Alterations in Grapevine Leaf Metabolism Occur Prior to Esca Apoplexy Appearance

The Combination of Both Heat and Water Stresses May Worsen Botryosphaeria Dieback Symptoms in Grapevine

(1) Background: Grapevine trunk diseases (GTDs) have become a global threat to vineyards worldwide. These diseases share three main common features. First, they are caused by multiple pathogenic micro-organisms. Second, these pathogens often maintain a long latent phase, which makes any research in pathology and symptomatology challenging. Third, a consensus is raising to pinpoint combined abiotic stresses as a key factor contributing to disease symptom expression. (2) Methods: We analyzed the impact of combined abiotic stresses in grapevine cuttings artificially infected by two fungi involved in Botryosphaeria dieback (one of the major GTDs), Neofusicoccum parvum and Diplodia seriata. Fungal-infected and control plants were subjected to single or combined abiotic stresses (heat stress, drought stress or both). Disease intensity was monitored thanks to the measurement of necrosis area size. (3) Results and conclusions: Overall, our results suggest that combined stresses might have a stronger impact on disease intensity upon infection by the less virulent pathogen Diplodia seriata. This conclusion is discussed through the impact on plant physiology using metabolomic and transcriptomic analyses of leaves sampled for the different conditions.

The hidden world within plants: metatranscriptomics unveils the complexity of wood microbiomes

The importance of plants as complex entities influenced by genomes of the associated microorganisms is now seen as a new source of variability for a more sustainable agriculture, also in the light of ongoing climate change. For this reason, we investigated through metatranscriptomics whether the taxa profile and behaviour of microbial communities associated with the wood of 20-year-old grapevine plants are influenced by the health status of the host. We report for the first time a metatranscriptome from a complex tissue in a real environment, highlighting that this approach is able to define the microbial community better than referenced transcriptomic approaches. In parallel, the use of total RNA enabled the identification of bacterial taxa in healthy samples that, once isolated from the original wood tissue, displayed potential biocontrol activities against a wood-degrading fungal taxon. Furthermore, we revealed an unprecedented high number of new viral entities (~120 new viral species among 180 identified) associated with a single and limited environment and with potential impact on the whole holobiont. Taken together, our results suggest a complex multitrophic interaction in which the viral community also plays a crucial role in raising new ecological questions for the exploitation of microbial-assisted sustainable agriculture.

Modification of Early Response of Vitis vinifera to Pathogens Relating to Esca Disease and Biocontrol Agent Vintec® Revealed By Untargeted Metabolomics on Woody Tissues

Esca disease is one of the most destructive grapevine trunk diseases. Phaeoacremonium minimum and Phaeomoniella chlamydospora are two of the known fungal pathogens associated with this disease. Today, biocontrol agents against Esca are mainly based on the use of the strain of the mycoparasite fungal genus Trichoderma such as the Vintec® product. The aim of this study was to investigate early response of woody tissues to Esca pathogens and identify metabolites that could be correlated with a biocontrol activity within a complex woody matrix. An untargeted liquid chromatography-high-resolution mass spectrometry metabolomic approach coupled to a spectral similarity network was used to highlight clusters of compounds associated with the plant response to pathogens and biocontrol. Dereplication highlighted the possible role of glycerophospholipids and polyphenol compounds, the latest mainly belonging to stilbenoids. Antifungal activity of some relevant biomarkers, evaluated in vitro on Phaeomoniella chlamydospora and Botrytis cinerea, suggests that some of these compounds can play a role to limit the development of Esca pathogens in planta.

