Genomics Approaches for a Better Understanding of the Hormone Interplay During Ripening in Climacteric and Non-Climacteric Fruit

Genomics tools are increasingly used for elucidating and studying transcript profile changes and gene regulation at ripening and following different postharvest conditions, practices and treatments aimed at prolonging storage- and taste-life and/or affecting composition in both climacteric and non-climacteric fruit. Microarray hybridizations have been in particular useful to describe the role of ethylene by means of exogenous treatments with the hormone and the use of its antagonist 1-MCP. In peach fruit, analyses performed on both melting flesh varieties and ripening mutants such as Stony Hard allowed to identify possible hormonal cross-talk mechanisms involving ethylene and auxins. The expression of ethylene- and/or auxin-dependent genes involved in the metabolism and the action (Transcription Factors) of the two hormones is differentially modulated throughout peach fruit ripening suggesting the presence of regulatory inter-dependent mechanisms with auxins playing a crucial role. Although the burst of ethylene is not present at ripening in non-climacteric fruit, ethylene-related genes appear to be differentially expressed at the transition from immature to mature fruit as observed in olives, using a cDNA library subtractive hybridization approach, and in grapes where ethylene treatments at veraison and in detached bunches deeply change transcript profiling (and the expression of genes involved in metabolism/action of other hormones) and affect berry ripening and composition. The presence of complex hormonal interplaying mechanisms governing grape berry development is confirmed by microarray analyses performed on berries treated with synthetic auxins at veraison extremely effective in delaying maturation and some specific ripening-related processes.