Simulation of fungal-mediated cell death by fumonisin B1 and selection of fumonisin B1-resistant (fbr) Arabidopsis mutants

Fumonisin B1 (FB1), a programmed cell death-eliciting toxin produced by the necrotrophic fungal plant pathogen Fusarium moniliforme, was used to simul ate pathogen infection in Arabidopsis. Plants infiltrated with 10 muM FB1 a nd seedlings transferred to agar media containing 1 muM FB1 develop lesions reminiscent of the hypersensitive response, including generation of reacti ve oxygen intermediates, deposition of phenolic compounds and callose, accu mulation of phytoalexin, and expression of pathogenesis-related (PR) genes. Arabidopsis FB1-resistant (fbr) mutants were selected directly by sowing s eeds on agar containing 1 muM FB1, on which wild-type seedlings fail to dev elop. Two mutants chosen for further analyses, fbr1 and fbr2, had altered P R gene expression in response to FB1. fbr1 and fbr2 do not exhibit differen tial resistance to the avirulent bacterial pathogen Pseudomonas syringae pv maculicola (ES4326) expressing the avirulence gene avrRpt2 but do display enhanced resistance to a virulent isogenic strain that lacks the avirulence gene. Our results demonstrate the utility of FB1 for high-throughput isola tion of Arabidopsis defense-related mutants and suggest that pathogen-elici ted programmed cell death of host cells may be an important feature of comp atible plant-pathogen interactions.