Metabolite profile data of grapevine plants with brown wood streaking and grapevine leaf stripe (esca complex disease) symptoms

Leaf samples were obtained from Vitis vinifera ‘Malvasia Fina’ plants with well-characterized esca complex disease symptoms (n = 18) and from healthy uninfected plants (n = 6). Leaves from diseased plants were divided into three groups: asymptomatic (ASY), chlorotic (SY1), and scorched leaves (SY2). The metabolic profile of these leaves was then examined using an ultrahigh performance liquid chromatography system coupled to a Q-Exactive Hybrid Quadrupole-Orbitrap high resolution/accurate mass spectrometer interfaced with a heated electrospray ionization source. The number of small molecules measured in a sample was increased by varying the reconstitution solvent, chromatographic column, and ionization source. Data on accurate masses, peak areas, and relative levels of several metabolites were documented for each leaf sample, using the abovementioned approach. In this paper, data on 235 metabolites of known structural identity are reported, along with the biochemical pathways to which the metabolites belong. The remaining data related to lipid species and with a different focus of the research question are reported elsewhere. The broad coverage of metabolites reported here resulted in a greater coverage of the biochemical pathways involved in grapevine metabolism, which could provide a better understanding of the biochemical changes occurring during the onset and progression of foliar symptoms after invasion of woods by esca-associated pathogens. To determine which metabolites varied according to the study design, the detected ion features were processed using different statistical methods, including mean and median values, fold changes, Welch's two-sample t-test, false discovery rate, and quartiles represented by box and whisker plots. The goal of this statistical evaluation was to assess the responses of healthy, asymptomatic, and symptomatic leaf groups using a pairwise comparison, thus providing an opportunity for detecting statistically significant compounds and uncovering the dynamic metabolic models underlying disease latency and symptom expression.

Esca-affected grapevine leaf metabolome is clone- and vintage-dependent

Esca is a complex grapevine trunk disease caused by wood-rotting ascomycetes and basidiomycetes and leading to several foliar and wood symptoms. Given that the esca expression can be influenced by several environmental, physiological, and genetic factors, foliar symptoms are inconsistent in incidence and prevalence and may appear 1 year but not the following. We have previously reported a clone-dependent expression of the disease in cv Chardonnay. Owing to metabolome analysis, we could discriminate the metabolite fingerprint of green leaves collected on diseased vines of clones 76 and 95. These clone-dependent fingerprints were year-dependent in intensity and nature. The present work was conducted to determine if the clone-dependent disease expression observed is specific to Chardonnay or if it also occurs in another cultivar. A plot located in the Jura vineyard (France) and planted with both 1004 and 1026 clones of Trousseau, a cultivar highly susceptible to esca, was thus selected and studied during 2017 and 2018. A year-dependent variation of the symptoms expression was first observed and a possible relationship with rainfall is hypothesized and discussed. Moreover, a higher percentage of the clone 1026 vines expressed disease, compared to the 1004 ones, suggesting the higher susceptibility of this clone. Finally, metabolomic analyses of the remaining green leaves (i.e, without symptom expression) of partial esca-apoplectic vines allowed us to confirm a clone-dependent metabolic response to the disease. The metabolite fingerprints obtained differed in nature and intensity to those previously reported for Chardonnay and also between years.

Cultivar- and Wood Area-Dependent Metabolomic Fingerprints of Grapevine Infected by Botryosphaeria Dieback

Botryosphaeria dieback is one of the most significant grapevine trunk diseases that affects the sustainability of the vineyards and provokes economic losses. The causal agents, Botryosphaeriaceae species, live in and colonize the wood of the perennial organs causing wood necrosis. Diseased vines show foliar symptoms, chlorosis, or apoplexy, associated to a characteristic brown stripe under the bark. According to the susceptibility of the cultivars, specific proteins such as PR-proteins and other defense-related proteins are accumulated in the brown stripe compared with the healthy woody tissues. In this study, we enhanced the characterization of the brown stripe and the healthy wood by obtaining a metabolite profiling for the three cultivars Chardonnay, Gewurztraminer, and Mourvèdre to deeper understand the interaction between the Botryosphaeria dieback pathogens and grapevine. The study confirmed a specific pattern according to the cultivar and revealed significant differences between the brown stripe and the healthy wood, especially for phytochemical and lipid compounds. This is the first time that such chemical discrimination was made and that lipids were so remarkably highlighted in the interaction of Botryosphaeriaceae species and grapevine. Their role in the disease development is discussed.

