The homologue of Lentinula edodes ctg1, a target for CDC5 and its interacting partner CIPB, from Coprinopsis cinerea is involved in fruitingbody morphogenesis of C. cinerea

We have previously isolated a target gene for the Lentinula edodes CDC5 (Le.CDC5) containing a c-Mybtype DNA-binding domain. The gene, termed ctg1, contains a 7-bp Le.CDC5-binding sequence (5′-GCAATCT3′) in its transcribed region downstream of the start codon and 6-bp CIPB-binding sequences in the 5′-upstream and transcribed regions. The expression of ctg1 appeared to be cooperatively regulated by Le.CDC5 and CIPB. Here, we found that the gene expression regulation system of ctg1–CDC5– CIPB is conserved in the basidiomycetous mushroom Coprinopsis cinerea. Similar to L. edodes, the Le.CDC5 homologue (named Cc.Cdc5) bound to a 7-bp sequence, 5′-GCAAGCT-3′, in the transcribed region of the ctg1 homologue (Cc.ctg1) and the CIPB homologue (Cc.CipB) to 6-bp sequences in its 5′-upstream and transcribed regions. To study the biological function of the Cc.ctg1 gene (and also the ctg1 gene) in C. cinerea, we bred the C. cinerea homokaryotic fruiting strains, consistently producing a large amount of the Cc.ctg1 (or ctg1) transcript. Analysis of the phenotype of these strains suggested that the Cc.ctg1 gene (or the ctg1 gene) is mainly involved in the regulation of stipe elongation.