Modulation of flavonoid biosynthetic pathway genes and anthocyanins due to virus infection in grapevine (Vitis vinifera L.) leaves

Transcriptional responses and secondary metabolites variation of tomato plant in response to tobacco mosaic virus infestation

The present study focused on the impact of infection with the tobacco mosaic virus (TMV). Specifically, changes in phytochemicals and gene activity related to pathogenesis-related and phenylpropanoid pathway genes in tomato plants (Solanum lycopersicum L.) during a period of 2-14 days post-inoculation (dpi). According to TEM investigation and coat protein sequence analysis, the purified TMV Egyptian AM isolate (PP133743) has a rod-shaped structure with a diameter of around 110 nm. The RT-qPCR analysis revealed that PR-1 showed an initial increase after TMV infection, as seen in the time-course analysis. In contrast, PR-2 was consistently elevated throughout the infection, suggesting a stronger reaction to the virus and suppressing PAL expression at 6 to 14 dpi. The expression levels of HQT and CHS transcripts exhibited alternating patterns of up-regulation and down-regulation at different time intervals. The HPLC and GC-MS analysis of control- and TMV-infected tomato extracts revealed that different phenolic, flavonoid, and fatty acid compounds were increased (such as naringenin, rutin, flavone, ferulic acid, and pyrogallol) or significantly decreased (such as salicylic acid and chlorogenic acid) after TMV infection. The ability of TMV to inhibit most polyphenolic compounds could potentially accelerate the viral life cycle. Consequently, focusing on enhancing the levels of such suppressed compounds may be critical for developing plant viral infection management strategies.

Improving grape fruit quality through soil conditioner: Insights from RNA-seq analysis of Cabernet Sauvignon roots

The application of fertilizers and soil quality are crucial for grape fruit quality. However, the molecular data linking different fertilizer (or soil conditioner [SC]) treatments with grape fruit quality is still lacking. In this study, we investigated three soil treatments, namely inorganic fertilizer (NPK, 343.5 kg/hm2 urea [N ≥ 46%]; 166.5 kg/hm2 P2O5 [P2O5 ≥ 64%]; 318 kg/hm2 K2O [K2O ≥ 50%]), organic fertilizer (Org, 9 t/hm2 [organic matter content ≥ 35%, N + P2O5 + K2O ≥ 13%]), and SC (SC, 3 t/hm2 [humic acid ≥ 38.5%; C, 56.1%; H, 3.7%; N, 1.5%; O, 38%; S, 0.6%]), on 4-year-old Cabernet Sauvignon grapevines. Compared with the NPK- and Org-treated groups, the SC significantly improved the levels of soluble solids, tannins, anthocyanins, and total phenols in the grape berries, which are important biochemical indicators that affect wine quality. Furthermore, we conducted RNA-seq analysis on the grapevine roots from each of the three treatments and used weighted gene co-expression network analysis to identify five hub genes that were associated with the biochemical indicators of the grape berries. Furthermore, we validated the expression levels of three hub genes (ERF, JP, and SF3B) and five selected genes related to anthocyanin biosynthesis (UFGT1, UFGT2, UFGT3, GST, and AT) by using quantitative reverse transcription-polymerase chain reaction. Compared to the NPK and Org treatment groups, the SC treatment resulted in a significant increase in the transcription levels of three hub genes as well as VvUFGT1, VvUFGT3, VvGST, and VvAT. These results suggest that the SC can improve grape fruit quality by altering gene transcription patterns in grapevine roots and further influence the biochemical indices of grape fruits, particularly anthocyanin content. This study reveals that the application of SC can serve as an important measure for enhancing vineyard SC and elevating grape quality.

Influence of mixed and single infection of grapevine leafroll-associated viruses and viral load on berry quality

