Ethylene and Fruit Ripening

Abstract The ripening of fleshy fruit is a developmentally regulated process unique to plants during which the majority of the sensory quality attributes are elaborated including aroma, flavour, texture and nutritional compounds. In climacteric fruit, the plant hormone ethylene is the key regulator of the ripening process as exemplified by the dramatic inhibition of fruit ripening that results from the down‐expression of ACC (1‐amino‐cyclopropane‐1‐carboxylic acid) synthase and ACC oxidase genes involved in ethylene biosynthesis. By contrast, the ripening of non‐climacteric fruit is not dependent on ethylene but rather on cues of unknown nature though ethylene may contribute at least partly to the control of some aspects of the ripening process. The expression of the ripening‐associated genes is regulated by a network of signalling pathways among which ethylene perception and transduction play a primary role. Building on the knowledge gained on the Arabidopsis thaliana model system, the importance of ethylene signalling in fruit ripening has been extensively studied. This chapter summarizes the present knowledge on the role of ethylene in fruit ripening and addresses the molecular mechanisms involved in ethylene perception and responses. It also highlights recent advances and prospects on the means by which the ethylene transduction pathway leads to diversified physiological responses and how ethylene signalling interacts with other hormones to activate the expression of ripening‐related genes. While this review mostly refers to the tomato as major model for fruit research, it also gives insight on the ripening process in other fruit species, including non‐climacteric types.