Regulation and genetic manipulation of ripening in climacteric fruit

Purpose of the review: Ri pening in climacteric fruit is controlled at many levels and by branches of several comp lex, interacting pathways. Regulatory genes and their protein products involved in ethylene, developmental and ligh t signal transduction pathways are reviewed, and the potential for plant improvement by their genetic manipulation is assessed. Ma in findings: So me genetic controls of ripening have been shown to succeed, for example suppression of ethylene b iosynthesis by post-transcriptional gene silencing of AC S or AC O, and t he generation of hybrid tomato lines heterozy gous for the ri n mutation, a defective version of a developmental regulatory gene. The fruit-specific silencing of protein factors in the light signal transduction pathway has also been used to increase the pigment content of some fru it, resulting in improved nutritional content. However, genetic manipulation of ethylene perception and response appear s insufficiently understood at present for commercial exploitation. D irections for future research: C ontrol of fruit ripening by suppression of et hylene biosynthesis is a successful te chnology that is currently being explored for a commercially useful application. Tropical fruit species with a very shor t shelf-life are a potential target. In tomato, shelf-life has been increased by introgression of the ri n ge ne, but fu ture research should attempt to reduce deleterious effects on f lavour and colour components of ripening. The use of ri n ho mologues to control shelf-life has promise in other species, including non-climacteric varieties, but flavour, co lour and nutritional content should no t be compromised. Ke ywords: et hylene biosynthesis; ethylene perception; fruit ri pening; fruit quality; shelf-life; biotechnology