Dataset of levels and masses of lipid species in healthy, asymptomatic and symptomatic leaves of vitis vinifera L. 'Malvasia fina' affected by ESCA complex disease

The dataset presented in this paper comprises the masses of 208 lipid species and other compounds of lipid metabolism, and their levels in leaves of vines with brown wood streaking and grapevine leaf stripe, two symptomatic expressions of Esca complex disease (ESCA). Healthy, asymptomatic and symptomatic leaves were collected from the cultivar Malvasia Fina grown in a vineyard. The lipidome of these leaves was characterized using a platform consisting of an Ultrahigh Performance Liquid Chromatography and a Gas chromatography equipment coupled to a Q-Exactive Hybrid Quadrupole-Orbitrap high resolution/accurate Mass Spectrometer interfaced with a heated electrospray ionization source. The analysis permitted the detection of 158 molecular species of known identity and 50 species of unknown structural identity. The area counts of these molecular species is reported in the dataset, along with fold changes (log2-ratio), P-values (Welch's two-sample t-test), and q-values (false discovery rate) from all pairwise comparisons among experimental groups. These statistical data are intended to serve as means of identification for lipid species whose levels were altered by the disease, and which could be used as biomarkers of symptom emergence and disease progression. Because of few studies on the subject, the association between modulation of lipid biosynthetic pathways and disease progression in grapevine has remained poorly understood. The analysis of the data described here has already provided new perspectives regarding the pathogenesis of ESCA leaf symptom formation. Reanalysis of these data would undoubtedly unravel some physiological roles played by lipids in the adaptation of vine plants to stressful conditions.

A Lipidomic Analysis of Leaves of Esca-Affected Grapevine Suggests a Role for Galactolipids in the Defense Response and Appearance of Foliar Symptoms

Both qualitative and quantitative changes occur in the lipid composition of Vitis vinifera L. tissues, which may compromise the defense response against Esca complex disease, a widespread and damaging trunk disease. In this study, a lipidomic analysis of grapevine leaves is conducted to assess how lipid membrane remodeling relates to the emergence and progression of Esca foliar symptoms. In total, 208 molecular species (including lipids, four hormones, and some other compounds of the metabolism of lipids) were detected. Lipid species were readily assigned to the classes fatty acyls, glycerolipids, glycerophospholipids, sphingolipids, sterols, and prenol lipids. Using different clustering analyses, distinct metabolic pathways stimulated at different stages of disease development were characterized. These analyses revealed consistent changes in the abundance of 13 galactolipids and two diacylglycerolipids. Overall, the observations indicated an increment in the levels of these lipid species in leaves of asymptomatic vines and a progressive drop with increasing foliar symptom severity in symptomatic vines. Five fatty acids also appear to exert a central role in the etiopathogenesis of Esca complex disease because of their accumulation in leaves of asymptomatic vines, namely, heptadecanoic, linoleic, γ-linolenic, arachidonic, and stearic acids. Symptomatic leaves were characterized by high levels of all lipid classes, except for galactolipids, lyso-galactolipids, and compounds relevant to the biosynthesis of chlorophylls and carotenoids, that exhibited decreased levels. The data also suggested a jasmonic acid-associated signaling mechanism activation upon the invasion of woods by Esca-associated fungi, compared with abscisic and salicylic acids. Further research is required for validation of these results with additional molecular analyses using more vine cultivars.

