Abstract
Arabidopsis exhibits durable preinvasion resistance against nonadapted fungal pathogens including Colletotrichum species. We have found recently that EDR1 is involved in this cell-periphery resistance. In this study, we investigated the transcript profiles of the edr1 mutant during nonhost defense response by DNA microarray. The analysis revealed that the expression of four plant defensin genes is significantly reduced in the mutant. Real-time PCR analysis showed that the wild-type plant, but not the edr1 mutant, exhibits induced expression of the defensins in response to nonadapted Colletotrichum. The results suggest that EDR1 is required for induced expression of the defensins against the fungal invasion trial. MYC2 transcription factor negatively regulates defensin expression. In contrast to the edr1 mutant, the edr1 myc2mutant exhibited pathogen-induced expression of the defensins with increased resistance against the nonadapted pathogen. Furthermore, constitutive expression of the defensins also partially restored preinvasion resistance in the edr1 mutant. These results strongly suggest that EDR1-mediated induction of plant defensins is involved in nonhost resistance.
