Specific HR-associated recognition of secreted proteins from Cladosporium fulvum occurs in both host and non-host plants

The resistance of tomato (Lycopersicon esculentum) to the pathogenic fungus Cladosporium fulvum complies with the gene-for-gene concept. Host resistance is based on specific recognition of extracellular fungal proteins, resulting in a hypersensitive response (HR). Five proteins secreted by C. fulvum were purified and the encoding cDNA clone was obtained from two novel ones among them. Various tomato breeding lines and accessions of Lycopersicon pimpinellifolium were tested for their recognitional specificity by injection of the purified proteins or potato virus X-based expression of the cDNA. We found that HR-associated recognition of one or more of these proteins, in addition to recognition of the race-specific elicitors AVR4 and AVR9 of C. fulvum, occurs among Lycopersicon species. Studies on the inheritance of this recognition confirmed that single dominant genes are involved. Furthermore, one of the extracellular proteins of C. fulvum is specifically recognized by Nicotiana paniculata, which is not a host for C. fulvum. These results indicate that plants have a highly effective surveillance system for the presence of 'foreign' proteins, which, together with the high mutation rate of pathogens, can explain the complex gene-for-gene relationships frequently observed in pathosystems

Specific HR-associated recognition of secreted proteins from Cladosporium fulvum occurs in both host and non-host plants

The resistance of tomato (Lycopersicon esculentum) to the pathogenic fungus Cladosporium fulvum complies with the gene-for-gene concept. Host resistance is based on specific recognition of extracellular fungal proteins, resulting in a hypersensitive response (HR). Five proteins secreted by C. fulvum were purified and the encoding cDNA clone was obtained from two novel ones among them. Various tomato breeding lines and accessions of Lycopersicon pimpinellifolium were tested for their recognitional specificity by injection of the purified proteins or potato virus X-based expression of the cDNA. We found that HR-associated recognition of one or more of these proteins, in addition to recognition of the race-specific elicitors AVR4 and AVR9 of C. fulvum, occurs among Lycopersicon species. Studies on the inheritance of this recognition confirmed that single dominant genes are involved. Furthermore, one of the extracellular proteins of C. fulvum is specifically recognized by Nicotiana paniculata, which is not a host for C. fulvum. These results indicate that plants have a highly effective surveillance system for the presence of 'foreign' proteins, which, together with the high mutation rate of pathogens, can explain the complex gene-for-gene relationships frequently observed in pathosystems

Recognition of Cladosporium fulvum Ecp2 elicitor by non-host Nicotiana spp. is mediated by a single dominant gene that is not homologous to known Cf-genes

Cladosporium fulvum is a fungal pathogen of tomato that grows exclusively in the intercellular spaces of leaves. Ecp2 is one of the elicitor proteins that is secreted by C. fulvum and is specifically recognized by tomato plants containing the resistance gene Cf-Ecp2. Recognition is followed by a hypersensitive response (HR) resulting in resistance. HR-associated recognition of Ecp2 has been observed in Nicotiana paniculata, N. sylvestris, N. tabacum and N. undulata that are non-host plants of C. fulvum. Absence of Ecp2-recognition did not lead to growth of C. fulvum on Nicotiana plants. We show that HR-associated recognition of Ecp2 is mediated by a single dominant gene in N. paniculata. However, based on PCR and hybridization analysis this gene is not homologous to known Cf-gene