Differential phenolic production in leaves of Vitis vinifera cv. Alvarinho affected with esca disease

Phenolic profile changes of grapevine leaves infected with Erysiphe necator

BACKGROUND

Powdery mildew in grapevine is caused by Erysiphe necator and its control requires many chemical treatments. Numerous efforts are being made to improve disease management to achieve crop sustainability goals. The exogenous induction of plant immune responses is one of the most encouraging strategies currently being developed. The objective of this research was to analyse differences in phenolic compound concentrations in E. necator-infected leaves of two varieties of Vitis vinifera, Tempranillo and Tempranillo Blanco, using ultra performance liquid chromatography coupled with mass spectrometry. To understand the susceptibility of the varieties, in vitro assays using whole leaves were done.

RESULTS

Differences in susceptibility between varieties were found in the early stage of the disease. In both varieties, total phenolic compounds were higher in infected leaves; however, hydroxycinnamic acid, anthocyanins and stilbenes were higher only in Tempranillo. Twenty-six compounds showed differential responses to the fungal disease in Tempranillo, but only two in Tempranillo Blanco: syringa resinol, which was not detected in diseased leaves; and gallocatechin, which increased at 5 days post inoculation. In Tempranillo, four anthocyanidins, six hydroxycinnamic acids, mainly feruloyl derivates, and epigallocatechin gallate were higher in infected leaves at the beginning of the infection, whereas (-)-epicatechin and protocatechuic hexoside contents were lower.

CONCLUSION

Disease-induced changes in phenolic compound biosynthesis were found. The increase in anthocyanidin content and flavan-3-ol galloylation could have a role in delaying E. necator growth in Tempranillo. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Alterations induced by Colomerus vitis on the structural and physiological leaf features of two grape cultivars

Vitis vinifera is cultivated worldwide for its high nutritional and commercial value. More than 60 grape cultivars are cultivated in Chile. Two of these, the país and the corinto cultivars, are the oldest known and widely used for the preparation of traditional homemade drinks and consumption as table grapes. These two grape cultivars are affected by Colomerus vitis, an eriophyid mite which establishes on their leaves and forms erinea, where the mite and its offspring obtain shelter and food. Although C. vitis has a cosmopolitan distribution, few studies of its impact on the structure and physiology of affected plants have been reported. Herein we aimed to evaluate the impact of C. vitis infection on the structural and physiological leaf performance of the two grape cultivars. The results showed tissue hyperplasia and cell hypertrophy in the epidermis, with an overproduction of trichomes and emergences in the abaxial epidermis in both cultivars. The anatomical changes were similar between the país and corinto cultivars, but they were proportionally greater in the país, where the area affected by the erinea were greater. No significant changes were detected in the photosynthetic pigment content; however, there was an increase in the total soluble sugars content in the erineum leaves of the país cultivar. Higher contents of anthocyanins and total phenols, as well as the presence of the pinocembrin in the corinto cultivar, which was less affected by C. vitis, could also indicate some resistance to mites' attack, which should be investigated in future studies.

Nutraceutical Potential of Grape (Vitis vinifera L.) Seed Oil in Oxidative Stress, Inflammation, Obesity and Metabolic Alterations

Vitis vinifera L. (grapevine) is a perennial plant of the Vitaceae family that is widely used to produce grapes and wines. Grape seed oil is rich in fatty acids such as linoleic acid (65-75%), vitamin E (50 mg), and phytosterols in addition to phenolic compounds, such as catechins (414 mg), epicatechins (130.4 mg), and gallic acid (77 µg), shows promise as a nutritional compound and is outstanding as a therapeutic substance with active properties for health, detected mainly by in vitro studies, as well as some in vivo studies. The benefits of consuming this oil include modulating the expression of antioxidant enzymes, anti-atherosclerotic and anti-inflammatory effects, and protection against oxidative cell damage and some types of cancer. However, experimental findings confirm that therapeutic functions remain scarce; thus, more studies are needed to determine the mechanisms of action involved in the indicated therapeutic qualities.

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.

