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ARS Home » Pacific West Area » Albany, California » Western Regional Research Center » Foodborne Toxin Detection and Prevention Research » Research » Publications at this Location » Publication #309723
Title: First report of an atypical new Aspergillus parasiticus isolates with nucleotide insertion in aflR gene resembling to A. sojae

Author
item Hua, Sui Sheng
item PARFITT, DAN - University Of California, Davis
item Sarreal, Siov
item Lee, Bertram
item Wood, Delilah - De

Submitted to: Mycotoxin Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/6/2018
Publication Date: 2/20/2018
Publication URL: http://handle.nal.usda.gov/10113/5929172
Citation: Hua, S.T., Parfitt, D.E., Sarreal, S.L., Lee, B.G., Wood, D.F. 2018. First report of an atypical new Aspergillus parasiticus isolates with nucleotide insertion in aflR gene resembling to A. sojae. Mycotoxin Research. 34(2):151-157. https://doi.org/10.1007/s12550-018-0309-2.
DOI: https://doi.org/10.1007/s12550-018-0309-2

Interpretive Summary: Aspergillus parasiticus produces four types aflatoxins, B1, B2, G1 and G2 and virtually all known isolates are toxigenic and has been found in all continents . A. sojae is 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, whereas A. parasiticus are associated with the production of carcinogenic aflatoxins. All the PWE strains described in this report had the six base insertion (CTCATG) in the regulator gene aflR similar to domesticated A. sojae but the stop codon TGA was absent. Full functional AFRL transcriptional activator initiates aflatoxin biosynthesis and produced aflatoxins. in PWE strains. Phylogenetic tree indicates that PWE strain is very similar to A. sojae and is probably the link between A. parasiticus and A. sojae. Because PWE produced all four aflatoxin B1, B2, G1 and G2, these strains are new source of aflatoxigenic strains causes contamination in food crops.

Technical Abstract: Aflatoxins are toxic and carcinogenic secondary metabolites produced primarily by the filamentous fungi Aspergillus favus and Aspergillus parasitic 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 is generally recognized as safe (GRAS). Fungal iolates were collected from a California orchard and named as PWE strains. Several PWE strains were found to produce aflatoxins B1, B2, G1 and G2 and were initially identified to be A. sojae using '-tublin gene sequences. Thus it is very important to conduct reliable identification of these strains for food safety purposes. Comparison of aflR DNA sequences from PWE , A. parasiticus and A. sojae, indicated the aflatoxigenic PWE strains had the six base insertion (CTCATG) similar to domesticated A. sojae but a pre-termination coden TGA at nucleotide positions1153-1155 was absent. Colony morphology and scanning microscopic imaging of spore surfaces showed similarity of PWE to both A. parasiticus and A. sojae. Concordance analysis of multi locus DNA sequences indicated PWE strains were most likely to be a link between A. parasiticus and A. sojae. This is the first report that aflatoxigenic pseudo A. sojae has been found in North America.