Identification and expression analysis of two fungal cDNAs regulated by ectomycorrhiza and fruit body formation

Ectomycorrhiza formation is a complex developmental process that is still n ot well understood. To study this process, we identified genetic markers fo r mycorrhiza development by differential screening of a cDNA library obtain ed from fully developed Picea abies-Amanita muscaria mycorrhizas. Twenty-th ree cDNA clones were identified that showed significantly altered gene expr ession during the ectomycorrhizal interaction. A detailed analysis was perf ormed for two fungal cDNA clones, SC13 and SC25, exhibiting the most pronou nced differences. SC13 encodes a protein of 184 amino acid residues that sh ows no homology with any sequence in databases. It was highly expressed in non-mycorrhizal hyphae, whereas its expression was decreased at least 50-fo ld in mycorrhizas and fruit bodies. SC25 encodes a protein of 198 residues that shows weak sequence homology with extensin-like plant proteins. The ex pression of this gene was weak in non-mycorrhizal hyphae but approx. 30-fol d higher in mycorrhizas and fruit bodies. Because the expression of both de velopmentally regulated fungal genes was identical for mycorrhizas and frui t bodies, a common regulation mechanism for both developmental processes is proposed.