Wood Metabolomic Responses of Wild and Cultivated Grapevine to Infection with Neofusicoccum parvum, a Trunk Disease Pathogen

Grapevine trunk diseases (GTDs), which are associated with complex of xylem-inhabiting fungi, represent one of the major threats to vineyard sustainability currently. Botryosphaeria dieback, one of the major GTDs, is associated with wood colonization by Botryosphaeriaceae fungi, especially Neofusicoccum parvum. We used GC-MS and HPLC-MS to compare the wood metabolomic responses of the susceptible Vitis vinifera subsp. vinifera (V. v. subsp. vinifera) and the tolerant Vitis vinifera subsp. sylvestris (V. v. subsp. sylvestris) after artificial inoculation with Neofusicoccum parvum (N. parvum). N. parvum inoculation triggered major changes in both primary and specialized metabolites in the wood. In both subspecies, infection resulted in a strong decrease in sugars (fructose, glucose, sucrose), whereas sugar alcohol content (mannitol and arabitol) was enhanced. Concerning amino acids, N. parvum early infection triggered a decrease in aspartic acid, serine, and asparagine, and a strong increase in alanine and β-alanine. A trend for more intense primary metabolism alteration was observed in V. v. subsp. sylvestris compared to V. v. subsp. vinifera. N. parvum infection also triggered major changes in stilbene and flavonoid compounds. The content in resveratrol and several resveratrol oligomers increased in the wood of both subspecies after infection. Interestingly, we found a higher induction of resveratrol oligomer (putative E-miyabenol C, vitisin C, hopeaphenol, ampelopsin C) contents after wood inoculation in V. v. subsp. sylvestris.

Sodium arsenite effect on Vitis vinifera L. Physiology

Sodium arsenite (NaAsO₂) was especially used as a dormant spray to control grapevine trunk diseases (GTDs) in European vineyards until 2003 when it was banned. It was an efficient product but it was banned due to high risk for human health and the environment. Now, as one of the consequences with climatic changes, GTDs threaten the sustainability of vineyards since no similar and efficacious sprays are presently available to reduce the impact of GTDs. Research efforts were devoted to identify other active ingredients and biological control agents but they remained limited in term of efficacy. New solutions might follow from a better understanding of the modes of action of sodium arsenite which are currently lacking, specially its impact on grapevine physiology. For this study, grafted plants cv. Tempranillo were sprayed by sodium arsenite at the end of the winter. During the vegetative period, the impact on plant physiology was studied by measurement of the photosynthetic activity, the vine growth and development, and some defense responses. Our results showed that arsenic was translocated throughout the vine with an increasing gradient from the leaves to the root system, that photosynthesis was firstly reduced and then stimulated, and that plant tolerance responses were induced especially antioxidant system. The activation of grapevine defense responses by sodium arsenite could be a complementary action to fight fungal pathogens in addition to the fungicide effect.

The Arabidopsis glutathione transferases, AtGSTF8 and AtGSTU19 are involved in the maintenance of root redox homeostasis affecting meristem size and salt stress sensitivity

The tau (U) and phi (F) classes of glutathione transferase (GST) enzymes reduce the glutathione (GSH) pool using GSH as a co-substrate, thus influence numerous redox-dependent processes including hormonal and stress responses. We performed detailed analysis of the redox potential and reactive oxygen species levels in longitudinal zones of 7-day-old roots of Arabidopsis thaliana L. Col-0 wild type and Atsgtf8 and Atgstu19 insertional mutants. Using redox-sensitive cytosolic green fluorescent protein (roGFP2) the redox status of the meristematic, transition, and elongation zones was determined under control and salt stress (3-hour of 75 or 150 mM NaCl treatment) conditions. The Atgstu19 mutant had the most oxidized redox status in all root zones throughout the experiments. Using fluorescent dyes significantly higher superoxide radical (O₂^-) levels was detected in both Atgst mutants than in the Col-0 control. Salt treatment resulted in the highest O₂^- increase in the Atgstf8 root, while the amount of H₂O₂ elevated most in the case of Atgstu19. Moreover, vitality decreased in Atgstu19 roots more than in wild type under salt stress. Our results indicate that AtGSTF8 and especially the AtGSTU19 proteins function in the root fine-tuning the redox homeostasis both under control and salt stress conditions.

