Drawing Links from Transcriptome to Metabolites: The Evolution of Aroma in the Ripening Berry of Moscato Bianco (Vitis vinifera L.)

Abstract

Monoterpenes confer typical floral notes to “Muscat” grapevine varieties and, to a lesser extent, to other aromatic non-Muscat varieties. Previous studies have led to the identification and functional characterization of some enzymes and genes in this pathway. However, the underlying genetic map is still far from being complete. For example, the specific steps of monoterpene metabolism and its regulation are largely unknown. With the aim of identifying new candidates for the missing links, we applied an integrative functional genomics approach based on the targeted metabolic and genome-wide transcript profiling of Moscato Bianco ripening berries. In particular, gas chromatography-mass spectrometry analysis of free and bound terpenoid compounds was combined with microarray analysis in the skins of berries collected at five developmental stages from pre-veraison to over-ripening. Differentially expressed metabolites and probes were identified in the pairwise comparison between time points by using the early stage as a reference. Metabolic and transcriptomic data were integrated through pairwise correlation and clustering approaches to discover genes linked with particular metabolites or groups of metabolites. These candidate transcripts were further checked for co-localization with quantitative trait loci (QTLs) affecting aromatic compounds. Our findings provide insights into the biological networks of grapevine secondary metabolism, both at the catalytic and regulatory levels. Examples include a nudix hydrolase as component of a terpene synthase-independent pathway for monoterpene biosynthesis, genes potentially involved in monoterpene metabolism (cytochrome P450 hydroxylases, epoxide hydrolases, glucosyltransferases), transport (vesicle-associated proteins, ABCG transporters, glutathione S-transferases, amino acid permeases), and transcriptional control (transcription factors of the ERF, MYB and NAC families, intermediates in light- and circadian cycle-mediated regulation with supporting evidence from the literature and additional regulatory genes with a previously unreported association to monoterpene accumulation).

Annotation of genes involved in high level of dihydromyricetin production in vine tea (Ampelopsis grossedentata) by transcriptome analysis

“…Secondary metabolites play an essential role in plant defense system and development processes [14][15][16]. The accumulation of secondary metabolites can be influenced by environmental factors and different plant growth stages [17][18][19][20]. Previous studies have reported that the metabolites of green tea (C. sinensis) varied according to geography, developmental stages, and cultivars [2,21,22].…”

Induction of Terpene Biosynthesis in Berries of Microvine Transformed with VvDXS1 Alleles

“…In this regard, the analysis of additional metabolites (e.g., carotenoids and chlorophylls) could point out potentially competing reactions. The involvement of multiple key enzymes might also explain the lack of linalool in the microvines under investigation; in particular, terpene synthases or other genes in the confidence interval of the previously identified linalool-specific QTL on chromosome 10 (Battilana et al, 2009 ; Emanuelli et al, 2011 ; Costantini et al, 2017 ) might play a limiting role in linalool production in combination with VvDXS1 , as highlighted in the grapevine germplasm (Figures 5C,D ) and reported in other plants (Zeng et al, 2016 ).…”

Annotation, classification, genomic organization and expression of the Vitis vinifera CYPome

“…We also found that the expression of the CYP76 family was mostly upregulated in grapevine flowers, similarly to what Boachon and coworkers [ 21 ] found in Arabidopsis . Interestingly, grapevine flowers, just like berries, are very rich in terpenes, some of the most important volatile compounds contributing to the floral bouquet of wine [ 75 , 83 , 84 ] and CYP76s were already found to be involved in terpene biosynthesis in Arabidopsis and grapevine [ 21 , 31 , 85 , 86 ]. More, CYP76 family showed the greatest number of genes with varietal-specific expression patterns during berry development.…”