Sensory and aroma impact of mitigation strategies against sunburn in Riesling

Climate change is an environmental challenge that impacts the wine industry due to frequent sunburn damage triggered by heat waves, sun radiation and severe water deficits. This leads to severe yield losses and sensory changes in the resulting wines, presumably caused by climate-induced off-flavours. This study aims to develop viticultural and oenological strategies to mitigate sunburn damage in the highly sensitive variety Riesling and its detrimental sensory properties. In 2020, we combined the timing and intensity of defoliation measures with the application of kaolin and calcium hydroxide suspensions, reflecting a portion of the solar radiation. Seven treatments were replicated in three field experiments. Grapes from each field replication were maintained as a fermentation replication and, therefore, separately vinified following a standardised protocol. Replicates, including field and fermentation replicates, were further used as sensory replications. Descriptive analysis (DA) and temporal dominance of sensations (TDS) revealed a significant sensory impact of experimental trials in eight of twelve attributes. Additionally, wines were analysed by gas chromatography-mass spectrometry. The early sun exposition treatment with partial defoliation of the grape zone after flowering, followed by a second defoliation at berry closure, reduced fruity aroma but increased smoky notes due to enhanced 4-vinylguajacol formation as well as the intensity of the atypical ageing note (ATA) reminiscent of acacia blossom, naphthalene and fusel alcohols. Applying kaolin or calcium hydroxide particles on the berry skin slightly mitigated these unpleasant effects and even increased fruitiness and sweetness. Late defoliation at berry closure diminished the green note, which was most prominent in the non-defoliated control. Further smokiness and ATA intensities were lowered, in contrast to their rise due to early defoliation. However, late defoliation increased 1,1,6-trimethyl-1,2-dihydronaphthalene (TDN), causing the petrol off-flavour. TDS analysis revealed a higher fruity and sweet dominance during the first 10 seconds due to early defoliation, while late defoliation fostered dominant and lingering sourness. In conclusion, early defoliation, which lowers sunburn incidence due to an early adaptation towards sun exposure, increases smoky and ATA flavours and diminishes fruitiness. These detrimental sensory effects could be significantly mitigated by applying reflecting particles of kaolin and calcium hydroxide on berry skins

A single amino acid change within the R2 domain of the VvMYB5b transcription factor modulates affinity for protein partners and target promoters selectivity

<p>Abstract</p> <p>Background</p> <p>Flavonoid pathway is spatially and temporally controlled during plant development and the transcriptional regulation of the structural genes is mostly orchestrated by a ternary protein complex that involves three classes of transcription factors (R2-R3-MYB, bHLH and WDR). In grapevine (<it>Vitis vinifera </it>L.), several MYB transcription factors have been identified but the interactions with their putative bHLH partners to regulate specific branches of the flavonoid pathway are still poorly understood.</p> <p>Results</p> <p>In this work, we describe the effects of a single amino acid substitution (R69L) located in the R2 domain of VvMYB5b and predicted to affect the formation of a salt bridge within the protein. The activity of the mutated protein (name VvMYB5b^L, the native protein being referred as VvMYB5b^R) was assessed in different <it>in vivo </it>systems: yeast, grape cell suspensions, and tobacco. In the first two systems, VvMYB5b^Lexhibited a modified trans-activation capability. Moreover, using yeast two-hybrid assay, we demonstrated that modification of VvMYB5b transcriptional properties impaired its ability to correctly interact with VvMYC1, a grape bHLH protein. These results were further substantiated by overexpression of <it>VvMYB5b^R</it>and <it>VvMYB5b^L</it>genes in tobacco. Flowers from <it>35S::VvMYB5b^L</it>transgenic plants showed a distinct phenotype in comparison with <it>35S::VvMYB5b^R</it>and the control plants. Finally, significant differences in transcript abundance of flavonoid metabolism genes were observed along with variations in pigments accumulation.</p> <p>Conclusions</p> <p>Taken together, our findings indicate that VvMYB5b^Lis still able to bind DNA but the structural consequences linked to the mutation affect the capacity of the protein to activate the transcription of some flavonoid genes by modifying the interaction with its co-partner(s). In addition, this study underlines the importance of an internal salt bridge for protein conformation and thus for the establishment of protein-protein interactions between MYB and bHLH transcription factors. Mechanisms underlying these interactions are discussed and a model is proposed to explain the transcriptional activity of VvMYB5^Lobserved in the tobacco model.</p

The photomorphogenic factors UV-B RECEPTOR 1, ELONGATED HYPOCOTYL 5, and HY5 HOMOLOGUE are part of the UV-B signalling pathway in grapevine and mediate flavonol accumulation in response to the environment

