Negative Regulation of the Ethylene Response by Differential Cooperations of the Ethylene Receptor Family Members and the Raf-Like Protein CTR1

With the use of Arabidopsis as a model plant, studies in the past two decades have substantially advanced our understanding towards the ethylene signal transduction. A linear ethylene signal transduction has been proposed based on genetic and biochemical studies. The current model explains how the signaling components are involved in the pathway; yet, there are questions to be answered. For instance, how the different members of the ethylene receptor family may coordinate with the downstream Raf-like protein CONSTITUTIVE TRIPLE-RESPONSE1. It is to be answered for how ETHYLENE INSENSITIVE2 (EIN2) may mediate the ethylene signaling to the transcription factor EIN3. This review focuses on the differential regulation of the ethylene signaling via differential cooperation of different members of the ethylene receptor family, biological significance of the use of multiple ethylene receptor isoforms for the ethylene perception, and possible regulation of the ethylene signaling by a pathway that is independent of the negative regulation of CTR1 on EIN2.