AP2/ERF proteins play crucial roles in various biological processes. RAP2.6, an Arabidopsis AP2/ERF family member, has been reported to function in plant response to biotic stress, but whether it also functions in plant response to abiotic stress is not known. In this work, we demonstrate that in wild-type Arabidopsis, the expression of RAP2.6 is responsive to abscisic acid (ABA) and different stress conditions such as high salt, osmotic stress, and cold. Trans-activating ability tests in yeast demonstrate that RAP2.6 could act as a transactivator. RAP2.6 is able to bind to the GCC and CE1 cis-elements, as confirmed by both electrophoretic mobility shift assay (EMSA) and yeast one-hybrid assay. Experiments with RAP2.6-YFP fusion protein indicated that RAP2.6 is nuclear localized. Overexpression of RAP2.6 conferred hypersensitivity to exogenous ABA and abiotic stresses during seed germination and early seedling growth in Arabidopsis. The ABA content in RAP2.6 overexpressor lines decreased after being treated with salt. Furthermore, transcripts of AtABI4 and some stress inducible genes increased, and loss of ABI4 function rescues the hypersensitive phenotype of RAP2.6 overexpression lines under ABA and stress treatment. These results suggest that RAP2.6 participates in abiotic stress, possibly through the ABA-dependent pathway.
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