Grapevine leafroll disease is a viral disease that affects grapevines (Vitis vinifera L.) and has a severe economic impact on viticulture. In this study, the effect of grapevine leafroll-associated viruses (GLRaV) on berry quality was investigated in clones of cultivar cv. Crimson Seedless table grapes infected with GLRaV. RT-PCR confirmed the identity of the clones: clone 3236, infected only with GLRaV-3 (termed single); clone 3215, infected with GLRaV-3, GLRaV-4 strain 9 and grapevine virus A (termed mixed); and a viral free clone of the same genetic background of the infected clones (termed control). The berry quality indices of size, sugar, acidity and anthocyanin content were measured at harvest maturity. RT-qPCR was used to determine the viral load. The study was repeated over 2 year. A two-way, multivariate analysis of variance was applied with clone and year as independent variables and the measured berry quality parameters as a dependent variable. All dependent variables were significantly affected by viral infection (Wilks, λ, (2,33) = 0.033895, P-value <0.001), while only titratable acidity was affected by year. The average berry dry mass decreased (P-value <0.001). The water content of both infected clones was greater than that of the control (P-value <0.001). Both infected clones displayed reduced sugar content as a fraction of the berry dry mass (P-value <0.001). The anthocyanin and the phenol content of the infected clones were significantly reduced compared with the control clone (P < 0.001, P < 0.05, clone 3236 and clone 3215, respectively). Finally, the viral load was highly variable, and no quantitative relationship between viral load and berry composition was found.

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.

Longer cluster hanging time decreases the impact of grapevine red blotch disease in Vitis vinifera L. Merlot across two seasons

BACKGROUND

Grapevine red blotch virus (GRBV) is a recently discovered virus and a major concern for the wine industry. Prior research indicated that GRBV delays grape ripening by reducing °Brix and anthocyanin concentrations in grapes from infected vines, resulting in higher ethanol concentrations in wines made from healthy fruit compared to diseased vines, which have an impact on sensory properties. In this study, infected fruit (Vitis vinifera L. Merlot) was sequentially harvested (in 2016 and 2017) and chaptalized (in 2017) to ameliorate the impact of GRBV on grape and final wine composition.

RESULTS

Chemical parameters including phenolic and volatile profiles of grapes and their subsequent wines were measured. Sensory properties were determined by descriptive analyses. Results demonstrated that GRBV decreased sugar accumulation and anthocyanin synthesis in grapes. Wines from GRBV grapes harvested at later ripening stage produced wines that were more similar chemically and sensorially to wines made from healthy fruit than to wines made from GRBV fruit harvested earlier.

CONCLUSION

A longer hang time of GRBV grapes is a potential strategy to mitigate the impacts of GRBV. However, chaptalization of diseased fruit must was inefficient at increasing similarities to wines made from healthy fruit. © 2023 Society of Chemical Industry.

Genome-Wide Identification of PAP1 Direct Targets in Regulating Seed Anthocyanin Biosynthesis in Arabidopsis

Anthocyanins are widespread water-soluble pigments in the plant kingdom. Anthocyanin accumulation is activated by the MYB-bHLH-WD40 (MBW) protein complex. In Arabidopsis, the R2R3-MYB transcription factor PAP1 activates anthocyanin biosynthesis. While prior research primarily focused on seedlings, seeds received limited attention. This study explores PAP1's genome-wide target genes in anthocyanin biosynthesis in seeds. Our findings confirm that PAP1 is a positive regulator of anthocyanin biosynthesis in Arabidopsis seeds. PAP1 significantly increased anthocyanin content in developing and mature seeds in Arabidopsis. Transcriptome analysis at 12 days after pollination reveals the upregulation of numerous genes involved in anthocyanin accumulation in 35S:PAP1 developing seeds. Chromatin immunoprecipitation and dual luciferase reporter assays demonstrate PAP1's direct promotion of ten key genes and indirect upregulation of TT8, TTG1, and eight key genes during seed maturation, thus enhancing seed anthocyanin accumulation. These findings enhance our understanding of PAP1's novel role in regulating anthocyanin accumulation in Arabidopsis seeds.

Investigating Protein-Protein Interactions Between Grapevine Leafroll-Associated Virus 3 and Vitis vinifera

Grapevine leafroll disease (GLD) is a globally important disease that affects the metabolic composition and biomass of grapes, leading to a reduction in grape yield and quality of wine produced. Grapevine leafroll-associated virus 3 (GLRaV-3) is the main causal agent for GLD. This study aimed to identify protein-protein interactions between GLRaV-3 and its host. A yeast two-hybrid (Y2H) library was constructed from Vitis vinifera mRNA and screened against GLRaV-3 open reading frames encoding structural proteins and those potentially involved in systemic spread and silencing of host defense mechanisms. Five interacting protein pairs were identified, three of which were demonstrated in planta. The minor coat protein of GLRaV-3 was shown to interact with 3-deoxy-D-arabino-heptulosonate 7-phosphate synthase 02, a protein involved in primary carbohydrate metabolism and the biosynthesis of aromatic amino acids. Interactions were also identified between GLRaV-3 p20A and an 18.1-kDa class I small heat shock protein, as well as MAP3K epsilon protein kinase 1. Both proteins are involved in the response of plants to various stressors, including pathogen infections. Two additional proteins, chlorophyll a-b binding protein CP26 and a SMAX1-LIKE 6 protein, were identified as interacting with p20A in yeast but these interactions could not be demonstrated in planta. The findings of this study advance our understanding of the functions of GLRaV-3-encoded proteins and how the interaction between these proteins and those of V. vinifera could lead to GLD.

