Cloning and functional analysis of the Aspergillus oryzae conidiation regulator gene brlA by its disruption and misscheduled expression

Abstract

We cloned the brlA gene from Aspergillus oryzae genomic DNA using the A. nidulans brlA gene as a probe. A 3.1-kb EcoRI- BalI genomic DNA fragment was cloned and sequenced. The deduced amino acid sequence revealed 70% identity with A. nidulans BRLA and contained two C2H2 zinc finger motifs in its carboxyl terminus, and the promoter sequence contained a 43-bp highly conserved region, indicating that the cloned gene was an A. oryzae homologue of A. nidulans brlA. Disruption of the brlA gene by homologous recombination resulted in the loss of ability to form conidiophores. These results suggest that the brlA gene of A. oryzae plays a fundamental role in controlling conidiophore development. When the brlA gene was expressed under the control of the amyB promoter in A. oryzae transformants, highly differentiated and compact colonies were observed on a solid medium. The misscheduled expression of the brlA gene in submerged culture, in which conidiation does not normally occur, caused the development of complex conidiophore structures with vesicles, phialides and conidia.