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ARS Home » Southeast Area » New Orleans, Louisiana » Southern Regional Research Center » Food and Feed Safety Research » Research » Publications at this Location » Publication #315029
Title: Regulation of the aflatoxin-like toxin dothistromin by AflJ

Author
item CHETTRI, PRANAV - Massey University
item EHRLICH, KENNETH - Retired ARS Employee
item BRADSHAW, ROSIE - Massey University

Submitted to: Fungal Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/30/2015
Publication Date: 2/12/2015
Citation: Chettri, P., Ehrlich, K.C., Bradshaw, R.E. 2015. Regulation of the aflatoxin-like toxin dothistromin by AflJ. Fungal Biology. 119:503-508.

Interpretive Summary: It is well known that Aspergillus flavus produces the highly toxic and carcinogenic compounds called aflatoxins when the fungus contaminates foods such as corn and peanuts. How aflatoxin is made has been investigated for the last 60 years but the regulation of the genes, the biological switches, involved in making these compounds is less well understood. Surprisingly, unlike the production of many other metabolites in fungi, including Aspergillus flavus, two very different types of regulatory genes appear to be required for turning on the genes. In the present study, the molecule dothistromin, a contaminant of pine produced by the fungus, Dothistroma septosporum, also was found to have the same regulatory genes for its production. Although these genes appear to be very similar in both types of fungi and normally similar genes can be taken from one type of fungus and placed in a second different type of fungus, in this case the gene for the second regulatory molecule called aflJ was not able to substitute for the gene in the other organism. These results prove that this unusual gene is specific to the organism and, although similar, must regulate the production of its product, dothistromin, differently than the AflJ does from Aspergillus flavus.

Technical Abstract: Biosynthesis by Aspergillus parasiticus of aflatoxin, one of the most potent known naturally occurring carcinogens, requires the activity of two regulatory proteins, AflR and AflJ, which are encoded by divergently transcribed genes within the aflatoxin gene cluster. Although the Zn2Cys6 transcription factor, AflR, has been well-studied, the role of AflJ as a transcription regulatory factor is not well understood. An AflJ-like gene (DsAflJ ) is also present in the genome of the pine needle pathogen Dothistroma septosporum and is similarly divergently transcribed from an AflR orthologue (DsAflR). These genes are involved in biosynthesis of dothistromin, a toxic virulence factor related to aflatoxin. DsAflJ mutants produced low levels of dothistromin (<25-fold less than wild-type); this was in contrast to earlier work with A. parasiticus AflJ mutants in which aflatoxin production was more severely impaired. As expected, complementation of D. septosporum mutants with an intact copy of the DsAflJ gene regained production of wild-type levels of dothistromin, although levels were not further increased by over-expression in multi-copy strains. However, heterologous AflJ genes from Aspergillus spp. were unable to complement DsAflJ mutants, suggesting that the proteins function differently in these species.