Preliminary Studies on the In Vitro Interactions Between the Secondary Metabolites Produced by Esca-Associated Fungi and Enological Saccharomyces cerevisiae Strains

Esca-affected vines alter the carbohydrate metabolism, xylem transport of water and photosynthesis and show regular grapes (but berries do not reach maturity), and phenolic compounds are reduced in concentration, oxidate and polymerizate. Pullulan and a mixture of scytalone and isosclerone (9:1; w/w), secondary metabolites produced in vitro and in planta by Phaeoacremonium minimum (syn. P. aleophilum) and Phaeomoniella chlamydospora, were assayed against the strains Byosal HS1 and IOC 18-2007 in microvinifications with synthetic grape must. The presence of pullulan and pentaketides mix affects the growth and metabolism of the tested Saccharomyces cerevisiae strains. Assays at 100 and 1000 µg mL−1 inhibited the growth of both strains, while no effects were recorded when evaluated at 1 and 5 µg mL−1. In comparison with the controls, pullulan and the scytalone/isosclerone mixture at 10 µg mL−1 had a growth reduction, a lower alcohol yield, reduced the concentration of tartaric acid and malic acid; and slowed down the production of lactic acid, acetic acid and total polyphenol content of the tested S. cerevisiae strains. These metabolites could be applied as an alternative to the sulfite addition in the early stages of vinification to support the action of selected Saccharomyces. Appealing is the subtractive action of pullulan against tartaric acid. Further data are needed to confirm and validate the enological performance in freshly pressed grape juice.

Physiological and Molecular Responses of Vitis vinifera cv. Tempranillo Affected by Esca Disease

Esca is a multi-fungal disease affecting grapevines. The objective of the study was to evaluate the physiological and molecular response of the grapevine cv. Tempranillo to esca disease, carried out in a vineyard under Mediterranean climatic conditions in western Spain. The photosynthetic pigments in the leaves decreased, with a strong decrease in the photosynthetic efficiency. The proline content increased significantly in the early stages of affected leaves, being possibly involved in the maintenance of lipid peroxidation levels in leaves, which do not increase. The phenol, flavonoid, and phenylpropanoid content decreased in esca-affected leaves, as does the total antioxidant capacity (FRAP), while the polyphenol oxidase (PPO) activity suffers a strong increase with the development of the disease. In affected grapes, the lipid peroxidation and the total phenol content decrease, but not the anthocyanin content. The ascorbate pool decreases with the disease and with time. On the other hand, pool GSH + GSSG is lower in affected leaves, but increases with time. These alterations show a clear change in the redox homeostasis. The expression of genes phenylalanine ammonia lyase (PAL), polyphenol oxidase (PPO), superoxide dismutase (SOD), and chalcone synthase (ChaS1 and ChaS3) become considerably higher in response to esca, being even higher when the infection time increases. The alteration of AsA and GSH levels, phenolic compounds, PPO activity, proline content, and FRAP, together with the increase of the PAL, PPO, SOD,ChaS1, and ChaS3 gene expression, are clearly implicated in the esca response in plants. The expression of these genes, similar to the PPO activity, can be used as markers of state in the development of the disease.

Effects of aging and inflammation on catalase activity in human dental pulp

OBJECTIVES

In this study, it was aimed to examine the catalase activity in clinically healthy and caries-related inflamed symptomatic human dental pulps of young and old individuals.

DESIGN

Sixty pulp samples from young and old healthy donors, were collected depending on pulpal status. 48 samples were used for spectrophotometric analysis and 12 samples for immunohistochemistry. Healthy pulps were maintained from non-carries, extracted third molars. Reversible and irreversible pulpitis samples were obtained by pulp extirpation during endodontic treatment. Following homogenization catalase enzyme activity was determined by spectrophotometry. Additionally, two pulp tissue samples from each group were fixed and evaluated for catalase immunoreactivity.

