Abstract
Aspergillus nidulans possessed 16 putative amylolytic genes consisting of 7 α-glucosidase (agdA-F), 7 α-amylase (amyA-F), and 2 glucoamylase (glaA and B) genes on the genome. Among them, the agdA, agdB, agdE, agdF, amyA, amyB, amyF, and glaB genes were induced by isomaltose. AmyR, a Zn(II)2Cys6 transcription factor, was required for the induction. The isomaltose-inducible genes possessed at least one consensus sequence for AmyR binding, 5′-CGGN8CGG, on each promoter region. None of the amylolytic genes was induced by maltose.
The mRNA levels of the amylolytic genes except for agdC, amyD, and amyG increased under carbon-starved conditions. Release from CreA-dependent carbon catabolite repression was the main cause of the increase, but, the mRNA levels of agdB, agdF, amyB, amyF, and glaB increased to some extent even in a creA mutant. Therefore, both CreA-dependent and -independent mechanisms are involved in the up-regulation of the amylolytic genes under carbon-starved conditions.
