Regulation of 1-aminocyclopropane-1-carboxylic acid synthase (ACS) expression and its functions in plant life

Ethylene is a unique plant hormone and plays an important role throughout the entire life cycle of plants. The biosynthetic pathway of ethylene is relatively simple. Under the catalysis of 1-aminocyclopropane-1-carboxylic acid (ACC) synthase (ACS), S-adenosyl-L-methionine (SAM) is transformed into ACC and 5'-methylthioribose (MTA), and subsequently, ACC oxidase (ACO) converts ACC into ethylene. Notably, ACS is the rate-limiting enzyme in the biosynthesis of ethylene. Recent molecular and genetic investigations have revealed that ACS undergoes intricate multi-level regulation, encompassing transcriptional and post-translational mechanisms, to maintain the balance of ethylene production, thus facilitating normal plant growth and resilience to environmental stress. This review will discuss the multi-faceted regulatory mechanisms of ACS at the molecular level and explore the pivotal contributions of ACS family members in plant growth, development, and stress response, based on recent research.