Identification of the <i>SAAT</i> Gene Involved in Strawberry Flavor Biogenesis by Use of DNA Microarrays

TLDR

Fruit flavor arises from a complex mixture of compounds whose formation is closely linked to metabolic changes during fruit maturation, with volatile esters being the most important contributors to fruity odors. The study uses DNA microarrays and statistical analyses to dissect the developmental process underlying strawberry flavor biogenesis. DNA microarrays identified candidate genes, and recombinant expression of SAAT in *E. coli* was used to characterize its enzymatic activity, providing biochemical evidence of its role in fruity ester formation.

Abstract

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).