[Research progress of ethylene signal transduction in plants]

During the past decade, molecular genetic studies on the model plant Arabidopsis have established a largely linear signal transduction pathway for the response to ethylene gas. Ethylene response occurs by receptors binding ethylene and signaling along a linear signal transduction pathway comprising of MAPK and transcriptional cascades. Ethylene receptor family in Arabidopsis consists of five components, ETR1, ERS1, ETR2, ERS2 and EIN4. Each receptor contains an amino-terminal ethylene-binding domain (also called the sensor domain). Some receptors contain a well-conserved carboxy terminal histidine (His) kinase domain and some have an additional receiver domain. Some contain a degenerate His-kinase-like domain that lacks one or more elements and some lack the receiver domain. The ETR1 localizing to endoplasmic reticulum and activating CTR1 negatively regulates the ethylene response as an inhibitive ETR-CTR1 complex. ENI2, EIN3, ERF in turn act downstream of CTR1 and positively regulate the ethylene response. EIN3/EIL, members of regulative protein family activating transcription factor, is posttranscriptionally regulated and stabilized by ethylene. F box protein EBF1/EBF2 accelerate the EIN3 degeneration. ERF1, one of transcription factor family, also called ethylene response element binding protein, is the direct target of EIN3. The biochemical mechanisms of components interaction with each other in the signal transduction pathway are still unknown and largely further research are needed. The signaling pathway is possibly a network consisting of many branches, in which various ethylene-dependent and independent signaling factors cooperate with each other, and complete the specific regulation of different species, developmental stages and tissues response to ethylene.