Finding flavor genes

A key enzyme involved in flavor biogenesis in ripening strawberries has been discovered using customized cDNA microarrays.
Identification of the SAAT Gene Involved in Strawberry Flavor Biogenesis by Use of DNA Microarrays
Fruit flavor is a result of a complex mixture of numerous compounds. The formation of these compounds is closely correlated with the metabolic changes occurring during fruit maturation. Here, we describe the use of DNA microarrays and appropriate statistical analyses to dissect a complex developmental process. In doing so, we have identified a novel strawberry alcohol acyltransferase (SAAT) gene that plays a crucial role in flavor biogenesis in ripening fruit. Volatile esters are quantitatively and qualitatively the most important compounds providing fruity odors. Biochemical evidence for involvement of the SAAT gene in formation of fruity esters is provided by characterizing the recombinant protein expressed in Escherichia coli. The SAAT enzyme showed maximum activity with aliphatic medium-chain alcohols, whose corresponding esters are major components of strawberry volatiles. The enzyme was capable of utilizing short- and medium-chain, branched, and aromatic acyl-CoA molecules as cosubstrates. The results suggest that the formation of volatile esters in fruit is subject to the availability of acyl-CoA molecules and alcohol substrates and is dictated by the temporal expression pattern of the SAAT gene(s) and substrate specificity of the SAAT enzyme(s).
Isolation of a set of ripening-related genes from strawberry: their identification and possible relationship to fruit quality traits
Abstract. The ripening of strawberry (Fragaria ananassa Duch.), a non-climacteric fruit, is a complex developmental process that involves many changes in gene expression. To understand how these changes relate to the biochemistry and composition of the fruit the specific genes involved have been examined. A high-quality cDNA library prepared from ripe strawberry fruit was differentially screened for ripening-related clones using cDNA from ripe and white fruits. From 112 up-regulated clones obtained in the primary screen, 66 differentially expressed clones were isolated from the secondary screen. The partial sequences of these cDNAs were compared with database sequences and 26 families of non-redundant clones were identified. Northern analysis confirmed that all of these cDNAs were ripening-enhanced. The expression of many of their corresponding genes was negatively regulated in auxin-treated fruit. These sequences, several of which are novel to fruits, encode proteins involved in key metabolic events including anthocyanin biosynthesis, cell wall degradation, sucrose and lipid metabolism, protein synthesis and degradation, and respiration. These findings are discussed in relation to the role of these genes in determining fruit quality characteristics.