Quantitative analysis of expressed genes Aspergillus oryzae by sequencing 3′-directed cDNA clones

Sequence analysis of randomly selected 3'-directed cDNA clones has been known to be one of the most powerful methods of examining the genes highly expressed in a tissue or cell type. We constructed a S'-directed cDNA Library from Aspergillus oryzae mycelia, and sequenced 345 randomly selected 3'-directed cDNA clones. Determined nucleotide sequences, not shorter than 30 nt, were compared with one other to generate gene signatures (GSs) and were then compared with GenBank entries to analyze sequence similarity to known genes. A GS for the most highly expressed gene appeared six times, one GS five times, five GSs four times, five GSs three times and 22 GSs twice. In total, 324 clones yielded 268 GSs consisting of 34 redundant GSs appearing at least twice and 234 solitary ones. Forty-three GSs showed similarities ranging from 60% to 99% with known sequences from Genbank. A considerable number of A. oryzae GSs matched those obtained from the sexual structures of A. nidulans suggests that A. oryzae may not be phylogenetically distant from A. nidulans and that A. oryzae may have a sexual life cycle from the ancient period.