The role of ethylene in grape ripening
Grapes are an important crop in Europe both as fresh produce and for winemaking, and the ripening process is key to producing good wine. The ripening process, the onset of which is called véraison, is a complex one, involving a number of different genes encompassing several metabolic routes. The EU-funded project GRAPERIPE (The role of ethylene and of ERF gene regulators in the grapevine berry ripening) measured the endogenous ethylene gas in grapes of different cultivars and studied the function of one protein termed ethylene responsive factor (ERF) that switches grape-ripening genes on and off. Ethylene gas is a common ripening agent in many fruits, but the role of ethylene in véraison is not clear. GRAPERIPE showed that in all cultivars tested, there is a peak in ethylene production about 10 days before grapes start to ripen, but the level is generally very low, though still likely playing a physiological role. To gain more insight into climacteric and non-climacteric ripening, the researchers used melon, which is a perfect model for this type of study. They studied the variability in ripening behaviour and sugar accumulation in a collection of 175 melon accessions of different origin. The same samples were also investigated at the genetic level to compare the DNA sequence variability in 53 candidate genes involved in fruit ripening. Another important result of GRAPERIPE has been the characterisation of transgenic grapevines with a high expression of an ERF encoding gene. The major finding was that this gene plays a key role in the morphology and structure of the leaf epicuticular waxes, besides other roles. This could make it of interest for future exploitation in terms of drought resistance as a result of reduced water transpiration, still to be tested. GRAPERIPE findings will be useful for plant scientists studying fruit ripening, grapevine molecular biology and the role of ethylene, as well as for grapevine breeders and growers.
Keywords
Ethylene, grape ripening, veraison, GRAPERIPE, grapevine
