FUNCTIONAL CHARACTERIZATION OF TERPENE SYNTHASES OF 'AROMATIC' AND 'NON-AROMATIC' GRAPEVINE CULTIVARS

Abstract

Grape-derived flavour compounds and some flavour precursors modified during fermentation, wine evolution and ageing, are fundamental in determining the organolectic parameters used to define wine quality. The knowledge of the biosyn-thesis of secondary metabolites that contribute to grape and wine flavour is not well understood and only a few genes involved in berry flavour biosynthesis pathways have been discovered and characterised. The aim of this research is the functional characterization of candidate genes thought to contribute to the volatile profiles of ?aromatic? (?Aleatico?, ?Moscato bianco?) and ?non-aromatic? (?Sangiovese?) cultivars. Samples of flowers and berries covering developmental stages from fruit set to technological ripening, of ?Aleatico?, ?Moscato bianco?, and ?Sangiovese? have been analysed for their aroma content and the expression of genes that are predicted to be involved in grape sesquiterpene and monoterpene biosynthesis. The aroma com-pounds have been extracted by SPE and SPME procedures and analysed by GS-MS, while the expression of characterised grape aroma genes and some candidate genes have been analysed by real-time RT-PCR. Some of the genes studied show correlations between their expression patterns and the accumulation of certain aroma compounds during berry development. These genes have been the focus of functional character¬ization studies and include a sesquiterpene synthase (which has an expression pattern that correlates with the production of farnesene in flowers buds and open flowers), putative monoterpene synthases that are expressed when linalool accumulates in flowers or during ripening, and putative linalool epoxidases that are expressed when trans-pyran-linalool oxide accumulates during berry ripening of all three grapevine cultivars studied. Some of these genes have been cloned in E. coli and the enzymatic activity characterized. The discovery and characterization of genes that encode enzymes from grapevine flavour biosynthesis pathways and knowledge of factors that influence their expression and activity during berry development would support decisions on management of genotype, environment and viticultural practices for improving grape flavour and aroma potential.