FIGURE 1.

Model of ethylene signaling. CTR1 is a serine/threonine protein kinase that directly phosphorylates and inhibits EIN2 in the absence of ethylene. EIN2 contains multiple transmembrane domains at its N terminus and a cytoplasmic C terminus. In the presence of ethylene, the EIN2 C-terminal domain is cleaved and translocated into the nucleus. ETHYLENE INSENSITIVE3 BINDING F-BOX (EBF) proteins are responsible for targeting and degrading EIN3/EIL. EIN2 binds to and leads to the degradation of mRNAs encoding EBF1 and EBF2. In addition, EIN2 can regulate EIN3-dependent transcription. The accumulation and stabilization of EIN3/EIL lead to numerous transcriptional changes. Arrows represent activation, T-bars indicate repression.