Molecular cloning and characterization of a transcriptional activator gene, amyR, involved in the amylolytic gene expression in Aspergillus oryzae

A gene, designated amyR, coding for a transcriptional activator involved in amylolytic gene expression has been cloned from Aspergillus oryzae by scre ening for a clone that enabled to reverse the reduced expression of the a-a mylase gene (amyB) promoter, amyR encodes 604 amino acid residues of a puta tive DNA-binding protein carrying a zinc binuclear cluster motif (Zn(II)(2) Cys(6)) belonging to the GAL4 family of transcription factors. The amyR gen e disruptants showed a significant restricted growth on starch medium and p roduced little of the amylolytic enzymes including alpha-amylase and glucoa mylase compared with a non-disruptant, indicating that amyR is a transcript ional activator gene involved in starch/maltose-induced efficient expressio n of the amylolytic genes in A. oryzae. In addition, sequencing analysis fo und that amyR, agdA (encoding alpha-glucosidase), and amyA (encoding alpha- amylase), are clustered on a 12-kb DNA fragment of the largest chromosome i n A, oryzae, and that amyR is about 1.5 kb upstream of agdA and transcribed in the opposite direction. Furthermore, transcriptional analysis revealed that the amyR gene was expressed in the presence of glucose comparable to t he level in the presence of maltose, while the amylolytic genes were transc ribed at high levels only in the presence of maltose.