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

Abstract

Ectomycorrhiza formation is a complex developmental process that is still not well understood. To study this process, we identified genetic markers for mycorrhiza development by differential screening of a cDNA library obtained from fully developed Picea abies – Amanita muscaria mycorrhizas. Twenty‐three cDNA clones were identified that showed significantly altered gene expression during the ectomycorrhizal interaction. A detailed analysis was performed for two fungal cDNA clones, SC13 and SC25, exhibiting the most pronounced differences. SC13 encodes a protein of 184 amino acid residues that shows no homology with any sequence in databases. It was highly expressed in non‐mycorrhizal hyphae, whereas its expression was decreased at least 50‐fold in mycorrhizas and fruit bodies. SC25 encodes a protein of 198 residues that shows weak sequence homology with extensin‐like plant proteins. The expression of this gene was weak in non‐mycorrhizal hyphae but approx. 30‐fold higher in mycorrhizas and fruit bodies. Because the expression of both developmentally regulated fungal genes was identical for mycorrhizas and fruit bodies, a common regulation mechanism for both developmental processes is proposed.