Mechanisms of signal transduction by ethylene

The gaseous hormone ethylene plays multiple roles in regulating plant growth and development. In terms of growth, ethylene is most commonly associated with the regulation of cell size, particularly as an inhibitor of cell elongation. However, ethylene may also serve as a signal to promote cell expansion, an important response to submergence stress in some species. In addition to regulating cell expansion, ethylene has also been found to regulate growth through control of cell division in some instances. In terms of development, ethylene is most commonly associated with ‘ageing’, particularly for its ability to accelerate such processes as senescence, ripening and abscission. In addition, ethylene serves as a key modulator of the plant’s response to biotic or abiotic stresses.

A new paper in AoB PLANTS describes genetic analysis conducted over the past couple of decades, primarily with the model plant Arabidopsis, which has resulted in the identification of key elements that mediate the primary response to ethylene.

Mechanisms of signal transduction by ethylene: overlapping and non-overlapping signalling roles in a receptor family. (2013) AoB PLANTS 5: plt010 doi: 10.1093/aobpla/plt010
Abstract
The plant hormone ethylene regulates growth and development as well as responses to biotic and abiotic stresses. Over the last few decades, key elements involved in ethylene signal transduction have been identified through genetic approaches, these elements defining a pathway that extends from initial ethylene perception at the endoplasmic reticulum to changes in transcriptional regulation within the nucleus. Here, we present our current understanding of ethylene signal transduction, focusing on recent developments that support a model with overlapping and non-overlapping roles for members of the ethylene receptor family. We consider the evidence supporting this model for sub-functionalization within the receptor family, and then discuss mechanisms by which such a sub-functionalization may occur. To this end, we consider the importance of receptor interactions in modulating their signal output and how such interactions vary in the receptor family. In addition, we consider evidence indicating that ethylene signal output by the receptors involves both phosphorylation-dependent and phosphorylation-independent mechanisms. We conclude with a current model for signalling by the ethylene receptors placed within the overall context of ethylene signal transduction.