History of Research on the Plant Hormone Ethylene

Ethylene is the simplest of the olefin gasses and was the first known gaseous biological signaling molecule. It is synthesized by plants during certain stages of development and in response to abiotic and biotic stresses. Ethylene affects many aspects of plant growth, development as well as responses to environmental cues. Research leading to the discovery of ethylene as a plant hormone started in the 1800s with scientists examining the effects of illuminating gas on plants. In 1901, Dimitry Neljubow determined that ethylene is the active component of illuminating gas that affects plants and thus launched this important field of research. It is generally accepted that in 1934 Richard Gane provided the conclusive evidence that plants biosynthesize ethylene. This early research showed that ethylene is both biosynthesized and sensed by plants. From the 1930s to the 1960s, there was scant research on ethylene as a hormone because many researchers did not believe that ethylene was indeed a plant hormone and because that the detection of ethylene was difficult. However, in the late 1950s, the application of gas chromatography led to an increased interest in ethylene research. From the 1960s through the early 1980s, the biochemical pathway for ethylene biosynthesis in plants was elucidated and membrane-bound ethylene-binding sites were discovered and characterized. The use of Arabidopsis thaliana as a model plant system and the widespread use of molecular biological techniques starting in the 1980s correlates with a second and larger increase in ethylene research productivity. Information gleaned from this model plant is now being applied to many plant species. In recent years, detailed models for the regulation of ethylene biosynthesis and ethylene signal transduction have emerged. This article provides an overview of the key historical discoveries regarding ethylene as a plant hormone.