Isolation and Characterization of a Genomic DNA Fragment Complementing an nsdD Mutation of Aspergillus nidulans

A genomic DNA fragment of Aspergillus nidulans which complements an nsdD19 mutation of A. nidulans in a cosmid pNSD19 was isolated from the NsdD19+ transformant by in vitro packaging. When the host was transformed by pNSD19, the resulting transformants showed four different kinds (named Tl, T2, T3 and T4) of phenotype, including one (T1 type) identical to the original transformant at a frequency higher than 70% among TrpC+ colonies. They developed sexual organs at different degrees from only sexual development to a little sexual development. The copy number of the transforming DNA was analyzed by Southern hybridization, and gradually reduced from Tl to T4, indicating that more copy number of the DNA yields more sexual organs. The essential region for complementation in pNSD19 was localized to 4.0 kb. Northern blot analysis for total RNA showed an mRNA transcript of about 2.5 kb.