Molecular characterization of the Pri3 gene encoding a cysteine-rich protein, specifically expressed during fruiting initiation within the Agrocybe aegerita complex.

Coding and regulating sequences of Pri3 (a novel gene specifically expressed in both nucleus types of dikaryons during fruiting initiation) were compared within nine strains of the Agrocybe aegerita complex originating from Europe, Asia and Latin America. Highly homologous coding sequences were found; and the 95-amino-acid-long PRI3 deduced proteins all shared eight cysteines and eight glycines, a putative signal peptide suggesting an extra-cellular localization, a protein kinase C site (T(70)) and a cAMP-dependent kinase site (S(74)). The PRI3 proteins presented no significant homologies with already known proteins and constitute a new class of small cysteine-rich proteins. Within the 5' uncoding regions, two leader introns and a putative upstream regulating sequence resembling the QA1-F activator site were highly conserved. Comparison of the gene sequences within the A. aegerita complex suggested a divergent evolution of the European and Asian/Latin American groups of genes.