BACKGROUND: The interaction of Arabidopsis with
Alternaria brassicicola provides a model for disease caused by
necrotrophs, but a drawback has been the lack of a compatible
pathosystem.
Infection of most ecotypes, including the widely-studied line Col-0, with this
pathogen generally leads to a
lesion that does not expand beyond the inoculated area. This study examines an ecotype, Dijon G (DiG), which is considered sensitive to A. brassicicola. RESULTS: We show that the interaction has the characteristics of a compatible one, with expanding rather than limited
lesions. To ask whether DiG is merely more sensitive to the
pathogen or, rather, interacts in distinct manner, we identified genes whose regulation differs between Col-0 and DiG challenged with A. brassicicola. Suppression subtractive hybridization was used to identify differentially
expressed genes, and their expression was verified using semi-quantitative
PCR. We also tested a set of known defense-related genes for differential regulation in the two plant-pathogen interactions. Several known pathogenesis-related (PR) genes are up-regulated in both interactions. PR1, and a monooxygenase gene identified in this study, MO1, are preferentially up-regulated in the compatible interaction. In contrast, GLIP1, which encodes a
secreted lipase, and DIOX1, a pathogen-response related
dioxygenase, are preferentially up-regulated in the incompatible interaction. CONCLUSION: The results show that DiG is not only more
susceptible, but demonstrate that its interaction with A. brassicicola has a specific
transcriptional signature.
