Molecular characterization of two ethylene response factor genes in sweetpotato that respond to stress and activate the expression of defense genes in tobacco leaves

Two ethylene response factor (ERF) genes, IbERF1 and IbERF2, were isolated from a library of expressed sequence tags (EST) prepared from suspension-cultured cells and dehydration-treated fibrous roots of sweetpotato (Ipomoea batatas). The deduced IbERFs contained a nuclear localization signal and the AP2/ERF DNA-binding domain. RT-PCR analysis revealed that IbERF1 was expressed abundantly during the growth of suspension-cultured cells, whereas the expression levels of IbERF2 transcripts were high in fibrous, thick pigmented roots. Two ERF genes also showed different responses to various types of abiotic stress and pathogen infection. Transient expression of the two ERF genes in tobacco (Nicotiana tabacum) leaves resulted in increased transcript levels of the pathogenesis-related 5 (PR5) gene, the early response to dehydration ten gene (ERD10), the CuZn superoxide dismutase gene (CuZnSOD) and the catalase gene (CAT). It is suggested that the two ERF genes play roles in the stress defense-signaling pathway as transcriptional regulators of the PR5, ERD10, CuZnSOD and CAT genes.