Hybrid Vitis Cultivars with American or Asian Ancestries Show Higher Tolerance towards Grapevine Trunk Diseases.

Grape production worldwide is increasingly threatened by grapevine trunk diseases (GTDs). No grapevine cultivar is known to be entirely resistant to GTDs, but susceptibility varies greatly. To quantify these differences, four Hungarian grape germplasm collections containing 305 different cultivars were surveyed to determine the ratios of GTDs based on symptom expression and the proportion of plant loss within all GTD symptoms. The cultivars of monophyletic Vitis vinifera L. origin were amongst the most sensitive ones, and their sensitivity was significantly (p < 0.01) higher than that of the interspecific (hybrid) cultivars assessed, which are defined by the presence of Vitis species other than V. vinifera (e.g., V. labrusca L., V. rupestris Scheele, and V. amurensis Rupr.) in their pedigree. We conclude that the ancestral diversity of grapes confers a higher degree of resilience against GTDs.

Two ways to die: Species dependent PCD modes in grapevine cells.

Programmed cell death (PCD) is considered as a hallmark of strain-specific immunity. In contrast, generic basal immunity is thought to act without PCD. This classical bifurcation has been questioned during recent years. Likewise, the role of jasmonate signalling for these two modes of innate immunity has remained ambiguous. We have addressed both questions using two closely related grapevine cell lines (V. rupestris, V. vinifera cv. 'Pinot Noir') that contrast in their cell-death response to the bacterial elicitor harpin and the hormonal trigger methyl jasmonate (MeJA). We follow different cellular (loss of membrane integrity, mortality), molecular (induction of transcripts for phytoalexin synthesis and for metacaspases), as well as metabolic (sphingolipid profiles) responses to the two triggers in the two cell lines. The role of NADPH oxidases and induction of transcripts for the class-II metacaspases MC5 differ qualitatively between the two cell lines. We tested a possible role of sphingolipid metabolism but can rule this out. We propose a model, where V. rupestris, originating from co-evolution with several biotrophic pathogens, readily activates a hypersensitive cell death in response to harpin, while the context of MeJA-induced cell death in 'Pinot Noir' might not be related to immunity at all. We propose that the underlying signalling is modular, recruiting metacaspases differently depending on upstream signalling.

Comparative Study on Grape Berry Anthocyanins of Various Teinturier Varieties.

The red-fleshed grape cultivars, called teinturier or dyer grapes, contain anthocyanins in both the skin and flesh. These phenolic compounds exhibit excellent coloring ability, and as antioxidants, they are important bioactive compounds in food crops. In this work, anthocyanin patterns of grape berries of fifteen teinturier varieties collected from the gene bank located at Pécs in the southwest of Hungary were compared. Anthocyanin profiles of numerous varieties originating from Hungary such as 'Bíborkadarka', 'Kármin', 'Kurucvér', and 'Turán' are reported for the first time. Anthocyanins extracted separately from the skin and juice were analyzed using high-performance liquid chromatography coupled with a photodiode array detector. For the identification of compounds, high-resolution orbitrap mass spectrometry was used. All in all, twenty-one anthocyanins were identified and quantified. We found that anthocyanin patterns differed significantly in the skin and juice for all investigated cultivars. For Vitis vinifera varieties, the predominant anthocyanin in the skin was malvidin-3-O-glucoside, while the main pigment in the juice was peonidin-3-O-glucoside. For the first time, a significant amount of diglucosides was detected in two Vitis Vinifera cultivars with a direct relationship. In general, the pigment composition of the skin was much more complex than that of the juice. The comparative study with presented patterns gives valuable and beneficial information from a chemotaxonomical point of view. Our results also help to choose the appropriate teinturier varieties with the desired anthocyanins for food coloring or winemaking purposes.

Transcriptome Analysis and Cell Morphology of Vitis rupestris Cells to Botryosphaeria Dieback Pathogen Diplodia seriata.

Diplodia seriata, one of the major causal agents of Botryosphaeria dieback, spreads worldwide causing cankers, leaf spots and fruit black rot in grapevine. Vitis rupestris is an American wild grapevine widely used for resistance and rootstock breeding and was found to be highly resistant to Botryosphaeria dieback. The defence responses of V. rupestris to D. seriata 98.1 were analysed by RNA-seq in this study. There were 1365 differentially expressed genes (DEGs) annotated with gene ontology (GO) and enriched by the Kyoto Encyclopedia of gene and genome (KEGG) database. The DEGs could be allocated to the flavonoid biosynthesis pathway and the plant-pathogen interaction pathway. Among them, 53 DEGs were transcription factors (TFs). The expression levels of 12 genes were further verified by real-time quantitative reverse transcription polymerase chain reaction (qRT-PCR). The aggregation of proteins on plasma membrane, formation variations in cytoskeleton and plasmodesmata, as well as hormone regulations revealed a declined physiological status in V. rupestris suspension cells after incubation with the culture filtrates of D. seriata 98.1. This study provides insights into the molecular mechanisms in grapevine cells response to D. seriata 98.1, which will be valuable for the control of Botryosphaeria dieback.

