beta-aminobutyric acid-induced protection of Arabidopsis against the necrotrophic fungus Botrytis cinerea

The non-protein amino acid p-aminobutyric acid (BABA) protects numerous pla nts against various pathogens. Protection of Arabidopsis plants against vir ulent pathogens involves the potentiation of pathogen-specific defense resp onses. To extend the analysis of the mode of action of BABA to necrotrophs we evaluated the effect of this chemical on Arabidopsis plants infected wit h the gray mold fungus Botrytis cinerea. BABA-treated Arabidopsis were foun d to be less sensitive to two different strains of this pathogen. BABA prot ected mutants defective in the jasmonate and ethylene pathways, but was ina ctive in plants impaired in the systemic acquired resistance transduction p athway. Treatments with benzo-(1,2,3)-thiadiazole-7-carbothioic acid S-meth yl ester, a functional analog of salicylic acid (SA), also markedly reduced the level of infection. Moreover, BABA potentiated mRNA accumulation of th e SA-associated PX-1, but not the jasmonate/ethylene-dependent PDF1.2 gene. Thus, besides jasmonate/ethylene-dependent defense responses, SA-dependent signaling also contributes to restrict B. cinerea infection in Arabidopsis . Our results also suggest that SA-dependent signaling is downregulated aft er infection by B. cineuen. The observed up-regulation of the PDF1.2 gene i n mutants defective in the SA-dependent signaling pathway points to a cross -talk between SA- and jasmonate/ethylene-dependent signaling pathways durin g pathogen ingress.