Directed deletions in the aflatoxin biosynthesis gene homolog cluster of Aspergillus oryzae

Abstract

To investigate the structure of the aflatoxin gene cluster in Aspergillus oryzae, 39 strains belonging to this species were examined for the existence of pksA, fas1A, aflR and vbs, and the results compared with those for ver-1 obtained previously. These five genes are involved in aflatoxin biosynthesis in Aspergillus parasiticus. The strains examined were categorized into three groups; group 1, having the five homologs; 2, having ver-1 and vbs; and 3, having vbs homologs. Long-PCR analysis of the regions between the five homologs in A. oryzae IFO 4135, coupled with Southern-hybridization analysis, shows that those homologs are clustered with the same arrangement as in A. parasiticus. These results suggest that directed deletions of the cluster occur in A. oryzae strains. The possible breakpoints of the deletions in the strains of group 2 and 3 were estimated.

Molecular characterization of atoxigenic strains for biological control of aflatoxins in Nigeria

“…The cypA gene is located toward the telomeric region at the beginning of the aflatoxin gene cluster. The location of the aflatoxin gene cluster in the telomeric region of A. nidulans, A. oryzae and A. flavus facilitates gene loss as well as recombination, DNA inversions, partial deletions, translocations and other genomic rearrangements (Kusumoto et al 2000;Chang et al 2005;Ehrlich et al 2005;Wong and Kenneth 2005;Carbone et al 2007). The large deletions found in the current and previous studies are consistent with these suggestions.…”

“…This gene is involved in the regulation of aflatoxin biosynthesis (Meyers et al 1998;Ehrlich et al 1999;Chang et al 2000). Similar to the current study, the majority of atoxigenic A. flavus and A. oryzae had aflatoxin gene clusters without significant deletions (Kusumoto et al 2000;Chang et al 2005;Lee et al 2006). In these cases, atoxigenicity probably results from SNPs or small deletions in aflatoxin-cluster genes (Calvo et al 2004).…”

“…In the present study, atoxigenic A. flavus isolates from Nigeria were found that did not generate PCR products for several regions within the aflatoxin gene cluster, indicating the presence of large deletions. Deletions within the aflatoxin gene cluster were found previously in isolates of both A. flavus and the closely related A. oryzae (Kusumoto et al 2000;Chang et al 2005). Kusumoto et al (2000) classified strains of A. oryzae into three groups based on the deletion pattern.…”

“…Deletions within the aflatoxin gene cluster were found previously in isolates of both A. flavus and the closely related A. oryzae (Kusumoto et al 2000;Chang et al 2005). Kusumoto et al (2000) classified strains of A. oryzae into three groups based on the deletion pattern. Strains belonging to groups 2 and 3 contained large deletions, while group 1 had a nearly intact aflatoxin gene cluster.…”

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

“…The molecular mechanisms that prevent production of aflatoxins by A. oryzae isolates have been examined only recently. Kusumoto et al (15) found that several strains of A. oryzae (groups 2 and 3) have partial deletions in the aflatoxin gene cluster. However, other A. oryzae strains (group 1) with intact aflatoxin gene clusters also were identified.…”