Effect of rootstocks on volatile composition of Merlot wines.

BACKGROUND: Scion physiology and grape quality are impacted by rootstock choice. There is little available information about the effects of rootstock on wine volatile composition, particularly when comparing grafted with own-rooted grapevines. This field trial was aimed at studying the influence of rootstock choice on volatile composition of Merlot wines. RESULTS: Wines made from grapes harvested from own-rooted grapevines had the lowest content of (E)-3-hexenol, diethyl succinate and total ethyl esters and the highest content of 1-pentanol, 1-hexanol, (Z)-3-hexenol, diethyl malate and acetovanillone. Rootstocks such as 99R and 140Ru led to a higher content of total ethyl esters in wines followed by 110R, 1103P and Gravesac. According to odor activity values, Merlot wines were characterized by roses, sweat, cheese and banana aromas. CONCLUSIONS: This work provides valuable information about the potential impact of rootstocks on wine volatile composition for Merlot wines. © 2020 Society of Chemical Industry.

Two grapevine metacaspase genes mediate ETI-like cell death in grapevine defence against infection of Plasmopara viticola.

Metacaspase, as hypersensitive response (HR) executors, has been identified in many plant species. Previously, the entire gene family of metacaspase has been uncovered, but there are still questions that remain unclear regarding HR-regulating gene members. In this study, based on metacaspase expression during different grapevine genotypes interacting with Plasmopara viticola, we identified MC2 and MC5 as candidates involved in HR. We overexpressed both metacaspases as GFP fusions in tobacco BY-2 cells to address subcellular localization and cellular functions. We found MC2 located at the ER, while MC5 was nucleocytoplasmic. In these overexpressor lines, cell death elicited by the bacterial protein harpin, is significantly enhanced, indicating MC2 and MC5 mediated defence-related programmed cell death (PCD). This effect was mitigated, when the membrane-located NADPH oxidase was inhibited by the specific inhibitor diphenylene iodonium, or when cells were complemented with methyl jasmonate, a crucial signal of basal immunity. Both findings are consistent with a role of MC2 and MC5 in cell death-related immunity. Using a dual-luciferase reporter system in grapevine cells we demonstrated both MC2 and MC5 promoter alleles from V. rupestris were more responsive to harpin than those from V. vinifera cv 'Müller-Thurgau', while they were not induced by MeJA as signal linked with basal immunity. These findings support a model, where MC2 and MC5 act specifically as executors of the HR.

Cold sensing in grapevine-Which signals are upstream of the microtubular "thermometer".

Plants can acquire freezing tolerance in response to cold but non-freezing temperatures. To efficiently activate this cold acclimation, low temperature has to be sensed and processed swiftly, a process that is linked with a transient elimination of microtubules. Here, we address cold-induced microtubules elimination in a grapevine cell line stably expressing a green fluorescent protein fusion of Arabidopsis TuB6, which allows to follow their response in vivo and to quantify this response by quantitative image analysis. We use time-course studies with several specific pharmacological inhibitors and activators to dissect the signalling events acting upstream of microtubules elimination. We find that microtubules disappear within 30 min after the onset of cold stress. We provide evidence for roles of calcium influx, membrane rigidification, and activation of NAD(P)H oxidase as factors in signal susception and amplification. We further conclude that a G-protein in concert with a phospholipase D convey the signal towards microtubules, whereas calmodulin seems to be not involved. Moreover, activation of jasmonate pathway in response to cold is required for an efficient microtubule response. We summarize our findings in a working model on a complex signalling hub at the membrane-cytoskeleton interphase that assembles the susception, perception and early transduction of cold signals.

Tubulin marker line of grapevine suspension cells as a tool to follow early stress responses.

Plant microtubules (MTs), in addition to their role in cell division and cell expansion, respond to various stress signals. To understand the biological function of this early response requires non-destructive strategies for visualization in cellular models that are highly responsive to stress signals. We have therefore generated a transgenic tubulin marker line for a cell line from the grapevine Vitis rupestris that readily responds to stress factors of defense-related and abiotic stresses based on a fusion of the green fluorescent protein with Arabidopsis ß-tubulin 6. By a combination of spinning-disk confocal microscopy with quantitative image analysis, we could detect early and specific responses of MTs to defense-related and abiotic stress factors in vivo. We observed that Harpin Z (HrpZ), a bacterial elicitor that can trigger programmed cell death, rapidly eliminated radial MTs, followed by a slower depletion of the cortical array. Jasmonic acid (JA), in contrast, induced bundling of cortical MTs. Auxin reduced the thickness of cortical MTs. This effect followed a characteristic bell-shaped dose-dependency and could revert JA-induced bundling. Impeded cell expansion as a consequence of stress treatment or superoptimal auxin was linked with the appearance of intranuclear tubulin speckles. The early and stimulus-specific responses of MTs are discussed with respect to a function in processing or decoding of stress signals.