Grapevine (Vitis vinifera L.) is a species well known for its adaptation to radiation. However, photomorphogenic factors related to UV-B responses have not been molecularly characterized. We cloned and studied the role of UV-B RECEPTOR (UVR1), ELONGATED HYPOCOTYL 5 (HY5), and HY5 HOMOLOGUE (HYH) from V. vinifera We performed gene functional characterizations, generated co-expression networks, and tested them in different environmental conditions. These genes complemented the Arabidopsis uvr8 and hy5 mutants in morphological and secondary metabolic responses to radiation. We combined microarray and RNA sequencing (RNA-seq) data with promoter inspections to identify HY5 and HYH putative target genes and their DNA binding preferences. Despite sharing a large set of common co-expressed genes, we found different hierarchies for HY5 and HYH depending on the organ and stress condition, reflecting both co-operative and partially redundant roles. New candidate UV-B gene markers were supported by the presence of HY5-binding sites. These included a set of flavonol-related genes that were up-regulated in a HY5 transient expression assay. We irradiated in vitro plantlets and fruits from old potted vines with high and low UV-B exposures and followed the accumulation of flavonols and changes in gene expression in comparison with non-irradiated conditions. UVR1, HY5, and HYH expression varied with organ, developmental stage, and type of radiation. Surprisingly, UVR1 expression was modulated by shading and temperature in berries, but not by UV-B radiation. We propose that the UV-B response machinery favours berry flavonol accumulation through the activation of HY5 and HYH at different developmental stages at both high and low UV-B exposure

A systems-oriented analysis of the grapevine R2R3-MYB transcription factor family uncovers new insights into the regulation of stilbene accumulation

R2R3-MYB transcription factors (TFs) belong to a large and functionally diverse protein superfamily in plants. In this study, we explore the evolution and function of this family in grapevine (Vitis vinifera L.), a high-value fruit crop. We identified and manually curated 134 genes using RNA-Seq data, and named them systematically according to the Super-Nomenclature Committee. We identified novel genes, splicing variants and grapevine/woody-specific duplicated subgroups, suggesting possible neo- and sub-functionalization events. Regulatory network analysis ascribed biological functions to uncharacterized genes and validated those of known genes (e.g. secondary cell wall biogenesis and flavonoid biosynthesis). A comprehensive analysis of different MYB binding motifs in the promoters of co-expressed genes predicted grape R2R3-MYB binding preferences and supported evidence for putative downstream targets. Enrichment of cis-regulatory motifs for diverse TFs reinforced the notion of transcriptional coordination and interaction between MYBs and other regulators. Analysis of the network of Subgroup 2 showed that the resveratrol-related VviMYB14 and VviMYB15 share common co-expressed STILBENE SYNTHASE genes with the uncharacterized VviMYB13. These regulators have distinct expression patterns within organs and in response to biotic and abiotic stresses, suggesting a pivotal role of VviMYB13 in regulating stilbene accumulation in vegetative tissues and under biotic stress conditions

Rpv3–1 mediated resistance to grapevine downy mildew is associated with specific host transcriptional responses and the accumulation of stilbenes

Background: European grapevine cultivars (Vitis vinifera spp.) are highly susceptible to the downy mildew pathogen Plasmopara viticola. Breeding of resistant V. vinifera cultivars is a promising strategy to reduce the impact of disease management. Most cultivars that have been bred for resistance to downy mildew, rely on resistance mediated by the Rpv3 (Resistance to P. viticola) locus. However, despite the extensive use of this locus, little is known about the mechanism of Rpv3-mediated resistance. Results: In this study, Rpv3-mediated defense responses were investigated in Rpv3+ and Rpv3ˉ grapevine cultivars following inoculation with two distinct P. viticola isolates avrRpv3+ and avrRpv3ˉ, with the latter being able to overcome Rpv3 resistance. Based on comparative microscopic, metabolomic and transcriptomic analyses, our results show that the Rpv3–1-mediated resistance is associated with a defense mechanism that triggers synthesis of fungi-toxic stilbenes and programmed cell death (PCD), resulting in reduced but not suppressed pathogen growth and development. Functional annotation of the encoded protein sequence of genes significantly upregulated during the Rpv3–1-mediated defense response revealed putative roles in pathogen recognition, signal transduction and defense responses. Conclusion: This study used histochemical, transcriptomic and metabolomic analyses of Rpv3+ and susceptible cultivars inoculated with avirulent and virulent P. viticola isolates to investigate mechanism underlying the Rpv3–1-mediated resistance response. We demonstrated a strong correlation between the expressions of stilbene biosynthesis related genes, the accumulation of fungi-toxic stilbenes, pathogen growth inhibition and PCD