RESULTS

Catalase enzyme activity in old healthy pulp samples were significantly higher than healthy young samples (p ≤ 0.05). Reversible and irreversible pulpitis samples indicated significantly decreased activity compared to healthy samples in elderly group (p ≤ 0.05). Young reversible pulpitis samples showed significantly increased catalase activity when compared to irreversible pulpitis and the reversible pulpitis samples in elderly group (p ≤ 0.05). Immunohistochemical evaluation indicated that there was intense catalase immunoreactivity in young patients with reversible pulpitis compared with reversible pulpitis in elderly group. However, weak immunoreactivity was observed in young irreversible pulpitis and elderly reversible pulpitis samples.

CONCLUSIONS

The pulp tissues presented different levels of catalase activities against pulpitis and aging.

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.

White Rot Fungi (Hymenochaetales) and Esca of Grapevine: Insights from Recent Microbiome Studies

Esca is a major grapevine trunk disease that heavily affects vineyards in the Northern hemisphere. The etiology and epidemiology of this disease have been subject of dispute ever since the earliest disease reports. The reason behind such debate is the presence of multiple internal and external symptoms, as well as several putative and confirmed wood pathogens. While the role of pathogenic fungi, as causal agents of wood symptoms, has been thoroughly assessed, their role in the expression of leaf symptoms remains to be fully elucidated. In this review, we analyzed etiological and epidemiological data, with a special focus on the microbiological aspect of esca and the involvement of Hymenochaetales (Basidiomycota). Vineyard studies have associated leaf symptoms with the presence of white rot, most frequently caused by Fomitiporia mediterranea (Hymenochaetales), while tracheomycotic fungi are commonly found, with similar abundance, in symptomatic and asymptomatic vines. Pathogenicity trials have excluded a direct effect of Hymenochaetales species in triggering leaf symptoms, while the data concerning the role of tracheomycotic fungi remains controversial. Recent microbiome studies confirmed that F. mediterranea is more abundant in leaf-symptomatic vines, and treatments that effectively control leaf symptoms, such as sodium arsenite spray and trunk surgery, act directly on the abundance of F. mediterranea or on the presence of white rot. This suggest that the simultaneous presence of Hymenochaetales and tracheomycotic fungi is a pre-requisite for leaf symptoms; however, the relation among fungal pathogens, grapevine and other biotic and abiotic factors needs further investigation.

Neurotherapeutic effect of Hyptis spp. leaf extracts in Caenorhabditis elegans models of tauopathy and polyglutamine disease: Role of the glutathione redox cycle

Hyptis suaveolens (HS), Hyptis pectinata (HP) and Hyptis marrubioides (HM) are plants used in folk medicine for treatment of several diseases. Here, we tested the in vivo antioxidant and neuroprotective potential of methanolic extracts from these plants, containing several rosmarinic acid derivatives and isoquercetin. In C. elegans, HS, HP and HM leaf extracts enhanced the antioxidant responses through the induction of specific antioxidant enzymes and demonstrated neurotherapeutic potential in transgenic models of genetically determined human neurodegenerative diseases - Frontotemporal dementia with parkinsonism linked to chromosome 17 and Machado-Joseph disease. Chronic treatment of disease models with HS, HP and HM leaf extracts improved the animals' motor function and increased their tolerance to an oxidative insult. The restorative effect of HM extract in motor performance of both disease models required the presence of glutathione reductase (gsr-1), an enzyme that assures the glutathione redox cycle, highlighting the role of this pathway and unveiling a common candidate therapeutic target for these diseases. Our findings strengthen the relevance of plant-derived bioactive compound discovery for neurodegenerative disorders that remain without effective treatment.

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.

