase was produced in greater quantities in the veA mutant. Quantitative real-time PCR and western blot analyses using anti-glucoamylase or alpha-amylase antisera supported the proteomics results. Additionally, an overall reduction in protease activity was observed in the veA mutant including production of the alkaline protease, oryzin, compared to the control strain. These findings contribute to our knowledge of mechanisms controlling production of hydrolases and other extracellular proteins during growth of A. flavus on natural starch-based substrates.

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Acknowledgements

This project was funded by USDA-SCA 58-6435-9-386 and the Department of Biological Sciences at NIU. We wish to thank Jessica Lohmar and Barbara Ball for technical support.

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Authors and Affiliations

  1. Department of Biological Sciences, Northern Illinois University, Dekalb, IL, 60115, USA

    Rocio M. Duran, Scott Gregersen, Timothy D. Smith, Preetida J. Bhetariya & Ana M. Calvo

  2. Food and Feed Safety Research Unit, USDA/ARS, Southern Regional Research Center, New Orleans, LA, 70124, USA

    Jeffrey W. Cary, Pamela Y. Harris-Coward, Christopher P. Mattison & Casey Grimm

Authors
  1. Rocio M. Duran
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  2. Scott Gregersen
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  3. Timothy D. Smith
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  4. Preetida J. Bhetariya
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  5. Jeffrey W. Cary
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  6. Pamela Y. Harris-Coward
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  7. Christopher P. Mattison
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  8. Casey Grimm
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  9. Ana M. Calvo
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Correspondence to Ana M. Calvo.

Additional information

Rocio M. Duran and Scott Gregersen contributed equally to this work.

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Duran, R.M., Gregersen, S., Smith, T.D. et al. The role of Aspergillus flavus veA in the production of extracellular proteins during growth on starch substrates. Appl Microbiol Biotechnol 98, 5081–5094 (2014). https://doi.org/10.1007/s00253-014-5598-6

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  • DOI: https://doi.org/10.1007/s00253-014-5598-6

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