Abstract
As climate changes, there is a need to understand the expected effects on viticulture. In nature, stresses exist in a combined manner, hampering the elucidation of the effect of individual cues on grape berry metabolism. Cell suspension culture originated from pea-size Gamy Red grape berry was used to harness metabolic response to high light (HL; 2500 μmol m-2s-1), high temperature (HT; 40°C) and their combination in comparison to 25°C and 100 μmol m-2s-1 under controlled condition. When LC–MS and GC–MS based metabolite profiling was implemented and integrated with targeted RT-qPCR transcript analysis specific responses were observed to the different cues. HL enhanced polyphenol metabolism while HT and its combination with HL induced amino acid and organic acid metabolism with additional effect on polyphenols. The trend of increment in TCA cycle genes like ATCs, ACo1, and IDH in the combined treatment might support the observed increment in organic acids, GABA shunt, and their derivatives. The apparent phenylalanine reduction with polyphenol increment under HL suggests enhanced fueling of the precursor toward the downstream phenylpropanoid pathway. In the polyphenol metabolism, a differential pattern of expression of flavonoid 3′,5′ hydroxylase and flavonoid 3′ hydroxylase was observed under high light (HL) and combined cues which were accompanied by characteristic metabolite profiles. HT decreased glycosylated cyanidin and peonidin forms while the combined cues increased acetylated and coumarylated peonidin forms. Transcription factors regulating anthocyanin metabolism and their methylation, MYB, OMT, UFGT, and DFR, were expressed differentially among the treatments, overall in agreement with the metabolite profiles. Taken together these data provide insights into the coordination of central and secondary metabolism in relation to multiple abiotic stresses.
Highlights
Grape (Vitis vinifera L.) is an important crop grown worldwide to produce wine, fresh fruit and derived products (Reisch et al, 2012)
GC–MS Based Central Metabolism Central metabolites change in response to high light (HL), high temperature (HT), and their HLT during the four exposure times were normalized to their respective control and are expressed in
Principal Component Analysis (PCA) plot of GC–MS based annotated metabolite profile showed the difference among HL, HT, and HLT treatments over time (Figure 2A)
Summary
Grape (Vitis vinifera L.) is an important crop grown worldwide to produce wine, fresh fruit and derived products (Reisch et al, 2012). That being said environmental cues in the field occur in a combined and complex manner that hampers the understanding of the stress specific regulatory mechanisms involved and the making of appropriate cultural practice for enhanced or reduced effect on fruit traits (Mittler, 2006; Atkinson and Urwin, 2012). Light affects grape berries growth and development though it often occurs with increased temperature under field condition. Exposure derived increased temperature of the berry can lead to degradation of anthocyanin and to a down-regulation of the associated gene transcripts (Haselgrove et al, 2000; Mori et al, 2007) in a development-dependent manner (Mullins et al, 1992; Tarara et al, 2008). The intimate association between these two environmental cues becomes hardly discernable in the field hampering stress specific effects
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