Is losing ethylene a losing game?

Abstract

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. Non-seed plants (e.g., ferns, bryophytes) lack ACO homologs ( Li et al., 2018 Li F.-W. Brouwer P. Carretero-Paulet L. Cheng S. de Vries J. Delaux P.-M. Eily A. Koppers N. Kuo L.Y. Li Z. et al. Fern genomes elucidate land plant evolution and cyanobacterial symbioses. Nat. Plants. 2018; 4: 460-472https://doi.org/10.1038/s41477-018-0188-8 Crossref PubMed Scopus (209) Google Scholar ) and produce ethylene presumably by an unknown non-ACC-dependent pathway. Numerous responses to ethylene have been identified by treating plants with exogenous ethylene. However, the removal of internally synthesized ethylene is required to determine the roles of endogenous ethylene.