Arabidopsis ERF4 is a transcriptional repressor capable of modulating ethylene and abscisic acid responses

ERFs (ethylene-responsive element binding factors) belong to a large family of plant transcription factors that are found exclusively in plants. A small subfamily of ERF proteins can act as transcriptional repressors. The Arabidopsis genome contains eight ERF repressors, namely AtERF3, AtERF4, and AtERF7 to AtERF12. Members of ERF repressors show differential expression, suggesting that they may have different function. Using a transient expression system, we demonstrated that AtERF4, AtERF7, AtERF10, AtERF11 and AtERF12 can function as transcriptional repressors. The expression of AtERF4 can be induced by ethylene, jasmonic acid, and abscisic acid (ABA). By using green fluorescent protein fusion, we demonstrated that AtEFR4 accumulated in the nuclear bodies of Arabidopsis cells. Expression of 35S:AtERF4-GFP in transgenic Arabidopsis plants conferred an ethylene-insensitive phenotype and repressed the expression of Basic Chitinase and beta-1,3-Glucanase, the GCC-box-containing genes. In comparison with wild-type plants, 35S:AtERF4-GFP transgenic plants had decreased sensitivity to ABA and were hypersensitive to sodium chloride. The expression of the ABA responsive genes, ABI2, rd29B and rab18, was decreased in the 35S:AtERF4-GFP transgenic plants. Our study provides evidence that AtERF4 is a negative regulator capable of modulating ethylene and abscisic acid responses.