Grapevine trunk diseases under thermal and water stresses

Heat and water stresses, individually or combined, affect both the plant (development, physiology, and production) and the pathogens (growth, morphology, dissemination, distribution, and virulence). The grapevine response to combined abiotic and biotic stresses is complex and cannot be inferred from the response to each single stress. Several factors might impact the response and the recovery of the grapevine, such as the intensity, duration, and timing of the stresses. In the heat/water stress-GTDs-grapevine interaction, the nature of the pathogens, and the host, i.e., the nature of the rootstock, the cultivar and the clone, has a great importance. This review highlights the lack of studies investigating the response to combined stresses, in particular molecular studies, and the misreading of the relationship between rootstock and scion in the relationship GTDs/abiotic stresses. Grapevine trunk diseases (GTDs) are one of the biggest threats to vineyard sustainability in the next 30 years. Although many treatments and practices are used to manage GTDs, there has been an increase in the prevalence of these diseases due to several factors such as vineyard intensification, aging vineyards, or nursery practices. The ban of efficient treatments, i.e., sodium arsenite, carbendazim, and benomyl, in the early 2000s may be partly responsible for the fast spread of these diseases. However, GTD-associated fungi can act as endophytes for several years on, or inside the vine until the appearance of the first symptoms. This prompted several researchers to hypothesise that abiotic conditions, especially thermal and water stresses, were involved in the initiation of GTD symptoms. Unfortunately, the frequency of these abiotic conditions occurring is likely to increase according to the recent consensus scenario of climate change, especially in wine-growing areas. In this article, following a review on the impact of combined thermal and water stresses on grapevine physiology, we will examine (1) how this combination of stresses might influence the lifestyle of GTD pathogens, (2) learnings from grapevine field experiments and modelling aiming at studying biotic and abiotic stresses, and (3) what mechanistic concepts can be used to explain how these stresses might affect the grapevine plant status.

Specific profile of Tempranillo grapevines related to Esca-leaf symptoms and climate conditions

Esca is a destructive fungal disease affecting grapevines worldwide. In the Esca complex, grapevine leaf stripe disease (GLSD) designates specifically the disease that causes the typical leaf symptoms on infected vines. Understanding foliage alterations produced by GLSD may help to identify potential markers of tolerance to this disease. In this work, changes related to physiological parameters, photosynthetic pigments and phenolic compounds were evaluated. Moreover, the expression of 10 genes was tracked determined by quantitative reverse transcription-PCR. For this, symptomatic and asymptomatic vines from three different Tempranillo vineyards were evaluated. Vineyards differed in climate classification and water resources. Botryosphaeriaceae species and Esca causal agents (Phaeomoniella chlamydospora, Phaeoacremonium spp. and Fomitiporia mediterranea) were isolated and identified from symptomatic vines. Under water restriction, a significant decrease on the physiological activity of symptomatic vines was observed. Also, symptomatic leaves showed lower content on chlorophylls and carotenoids and some alterations on their phenolic profiles. GLSD symptoms induced the expression of defense-related genes, especially PR6, STS and Chit 1b. This research provides valuable information regarding physiological, chemical and molecular changes in Esca affected leaves of Tempranillo grown in vineyards related to the climate conditions.

Clone-Dependent Expression of Esca Disease Revealed by Leaf Metabolite Analysis

Grapevine trutk diseases, especially Esca, are of major concern since they gradually alter vineyards worldwide and cause heavy economic losses. The expression of Esca disease symptoms depends on several factors, including the grapevine cultivar. In this context, a possible clone-dependent expression of the Esca disease was studied. Two clones of 'Chardonnay' grown in the same plot were compared according to their developmental and physiological traits, metabolome, and foliar symptom expression. Analysis of their leaf metabolome highlighted differences related to symptom expression. Interestingly, the content of a few specific metabolites exhibited opposite variations in leaves of symptomatic shoots of clones 76 and 95. Altogether this study showed a clone-dependent expression of Esca disease in 'Chardonnay' and the relevance of GC-MS and 3D fluorescence methods to analyze the impact of the disease on the leaf metabolome.

