Functional analysis of Arabidopsis ethylene-responsive element binding protein conferring resistance to Bax and abiotic stress-induced plant cell death

Arabidopsis ( Arabidopsis thaliana) ethylene-responsive element binding protein ( AtEBP) gene was isolated as a suppressor of Bax-induced cell death by functional screening in yeast ( Saccharomyces cerevisiae). To further examine the cell death suppressive action of AtEBP in plant cells, we established transgenic tobacco ( Nicotiana tabacum) plants overexpressing AtEBP as well as transgenic tobacco plants ectopically expressing mouse Bax protein under a dexamethasone-inducible promoter. We prepared the crosses of the selective lines of each transgenic plant, which were evaluated in terms of cell death suppression activity. Results indicate that AtEBP suppressed Bax- induced cell death in tobacco plants, an action also associated with a lowered level of ion leakage. Furthermore, tobacco Bright Yellow-2 cells overexpressing AtEBP conferred resistance to hydrogen peroxide ( H2O2) and heat treatments. AtEBP protein localized in the nucleus and functioned as an in vivo transcription activator as confirmed in transient assays and experiments using stable transgenic system. Up-regulation of defense genes was observed in transgenic Arabidopsis plants overexpressing AtEBP. Based on the analysis of mRNA accumulation in ethylene-related mutants, the position of AtEBP in signaling pathway is presented.