Ethylene signalling and response pathway: a unique signalling cascade with a multitude of inputs and outputs

Plants as immobile organisms need to constantly monitor the changes in the environment to modify and adjust developmental and metabolic pathways accordingly. The responses to these environmental cues require an integrative mechanism where external and internal signals are detected and processed to trigger an appropriate 'reaction' in the plant. Hormones play a key role in mediating some of these integrative processes and in generating the response reactions. The identification and characterization of the basic hormone signalling components and their interactions represent the first step towards comprehensive understanding of plant responses to intrinsic and extrinsic cues. A relatively well-characterized ethylene signalling and response pathway, together with numerous evidences of its interactions with other signalling/response pathways, provide an excellent example to illustrate our current knowledge and perspective on how signal integration occurs in plants.