Glutathione S-Transferase Enzymes in Plant-Pathogen Interactions

Plant glutathione S-transferases (GSTs) are ubiquitous and multifunctional enzymes encoded by large gene families. A characteristic feature of GST genes is their high inducibility by a wide range of stress conditions including biotic stress. Early studies on the role of GSTs in plant biotic stress showed that certain GST genes are specifically up-regulated by microbial infections. Later numerous transcriptome-wide investigations proved that distinct groups of GSTs are markedly induced in the early phase of bacterial, fungal and viral infections. Proteomic investigations also confirmed the accumulation of multiple GST proteins in infected plants. Furthermore, functional studies revealed that overexpression or silencing of specific GSTs can markedly modify disease symptoms and also pathogen multiplication rates. However, very limited information is available about the exact metabolic functions of disease-induced GST isoenzymes and about their endogenous substrates. The already recognized roles of GSTs are the detoxification of toxic substances by their conjugation with glutathione, the attenuation of oxidative stress and the participation in hormone transport. Some GSTs display glutathione peroxidase activity and these GSTs can detoxify toxic lipid hydroperoxides that accumulate during infections. GSTs can also possess ligandin functions and participate in the intracellular transport of auxins. Notably, the expression of multiple GSTs is massively activated by salicylic acid and some GST enzymes were demonstrated to be receptor proteins of salicylic acid. Furthermore, induction of GST genes or elevated GST activities have often been observed in plants treated with beneficial microbes (bacteria and fungi) that induce a systemic resistance response (ISR) to subsequent pathogen infections. Further research is needed to reveal the exact metabolic functions of GST isoenzymes in infected plants and to understand their contribution to disease resistance.

Understand the Potential Role of Aureobasidium pullulans, a Resident Microorganism From Grapevine, to Prevent the Infection Caused by Diplodia seriata

Grapevine trunk diseases (GTDs) are one of the major concern amongst grapevine diseases, responsible for the decline of vineyards and for several economical losses. Since grapevine is naturally colonized by resident microorganisms such as Aureobasidium pullulans, the present challenge is to understand their biocontrol potential and how such microorganisms can be successfully integrated in the control of GTDs. In this context, the first priority consists to exploit the plant-beneficial-phytopathogen interactions in plant model systems, to identify the most prevalent equilibrium limiting expression of GTDs. In the current study, we deep characterized the interaction of a resident and abundant microorganism from grapevine - Aureobasidium pullulans strain Fito_F278 - against D. seriata F98.1, a Botryosphaeria dieback agent, and with plant (cv Chardonnay). Results revealed that A. pullulans strain Fito_F278 was able to reduce significantly the mycelium growth of D. seriata F98.1 at 33.41 ± 0.55%, under in vitro conditions, though this reduction is possibly dependent on a direct interaction between strain Fito_F278 and pathogen. Furthermore, strain Fito_F278 was able to promote an induction of some plant defense responses in cutting plants, 1 week after the D. seriata F98.1 infection. Results evidenced that strain Fito_F278 colonized efficiently grapevine at both epiphyte and endophyte level, could persist on plant roots for long-periods (up to 2 months after its inoculation) and grow at different pH and high salinity conditions. Moreover, a significant decrease of the microbial load from soil and rhizosphere was observed in plants treated with the strain Fito_F278, suggesting its competitivity potential in a microbial ecosystem. Altogether, the present study gives the first insights about the interaction of A. pullulans strain Fito_F278, a resident microorganism, with grapevine, its potential role against a Botryosphaeria dieback agent, and highlights its importance to toward more resilient grapevine.