Expression and localization of two in planta induced extracellular proteins of the fungal tomato pathogen Cladosporium fulvum.

Expression of two in planta induced genes of the biotrophic fungal tomato pathogen Cladosporium fulvum and accumulation of their products, extracellular proteins (ECPs), were studied in time and space during pathogenesis. Immunogold localization revealed that proteins ECP1 and ECP2 accumulated abundantly in extracellular material in the vicinity of fungal and host cell walls. Expression of the genes encoding ECP1 and ECP2 was studied in transformants carrying the reporter gene Gus fused to promoter sequences of the ecp genes. In germinated conidia on the leaf surface no expression of gene ecp1 and only low expression of gene ecp2 could be detected. Expression of both ecp1 and ecp2 was strongly induced during colonization of the intercellular space between tomato mesophyll cells. The highest expression was observed in hyphae growing near vascular tissue. Expression levels were low in newly formed conidia on leaves. Possible functions of ECP1 and ECP2 for C. fulvum during pathogenesis are discussed.