Regulation of ethylene biosynthesis through protein degradation.

The function of hormones during plant growth, development and response to environmental stresses relies heavily upon the actions of the ubiquitin proteasome system (UPS), which selectively degrades numerous proteins. Synthesis of ethylene, a growth and stress hormone, is regulated in part by the ubiquitin-dependent degradation of the rate-limiting enzymatic protein aminocyclopropane-1-carboxylic acid synthase (ACS). Regulation of ACS protein stability, and therefore ethylene production, is mediated by non-catalytic sequences within the C-terminal extension of many ACS proteins. In this review we provide a brief overview of the E3 ligases that target ACS proteins for degradation and discuss how post-translational modification of the C-terminal extensions influence protein stability.