Age- and season-dependent pattern of flavonol glycosides in Cabernet Sauvignon grapevine leaves

Flavonols play key roles in many plant defense mechanisms, consequently they are frequently investigated as stress sensitive factors in relation to several oxidative processes. It is well known that grapevine (Vitis vinifera L.) can synthesize various flavonol glycosides in the leaves, however, very little information is available regarding their distribution along the cane at different leaf levels. In this work, taking into consideration of leaf position, the main flavonol glycosides of a red grapevine cultivar (Cabernet Sauvignon) were profiled and quantified by HPLC–DAD analysis. It was found that amount of four flavonol glycosides, namely, quercetin-3-O-galactoside, quercetin-3-O-glucoside, kaempferol-3-O-glucoside and kaempferol-3-O-glucuronide decreased towards the shoot tip. Since leaf age also decreases towards the shoot tip, the obtained results suggest that these compounds continuously formed by leaf aging, resulting in their accumulation in the older leaves. In contrast, quercetin-3-O-glucuronide (predominant form) and quercetin-3-O-rutinoside were not accumulated significantly by aging. We also pointed out that grapevine boosted the flavonol biosynthesis in September, and flavonol profile differed significantly in the two seasons. Our results contribute to the better understanding of the role of flavonols in the antioxidant defense system of grapevine.

New Insights into the Exploitation of Vitis vinifera L. cv. Aglianico Leaf Extracts for Nutraceutical Purposes

The leaves of Vitis vinifera L. have been used for a long time in traditional medicine for the treatment of many ailments. Grape polyphenols, indeed, have been demonstrated to be able to defend against oxidative stress, responsible for various disorders such as cancer, diabetes and neurodegenerative diseases. The effects of different extraction techniques, Soxhlet (SOX), Accelerated Solvent (ASE 40, ASE 50) and Ultrasound Assisted Extraction (UAE) were studied in this work to evaluate their impact on the chemical profile and bioactive potential of Vitis vinifera L. (cv. Aglianico) leaf extracts. The phytochemical profile was investigated by HPLC-DAD and 9 phenolic compounds were identified and quantified in the extract. Moreover, the antioxidant, anticholinesterase and antityrosinase activities were evaluated. In detail, the total polyphenol content and antioxidant activity (2,2-diphenyl-1-picrylhydrazyl, Oxygen Radical Absorbance Capacities and β-Carotene Bleaching assays) were evaluated and compared to assess the Relative Antioxidant Capacity Index (RACI). To test the inhibitory activity of extracts towards cholinesterases, acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibition assays were performed. SOX and ASE 50 have shown the highest value of RACI, 0.76 and 0.65, respectively. Regarding enzymatic inhibitory activity, ASE 50 (IC₅₀ = 107.16 ± 8.12 μg/mL) and SOX (IC₅₀ = 171.34 ± 12.12 μg/mL) extracts exhibited the highest AChE and BChE inhibitory activity, respectively, while UAE (IC₅₀ = 293.2 ± 25.6 μg/mL, followed by SOX (IC₅₀ = 302.5 ± 38.3 μg/mL) showed the highest tyrosinase inhibition value. Our results demonstrated for the first time that Aglianico leaves are important sources of phenols that could be used to prevent oxidative stress and be potentially helpful in diseases treatable with tyrosinase and cholinesterase inhibitors, like myasthenia gravis or Alzheimer’s.

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.

A Reference List of Phenolic Compounds (Including Stilbenes) in Grapevine (Vitis vinifera L.) Roots, Woods, Canes, Stems, and Leaves

Due to their biological activities, both in plants and in humans, there is a great interest in finding natural sources of phenolic compounds or ways to artificially manipulate their levels. During the last decade, a significant amount of these compounds has been reported in the vegetative organs of the vine plant. In the roots, woods, canes, stems, and leaves, at least 183 phenolic compounds have been identified, including 78 stilbenes (23 monomers, 30 dimers, 8 trimers, 16 tetramers, and 1 hexamer), 15 hydroxycinnamic acids, 9 hydroxybenzoic acids, 17 flavan-3-ols (of which 9 are proanthocyanidins), 14 anthocyanins, 8 flavanones, 35 flavonols, 2 flavones, and 5 coumarins. There is great variability in the distribution of these chemicals along the vine plant, with leaves and stems/canes having flavonols (83.43% of total phenolic levels) and flavan-3-ols (61.63%) as their main compounds, respectively. In light of the pattern described from the same organs, quercetin-3-O-glucuronide, quercetin-3-O-galactoside, quercetin-3-O-glucoside, and caftaric acid are the main flavonols and hydroxycinnamic acids in the leaves; the most commonly represented flavan-3-ols and flavonols in the stems and canes are catechin, epicatechin, procyanidin B1, and quercetin-3-O-galactoside. The main stilbenes (trans-ε-viniferin, trans-resveratrol, isohopeaphenol/hopeaphenol, vitisin B, and ampelopsins) accumulate primarily in the woods, followed by the roots, the canes, and the stems, whereas the leaves, which are more exposed to environmental stresses, have a low concentration of these compounds. Data provided in this review could be used as (i) a metabolomic tool for screening in targeted and untargeted analyses and (ii) a reference list in studies aimed at finding ways to induce naturally occurring polyphenols on an industrial scale for pant and human disease control.

