Cpc1 mediates cross-pathway control independently of Mbf1 in Fusarium fujikuroi.

The deletion of glnA, encoding the glutamine synthetase (GS), had led to the down-regulation of genes involved in secondary metabolism and up-regulation of cpc1, the cross-pathway control transcription factor. In the present study, a Deltacpc1 mutant was created and used for transcriptional profiling by macroarray analysis. Most of the Cpc1 target genes were amino acid biosynthesis genes besides a homologue of the multi-protein bridging factor MBF1 that binds to the yeast Cpc1 homologue GCN4. We show that Deltambf1 mutants exhibit no Cpc1-related phenotype and that both proteins do not interact with each other in Fusarium fujikuroi. Moreover, results presented here suggest that Cpc1 is not responsible for the GS-dependent down-regulation of secondary metabolism and that its role is focused on the activation of amino acid biosynthesis in response to the amino acid status of the cell. Surprisingly, cross-pathway control is repressed by nitrogen limitation in an AreA-dependent manner.