Linking Terpene Synthases to Sesquiterpene Metabolism in Grapevine Flowers

Abstract

Grapevine ( Vitis vinifera L.) terpene synthases (VviTPS) are responsible for the biosynthesis of terpenic volatiles. Volatile profiling of nine commercial wine cultivars showed unique cultivar-specific variation in volatile terpenes emitted from grapevine flowers. The flower chemotypes of three divergent cultivars, Muscat of Alexandria, Sauvignon Blanc and Shiraz were subsequently investigated at two flower developmental stages (EL-18 and -26). The cultivars displayed unique flower sesquiterpene compositions that changed during flower organogenesis and the profiles were dominated by either ( E )-β-farnesene, ( E,E )-α-farnesene or (+)-valencene. In silico remapping of microarray probes to VviTPS gene models allowed for a meta-analysis of VviTPS expression patterns in the grape gene atlas to identify genes that could regulate terpene biosynthesis in flowers. Selected sesquiterpene synthase genes were isolated and functionally characterized in three cultivars. Genotypic differences that could be linked to the function of a targeted gene model resulted in the isolation of a novel and cultivar-specific single product sesquiterpene synthase from Muscat of Alexandria flowers (VvivMATPS10), synthesizing ( E )-β-farnesene as its major volatile. Furthermore, we identified structural variations (SNPs, InDels and splice variations) in the characterized VviTPS genes that potentially impact enzyme function and/or volatile sesquiterpene production in a cultivar-specific manner.

The genetic basis of grape and wine aroma

“…While the publication of the PN40024 reference genome has been invaluable in the identification of grapevine genes, it is not without its limitations. Reliance on a single genome sequence of a genotype for which we have no volatile compound data can be misleading due to structural variants that result in altered gene expression and function in other genotypes 85,221 . Drastic changes in aroma profile due to small mutations in key genes such as VviDXS or the VviGuaS variant of VviTPS24 that are absent in PN40024 exemplify the limitations of a single reference genome 43,84,222 .…”

“…The existence of an allele with a major effect on the volatile profile of a cultivar and its absence in the reference genome illustrates a limitation of the PN40024 genome particularly as it derives from a genotype for which there is limited phenotypic data 18 . Recently, Smit et al conducted a functional characterization of VviTPS-a genes expressed in the inflorescences of several V. vinifera cultivars and found cultivar-specific structural variations with major impacts on gene function and floral sesquiterpene profile 85 . It is likely that structural variations are also important contributors to differences in berry and wine aroma profiles.…”

Terpene Synthases and Terpene Variation in Cannabis sativa

“…This includes both cultivated and noncultivated plants, as well as angiosperms and gymnosperms. For example, in grapevine, members of a large VvTPS gene family are differentially expressed between tissues, developmental stages, and cultivars, leading to differences in terpene profiles depending on the specific combination of TPS genes that are expressed during flowering and fruit ripening (Martin et al, 2009(Martin et al, , 2010Drew et al, 2016;Smit et al, 2019). In rice (Oryza spp.…”

Comparative (Within Species) Genomics of the Vitis vinifera L. Terpene Synthase Family to Explore the Impact of Genotypic Variation Using Phased Diploid Genomes

“…Sesqui-TPS enzymes are more promiscuous in their product profile due to increased number of orientations that can arise from the added double bond of the FPP substrate, i.e., more possible carbocation intermediates. Enzyme promiscuity is known to be affected by subtle sequence variations in and around the enzyme active site that alter the product specificity or change the enzyme function completely (Li et al, 2013;Drew et al, 2015;Smit et al, 2019). By combining sequence homology of the active site with enzyme functions it is possible to predict how a TPS will interact with its substrate as well as predict the initial step in the carbocation cascade (Durairaj et al, 2019).…”