Interactions of Ethylene and Polyamines in Regulating Fruit Ripening

Abstract

Ethylene is one of the simplest organic molecules which affects many aspects of growth, development and senescence of higher plants - biological effects that make it a very versatile plant hormone [21]. For instance, ethylene promotes seed germination [31], leaf senescence [19], flower abscission [27], fruit ripening [6] and development of plant defense systems [5]. In addition, it inhibits cell division and cell differentiation [2, 18, 32]. The biochemical pathway of ethylene synthesis has been elucidated and the enzymes involved have been characterized. The key enzymes regulating the production of ethylene are 1-aminocyclopropane-1-carboxylic acid [ACC) synthase, which catalyzes the formation of ACC from S-adenosylmethionine (AdoMet), and ACC oxidase, which catalyzes the synthesis of ethylene from ACC, in the following metabolic sequence: methionine→ AdoMet→ ACC→ ethylene [35]. The genes encoding ACC synthase and ACC oxidase have been cloned and sequenced from a wide variety of horticultural, agronomic and model plants [14, 33]. Also, molecular analysis of Arabidopsis and tomato mutants has identified the genes that encode proteins that either bind ethylene or regulate ethylene signal transduction pathway [14, 34].