Repression of hyphal proteinase expression by the mitogen activated protein (MAP) kinase phosphatase Cpp1p of Candida albicans is independent of the MAP kinase Cek1p

Cpp1p is a putative mitogen-activated protein (MAP) kinase phosphatase that suppresses Candida albicans hyphal formation at 25 degreesC through its pr obable substrate, the Cek1p filamentation MAP kinase. Here we report that e xpression of the serum-induced genes SAP4-6 and HYR1 increased several fold in hyphal forms of a cpp1/cpp1 null mutant, while the rate and extent of h yphal development up to 5 h were normal. Therefore, we provide evidence tha t Cpp1p represses hyphal gene expression by acting through a Cek1p-independ ent mechanism. SAP4-6 and HYR1 transcripts were undetectable in a null muta nt of another key regulator of filamentation, Efg1p; thus, Efg1p and Cpp1p oppose each other during the expression of these genes in hyphal forms.