Mycotoxin Research

, Volume 34, Issue 2, pp 151–157 | Cite as

First report of an atypical new Aspergillus parasiticus isolates with nucleotide insertion in aflR gene resembling to A. sojae

  • Sui Sheng T. Hua
  • Dan E. Parfitt
  • Siov Bouy L. Sarreal
  • Bertram G. Lee
  • Delilah F. Wood
Original Article

Abstract

Aflatoxins are toxic and carcinogenic secondary metabolites produced primarily by the filamentous fungi Aspergillus flavus and Aspergillus parasiticus and cause toxin contamination in food chain worldwide. Aspergillus oryzae and Aspergillus sojae are highly valued as koji molds in the traditional preparation of fermented foods, such as miso, sake, and shoyu. Koji mold species are generally perceived of as being nontoxigenic and are generally recognized as safe (GRAS). Fungal isolates were collected from a California orchard and a few were initially identified to be A. sojae using β-tubulin gene sequences blasted against NCBI data base. These new isolates all produced aflatoxins B1, B2, G1, and G2 and were named as Pistachio Winter Experiment (PWE) strains. Thus, it is very important to further characterize these strains for food safety purposes. The full length of aflR gene of these new isolates was sequenced. Comparison of aflR DNA sequences of PWE, A. parasiticus and A. sojae, showed that the aflatoxigenic PWE strains had the six base insertion (CTCATG) similar to domesticated A. sojae, but a pre-termination codon TGA at nucleotide positions 1153–1155 was absent due to a nucleotide codon change from T to C. Colony morphology and scanning microscopic imaging of spore surfaces showed similarity of PWE strains to both A. parasiticus and A. sojae. Concordance analysis of multi locus DNA sequences indicated that PWE strains were closely linked between A. parasiticus and A. sojae. The finding documented the first report that such unique strains have been found in North America and in the world.

Keywords

Aflatoxins Aspergillus sojae Aspergillus parasiticus aflR Phylogenetics 

Notes

Acknowledgements

This work is supported by in-house research program funds from US Department of Agriculture, Agricultural Research Services (Project Numbers: 5325-42000-038 and 5325-42000-039). We thank Perng Kuang Chang for valuable discussion; Debbie L Chingcuanco for comments; Tina Williams, John Pool, and Curtis Tsai for technical assistance.

Compliance with ethical standards

Conflict of interest

The authors declare that they have no conflicts of interest.

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Copyright information

© This is a U.S. Government work and not under copyright protection in the US; foreign copyright protection may apply 2018

Authors and Affiliations

  • Sui Sheng T. Hua
    • 1
  • Dan E. Parfitt
    • 2
  • Siov Bouy L. Sarreal
    • 1
  • Bertram G. Lee
    • 1
  • Delilah F. Wood
    • 1
  1. 1.US Department of Agriculture, Agricultural Research ServiceWestern Regional Research CenterAlbanyUSA
  2. 2.Department of Plant SciencesUniversity of California, DavisDavisUSA

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