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Applied and Environmental Microbiology, August 2002, p. 3737-3743, Vol. 68, No. 8
0099-2240/02/$04.00+0     DOI: 10.1128/AEM.68.8.3737-3743.2002
Copyright © 2002, American Society for Microbiology. All Rights Reserved.

Nonfunctionality of Aspergillus sojae aflR in a Strain of Aspergillus parasiticus with a Disrupted aflR Gene

Tadashi Takahashi,1* Perng-Kuang Chang,2 Kenichiro Matsushima,1 Jiujiang Yu,2 Keietsu Abe,1,{dagger} Deepak Bhatnagar,2 Thomas E. Cleveland,2 and Yasuji Koyama1

Research and Development Division, Kikkoman Corporation, 399 Noda, Noda-City 278-0037, Japan,1 Southern Regional Research Center, Agricultural Research Service, U.S. Department of Agriculture, New Orleans, Louisiana 701242

Received 13 July 2001/ Accepted 3 January 2002

Aspergillus sojae belongs to the Aspergillus section Flavi but does not produce aflatoxins. The functionality of the A. sojae aflR gene (aflRs) was examined by transforming it into an {Delta}aflR strain of A. parasiticus, derived from a nitrate-nonutilizing, versicolorin A (VERA)-accumulating strain. The A. parasiticus aflR gene (aflRp) transformants produced VERA, but the aflRs transformants did not. Even when aflRs was placed under the control of the amylase gene (amyB) promoter of Aspergillus oryzae, the amy(p)::aflRs transformants did not produce VERA. A chimeric construct containing the aflRs promoter plus the aflRs N- and aflRp C-terminal coding regions could restore VERA production, but a construct containing the aflRp promoter plus the aflRp N- and aflRs C-terminal coding regions could not. These results show that the A. sojae aflR promoter is functional in A. parasiticus and that the HAHA motif does not affect the function of the resulting hybrid AflR. We conclude that the lack of aflatoxin production by A. sojae can be attributed, at least partially, to the premature termination defect in aflRs, which deletes the C-terminal transcription activation domain that is critical for the expression of aflatoxin biosynthetic genes.

* Corresponding author. Mailing address: Research and Development Division, Kikkoman Corporation, 399 Noda, Noda City, Chiba 278-0037, Japan. Phone: 81(0)471-23-5527. Fax: 81(0)471-23-5550. E-mail: ttakahashi{at}mail.kikkoman.co.jp.

{dagger} Present address: Graduate School of Agricultural Sciences, Tohoku University, 1-1 Amamiya, Tsutsumi-dori, Aoba-ku, Sendai 981-8555, Japan.

Applied and Environmental Microbiology, August 2002, p. 3737-3743, Vol. 68, No. 8
0099-2240/02/$04.00+0     DOI: 10.1128/AEM.68.8.3737-3743.2002
Copyright © 2002, American Society for Microbiology. All Rights Reserved.



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