Brassica species produce the antifungal indolyl compounds
brassinin and its derivatives, during microbial
infection. The fungal pathogen Alternaria brassicicola detoxifies
brassinin and possibly its derivatives. This ability is an important property for the successful
infection of brassicaceous plants. Previously, we identified a
transcription factor, Bdtf1, essential for the detoxification of
brassinin and full virulence. To discover genes that encode putative
brassinin-digesting
enzymes, we compared gene expression profiles between a mutant strain of the
transcription factor and wild-type A. brassicicola under two different experimental conditions. A total of 170 and 388 genes were expressed at higher levels in the mutants than the wild type during the
infection of host plants and saprophytic growth in the presence of
brassinin, respectively. In contrast, 93 and 560 genes were expressed, respectively, at lower levels in the mutant than the wild type under the two conditions. Fifteen of these genes were expressed at lower levels in the mutant than in the wild type under both conditions. These genes were assumed to be important for the detoxification of
brassinin and included Bdtf1 and 10 putative
enzymes. This list of genes provides a resource for the discovery of
enzyme-coding genes important in the chemical modification of
brassinin.