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Toxins (Basel). 2017 Oct 12;9(10). pii: E315. doi: 10.3390/toxins9100315.

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

Author information

1
Food and Feed Safety Research Unit, USDA/ARS, Southern Regional Research Center, New Orleans, LA 70124, USA. jeff.cary@ars.usda.gov.
2
Food and Feed Safety Research Unit, USDA/ARS, Southern Regional Research Center, New Orleans, LA 70124, USA. pamyvette@cox.net.
3
Food and Feed Safety Research Unit, USDA/ARS, Southern Regional Research Center, New Orleans, LA 70124, USA. les.scharfenstein@ars.usda.gov.
4
Food and Feed Safety Research Unit, USDA/ARS, Southern Regional Research Center, New Orleans, LA 70124, USA. brian.mack@ars.usda.gov.
5
Food and Feed Safety Research Unit, USDA/ARS, Southern Regional Research Center, New Orleans, LA 70124, USA. perngkuang.chang@ars.usda.gov.
6
Food and Feed Safety Research Unit, USDA/ARS, Southern Regional Research Center, New Orleans, LA 70124, USA. qijian.wei@ars.usda.gov.
7
Food and Feed Safety Research Unit, USDA/ARS, Southern Regional Research Center, New Orleans, LA 70124, USA. matthew.lebar@ars.usda.gov.
8
Food and Feed Safety Research Unit, USDA/ARS, Southern Regional Research Center, New Orleans, LA 70124, USA. carol.carter@ars.usda.gov.
9
Food and Feed Safety Research Unit, USDA/ARS, Southern Regional Research Center, New Orleans, LA 70124, USA. raj.majumdar@ars.usda.gov.
10
Environmental Health Sciences, Arnold School of Public Health, University of South Carolina, Columbia, SC 29208, USA. cmitra@email.sc.edu.
11
Department of Mechanical Engineering, University of South Carolina, Columbia, SC 29208, USA. banerjes@cec.sc.edu.
12
Environmental Health Sciences, Arnold School of Public Health, University of South Carolina, Columbia, SC 29208, USA. achanda@mailbox.sc.edu.

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.

KEYWORDS:

Aspergillus flavus; aflatoxin; development; homeobox; secondary metabolism

PMID:
29023405
PMCID:
PMC5666362
DOI:
10.3390/toxins9100315
[Indexed for MEDLINE]
Free PMC Article

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