PUTATIVE MEMBRANE-COMPONENTS OF SIGNAL-TRANSDUCTION PATHWAYS FOR AMBIENT PH REGULATION IN ASPERGILLUS AND MEIOSIS IN SACCHAROMYCES ARE HOMOLOGOUS

The zinc finger regions of the Aspergillus nidulans PacC transcription factor, mediating regulation of gene expression by ambient pH, and th e Saccharomyces cerevisiae Rim1p transcription factor; mediating contr ol of meiosis and invasiveness, are homologous and both transcription factors undergo proteolytic processing of the C-terminus for conversio n to the functional form. in both cases, functioning of a signal trans duction pathway involving several gene products is a necessary prerequ isite for processing. We now show that the Aspergillus Pall pH signal transduction component is homologous to the Saccharomyces Rim9p meioti c signal transduction component throughout a region containing four hy drophobic, putative membrane-spanning segments. This suggests that Pal l might be a membrane sensor for ambient pH. Deletion of the pall gene established that the less extreme phenotype of pall mutations compare d with mutations in the other five genes of the pH signalling pathway is a general feature of pall mutations.