pah1: a homeobox gene involved in hyphal morphology and microconidiogenesis in the filamentous ascomycete Podospora anserina

Homeobox-containing genes are widely described among eukaryotic species oth er than filamentous ascomycetes. We describe here the isolation and charact erization of the first homeobox gene (pah1) identified in a filamentous asc omycete. It encodes a putative protein of 610 amino acids containing a typi cal homeodomain with 60 amino acids. Deletion of the pah1 gene enhances the number of male gametes (microconidia), whereas overexpression of pah1 resu lts in a decrease in microconidia. These results led us to suppose that pah 1 may be a repressor of genes involved in the microconidiation process. Mor eover, pah1 is involved in hyphal branching and possibly in the development of female organs.