Isolation and functional characterization of the JcERF gene, a putative AP2/EREBP domain-containing transcription factor, in the woody oil plant Jatropha curcas

A cDNA clone, named JcERF, was isolated from Jatropha curcas seedlings (a woody oil plant). It was classified as an ERF subfamily member based on multiple sequence alignment and phylogenetic characterization. The deduced amino acid sequences of the JcERF clone showed no significant sequence similarity with other known ERF proteins except for the conserved AP2/EREBP DNA-binding domain. Expression of the JcERF gene was rapidly induced upon salinity, drought, ethylene and mechanical wounding treatments. No significant changes in the JcERF expression were observed under ABA stress. Gel retardation assay revealed that the JcERF protein could bind specifically to the GCC box as well as to the C/DRE motif. Also it can be inferred from the gel-shift that there is a possibility that the near sequence of the GCC box has an important effect on the DNA-binding activity. In yeast, the JcERF protein specifically bound to the DRE sequence and activated the transcription of two reporter genes His3 and LacZ driven by the DRE sequence. When fused to the LexA DNA-binding domain, the full-length JcERF functioned effectively as a trans-activator in the yeast one-hybrid assay. Overexpression of JcERF cDNA in transgenic Arabidopsis enhanced the salt and freezing tolerance. Meanwhile the seed germination of JcERF transgenic plants was not affected by various concentrations ABA in MS medium. Taken together, the results showed that JcERF functioned as a novel transcription factor and it exhibited a mechanism of plant response to environmental factors like the other AP2/EREBP regulons that also exist in tropical woody plants.