Is losing ethylene a losing game?

It is well established that the gaseous plant hormone ethylene modulates growth and development and mediates responses to biotic and abiotic stresses. Seed plants produce ethylene from S-adenosyl-L-methionine, which is converted to 1-aminocyclopropane-1-carboxylic acid (ACC) by ACC synthase (ACS); ACC is then converted to ethylene by a dedicated enzyme, ACC oxidase (ACO) (Figure 1A). Many seed plant genomes carry multiple ACO homologs, allowing for spatiotemporal fine-tuning of ethylene biosynthesis.