关键词: 植物激素, 乙烯, 信号转导

Abstract: As one of the five classical phytohormones, ethylene has been focused on by scientists since it was found. Although it has very simple structure, the gaseous phytohormone ethylene has important effects on the developmental processes and stress responses of plant. Through nearly two decades of research, scientists established a largely linear ethylene signal transduction pathway. In the model plant Arabidopsis, there are five ethylene receptors ETR1, ETR2, ERS1, ERS2 and EIN4 encoded by a multigene family in the upstream of this signaling pathway. A Raflike protein kinase CTR1 combines with ethylene receptors and colocalizes in the ER membrane together with these receptors. In the absence of ethylene, receptors and CTR1 can inhibit the downstream ethylene signaling together. A positive regulator EIN2 is the downstream of these two negative regulators. If EIN2 gene is mutated, the etiolated seedlings of plant will show completely ethylene insensitive phenotype even when high concentration of ethylene exists, which demonstrates that EIN2 plays a key role in ethylene signaling pathway. EIN3 and EILs are transcription factors downstream of EIN2. They will start the transcription of ethylene related genes in response to ethylene signal. It was also found that these transcription factors were regulated by ubiquitin/proteasome degradation pathway. The Fbox proteins, which are responsible for recognition and combination of EIN3 protein, are EBF1 and EBF2. EIN5 is a 5’→3’ exonuclease and antagonizes the negative feedback regulation on EIN3 by promoting EBF1 and EBF2 mRNA decay. Recently, studies have shown that EIN2 is also a short halflife protein and will be degraded by the ubiquitin/proteasome pathway. Another two Fbox proteins ETP1 and ETP2 are responsible for the regulation of EIN2 protein. Although great progress was made in ethylene signal transduction pathway, further research on the finetuning of ethylene signal transduction and the crosstalk between ethylene and other phytohormones still need to be detected.

Key words: phytohormone, ethylene, signal transduction