Ethylene Biosynthesis and Regulation in Plants

Abstract

Ethylene, a gaseous plant hormone, influences plant growth, development, and response to various stresses and pathogen infection. Ethylene is synthesized from S-adenosylmethionine (SAM) via 1-aminocyclopropane-1-carboxylic acid (ACC). In plants, ACC synthase (ACS) and ACC oxidase (ACO), two key enzymes in the ethylene biosynthetic pathway, are tightly regulated both transcriptionally and posttranscriptionally to modulate ethylene biosynthesis. This chapter summarizes the ethylene biosynthetic pathway and its regulation in higher plants, with a particular focus on the regulation of ACS, generally the rate-limiting enzyme of ethylene biosynthesis. Increasing evidence demonstrates that stability and turnover of the ACS protein is tightly regulated by phosphorylation, dephosphorylation, and ubiquitination-mediated proteasomal degradation. Together with the spatiotemporal-specific expression of the ACS gene family, multilevel regulation of cellular ACS activity can fine-tune the kinetics and magnitude of ethylene biosynthesis in response to diverse endogenous and environmental cues, which is critical to ethylene physiology.