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Toxins 2017, 9(10), 315; doi:10.3390/toxins9100315

The Aspergillus flavus Homeobox Gene, hbx1, Is Required for Development and Aflatoxin Production

1
Food and Feed Safety Research Unit, USDA/ARS, Southern Regional Research Center, New Orleans, LA 70124, USA
2
Environmental Health Sciences, Arnold School of Public Health, University of South Carolina, Columbia, SC 29208, USA
3
Department of Mechanical Engineering, University of South Carolina, Columbia, SC 29208, USA
*
Author to whom correspondence should be addressed.
Academic Editors: Giancarlo Perrone and Antonia Gallo
Received: 20 September 2017 / Revised: 6 October 2017 / Accepted: 9 October 2017 / Published: 12 October 2017
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Abstract

Homeobox proteins, a class of well conserved transcription factors, regulate the expression of targeted genes, especially those involved in development. In filamentous fungi, homeobox genes are required for normal conidiogenesis and fruiting body formation. In the present study, we identified eight homeobox (hbx) genes in the aflatoxin-producing ascomycete, Aspergillus flavus, and determined their respective role in growth, conidiation and sclerotial production. Disruption of seven of the eight genes had little to no effect on fungal growth and development. However, disruption of the homeobox gene AFLA_069100, designated as hbx1, in two morphologically different A. flavus strains, CA14 and AF70, resulted in complete loss of production of conidia and sclerotia as well as aflatoxins B1 and B2, cyclopiazonic acid and aflatrem. Microscopic examination showed that the Δhbx1 mutants did not produce conidiophores. The inability of Δhbx1 mutants to produce conidia was related to downregulation of brlA (bristle) and abaA (abacus), regulatory genes for conidiophore development. These mutants also had significant downregulation of the aflatoxin pathway biosynthetic genes aflC, aflD, aflM and the cluster-specific regulatory gene, aflR. Our results demonstrate that hbx1 not only plays a significant role in controlling A. flavus development but is also critical for the production of secondary metabolites, such as aflatoxins. View Full-Text
Keywords: homeobox; Aspergillus flavus; development; secondary metabolism; aflatoxin homeobox; Aspergillus flavus; development; secondary metabolism; aflatoxin
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MDPI and ACS Style

Cary, J.W.; Harris-Coward, P.; Scharfenstein, L.; Mack, B.M.; Chang, P.-K.; Wei, Q.; Lebar, M.; Carter-Wientjes, C.; Majumdar, R.; Mitra, C.; Banerjee, S.; Chanda, A. The Aspergillus flavus Homeobox Gene, hbx1, Is Required for Development and Aflatoxin Production. Toxins 2017, 9, 315.

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