Analysis of the transcriptional activators for plant defense response-related genes

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In this study, we investigated the structure and function of novel transcription factor E84 (ERDP) that is isolated from elicitor-treated pea epicotyls. E84 is a plant specific transcription factor possessing Dof-type DNA binding domain at the N-terminus. Random site selection assay for E84 revealed that the recombinant E84 protein binds to AAAG-containing DNA fragments. DNA binding assay using a model DNA fragment, BS4/37 (TCATTTAAAGTGTTTT) that could bind to E84, revealed that not only AAAG core sequence but also 3'-TGT sequence were required for high affinity of the binding. E84 protein also bound to the DNA fragments in the promoter of the elicitor-responsive gene, PsCHS1, which contain AAAG sequence. When we carried out transient transfection assay with pea protoplasts and reporter plasmid possessing 4 repeats of "BS4/37"/CaMV 35S minimal promoter plus reporter gene, we observed that the elicitor enhanced reporter gene activity, indicating the possible involvement of AAAG sequence in elicitor-mediated transcriptional activation. We also observed that E84 protein binds to the promoter sequence of E84 gene itself, indicating possible mechanism of auto-regulation. These results show that E84 protein and its binding sequences might contribute to the elicitor-mediated transcriptional regulation. Furthermore, we also found that at least 7 members of the Dof gene family in pea. These observations provide the information to elucidate the mechanism of the transcriptional activation for plant defense-response related genes.