Pierre De WitLaboratory of Phytopathology, Wageningen University, Wageningen, Netherlands F1000 Faculty Member (since 02 January 2002)
Laboratory of Phytopathology
Molecular basis of plant response to microbial invasion.
For many years we have used the Cladosporium fulvum-tomato pathosystem as a model to unravel the molecular communication between a fungal pathogen and its host plant. The pathogen is an imperfect fungus that penetrates stomata of tomato leaves and grows biotrophically as an endophyte in the intercellular space. In planta, the fungus secretes many small cysteine-rich peptides of which some (the Avr peptides) mediate Cf-dependent defence responses in tomato plants that carry the matching Cf resistance genes. The Cf resistance genes are very effective against C. fulvum and have been introgressed from wild relatives by breeders in commercially grown tomato cultivars since the 1930s. We have cloned four Avr genes (Avr2, Avr4, Avr4E and Avr9) that mediate Cf-dependent resistance in plants carrying Cf-2, Cf-4, Hcr9-4E, and Cf-9, respectively. In addition, we have cloned four Ecp (for extracellular proteins) genes (Ecp1, Ecp2, Ecp4 and Ecp5). The Ecps can also mediate Cf-ECP-dependent resistance in tomato plants carrying the matching genes. However, the Cf-ECP genes have not been cloned yet. The co-evolution between C. fulvum and tomato is poorly understood, but it is believed that the Avr and Ecp genes have played, and still play, an important role in this process. It is anticipated that the Avr and Ecp genes play a role in virulence of the pathogen and that during co-evolution tomato has acquired resistance genes that mediate recognition of the Avrs and Ecps, subsequently followed by active defence responses including the hypersensitive response (HR). In our research programme we focus on (i) the cloning, regulation and functional analysis of Avr and Ecp genes and (ii) the identification of tomato genes that play a role in signal perception and signal transduction leading to compatible (plant is susceptible) or incompatible interactions (plant is resistant).
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