Anti-inflammatory and anti-Candida Effects of Brazilian Organic Propolis, a Promising Source of Bioactive Molecules and Functional Food

Brazilian organic propolis (BOP) is an unexplored Brazilian propolis that is produced organically and certified according to international legislation. Our results showed that BOP has strong anti-inflammatory effects and acts by reducing nuclear factor κB activation, tumor necrosis factor α release, and neutrophil migration. In addition, BOP6 exhibited antifungal activity on planktonic and biofilm cultures of Candida albicans, Candida glabrata, Candida tropicalis, Candida krusei, and Candida parapsisolis and reduced in vitro yeast cell adhesion to human keratinocytes at sub-inhibitory concentrations. BOP demonstrated significantly low toxicity in Galleria melonella larvae at antifungal doses. Lastly, a chemical analysis revealed the presence of caffeoyltartaric acid, 3,4-dicaffeoylquinic acid, quercetin, and gibberellins A7, A9, and A20, which may be responsible for the biological properties observed. Thus, our data indicate that BOP is a promising source of anti-inflammatory and antifungal molecules that may be used as a functional food.

Exhibition of Local but Not Systemic Induced Phenolic Defenses in Vitis vinifera L. Affected by Brown Wood Streaking, Grapevine Leaf Stripe, and Apoplexy (Esca Complex)

Balance between constitutive and induced responses provides plants flexibility to cope with biotic stresses. This study tested the hypothesis that invasion of grapevine wood by esca-associated fungi induces the production of defensive compounds as part of locally- and systemically-induced responses. In a vineyard, different symptomatic expressions of "Esca complex" in Vitis vinifera L. 'Malvasia' were evaluated in annual inspections. Then, levels of phenolics and fatty acids were determined in asymptomatic leaves of brown wood streaking (BWS) and grapevine leaf stripe (GLSD) vines, and in symptomatic leaves of GLSD and apoplectic vines; the results were compared with levels in healthy vines. In asymptomatic leaves of BWS and some GLSD vines, levels of phenolics decreased, independent of the total phenolic group. Such responses were usually associated with an increase in levels of linoleic, γ-linolenic and arachidonic acids, well-known signal transduction mediators. In symptomatic leaves, levels of phenolics increased, which is consistent with a locally-induced response; the onset of symptoms coincided with the highest increases e.g., 35% for quercetin-3-O-glucuronide. Thus, the long latency period between trunk invasion by fungi and visible foliar damage and the year-to-year fluctuation in symptomatic expressions observed with "Esca complex" might be partially attributed to a better utilization of constitutive defenses.

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.

Nanostructured TiO2-induced photocatalytic stress enhances the antioxidant capacity and phenolic content in the leaves of Vitis vinifera on a genotype-dependent manner