Die europäische Integration und die Kirchen, Teil 2

Das Institut für Europäische Geschichte Mainz und die Johannes Gutenberg-Universität veranstalteten im akademischen Jahr 2010/2011 im Rahmen des Studienprogramms des gemeinsamen Graduiertenkollegs »Die christlichen Kirchen vor der Herausforderung ›Europa‹ (1890 bis zur Gegenwart)« eine Vorlesungsreihe, die unter dem Titel »Die Kirchen in Europa: Denker und Querdenker«. Die Vorträge gingen der Frage nach, wie sich kirchennahe Organisationen und ihre Entscheidungsträger zum Gedanken einer Einigung Europas positionierten und sich dem Prozess der europäischen Integration stellten. Der Fokus der Reihe richtete sich – als Pendant zu der ersten Ringvorlesung, die 2009–2010 stattfand und in einem Band »Die europäische Integration und die Kirchen. Akteure und Rezipienten« dokumentiert wurde – auf Persönlichkeiten und Gruppierungen, die in die Öffentlichkeit hineinwirkten und deren Meinungsbildung mitgestalteten. Der Band versammelt acht Beiträge von Kirchenhistorikern, Historikern und Politikwissenschaftlern. Die Beiträge decken einen langen Zeitraum ab und beleuchten in Fallbeispielen oder überblicksartig die Zeit vom ausgehenden 19. Jahrhundert bis an die Schwelle der Gegenwart. Trotz eines gewissen Schwerpunkts im deutschsprachigen Raum wird der Blick auch nach Estland und Italien gelenkt. In Betracht kommen Gruppen, wie politische Parteien; Konfessionskirchen, wie z. B. das Luthertum, und Institutionen, wie der Heilige Stuhl. Vorgestellt werden aber auch und vor allem Einzelpersonen und deren Haltung, wobei auch hier das Spektrum sehr weit ist und von der »Prominenz« bis hin zu weniger bekannten »Einzelgängern« reicht

Orchestration of the stilbene synthase gene family and their regulators by subgroup 2 MYB genes

The control of plant specialised metabolism is exerted by transcription factors and co-regulators acting on cis-regulatory DNA sequences of pathway-structural genes, determining when, where, and how metabolites are accumulated. A particularly interesting case for studying the transcriptional control of metabolism is represented by stilbenoids, produced within the phenylpropanoid pathway, as their ability to inhibit infection by coronaviruses MERS-CoV and SARS-CoV has been recently demonstrated in vitro. Integrative omic studies in grapevine (Vitis vinifera L.), including gene co-expression networks, have previously highlighted several transcription factors (TFs) from different gene families as potential modulators of stilbenoid accumulation, offering an ideal framework for gene function characterisation using genome-wide approaches. In the context of non-model plant species, DNA affinity purification sequencing (DAP-Seq) results a novel and potentially powerful tool for the analysis of novel uncharacterised regulators, however, it has not yet been applied in fruit crops. Accordingly, we tested as a proof-of-concept the binding of two previously characterised R2R3-MYB TFs to their known targets of the stilbene pathway, MYB14 and MYB15, obtaining 5,222 and 4,502 binding events assigned to 4,038 and 3,645 genes for each TF, respectively. Bound genes (putative targets) were overlapped with aggregated gene centred co-expression networks resulting in shared and exclusive High Confidence Targets (HCTs) suggesting a high, but not complete, redundancy. Our results show that in addition to the previously known but few STS targets, these regulators bind to almost half of the complete STS family in addition to other phenylpropanoid- and stilbenoid-related genes. We also suggest they are potentially involved in other processes such as the circadian rhythm or the synthesis of biotin. We searched the activated transcriptomes of transiently MYB15-overexpressing grapevine plants and observed a large activation of its high confidence targets, validating our methodological approach. Our results also show that MYB15 seems to play a role in regulating other stilbenoid-related TFs such as WRKY03.This work was supported by Grant PGC2018-099449-A-I00 and by the Ramón y Cajal program grant RYC-2017-23645, both awarded to J.T.M. and to the FPI scholarship PRE2019-088044 granted to L.O. from the Ministerio de Ciencia, Innovaci´on y Universidades (MCIU, Spain), Agencia Estatal de Investigaci´on (AEI, Spain), and Fondo Europeo de Desarrollo Regional (FEDER, European Union). C.Z. is supported by China Scholarship Council (CSC) no. 201906300087. This article is based upon work from COST Action CA 17111 INTEGRAPE, supported by COST (European Cooperation in Science and Technology). Data has been treated and uploaded in public repositories according to the FAIR principles.N

