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Aspergillus oryzae strains with a large deletion of the aflatoxin biosynthetic homologous gene cluster differentiated by chromosomal breakage

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Recently we divided Aspergillus oryzae RIB strains into group 1, having seven aflatoxin biosynthesis homologous genes (aflT, nor-1, aflR, norA, avnA, verB, and vbs), and group 2, having three homologues (avnA, verB, and vbs). Here, partial aflatoxin homologous gene cluster of RIB62 from group 2 was sequenced and compared with that of RIB40 from group 1. RIB62 showed a large deletion upstream of ver-1 with more than half of the aflatoxin homologous gene cluster missing including aflR, a positive transcriptional regulatory gene. Adjacent to the deletion of the aflatoxin homologous gene cluster, RIB62 has a unique sequence of about 8 kb and a telomere. Southern analysis of A. oryzae RIB strains with four kinds of probe derived from the unique sequence of RIB62 showed that all group 2 strains have identical hybridizing signals. Polymerase chain reaction with specific primer set designed to amplify the junction between ver-1 and the unique sequence of RIB62 resulted in the same size of DNA fragment only from group 2 strains. Based on these results, we developed a useful genetic tool that distinguishes A. oryzae group 2 strains from the other groups' strains and propose that it might have differentiated from the ancestral strains due to chromosomal breakage.

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Correspondence to Osamu Yamada.

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Lee, Y., Tominaga, M., Hayashi, R. et al. Aspergillus oryzae strains with a large deletion of the aflatoxin biosynthetic homologous gene cluster differentiated by chromosomal breakage. Appl Microbiol Biotechnol 72, 339–345 (2006).

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  • Aflatoxin
  • Southern Blot Analysis
  • Unique Sequence
  • Large Deletion
  • Aspergillus Oryzae