Ethylene signaling in plants: Introspection

Abstract

Ethylene is the simplest unsaturated hydrocarbon gas produced in most plants that regulates a number of biochemical processes. Ethylene regulates a wide array of developmental processes, but its precise role in the regulation of these processes is still not clear. Ethylene's role as a signal molecule depends on the cell response to its changing concentrations and the processing of this information in the form of physiological responses in the target cell. Ethylene is perceived by a family of ER-membranebound receptors encoded by the ethylene response 1 (ETR1) gene, and these receptors transduce the ethylene signal. Other ethylene receptors such as ERS1, ERS2, EIN4, ETR1, and ETR2 act as negative regulators via constitutive triple response 1 (CTR1) gene. The CTR1 is presumed to show similarities with Raf, a mitogen-activated protein kinase kinase kinase (MAPKKK) and thus is thought to function like Raf, in a typical MAPK cascade. It has been demonstrated that CTR1 binds ER membrane via ETR1 or by a direct association with ERS1 and ETR2 during ethylene signaling. Ethylene is thought to regulate several aspects of plant growth involving associations with other plant hormones primarily auxins and gibberellins.