NORTHERN ANALYSIS OF AFLATOXIN BIOSYNTHESIS GENES IN ASPERGILLUS-PARASITICUS AND ASPERGILLUS-SOJAE

RNAs from three Aspergillus parasiticus and three Aspergillus sojae is olates were probed with seven genes involved in aflatoxin biosynthesis . Previously published work and preliminary work in this study demonst rated that these aflatoxin biosynthesis genes were present in the DNA of the isolates. RNA from aflatoxin-producing and O-methylsterigmatocy stin-producing A. parasiticus strains SRRC 143 and SRRC 2043 hybridize d to all of the gene probes tested. However, RNA from a strain of A. p alasiticus that had lost its ability to produce aflatoxin in culture ( SRRC 77) and RNA from one of the A. sojae isolates did not hybridize t o any of the gene probes. Two of the A. sojae isolates hybridized to t he regulatory gene aflR and the structual gene uvm8, which is believed to code for a fatty acid synthase involved in an early step in aflato xin biosynthesis, but not to any of the other five genes of the aflato xin pathway tested. These results suggest that most of the genes invol ved in aflatoxin production are transcriptionally blocked in A. parasi ticus SRRC 77 and all of the A. sojae isolates. The cause of this bloc kage is unknown.