The photomorphogenic factors UV-B RECEPTOR 1, ELONGATED HYPOCOTYL 5, and HY5 HOMOLOGUE are part of the UV-B signalling pathway in grapevine and mediate flavonol accumulation in response to the environment

Grapevine (Vitis vinifera L.) is a species well known for its adaptation to radiation. However, photomorphogenic factors related to UV-B responses have not been molecularly characterized. We cloned and studied the role of UV-B RECEPTOR (UVR1), ELONGATED HYPOCOTYL 5 (HY5), and HY5 HOMOLOGUE (HYH) from V. vinifera. We performed gene functional characterizations, generated co-expression networks, and tested them in different environmental conditions. These genes complemented the Arabidopsis uvr8 and hy5 mutants in morphological and secondary metabolic responses to radiation. We combined microarray and RNA sequencing (RNA-seq) data with promoter inspections to identify HY5 and HYH putative target genes and their DNA binding preferences. Despite sharing a large set of common co-expressed genes, we found different hierarchies for HY5 and HYH depending on the organ and stress condition, reflecting both co-operative and partially redundant roles. New candidate UV-B gene markers were supported by the presence of HY5-binding sites. These included a set of flavonol-related genes that were up-regulated in a HY5 transient expression assay. We irradiated in vitro plantlets and fruits from old potted vines with high and low UV-B exposures and followed the accumulation of flavonols and changes in gene expression in comparison with non-irradiated conditions. UVR1, HY5, and HYH expression varied with organ, developmental stage, and type of radiation. Surprisingly, UVR1 expression was modulated by shading and temperature in berries, but not by UV-B radiation. We propose that the UV-B response machinery favours berry flavonol accumulation through the activation of HY5 and HYH at different developmental stages at both high and low UV-B exposures. © The Author 2016. Published by Oxford University Press on behalf of the Society for Experimental Biology

Direct regulation of shikimate, early phenylpropanoid, and stilbenoid pathways by subgroup 2 R2R3-MYBs in grapevine

The stilbenoid pathway is responsible for the production of resveratrol in grapevine (Vitis vinifera L.). A few transcription factors (TFs) have been identified as regulators of this pathway but the extent of this control has not been deeply studied. Here we show how DNA affinity purification sequencing (DAP-Seq) allows for the genome-wide TF-binding site interrogation in grape. We obtained 5190 and 4443 binding events assigned to 4041 and 3626 genes for MYB14 and MYB15, respectively (approximately 40% of peaks located within −10 kb of transcription start sites). DAP-Seq of MYB14/MYB15 was combined with aggregate gene co-expression networks (GCNs) built from more than 1400 transcriptomic datasets from leaves, fruits, and flowers to narrow down bound genes to a set of high confidence targets. The analysis of MYB14, MYB15, and MYB13, a third uncharacterized member of Subgroup 2 (S2), showed that in addition to the few previously known stilbene synthase (STS) targets, these regulators bind to 30 of 47 STS family genes. Moreover, all three MYBs bind to several PAL, C4H, and 4CL genes, in addition to shikimate pathway genes, the WRKY03 stilbenoid co-regulator and resveratrol-modifying gene candidates among which ROMT2-3 were validated enzymatically. A high proportion of DAP-Seq bound genes were induced in the activated transcriptomes of transient MYB15-overexpressing grapevine leaves, validating our methodological approach for delimiting TF targets. Overall, Subgroup 2 R2R3-MYBs appear to play a key role in binding and directly regulating several primary and secondary metabolic steps leading to an increased flux towards stilbenoid production. The integration of DAP-Seq and reciprocal GCNs offers a rapid framework for gene function characterization using genome-wide approaches in the context of non-model plant species and stands up as a valid first approach for identifying gene regulatory networks of specialized metabolism.This work was supported by Grant PGC2018-099449-A-I00 and by the Ramón y Cajal program (grant RYC-2017-23 645), both awarded to JTM, and to the FPI scholarship (PRE2019-088044) granted to LO from the Ministerio de Ciencia, Innovación y Universidades (MCIU, Spain), Agencia Estatal de Investigación (AEI, Spain), and Fondo Europeo de Desarrollo Regional (FEDER, European Union). CZ is supported by China Scholarship Council (CSC; no. 201906300087). KG and ZR were supported by the Slovenian Research Agency (grants P4-0165 and Z7-1888). SCH is partially supported by the National Science Foundation (grant PGRP IOS-1916804). This article is based upon work from COST Action CA 17111 INTEGRAPE, supported by COST (European Cooperation in Science and Technology).Peer reviewe