Deciphering g-decalactone biosynthesis in strawberry fruit using a combination of genetic mapping and next-generation transcriptomic analysis

Unraveling volatile organic compounds (VOCs) biosynthesis and regulation is of utmost importance for the genetic improvement of fruit flavor. Lactones constitute an essential group of fatty acid-derived VOCs conferring peach-like aroma to a number of fruits including peach, plum, pineapple and strawberry. Although early studies on lactone biosynthesis suggest that several enzymatic pathways could be responsible for the diversity of lactones, detailed information remains elusive. In this report, we have integrated genetic mapping and genome-wide transcriptome analysis to investigate the molecular basis of natural variation in g-decalactone content in strawberry. As a result, we have identified the fatty acid desaturase FaFAD1 as the gene underlying the locus that controls g-decalactone production in ripening strawberry fruits. Accordingly, FaFAD1 is specifically expressed in ripe fruits and its expression fully correlates with the presence or absence of g-decalactone in all 95 individuals of the mapping population. We also show that the expression of FaFAH1, encoding a hydroxylase, highly correlates with the content of g-decalactone in the mapping population, suggesting that this gene can be an additional regulatory control point in the biosynthetic pathway of lactones. All together, this study provides mechanistic information of how the content of g-decalactone is naturally controlled in strawberry and proposes enzymatic activities necessary for the formation of this VOC in plants.