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Comparative Physiological, Metabolomic, and Transcriptomic Analyses Reveal Developmental Stage-Dependent Effects of Cluster Bagging on Phenolic Metabolism in Cabernet Sauvignon Grape Berries

ABSTRACT: Light conditions significantly influence grape berry ripening and the accumulation of phenolic compounds, but the underlying molecular basis remains partially understood. Here, we applied integrated transcriptomics and pathway-level metabolomics analyses to investigate the effect of cluster bagging during various developmental stages on phenolic metabolism in Cabernet Sauvignon grapes. Bagging treatments had limited effects on berry quality attributes at harvest and did not consistently affect phenolic acid biosynthesis between seasons. Significantly elevated flavan-3-ol and flavonol contents were detected in re-exposed berries after bagging during early-developmental stages, while bagging after véraison markedly inhibited skin anthocyanin accumulation. Several anthocyanin derivatives and flavonol glycosides were identified as marker phenolic metabolites for distinguishing bagged and non-bagged grapes. Coordinated transcriptional changes in the light signaling components CRY2 and HY5/HYHs, transcription regulator MYBA1, and enzymes LAR, ANR, UFGT and FLS4, coincided well with light-responsive biosynthesis of the corresponding flavonoids. The activation of multiple hormone signaling pathways after both light exclusion and re-exposure treatments was inconsistent with the changes in phenolic accumulation, indicating a limited role of plant hormones in mediating light/darkness-regulated phenolic biosynthesis processes. Furthermore, gene-gene and gene-metabolite network analyses discovered that the light-responsive expression of genes encoding bHLH, MYB, WRKY, NAC, and MADS-box transcription factors, and proteins involved in genetic information processing and epigenetic regulation such as nucleosome assembly and histone acetylation, showed a high positive correlation with grape berry phenolic accumulation in response to different light regimes. Altogether, our findings provide novel insights into the understanding of berry phenolic biosynthesis under light/darkness and practical guidance for improving grape features.

ORGANISM(S): Vitis vinifera

PROVIDER: GSE129916 | GEO | 2019/11/25

REPOSITORIES: GEO

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Project description:UV radiation (UV) alters secondary metabolism in the skin of Vitis vinifera L. berries, which may affect on the final composition of both, grapes and wines. We compared berry skin transcriptome and phenolic composition between Tempranillo berries grown in the presence or absence of solar UV in a mid-altitude Tempranillo vineyard. By analysing two different ripening degrees, expression of 121 genes was significantly altered. Functional enrichment identified that, principally, secondary metabolism-related transcripts were induced by UV, including VvFLS1, VvGT5 and VvGT6 flavonol biosynthetic genes induction. Concurrently, flavonol accumulation was the most evident impact of UV on the berry skin phenolic composition. Monoterpenoid biosynthetic transcripts were also up-regulated by UV, whereas induction of stilbenoid biosynthetic transcripts and stilbenes accumulation was probably induced by the joint action of UV and other condition under the UV-blocking filter, likely higher temperature. Among regulatory genes, VvMYBF1, VvMYB24 and three bHLH transcription factors were up-regulated by UV. Homologs to Arabidopsis UVR8-dependent UV-B-induced genes were also induced, including VvHY5-1, VvHY5-2 and VvRUP UV-B signalling genes. This suggests that the UV-B-specific signalling pathway is activated in the skin of grapes grown at low-medium altitudes. The biosynthesis and accumulation of UV-absorbing compounds that are appreciated for winemaking were almost specifically triggered, which indicates that viticultural practices increasing solar UV incidence may improve grape features important to wine production. A total of 12 samples were hybridized. Grape skin RNA from berries ripening under a UV-transmitting filter (FUV+) and a UV-blocking filter (FUV-) was compared. Berry skin of two different ripening stages was analysed on each UV treatment. All samples were harvested simultaneously and a NaCl series was used to select the ripening degree in a non-invasive way. Three biological replicates were analyzed for each sample.

