Two different mechanisms control ethylene sensitivity in Arabidopsis via the regulation of EBF2 expression.

EIN3 is a key transcription factor in the ethylene signaling pathway in Arabidopsis and its action is controlled by SCFEBF1/2 complex-mediated ubiquitination and subsequent 26S proteasome-dependent degradation. Our recent study revealed that ethylene signaling is regulated by a negative feedback system involving the direct activation of the EBF2 promoter by EIN3. This negative feedback loop likely modulates both the magnitude of the response to ethylene and the recovery after its withdrawal. The sequence downstream of the EBF2 stop codon was also found to play a role in determining the EBF2 expression levels independently of ethylene signaling. The reduction in EBF2 expression via the function of this sequence was suggested to be important for coupling the EBF2 expression levels to growth control. Two different mechanisms thus appear to be involved in determining ethylene sensitivity in Arabidopsis.