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Molecular and General Genetics MGG

, Volume 248, Issue 3, pp 270–277 | Cite as

TheAspergillus parasiticus polyketide synthase genepksA, a homolog ofAspergillus nidulans wA, is required for aflatoxin B1 biosynthesis

  • Perng-Kuang Chang
  • Jeffrey W. Cary
  • Jiujiang Yu
  • Deepak Bhatnagar
  • Thomas E. Cleveland
Original Paper

Abstract

Aflatoxins comprise a group of polyketide-derived carcinogenic mycotoxins produced byAspergillus parasiticus andAspergillus flavus. By transformation with a disruption construct, pXX, we disrupted the aflatoxin pathway inA. parasiticus SRRC 2043, resulting in the inability of this strain to produce aflatoxin intermediates as well as a major yellow pigment in the transformants. The disruption was attributed to a single-crossover, homologous integration event between pXX and the recipientA. parasiticus genome at a specific locus, designatedpksA. Sequence analysis suggest thatpksA is a homolog of theAspergillus nidulans wA gene, a polyketide synthase gene involved in conidial wall pigment biosynthesis. The conservedβ-ketoacyl synthase, acyltransferase and acyl carrier-protein domains were present in the deduced amino acid sequence of thepksA product. Noβ-ketoacyl reductase and enoyl reductase domains were found, suggesting thatpksA does not encode catalytic activities for processingβ-carbon similar to those required for long chain fatty acid synthesis. ThepksA gene is located in the aflatoxin pathway gene cluster and is linked to thenor-1 gene, an aflatoxin pathway gene required for converting norsolorinic acid to averantin. These two genes are divergently transcribed from a 1.5 kb intergenic region. We propose thatpksA is a polyketide synthase gene required for the early steps of aflatoxin biosynthesis.

Key words

Polyketide synthase gene Aflatoxin Aspergillus parasiticus Gene cluster Anthraquinone 

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Copyright information

© Springer-Verlag 1995

Authors and Affiliations

  • Perng-Kuang Chang
    • 1
  • Jeffrey W. Cary
    • 2
  • Jiujiang Yu
    • 2
  • Deepak Bhatnagar
    • 2
  • Thomas E. Cleveland
    • 2
  1. 1.Department of Cell and Molecular BiologyTulane UniversityNew OrleansUSA
  2. 2.Southern Regional Research Center, Agricultural Research ServiceU.S. Department of AgricultureNew OrleansUSA

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