Ripening of fleshy fruit: molecular insight and the role of ethylene.

Development and ripening in fruit is a unique phase in the life cycle of higher plants which encompasses several stages progressively such as fruit development, its maturation, ripening and finally senescence. During ripening phase, several physiological and biochemical changes take place through differential expression of various genes that are developmentally regulated. Expression and/or suppression of these genes contribute to various changes in the fruit that make it visually attractive and edible. However, in fleshy fruit massive losses accrue during post harvest handling of the fruit which may run into billions of dollars worldwide. This encouraged scientists to look for various ways to save these losses. Genetic engineering appears to be the most promising and cost effective means to prevent these losses. Most fleshy fruit ripen in the presence of ethylene and once ripening has been initiated proceeds uncontrollably. Ethylene evokes several responses during ripening through a signaling cascade and thousands of genes participate which not only sets in ripening but also responsible for its spoilage. Slowing down post ripening process in fleshy fruit has been the major focus of ripening-related research. In this review article, various developments that have taken place in the last decade with respect to identifying and altering the function of ripening-related genes have been described. Role of ethylene and ethylene-responsive genes in ripening of fleshy fruit is also included. Taking clues from the studies in tomato as a model fruit, few case studies are reviewed.