Affiliation:
1. National Research Institute of Brewing (NRIB), 3-7-1 Kagamiyama, Higashi-Hiroshima 739-0046, Japan
2. Department of Molecular Biotechnology, Graduate School of Advanced Science of Matter, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima 739-8530, Japan
3. Bio’c Co., Ltd., 111-1 Murocho-Uchida, Toyohashi 441-8087, Japan
Abstract
ABSTRACT
To help assess the potential for aflatoxin production by
Aspergillus oryzae
, the structure of an aflatoxin biosynthesis gene homolog cluster in
A. oryzae
RIB 40 was analyzed. Although most genes in the corresponding cluster exhibited from 97 to 99% similarity to those of
Aspergillus flavus
, three genes shared 93% similarity or less. A 257-bp deletion in the
aflT
region, a frameshift mutation in
norA
, and a base pair substitution in
verA
were found in
A. oryzae
RIB 40. In the
aflR
promoter, two substitutions were found in one of the three putative AreA binding sites and in the FacB binding site. PCR primers were designed to amplify homologs of
aflT
,
nor-1
,
aflR
,
norA
,
avnA
,
verB
, and
vbs
and were used to detect these genes in 210
A. oryzae
strains. Based on the PCR results, the
A. oryzae
RIB strains were classified into three groups, although most of them fell into two of the groups. Group 1, in which amplification of all seven genes was confirmed, contained 122 RIB strains (58.1% of examined strains), including RIB 40. Seventy-seven strains (36.7%) belonged to group 2, characterized by having only
vbs
,
verB
, and
avnA
in half of the cluster. Although slight expression of
aflR
was detected by reverse transcription-PCR in some group 1 strains, including RIB 40, other genes (
avnA
,
vbs
,
verB
, and
omtA
) related to aflatoxin production were not detected.
aflR
was not detected in group 2 strains by Southern analysis.
Publisher
American Society for Microbiology
Subject
Ecology,Applied Microbiology and Biotechnology,Food Science,Biotechnology
Reference56 articles.
1. Barbesgaard, P., H. P. Heldt-Hansen, and B. Diderichsen. 1992. On the safety of Aspergillus oryzae: a review. Appl. Microbiol. Biotechnol.36:569-572.
2. Bennett, J. W. 1979. Aflatoxins and anthraquinones from diploids of Aspergillus parasiticus. J. Gen. Microbiol.113:127-136.
3. Bhatnagar, D., K. C. Ehrlich, and T. E. Cleveland. 2003. Molecular genetic analysis and regulation of aflatoxin biosynthesis. Appl. Microbiol. Biotechnol.61:83-93.
4. Bhatnagar, D., A. H. Ullah, and T. E. Cleveland. 1988. Purification and characterization of a methyltransferase from Aspergillus parasiticus SRRC 163 involved in aflatoxin biosynthetic pathway. Prep. Biochem.18:321-349.
5. LaeA, a Regulator of Secondary Metabolism in
Aspergillus
spp