Exploring a novel lipoxygenase as key enzyme in the biosynthesis of γ-dodecalactone in strawberry fruit.

Abstract

Domestical strawberries (Fragaria x ananassa) are consumed worldwide due to their organoleptic characteristics like their delicate aroma. Volatile organic compounds (VOCs) play an important role in strawberry volatilome and in their aroma. An interesting family of VOCs are the lactones, offering fruity and creamy notes to the complex aroma of strawberry fruit. Interestingly, lactones of 8-12 carbon atoms have been identified as potent flavor contributors of strawberry fruits. Moreover, both compounds γ-decalactone and γ-dodecalactone have been proposed as sweetness-enhancers molecules (Fan et al., 2021). Previously, in a quantitative trait loci (QTL) analysis performed in our group, a stable QTL controlling around the 15-25% of the total variation of γ-dodecalactone was found. Using data of genetics markers, relative quantification of γ-dodecalactone and RNAseq generated during this work, a candidate gene rise: a lipoxygenase involved in the metabolism of fatty acids like linolenic acid. This molecule is also important for the biosynthesis of jasmonate and volatile organic compounds. To further confirm this hypothesis, an agroinfiltration of F. x ananassa cv. ‘Candonga’ fruits with the candidate gene under the control of a 35S CaMV was performed. Strawberry fruits with high expression of the candidate gene were selected to analyze primary and secondary metabolites and volatile organic compounds. Fruits with overexpression of the candidate showed a decrease in the contain of certain aminoacids and sugars but also a high content in γ-dodecalactone and methyl jasmonate as well as other volatile organic compounds.