Fig. 4. Genetic determinants of ethylene production and their control for extended postharvest shelf-life.
Ethylene biosynthesis occurs in two enzymatic steps, catalyzed by ACC (1-aminocyclopropane-1-carboxylic acid) synthase (ACS) and ACC oxidase (ACO)274. In climacteric fruit, such as tomato, banana, mango, and apple, there is a rapid rate of increase in ethylene at the onset of ripening and continued production leads to ripening and senescence. Enzymatic inhibitors AVG (aminoethoxyvinylglycine) or AOA (aminooxyacetic acid) inhibit ACS275. Cobalt ions (Co2+), high temperatures (T°), and low oxygen concentration inhibit ACO or low oxygen concentration inhibits ACO276. Silver ion, silver thiosulfate (STS), potentially, carbon dioxide, and 1-methylcyclopropene (1-MCP) inhibit ethylene binding to the receptor for activation of ethylene signaling pathway277,278. For example, 1-MCP, a synthetic growth regulator structurally related to ethylene, is commercially used in fruit crops such as apple, kiwifruit, pear, avocado, melons and others, and it has also shown biological benefits in a range of other species16,279. SAM S-adenosyl methionine