Ethylene

Abstract

Abstract Ethylene, a simple hydrocarbon gas, is a plant growth regulator that profoundly affects growth and development. Ethylene plays an important role in a wide range of processes, including fruit ripening, abscission, senescence and responses to biotic and abiotic stresses. Plants synthesise ethylene in response to diverse developmental factors and environmental stimuli. Responses to ethylene occur through a conserved ethylene signalling pathway that was first elucidated by molecular genetic dissection in the plant Arabidopsis thaliana . The ethylene‐signalling pathway comprises a unique combination of signalling components, beginning with ethylene receptors localised primarily at the endoplasmic reticulum membrane. Ethylene signalling leads to changes in gene expression in the nucleus. Ethylene also exhibits complex interactions with the signalling pathways of a number of other plant signals. An understanding of the regulatory mechanisms involved in ethylene biosynthesis and ethylene signalling has important agricultural and economic implications. Key Concepts: Ethylene gas (C 2 H 4 ) is a plant growth regulator that has profound effects on growth and development. Plants synthesise ethylene from the amino acid l ‐methionine via a simple biosynthetic pathway consisting of three enzymatic steps. Gene family members encoding the ethylene biosynthesis enzymes are differentially expressed in response to diverse developmental and environmental factors; additionally, ACC synthase isozymes, which catalyse the penultimate step in the pathway, are regulated by protein turnover. The ethylene signalling pathway, which was genetically dissected in the reference plant Arabidopsis , is conserved in plants and involves a unique combination of signalling components. The ethylene signal is perceived by protein complexes residing at the ER membrane and transduction of the signal activates a transcriptional cascade resulting in rapid changes in gene expression. Protein turnover plays a critical role in both ethylene biosynthesis and ethylene signalling. Ethylene displays complex interactions with a variety of other signals to control a wide array of processes. The ability to control ethylene biology has far‐reaching consequences in agriculture and horticulture.