The Aspergillus nidulans stress response transcription factor StzA is ascomycete-specific and shows species-specific polymorphisms in the C-terminal region.

Abstract

Orthologues of the Aspergillus nidulans gene stzA were identified and characterised in an additional 19 fungi. These orthologues were restricted to, and found within all the Pezizomycotina subphyla of the Ascomycota, for which data are available, but not the Saccharomycotina or Taphrinomycotina subphyla. Intron analysis indicated that both intron loss and gain have occurred in this gene. The orthologous proteins demonstrate considerable size variation (between 663 and 897 amino acids); with almost all this variability accounted for by a hyper-variable region that is carboxy terminal to the zinc finger region. The Hypocrea jecorina orthologue (ACE1) has the binding site 5'AGGCA. There is evidence of competition, or interaction, between the ACE1/StzA and AreA binding sites in promoters of stzA and its orthologues, as well as genes involved in the metabolism of amino acids. The A. nidulans and A. fumigatus cpcA promoters have seven potential ACE1/StzA binding sites, six of which are highly conserved in position. Two very closely positioned sites are conserved across 14 of the 19 fungi analysed. Potential CpcA binding sites (5'TGAC/GTCA) have been identified between -50 and -170bp of the ATG start in the promoters of 16 of the stzA orthologues.