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Drawing links from transcriptome to metabolites: the evolution of aroma in the ripening berry of Moscato bianco (Vitis vinifera L.)

ABSTRACT: Flavor and aroma play a major role in the perceived quality of grapes and wines. Among the most important compounds determining the oenological quality are monoterpenes. They confer typical floral notes to ‘Muscat’ varieties and, to a lesser extent, to other aromatic varieties. In recent years an increasing number of studies on the biosynthesis of terpenes in grape 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 not known. 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 (14,562 probes) in the skins of berries collected at five developmental stages from pre-véraison to over-ripening. Differentially expressed metabolites and probesets 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. Finally, the candidate transcripts were checked for co-localization with QTLs controlling the level of aromatic compounds. The results provided novel insights into the biological networks of grapevine secondary metabolism, both at the regulatory and catalytic levels, and yielded a collection of previously undescribed genes related to the accumulation of target metabolites.

ORGANISM(S): Vitis vinifera

PROVIDER: GSE76834 | GEO | 2017/06/26

SECONDARY ACCESSION(S): PRJNA308739

REPOSITORIES: GEO

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Project description:Grapes (Vitis species) are economically the most important fruit crop worldwide. However, the complexity of molecular and biochemical events that lead to the onset of ripening in berries as well as how aroma is developed are aspects not fully understood. In an attempt to identify the common mechanisms associated with the onset of ripening independently of the cultivar, grapes of Portuguese elite cultivars, Trincadeira, AragonM-CM-*s, and Touriga Nacional, were studied. The mRNA expression profiles corresponding to veraison (EL35) and to mature berries (EL36) were compared. Across the three varieties, 9,8% (2255) probesets corresponding to 1915 unigenes were robustly differentially expressed at EL 36 compared to EL 35. Eleven functional categories were represented in this differential gene set: primary metabolism, M-bM-^@M-^\secondary metabolismM-bM-^@M-^], cellular metabolismM-bM-^@M-^], developmentM-bM-^@M-^], M-bM-^@M-^\cellular processM-bM-^@M-^], M-bM-^@M-^\diverse functionsM-bM-^@M-^], M-bM-^@M-^\regulation overviewM-bM-^@M-^], response to stimulus, stressM-bM-^@M-^], M-bM-^@M-^\signalingM-bM-^@M-^], M-bM-^@M-^\transport overviewM-bM-^@M-^], and M-bM-^@M-^\xenoprotein, transposable elementM-bM-^@M-^] besides 32.24% genes of M-bM-^@M-^\unknownM-bM-^@M-^] function. Information on gene expression related to primary and secondary metabolism was verified by RT-qPCR analysis of selected candidate genes at four developmental stages (EL32, EL35, EL36 and EL 38). Gene expression data were integrated with metabolic profiling data from GC-EI-TOF/ MS and headspace GC-EI-MS platforms. Molecular and metabolic markers of grape ripening related to primary and secondary metabolism were established and revealed a substantial developmental reprogramming of cellular metabolism. Altogether the results provide valuable new information on the main metabolic events leading to grape ripening. Furthermore, we provide first hints about how the development of a cultivar specific aroma is controlled at the transcriptional level. 2 time points in 2008 season. 3 biological replicates. 3 cultivars

Project description:Noble rot results from atypical infections of ripe grape berries by Botrytis cinerea. Unlike bunch rot, noble rot promotes favorable changes in grape berries and accumulation of secondary metabolites that enhance wine grape quality. Noble rot-infected berries of SÃ©millon, a white-skinned variety, were collected over three years from a commercial vineyard at the same time fruit were harvested for botrytized wine production. Transcriptomic and metabolomic data were integrated to identify pathways associated with distinct stages of noble rot. Botrytis induced the expression of known key regulators of pathways in secondary metabolism associated with berry ripening. The activation by Botrytis during noble rot of metabolic pathways associated with berry ripening was further supported by comparisons with transcriptomes of red-skinned varieties at vÃ©raison. A prominent and common outcome of noble rot and berry ripening was the enhancement of the phenylpropanoid metabolism. Induced synthesis of stilbenes, flavonoids, and anthocyanins was supported by both transcriptional and metabolite analyses. Enzyme assays and targeted gene expression analyses of samples from the three distinct years confirmed that the activation of central and peripheral phenylpropanoid pathways is a consistent hallmark of noble rot. Finally, we show that the impact of noble rot on grape metabolism is still detectable in botrytized wines. These results demonstrate that despite the late stage of terminal senescence of a plant organ, a biotic stress can cause a major reprogramming of plant metabolism leading, in case of noble rot, to the synthesis of important metabolites for grape berry flavor and aroma. The experimental design consists of 4 treatments, berries at 3 distinct stages of noble rot and berries without apparent symptoms of infection. From each treatment a total of 4 biological replicates were sequenced with RNAseq, each replicate corresponded to independent pools of 10-15 berries harvested from adjacent grapevines.

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Project description:Grapevine (Vitis vinifera L) is considered one of the most environmentally sensitive crops and is characterized by broad phenotypic plasticity, offering important advantages such as the large range of different wines that can be produced from the same cultivar, and the adaptation of existing cultivars to diverse growing regions. The uniqueness of berry quality traits reflects complex interactions between the grapevine plant and the combination of natural factors and human cultural practices, defined as terroir, which leads to the expression of wine typicity. Despite the scientific and commercial importance of genotype interactions with growing conditions, few studies have characterized the genes and metabolites directly involved in this phenomenon. Here we used two large-scale analytical approaches to explore the metabolomic and transcriptomic basis of the broad phenotypic plasticity of Garganega, a white berry variety grown at four sites characterized by different pedoclimatic conditions (altitudes, soil texture and composition). These conditions determine berry ripening dynamics in terms of sugar accumulation and the abundance of phenolic compounds. Multivariate analysis unraveled a highly plastic metabolomic response to different environments, especially the accumulation of hydroxycinnamic and hydroxybenzoic acids and flavonols. Principal component analysis revealed that the four sites strongly affected the berry transcriptome allowing the identification of environmentally-modulated genes and the plasticity of commonly-modulated transcripts at different sites. Many genes that control transcription, translation, transport and carbohydrate metabolism showed different expression depending on the environmental conditions, indicating a key role in the observed transcriptomic plasticity of Garganega berries. Interestingly, genes representing the phenylpropanoid/flavonoid pathway showed plastic responses to the environment mirroring the accumulation of the corresponding metabolites. The comparison of Garganega and Corvina berries showed that the metabolism of phenolic compounds is more plastic in ripening Garganega berries under different pedoclimatic conditions.

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Drawing links from transcriptome to metabolites: the evolution of aroma in the ripening berry of Moscato bianco (Vitis vinifera L.)

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