AFLATOXIN CONTROL THROUGH TARGETING MECHANISMS GOVERNING AFLATOXIN BIOSYNTHESIS IN CORN AND COTTONSEED
Location: Food and Feed Safety Research
Title: The Aflatoxin Pathway Regulatory Gene aflR Regulates Genes Outside of the Aflatoxin Biosynthetic Cluster
Submitted to: Ph D Dissertation
Publication Type: Other
Publication Acceptance Date: April 20, 2005
Publication Date: May 20, 2005
Citation: Price, M.S., Yu, J., Bhatnagar, D., Cleveland, T.E., Nierman, W.C., Pritchard, B., Payne, G.A. 2005. The Aflatoxin Pathway Regulatory Gene aflR Regulates Genes Outside of the Aflatoxin Biosynthetic Cluster [Ph D Dissertation]. Raleigh, NC: North Carolina State University. 80 p.
The carcinogen aflatoxin is synthesized by a cluster of genes that are regulated by the transcriptional factor, AflR. Most, but not all of these genes, have a consensus binding site for AflR in their 5’ untranslated region. Because aflR resides within the biosynthetic cluster, is has been assumed that it regulates only genes within the cluster. The objective of this study was to identify those genes transcriptionally regulated by aflR and to determine if it regulates any genes outside the aflatoxin biosynthetic cluster. To address this objective, we employed a cDNA microarray of 5,002 genes from Aspergillus flavus to monitor the expression of genes in a wild type and an aflR deletion strain of A. parasiticus. Nineteen of the twenty-five known genes in the cluster were more highly expressed in the wild type strain. These included all of the genes reported to have a consensus binding site for AflR, as well as other genes within the cluster. This research also identified a new gene within the cluster that has an AflR consensus binding site and is regulated by AflR. Further, nadA, a gene previously reported to be in an adjacent sugar cluster, was found to contain the consensus aflR binding site and to be upregulated in the wild type strain. Finally, two genes that were regulated by AflR in this study lie distant to the aflatoxin cluster. These two genes, one that encodes nitrite reductase and the other that is predicted to encode a hemolysin, were also found to contain an AflR binding site.