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Dissecting the biochemical and transcriptomic effects of locally applied heat stress on developing Cabernet Sauvignon grape berries

ABSTRACT: Studying the effect of varying durations (1, 7 and 14 days) of locally applied heat stress on grape berries at three developmental stages (middle green, veraison and middle ripening). Among various environmental factors, temperature is a major regulator affecting plant growth, development and fruit composition. Reproductive development of grapevine and berry composition, are both highly influenced by temperature. To date, the molecular mechanisms involved in grapevine berries tolerance to high temperatures (HS) are poorly understood. Although recent data addressed the consequences on berry development of elevated temperatures applied at the whole plant level, the present work particularly focuses on the fruit responses triggered by direct exposure to heat stress. In the context of climate change, this work focused on microclimate effect is of particular interest to better understand the consequences of leaf removal (a common viticultural practice) on berry development. HS (+ 8°C) was locally applied to clusters from Cabernet Sauvignon fruiting cuttings at three different developmental stages (middle green, véraison and middle ripening). Samples were collected 1, 7 and 14 days after treatment and used for metabolic and transcriptomic analyses. The results showed dramatic and specific biochemical and transcriptomic changes in heat exposed berries, depending on the developmental stage and the stress duration. When applied at the herbaceous stage, HS delayed the onset of véraison. Heating also strongly altered the berry concentration of amino acids and organic acids (e.g. PHE, GABA, and malate) and decreased the anthocyanin content at maturity. These physiological alterations could be partly explained by the deep remodelling of transcriptome in heated berries. More than 7000 genes were deregulated in at least one of the nine experimental conditions. The most affected processes belong to the categories “stress responses”, “protein metabolism” and “secondary metabolisms”, highlighting the intrinsic capacity of grape berries to perceive heat stress and to build adaptive responses. Additionally, important changes in processes related to “transport”, “hormone” and “transcription” might contribute to the postponing of véraison. Finally, opposite effects depending on heating duration were observed for genes encoding enzymes of the general phenylpropanoid pathway, suggesting that the HS-induced decrease in anthocyanin content may result from a combination of transcript abundance and product degradation.

ORGANISM(S): Vitis vinifera

PROVIDER: GSE86551 | GEO | 2017/03/08

SECONDARY ACCESSION(S): PRJNA342180

REPOSITORIES: GEO

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Project description:Background: Global climate change, in particular the entailed predicted temperature increase, will noticeably affect plants vegetative and reproductive development. High temperatures alter the composition of the grapevine fruit, one of the most important fruits produced worldwide. This is leading to variable yield and quality, already observed in many growing regions in recent years. However, physiological processes underlying temperature response and tolerance of the grapevine fruit have hardly been investigated. Currently, all studies on fleshy fruits investigating their abiotic stress response on a molecular level were conducted during the day but possible night-specific variations were overlooked. The present study explores the grapevine fruit transcriptomic response at different developmental stages upon heat stress at day and night. Methodology/Principal Results: Short heat stresses (2 h) were applied at day and night to vines bearing clusters sequentially ordered according to the developmental stages along their vertical axis. The recently proposed microvine model was grown in climatic chambers in order to circumvent common constraints and biases introduced in field experiments with perennial vines. Post-véraison berry heterogeneity inside clusters was evaded upon constituting homogenous batches following organic acid and sugar measurements on individual berries. A whole genome transcriptomic approach was subsequently conducted using NimbelGen® 090918 12X microarrays (30K). Results revealed important differences in heat stress responsive pathways according to day or night treatment, in particular regarding genes within phenylpropanoid metabolism. Precise distinction of post-véraison stages led to a stage-specific detection of anthocyanin-related transcripts repressed by heat. Important modifications in cell wall-related processes as well as indications for a heat-induced delay of ripening and sugar accumulation were observed at véraison and reversed in later stages. Conclusion: This first day - night study on heat stress adaption of the grapevine berry shows that the transcriptome of fleshy fruits is differentially affected by abiotic stress at night. The present results emphasize the necessity to include different developmental stages and especially different time points in transcriptomic studies. A total of 12 samples were analyzed representing three berry developmental stages (two after the onset of ripening, one during green growth). At each stage, heat stress was applied at day and night. Controls and treated berry samples were drawn in triplicates (two in duplicates) at day and at night on the microvine dwarf (Dwarf Rapid Cycling and Continous Flowering; DRCF) gibberellin-insensitive (GAI) mutant.

Project description: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.

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Dissecting the biochemical and transcriptomic effects of locally applied heat stress on developing Cabernet Sauvignon grape berries

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