CONICET | Buscador de Institutos y Recursos Humanos

Ethylene, jasmonate, and salicylate play important roles in plant defense responses to pathogens. To investigate thecontributions of these compounds in resistance of tomato (Lycopersicon esculentum) to the fungal pathogen Botrytis cinerea,three types of experiments were conducted: (a) quantitative disease assays with plants pretreated with ethylene, inhibitorsof ethylene perception, or salicylate; (b) quantitative disease assays with mutants or transgenes affected in the productionof or the response to either ethylene or jasmonate; and (c) expression analysis of defense-related genes before and afterinoculation of plants with B. cinerea. Plants pretreated with ethylene showed a decreased susceptibility toward B. cinerea,whereas pretreatment with 1-methylcyclopropene, an inhibitor of ethylene perception, resulted in increased susceptibility.Ethylene pretreatment induced expression of several pathogenesis-related protein genes before B. cinerea infection. Protein-ase inhibitor I expression was repressed by ethylene and induced by 1-methylcyclopropene. Ethylene also induced resistancein the mutant Never ripe. RNA analysis showed that Never ripe retained some ethylene sensitivity. The mutant Epinastic,constitutively activated in a subset of ethylene responses, and a transgenic line producing negligible ethylene were alsotested. The results confirmed that ethylene responses are important for resistance of tomato to B. cinerea. The mutantDefenseless, impaired in jasmonate biosynthesis, showed increased susceptibility to B. cinerea. A transgenic line with reducedprosystemin expression showed similar susceptibility as Defenseless, whereas a prosystemin-overexpressing transgene washighly resistant. Ethylene and wound signaling acted independently on resistance. Salicylate and ethylene acted synergis-tically on defense gene expression, but antagonistically on resistance.

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