Over the past decades, nanotechnology has received great attention and brought revolutionary solutions for a number of challenges in scientific fields. Industrial, agricultural and medical applications of engineered nanomaterials have increased intensively. The ability of titanium dioxide nanoparticles (TiO₂ NPs) to produce reactive oxygen species (ROS), when excited by ultra-violet (UV) light, makes them useful for effectively inactivate various pathogens. It is known that ROS also have signalling role in living organisms, therefore, TiO₂ NPs-induced ROS can influence both enzymatic and non-enzymatic defence systems, and could play a role in the resistance of plants to pathogens. Herein, we studied the photocatalytic stress responses of grapevine (Vitis vinifera L.) as model plant, when exposed to a well-known photocatalyst, Degussa P25 TiO₂ NPs. The photocatalytically produced ROS such as superoxide anion, hydroxyl radical and singlet oxygen were confirmed by electron paramagnetic resonance spectroscopy. Foliar exposure of five red cultivars (Cabernet sauvignon, Cabernet franc, Merlot, Kékfrankos and Kadarka) was carried out in blooming phenophase under field condition where plants are exposed to natural sunlight with relatively high UV radiation (with a maximum of ~ 45 W m^-2). After two weeks of exposure, the effects of photogenerated ROS on the total phenolic content, antioxidant capacity, flavonol profile and the main macro-, microelements of the leaves were studied in detail. We found that foliar application of TiO₂ NPs boosted the total phenolic content and biosynthesis of the leaf flavonols depending on the grapevine variety. Photocatalytically active TiO₂ NPs also increased K, Mg, Ca, B and Mn levels in the leaves as shown by ICP-AES measurements.

In Silico Identification and In Vitro Evaluation of Natural Inhibitors of Leishmania major Pteridine Reductase I

In a continuation of our computational efforts to find new natural inhibitors of a variety of target enzymes from parasites causing neglected tropical diseases (NTDs), we now report on 15 natural products (NPs) that we have identified as inhibitors of Leishmania major pteridine reductase I (LmPTR1) through a combination of in silico and in vitro investigations. Pteridine reductase (PTR1) is an enzyme of the trypanosomatid parasites’ peculiar folate metabolism, and has previously been validated as a drug target. Initially, pharmacophore queries were created based on four 3D structures of LmPTR1 using co-crystallized known inhibitors as templates. Each of the pharmacophore queries was used to virtually screen a database of 1100 commercially available natural products. The resulting hits were submitted to molecular docking analyses in the substrate binding site of the respective protein structures used for the pharmacophore design. This approach led to the in silico identification of a total of 18 NPs with predicted binding affinity to LmPTR1. These compounds were subsequently tested in vitro for inhibitory activity towards recombinant LmPTR1 in a spectrophotometric inhibition assay. Fifteen out of the 18 tested compounds (hit rate = 83%) showed significant inhibitory activity against LmPTR1 when tested at a concentration of 50 µM. The IC₅₀ values were determined for the six NPs that inhibited the target enzyme by more than 50% at 50 µM, with sophoraflavanone G being the most active compound tested (IC₅₀ = 19.2 µM). The NPs identified and evaluated in the present study may represent promising lead structures for the further rational drug design of more potent inhibitors against LmPTR1.

Metabolomic Study of Chardonnay Grapevines Double Stressed with Esca-Associated Fungi and Drought

Esca is a complex grapevine trunk disease associated with fungal infection of the xylem. However, the inconstancy of external symptoms and the ability of esca-associated fungi to inhabit grapevines without causing apparent disease suggests that abiotic factors might be involved in the disease. Water stress has been proposed to be one of the factors influencing esca symptom manifestation but the specific role played by water stress on esca development is unknown. We conducted a proton nuclear magnetic resonance spectroscopy-based metabolomic study aiming at unveiling drought-induced modifications in xylem sap composition that could contribute to esca-related infection progression. Vitis vinifera 'Chardonnay' plants were inoculated with Phaeomoniella chlamydospora or Phaeoacremonium minimum and exposed to water stress. Using this approach, 28 metabolites were identified in xylem sap. The results show that water stress induces a concentration increase of most metabolites in xylem sap. An average increase >100% was found for asparagine, isoleucine, leucine, methionine, phenylalanine, proline, tyrosine, valine, sarcosine, and trigonelline. The increase of these compounds seems to be also modulated by fungal infection. This study offers further support to the putative role of drought in esca expression, and opens new avenues of research by extending the current knowledge about metabolites possibly involved in esca disease.