Deciphering gamma-decalactone biosynthesis in strawberry fruit using a combination of genetic mapping, RNA-Seq and eQTL analyses

Abstract

BackgroundUnderstanding the basis for volatile organic compound (VOC) biosynthesis and regulation is of great 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. Early studies on lactone biosynthesis suggest that several enzymatic pathways could be responsible for the diversity of lactones, but detailed information on them remained elusive. In this study, we have integrated genetic mapping and genome-wide transcriptome analysis to investigate the molecular basis of natural variation in γ-decalactone content in strawberry fruit.ResultsAs a result, the fatty acid desaturase FaFAD1 was identified as the gene underlying the locus at LGIII-2 that controls γ-decalactone production in ripening fruit. The FaFAD1 gene is specifically expressed in ripe fruits and its expression fully correlates with the presence of γ-decalactone in all 95 individuals of the mapping population. In addition, we show that the level of expression of FaFAH1, with similarity to cytochrome p450 hydroxylases, significantly correlates with the content of γ-decalactone in the mapping population. The analysis of expression quantitative trait loci (eQTL) suggests that the product of this gene also has a regulatory role in the biosynthetic pathway of lactones.ConclusionsAltogether, this study provides mechanistic information of how the production of γ-decalactone is naturally controlled in strawberry, and proposes enzymatic activities necessary for the formation of this VOC in plants.

HaploSNP affinities and linkage map positions illuminate subgenome composition in the octoploid, cultivated strawberry ( Fragaria×ananassa )

“…The mapping studies performed in the cultivated strawberry have highlighted regions of extensive homozygosity in the genomes of modern F. ×ananassa cultivars attributed to repeated cycles of breeding and selection of specific loci, as well as rearrangements between the diploid and octoploid genomes [8,10]. Despite the molecular resources that have been developed for the cultivated strawberry, to date, only a few studies have reported the characterization of traits of economic importance [12][13][14][15][16], one of the main difficulties being finding sufficient numbers of markers to efficiently saturate QTL-containing regions of the genome.…”

Characterization of key aroma‐active compounds in four commercial egg flavor Sachimas with differing egg content

“…The Classical Sachima and Premiom Sachima were found to contain the higher relative content of n‐propylacetate with 17.67 and 16.72 μg/kg. Lactones are known to be associated with fruit aromas formed by the intramolecular esterification of hydroxyl acids (Sánchez‐Sevilla, José Cruz‐Rus, Valpuesta, Botella, & Amaya, ; Zhao et al, ). However, in the present study, there were no aroma‐active compounds of the lactones detected by the sensory panelists, it was suggested that lactones are not a key contributor to the aroma profile of Sachima.…”

A roadmap for research in octoploid strawberry

“…Among the many breeding-relevant loci discovered in the cultivated strawberry genome, flowering, and fruit quality loci have been prominent, as would be expected in a high-value fruit commodity. These, include discovery of the locus controlling day-neutrality or PF 51 and its subgenome localization 52 as well as multiple loci controlling volatile compounds such as gamma decalactone, mesifurane, and methyl anthranilate [53][54][55][56] . For uncovering disease resistance loci, quantitative trait locus (QTL) mapping has been the most prominent approach.…”

“…While locus-specific DNA tests are highly useful in parent and seedling selection for traits with simple genetics, genome-wide prediction has become the strategy of choice for improving genetically complex traits in crop species. The goal is predictive, and the utility of this strategy has been demonstrated in strawberry for parent selection for yield and quality traits where it was shown 52 Perrotte et al 84 ; Salinas et al 85 Fruit quality γ-decalactone FaFAD1 qFaFAD1 SCAR Sánchez-Sevilla et al 55 ;…”

“…Using a metabolomics approach combined with RNAseq, Chambers et al 53 identified the fatty acid desaturase gene (FaFAD1) essential to its biosynthesis. In parallel, Sánchez-Sevilla et al 55 discovered the same locus by combining transcriptome analysis with a map-based approach. Interestingly, about half of cultivars tested were nonproducers of this volatile and had a deletion of this gene, pointing to FaFAD1 as a potential target for breeding or engineering back into desirable cultivars.…”