Metabolite and transcript profiling of berry skin during fruit development elucidates differential regulation between Cabernet Sauvignon and Shiraz cultivars at branching points in the polyphenol pathway

Abstract

BackgroundGrapevine berries undergo complex biochemical changes during fruit maturation, many of which are dependent upon the variety and its environment. In order to elucidate the varietal dependent developmental regulation of primary and specialized metabolism, berry skins of Cabernet Sauvignon and Shiraz were subjected to gas chromatography–mass spectrometry (GC-MS) and liquid chromatography–mass spectrometry (LC-MS) based metabolite profiling from pre-veraison to harvest. The generated dataset was augmented with transcript profiling using RNAseq.ResultsThe analysis of the metabolite data revealed similar developmental patterns of change in primary metabolites between the two cultivars. Nevertheless, towards maturity the extent of change in the major organic acid and sugars (i.e. sucrose, trehalose, malate) and precursors of aromatic and phenolic compounds such as quinate and shikimate was greater in Shiraz compared to Cabernet Sauvignon. In contrast, distinct directional projections on the PCA plot of the two cultivars samples towards maturation when using the specialized metabolite profiles were apparent, suggesting a cultivar-dependent regulation of the specialized metabolism. Generally, Shiraz displayed greater upregulation of the entire polyphenol pathway and specifically higher accumulation of piceid and coumaroyl anthocyanin forms than Cabernet Sauvignon from veraison onwards. Transcript profiling revealed coordinated increased transcript abundance for genes encoding enzymes of committing steps in the phenylpropanoid pathway. The anthocyanin metabolite profile showed F3′5′H-mediated delphinidin-type anthocyanin enrichment in both varieties towards maturation, consistent with the transcript data, indicating that the F3′5′H-governed branching step dominates the anthocyanin profile at late berry development. Correlation analysis confirmed the tightly coordinated metabolic changes during development, and suggested a source-sink relation between the central and specialized metabolism, stronger in Shiraz than Cabernet Sauvignon. RNAseq analysis also revealed that the two cultivars exhibited distinct pattern of changes in genes related to abscisic acid (ABA) biosynthesis enzymes.ConclusionsCompared with CS, Shiraz showed higher number of significant correlations between metabolites, which together with the relatively higher expression of flavonoid genes supports the evidence of increased accumulation of coumaroyl anthocyanins in that cultivar. Enhanced stress related metabolism, e.g. trehalose, stilbene and ABA in Shiraz berry-skin are consistent with its relatively higher susceptibility to environmental cues.

Cultivar specific metabolic changes in grapevines berry skins in relation to deficit irrigation and hydraulic behavior

“…Ahead of extraction samples were freeze dried in a lyophilizer (Virtis Gardiner, N.Y. R525, Model 10-MR-TR). The samples were extracted for parallel metabolite profiling (LC-MS and GCeMS), according to Weckwerth et al (2004) and exactly as described in Degu et al, 2014. All chemicals were purchased from SigmaeAldrich if not indicated otherwise.…”

“…The field experiment was conducted exactly as described in Degu et al (2014). Five-year old commercial vines of two red wine grape varieties of V. vinifera L. (Shiraz and Cabernet Sauvignon e CS) grafted on Ruggeri rootstock were employed during the 2011 growing season.…”

“…For each treatment, berry weight, Brix and titratable acidity (TA) were assayed from whole berries exactly as described in Degu et al (2014).…”

“…The extent of accumulation of phenolic compounds in grape berries varies among cultivars, developmental stages, growing regions and horticultural practices in relation to irradiation, nutrient, and temperature interventions (Downey et al, 2006;Jackson and Lombard, 1993)). Recently, Degu et al (2014) showed the occurrence of differential regulation in the berry polyphenol metabolism of Shiraz and CS grown in an arid environment. Deluc et al (2009) have revealed significant differences in the flavonoid metabolism in responses to water deficit of white (Chardonnay) and red (Cabernet Sauvignon) cultivars.…”

The metabolic profile of grape berry skin and a comparison of metabolomes before veraison and at harvest

“…Recently, metabolome analyzes of various plants have been performed (Saito and Matsuda 2010). Some metabolome analyzes of grape detected >1,000 metabolite peaks (Degu et al 2014;Marti et al 2014;Sternad et al 2013;Suzuki et al 2015;Zamboni et al 2010). However, only a few studies discuss unidentified metabolite peaks (Zamboni et al 2010).…”