Diversity and function of terpene synthases in the production of carrot aroma and flavor compounds

Abstract

Carrot (Daucus carota L.) is an important root vegetable crop with high nutritional value, characteristic flavor, and benefits to human health. D. carota tissues produce an essential oil that is rich in volatile terpenes and plays a major role in carrot aroma and flavor. Although terpene composition represents a critical quality attribute of carrots, little is known about the biosynthesis of terpenes in this crop. Here, we functionally characterized 19 terpene synthase (TPS) genes in an orange carrot (genotype DH1) and compared tissue-specific expression profiles and in vitro products of their recombinant proteins with volatile terpene profiles from DH1 and four other colored carrot genotypes. In addition to the previously reported (E)-β-caryophyllene synthase (DcTPS01), we biochemically characterized several TPS proteins with direct correlations to major compounds of carrot flavor and aroma including germacrene D (DcTPS7/11), γ-terpinene (DcTPS30) and α-terpinolene (DcTPS03). Random forest analysis of volatiles from colored carrot cultivars identified nine terpenes that were clearly distinct among the cultivars and likely contribute to differences in sensory quality. Correlation of TPS gene expression and terpene metabolite profiles supported the function of DcTPS01 and DcTPS03 in these cultivars. Our findings provide a roadmap for future breeding efforts to enhance carrot flavor and aroma.

The carrot monoterpene synthase gene cluster on chromosome 4 harbours genes encoding flavour-associated sabinene synthases

“…The results observed in this study are in good agreement with findings reported in a very recent paper describing functional characterization of carrot TPSs 53 in the fully sequenced DH1 genotype 22 . This study also shows that the genomic region on chromosome 4 encodes TPSs catalysing the production of sabinene 53 . In complement to the findings of Muchlinski et al 53 we examined a sabinene-deficient carrot genotype.…”

“…This study also shows that the genomic region on chromosome 4 encodes TPSs catalysing the production of sabinene 53 . In complement to the findings of Muchlinski et al 53 we examined a sabinene-deficient carrot genotype. Taken together the complementary results of both studies are applicable in breeding programmes focused on modification of sabinene content in carrot.…”

Chromosome-scale genome assembly provides insights into the evolution and flavor synthesis of passion fruit (Passiflora edulis Sims)

“…In addition, terpenes are important members of passion fruit VOCs, including linalool, (E) -4,8-dimethylona-1,3,7-triene 3-buten-2-one, terpinen-4ol, beta-ionone, and 3-carene. Terpenes are biosynthesized from the 5-carbon isoprenoid precursor isopentenyl-diphosphate (IDP) and its isomer dimethylallyl diphosphate (DMADP) 60 , and TPS enzymes then convert them into structurally diverse volatile monoterpenes and sesquiterpenes or semivolatile and nonvolatile diterpenes 61 . Terpenes are also abundant in many plants, such as the foliage of Eucalyptus 62 , tea tree 63 , coriander 64 and carrot 61 , providing the characteristic smell of these plants.…”

Detection of Mycobacterium avium ssp. paratuberculosis in Cultures From Fecal and Tissue Samples Using VOC Analysis and Machine Learning Tools

“…As discussed in previous studies ( 17 , 38 ), random forests' ability to consider multiple compounds simultaneously makes it suitable for analysis of patterns in VOC data. Random forests have been applied before to analyze VOC patterns for other settings [see e.g., ( 39 – 43 )], and the random forest-based variable selection algorithm Boruta has been deployed in other VOC studies too to select relevant compounds ( 44 – 48 ). In the present study, the Boruta algorithm was favored over other variable selection methods to reduce the number of VOCs to a set of potential MAP marker compounds because of its proven performance in the context of random forest classifiers ( 49 ).…”