Molecular characterization and in planta detection of Sclerotinia sclerotiorum endopolygalacturonase genes

Sclerotinia sclerotiorum, a plant pathogenic ascomycete, secretes multiple pectinolytic enzymes that facilitate penetration, colonization, and maceration of the plant tissues. Molecular analysis has previously revealed that the pectinolytic system of the fungus is organized as a multigene family, among which a subfamily of three members encoding for neutral endopolygalacturonase (endoPG) isoforms has been characterized. Here we describe the isolation and characterization of three additional endoPG-encoding genes (pg5, pg6, and pg7) that belong to distinct phylogenetic groups. Pairwise sequence comparison between the known endoPGs from S. sclerotiorum revealed 43% to 97% identity, and the genomic organization of the pectinolytic system showed a great similarity to that of the related necrotroph Botrytis cinerea. During plant pathogenesis, a sequential expression of the endoPG-encoding genes was shown.