Although there is evidence for an interplay of signalling/recognition events at different stages during plant/interactions in arbuscular mycorrhiza, the nature of signalling molecules and signal perception/transduction cesses are so far unknown. Virtually nothing is known of molecular interactions during initial contact between arbuscular mycorrhizal symbionts, but plant mutants which limit fungal development to these first steps (myc-provide proof of the involvement of plant genes. One such pea mutant (P2) has been used to investigate gene expression during early plant-fungal interactions by differential RNA display. Partial transcriptome analysis indicated frequent similarities in up-regulated genes in Glomus mosseae- inoculated mutant and non-mutant genotypes. One of these has been putatively identified as a plant Cip serine protease and its eventual role in events of arbuscular mycorrhiza interactions is discussed.