Identification and analysis of differentially expressed cDNAs during nonself-competitive interaction between Phlebiopsis gigantea and Heterobasidion parviporum.

The molecular factors regulating interspecific interaction between the saprotrophic biocontrol fungus Phlebiopsis gigantea and the conifer pathogen Heterobasidion parviporum were investigated. We constructed cDNA libraries and used expressed sequence tag analysis for the identification and characterization of genes expressed during the self and nonself-hyphal interaction. cDNA clones from either the pathogen or biocontrol agent were arrayed on nylon membrane filters and differentially screened with cDNA probes made from mycelia forming the barrage zone during nonself-interactions, mycelia growing outside the barrage zones or monocultures. BlastX analysis of the differentially expressed clones led to the identification of genes with diverse functions, including those with potential as virulence factors, such as hydrophobins. Because of the high sequence conservation (r2 = 0.81) between P. gigantea and H. parviporum, a selected number of genes from either fungus were used to monitor the expression profile under varying interaction conditions by virtual northern blot. The results are discussed with respect to the potential role of the induced genes during the nonself-competitive interaction for space and nutrients between P. gigantea and H. parviporum.