Mycopathologia

, Volume 147, Issue 2, pp 105–112

Repressor-AFLR interaction modulates aflatoxin biosynthesis in Aspergillus parasiticus

  • Perng-Kuang Chang
  • Jiujiang Yu
  • Deepak Bhatnagar
  • Thomas E. Cleveland
Article

Abstract

Regulation of aflatoxin (AF) biosynthesis likely involves a complex interplay of positive- and negative-acting factors that are affected by physiological cues responsive to internal and external stimuli. These factors, presumably, modulate the expression of the AF pathway-specific regulatory gene, aflR, whose product, AFLR, a zinc cluster transcription factor, then turns on or off the transcription of other AF genes. To determine if the AFLR carboxyl region (AFLRC) interacts with positive-or negative-acting proteins, we fused the Aspergillus parasiticus aflR carboxyl coding region(aflRC) to the promoter of A. parasiticusnitrite reductase gene (niiA(p)::aflRC), and transformed it into A. parasiticus SRRC 2043. Transformants that contained two copies of niiA(p)::aflRC, one at the niaD locus and another at the aflR locus, over produced AF precursors independent of the nitrogen source. The higher copy number of the integrated niiA(p)::aflRC correlated with increased production of AF precursors by the transformants as well as increased expression of both aflRC and native aflR in potato dextrose broth and A & M medium. Since aflRC does not encode a DNA-binding domain, the expressed AFLRC should not bind to the promoters of AF pathway genes and affect transcription directly. The results are consistent with AFLRC titrating out a putative repressor that interacts with AFLR under different growth conditions and modulates AF biosynthesis. This interaction also indirectly affects sclerotial development.

Aflatoxin aflR Aspergillus parasiticus repressor sclerotia 

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Copyright information

© Kluwer Academic Publishers 1999

Authors and Affiliations

  • Perng-Kuang Chang
    • 1
  • Jiujiang Yu
    • 1
  • Deepak Bhatnagar
    • 1
  • Thomas E. Cleveland
    • 1
  1. 1.U.S. Department of AgricultureSouthern Regional Research Center, Agriculture Research ServiceNew OrleansU.S.A

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