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Authors: Xiaofang Li, Pingping Fang, Mingxuan Li and Pei Xu.
In Vitro Cellular & Developmental Biology - Plant (2023)
Abstract: "Structural analogs of enzyme substrates involved in plant hormone biosynthesis can either inhibit or enhance hormone-related responses depending on their specific chemical characteristics. Ethylene is an important gaseous phytohormone regulating a myriad of physiological and developmental processes. The substrate of the ethylene biosynthesis key enzyme ACC oxidase (ACO), 1-aminocyclopropane-1-carboxylate acid (ACC), is the direct precursor of ethylene. Previous studies have identified a series of ACC analogs as ethylene antagonists competitively binding with ACO. Here, this study identified methyl 1-aminocyclopropanecarboxylate (methyl-ACC), a structural analog of ACC, as an agonist of ethylene response in plants. Methyl-ACC triggered enhanced ethylene-related responses in plants similar to the effects of ACC, such as restrained root elongation, increased root hair number, promoted dark-induced leaf senescence, and accelerated ripening of postharvest tomato fruit. A higher amount of ethylene release was detected from the tomato leaves treated with methyl-ACC than from the mock control. These bioactivities of methyl-ACC render it a potential plant growth regulator (PGR) for the agricultural and postharvest industries. RT-qPCR revealed a generally upregulated expression of the ethylene biosynthesis genes in detached tomato leaves under methyl-ACC treatment. In vivo and in vitro enzymatic activity analyses showed that methyl-ACC had no obvious effect on the total ACO activity in detached tomato leaves nor on the activity of recombinant SlACO1, the predominantly expressed ACO family member in this tissue. This study offers a promising new PGR and adds to the current knowledge on the structure–function-regulation relationship of compounds associated with ethylene biosynthesis. The mechanism by which methyl-ACC exerts its function is discussed."
