Abstract
A plant hormone, ethylene, suppresses 26S proteasome-mediated proteolysis of the EIN3 transcription factor for ethylene signaling in Arabidopsis and allows the accumulation of EIN3. The proteolysis of EIN3 has been suggested to be mediated by SCFEBF1/2 that contains either of the closely related F-box proteins, EBF1 or EBF2. Here, we show a feedback regulation in ethylene signaling that is caused by direct up-regulation of EBF2 gene by EIN3. Although EBF1 and EBF2 showed a comparable activity for repression of the EIN3-dependent transcription, only the EBF2 promoter was induced by ethylene. Our results revealed that EIN3 directly binds and activates the EBF2 promoter. The ebf2 mutant transformed with the EBF2 gene under the control of a mutated EBF2 promoter in which the EIN3-binding site was disrupted displayed ethylene-hypersensitive phenotype as ebf2 did. These results indicate that ethylene signaling involves a feedback regulation mediated by EBF2 for fine-tuning signaling.
