CONICET | Buscador de Institutos y Recursos Humanos

Background: The establishment of compatibility between plants and pathogens requires compliance with variousconditions, such as recognition of the right host, suppression of defence mechanisms, and maintenance of anenvironment allowing pathogen reproduction. To date, most of the plant factors required to sustain compatibilityremain unknown, with the few best characterized being those interfering with defence responses. A suitablesystem to study host compatibility factors is the interaction between Arabidopsis thaliana and the powdery mildew(PM) Golovinomyces cichoracearum. As an obligate biotrophic pathogen, this fungus must establish compatibility inorder to perpetuate. In turn, A. thaliana displays natural variation for susceptibility to this invader, with someaccessions showing full susceptibility (Col-0), and others monogenic dominant resistance (Kas-1). Interestingly, Te-0,among other accessions, displays recessive partial resistance to this PM.Results: In this study, we characterized the interaction of G. cichoracearum with Te-0 plants to investigate the basisof this plant resistance. We found that Te-0´s incompatibility was not associated with hyper-activation of hostinducible defences. Te-0 plants allowed germination of conidia and development of functional haustoria, but couldnot support the formation of mature conidiophores. Using a suppressive subtractive hybridization technique, weidentified plant genes showing differential expression between resistant Te-0 and susceptible Col-0 plants at thefungal pre-conidiation stage.Conclusions: Te-0 resistance is likely caused by loss of host compatibility and not by stimulation of inducibledefences. Conidiophores formation is the main constraint for completion of fungal life cycle in Te-0 plants. Thesystem here described allowed the identification of genes proposed as markers for susceptibility to this PM.