Ethylene — Biosynthesis and perception

Abstract Ethylene is a plant hormone influencing plant processes such as seed germination, diageotropism, flowering, abscission, senescence, fruit ripening, and pathogenesis responses. Its biosynthesis involves multistep enzymatic pathway converting methionine to ethylene. Conjugated forms of ACC, l‐(malonylamino)cyclopropane‐1‐carboxylic acid and l‐(γ‐1‐glutamylamino)cyclopropane‐1‐carboxylic acid, and the enzymes catalyzing these reactions have also been demonstrated. The different ethylene biosynthesis enzymes are encoded each by a family of genes, which raises questions about their functional significance. In addition to transcriptional control of gene expression, posttranscriptional regulation seems to play an important role. Mutants of Arabidopsis and tomato have been used to dissect the ethylene signal transduction pathway. Analyses of ethylene‐insensitive mutants in Arabidopsis and tomato have identified ETR1 gene or its homologues, which codes for a protein similar to microbial two‐component regu...