Contribution Ratios of amyA, amyB, amyC Genes to High-Level α-Amylase Expression in Aspergillus oryzae

Aspergillus oryzae strains express alpha-amylases abundantly, and the genome reference strain RIB40 has three alpha-amylase genes (amyA, amyB, and amyC). However, there is no information on the contribution ratios of individual alpha-amylase genes to total expression. In this study, we generated single, double, and triple disruptants of alpha-amylase genes by employing a strain (Delta ligD) with high gene-targeting efficiency and pyrG marker recycling in A. oryzae. All the disruptants showed reduced activities of alpha-amylases, and the triple disruptant completely lost activity. Comparative analyses of the activities and mRNA amounts of the alpha-amylases suggest that the contribution of amyA to the alpha-amylase expression is smaller than those of amyB and amyC. The present study suggests that the ability to express a large amount of alpha-amylases in A. oryzae is attributed to gene duplication of genes such as amyB and amyC.