The synthesis and storage of flavour precursors in grape berries

Supervisors: Dr Paul Boss (08 8303 8614)
Location: Adelaide
Financial support: To be confirmed

Wine flavour and aroma perceived by the consumer results from a complex mixture of compounds many of which derive from grape berries. It is thought that free volatiles are most likely lost during fermentation, and so most grape-derived flavour compounds in the wine originate from less volatile precursors in the berries. The precursors are secondary metabolites that have been glycosylated, presumably to make them more water soluble and/or tagged for transport to the vacuole. 
The targeting is thought to occur via glutathione attachment and transport across the tonoplast membrane by ABC transporters. 
These glycosylated compounds accumulate during berry development and are then released as volatiles in the wine by the action of microbes and due to the acid nature of wine.

Aims: The aims of this project are to characterise the pathway leading to secondary metabolite storage in grape berries and to understand the influence these pathways have on wine flavour and aroma.

Experimental approach: Molecular techniques will be used to identify and characterize grapevine genes associated with the glycosylation and transport of flavour metabolites into the vacuole.  It is envisaged that the candidate will use yeast and Arabidopsis as model systems alongside grape in order to test gene function. The position forms part of a larger team studying and identifying grape-derived wine flavour compounds. 

References:     

• Rea PA et al. (1998) From vacuolar GS-X pumps to multispecific ABC transporters. Annual Review of Plant Physiology and Plant Molecular Biology 49: 727-760
• Bowles D et al. (2005) Glycosyltransferases: managers of small molecules. Current Opinion in Plant Biology 8: 254-263.