Abstract: The gaseous hormone ethylene has numerous effects during plant growth and development. It is important to know how ethylene is synthesized and how the signal is transduced. During the past twenty years, the isolation and characterization of various mutants that show an altered triple-response phenotype has uncovered a largely linear ethylene signaling pathway with branches in the downstream response pathway. In Arabidopsis, perception of ethylene is performed by five receptors, ETR1, ERS1, ETR2, ERS2, EIN4, which exhibit structural and functional redundancy and are negative regulators of ethylene signaling. The receptors are homodimer in vivo. The membrane-bound N-terminal of ETR1 binds ethylene with the assistance of a copper cofactor Cu (Ⅰ). Although ETR1 was reported to possess histidine kinase activity whereas other receptors have serine/theronine kinase activity, the mechanism of ethylene receptors signaling is largely unclear. The receptors interact with a Raf-like protein kinase CTR1, which is a negative regulator in the ethylene response. Inactivation of CTR1 leads to activation of EIN2, which consists of a novel C-terminal signaling domain, and a N-terminal transmembrane domain with sequence similarity to the Nramp family of metal ion transporters.Downstream of EIN2, EIN3 and EILs function as primary transcription factors that can induce expression of ERF1 and other secondary transcription factors, which in turn regulate a large number of ethylene response genes. EIN3 is regulated by a proteasome-mediated protein degradation pathway. As ethylene is a versatile phytohormone, its response pathway has multiple interactions (crosstalk) with other signaling pathway.