Overexpression of an AP2/ERF-type Transcription Factor CRF5 Confers Pathogen Resistance to Arabidopsis Plants

The cytokinin response factor 5 (CRF5) belongs to a family of plant-specific APETALA2 (AP2)/ethylene-responsive element binding proteins (EREBPs). The novel role of Arabidopsis CRF5, previously identified as a mediator of cytokinin signaling, has been suggested to increase pathogen resistance in this study. Endogenous CRF5 transcripts are expressed in all tissues, including the seedlings, leaf, stem, flower, silique and root, and were found to be induced at 1 h after infection with the bacterial pathogen, Pseudomonas syringae pv. tomato DC3000 (Psi DC3000). The results of a yeast one-hybrid assay revealed that an acidic region of CRF5, including the C-terminal 28 amino acids, functions as a transcriptional activator. Overexpression of CRF5 in transgenic Arabidopsis increases pathogen resistance and concomitantly activates the expression of a large number of GCC-box pathogenesis-related genes. These results indicate that CRF5 may be involved in disease resistance as a transcription activator, thus providing a mechanistic link between the plant pathogen response and cytokinin signaling.