Project description:Flavonols constitute a group of flavonoids with important photoprotective roles in plants. In addition, flavonol content and composition greatly influences fruit quality. We previously demonstrated that the grapevine R2R3-MYB transcription factor VviMYBF1 promotes flavonol accumulation by inducing the expression of flavonol synthase (VviFLS1/VviFLS4), a key step of the initial flavonol pathway. Despite this, gene networks underlying flavonol modification in grapevine including both structural and regulatory genes remain poorly understood. In order to identify flavonol modifying genes and transcription factors acting downstream of VviMYBF1 a microarray-based transcriptome analysis was performed on grapevine hairy roots ectopically expressing VviMYBF1 or a Green Fluorescent Protein as control. VviFLS1 was induced in VviMYBF1 transgenic roots and flavonols, mainly quercetin 3-glucoside and quercetin 3-galactoside, accumulated significantly compared with control lines. Among the differentially expressed genes, potential flavonol-modifying enzymes with predicted rhamnosyltransferase (e.g. RhaT1) or glycosyltransferase (e.g. GT3) activities were identified. In addition, important transcription factors of the MYB and bZIP families such as the proanthocyanidin regulator VviMYBPA1 and the UV-B light responsive HY5 homologue VviHYH were significantly altered in their expression pattern by overexpression of VviMYBF1. In silico promoter sequence analysis confirmed that the significantly differentially expressed genes contained binding sites similar to known MYB recognition elements. Co-temporal expression analysis demonstrated positive correlation of VviMYBF1 and accumulation of glycosylated flavonols with VviGT3 and VviRhaT1 during berry development and in fruits ripened with different light and UV-B radiation conditions at field. These results show that VviMYBF1 overexpression led to the identification of novel genes of the flavonol pathway and that the flavonol modifying machinery can be influenced by agricultural practices to optimize flavonol composition in grapes.

Project description:Background: The complex and dynamic changes during grape berry development have been studied in Vitis vinifera, but little is known about these processes in other Vitis species. The grape variety âNortonâ, with a major portion of its genome derived from Vitis aestivalis, maintains high levels of malic acid and phenolic acids in the ripening berries in comparison with V. vinifera varieties such as Cabernet Sauvignon. Furthermore, Norton berries develop a remarkably high level of resistance to most fungal pathogens while Cabernet Sauvignon berries remain susceptible to those pathogens. The distinct characteristics of Norton and Cabernet Sauvignon merit a comprehensive analysis of transcriptional regulation and metabolite pathways. Results: A microarray study was conducted on transcriptome changes of Norton berry skin during the period of 37 to 127 days after bloom, which represents berry developmental phases from herbaceous growth to full ripeness. Samples of six berry developmental stages were collected. Analysis of the microarray data revealed that a total of 3,352 probe sets exhibited significant differences at transcript levels, with two-fold changes between at least two developmental stages. Expression profiles of defense-related genes showed a dynamic modulation of nucleotide-binding site-leucine-rich repeat (NBS-LRR) resistance genes and pathogenesis-related (PR) genes during berry development. Transcript levels of PR-1 in Norton berry skin clearly increased during the ripening phase. As in other grapevines, genes of the phenylpropanoid pathway were up-regulated in Norton as the berry developed. The most noticeable was the steady increase of transcript levels of stilbene synthase genes. Transcriptional patterns of six MYB transcription factors and eleven structural genes of the flavonoid pathway and profiles of anthocyanins and proanthocyanidins (PAs) during berry skin development were analyzed comparatively in Norton and Cabernet Sauvignon. Transcriptional patterns of MYB5A and MYB5B were similar during berry development between the two varieties, but those of MYBPA1 and MYBPA2 were strikingly different, demonstrating that the general flavonoid pathways are regulated under different MYB factors. The data showed that there were higher transcript levels of the genes encoding flavonoid-3Â´-O-hydroxylase (F3Â´H), flavonoid-3Â´,5Â´-hydroxylase (F3Â´5Â´H), leucoanthocyanidin dioxygenase (LDOX), UDP-glucose:flavonoid 3Â´-O-glucosyltransferase (UFGT), anthocyanidin reductase (ANR), leucoanthocyanidin reductase (LAR) 1 and LAR2 in berry skin of Norton than in those of Cabernet Sauvignon. It was also found that the total amount of anthocyanins was markedly higher in Norton than in Cabernet Sauvignon berry skin at harvest, and five anthocyanin derivatives and three PA compounds exhibited distinctive accumulation patterns in Norton berry skin. Conclusions: This study provides an overview of the transcriptome changes and the flavonoid profiles in the berry skin of Norton, an important North American wine grape, during berry development. The steady increase of transcripts of PR-1 and stilbene synthase genes likely contributes to the developmentally regulated resistance during ripening of Norton berries. More studies are required to address the precise role of each stilbene synthase gene in berry development and disease resistance. Transcriptional regulation of MYBA1, MYBA2, MYB5A and MYBPA1 as well as expression levels of their putative targets F3Â´H, F3Â´5Â´H, LDOX, UFGT, ANR LAR1, and LAR2 are highly correlated with the characteristic anthocyanin and PA profiles of Norton berry skin. These results reveal a unique pattern of the regulation of transcription and biosynthesis pathways underlying the viticultural and enological characteristics of Norton grape, and yield new insights into the understanding of the flavonoid pathway in non-vinifera grape varieties. At each of six developmental stages, three biological replicates of berry samples were collected, each consists of ten randomly selected vines, a total of 18 samples were proccessed for analysis

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Comparative Physiological, Metabolomic, and Transcriptomic Analyses Reveal Developmental Stage-Dependent Effects of Cluster Bagging on Phenolic Metabolism in Cabernet Sauvignon Grape Berries

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