Signaling Cross-Talk between Salicylic and Gentisic Acid in the 'Candidatus Phytoplasma Solani' Interaction with Sangiovese Vines

"Bois noir" disease associated with 'Candidatus Phytoplasma solani' seriously compromises the production and survival of grapevines (Vitis vinifera L.) in Europe. Understanding the plant response to phytoplasmas should help to improve disease control strategies. Using a combined metabolomic and transcriptomic analysis, this work, therefore, investigated the phytoplasma-grapevine interaction in red cultivar Sangiovese in a vineyard over four seasonal growth stages (from late spring to late summer), comparing leaves from healthy and infected grapevines (symptomatic and symptomless). We found an accumulation of both conjugate and free salicylic acids (SAs) in the leaves of 'Ca. P. solani'-positive plants from early stages of infection, when plants are still asymptomatic. A strong accumulation of gentisic acid (GA) associated with symptoms progression was found for the first time. A detailed analysis of phenylpropanoids revealed a significant accumulation of hydroxycinnamic acids, flavonols, flavan 3-ols, and anthocyanin cyanidin 3-O-glucoside, which are extensively studied due to their involvement in the plant response to various pathogens. Metabolomic data corroborated by gene expression analysis indicated that phenylpropanoid biosynthetic and salicylic acid-responsive genes were upregulated in 'Ca. P. solani-positive plants compared to -negative ones during the observed period.

The Role of Anthocyanins in Plant Tolerance to Drought and Salt Stresses

Drought and salinity affect various biochemical and physiological processes in plants, inhibit plant growth, and significantly reduce productivity. The anthocyanin biosynthesis system represents one of the plant stress-tolerance mechanisms, activated by surplus reactive oxygen species. Anthocyanins act as ROS scavengers, protecting plants from oxidative damage and enhancing their sustainability. In this review, we focus on molecular and biochemical mechanisms underlying the role of anthocyanins in acquired tolerance to drought and salt stresses. Also, we discuss the role of abscisic acid and the abscisic-acid-miRNA156 regulatory node in the regulation of drought-induced anthocyanin production. Additionally, we summarise the available knowledge on transcription factors involved in anthocyanin biosynthesis and development of salt and drought tolerance. Finally, we discuss recent progress in the application of modern gene manipulation technologies in the development of anthocyanin-enriched plants with enhanced tolerance to drought and salt stresses.

Evaluation of reference genes for miRNA and mRNA normalization in tobacco infected with PVYNTN, PVYN-Wi and PVYZ-NTN strains

This is the first report on identification of the most suitable reference genes for RT-qPCR quantification of miRNA and mRNA in tobacco response to the prevalent recombinant potato virus Y (PVY) strains PVY^NTN, PVY^N-Wi and the newly identified PVY^Z-NTN. Of 10 tested genes, the expression levels of neIF5C, nU2af and nPP2A were the most stable in samples taken from non-inoculated, mock-inoculated, and infected plants at three days post-inoculation (dpi) and 14 dpi. While the homologues of eIF5 were most stably expressed in tobacco in this study and in potato in our previous study (Yin et al., 2021) following inoculation with the same three PVY strains, the homologues of other two genes PP2A and U2af were stably expressed only in tobacco but unstable in potato. The tobacco homologue of PP2A, which was the most stably expressed one in tobacco interaction with PVY^NTN, PVY^N-Wi and PVY^Z-NTN strains in this study, was the least stable one in tobacco interaction with the non-recombinant PVY^O strain in a previous study (Baek et al., 2017). This study provides evidence on the influence of host species on expression of housekeeping genes and points out virus strain as a new factor influencing expression stability of reference gene. Caution should be taken when choosing reference genes in gene expression study in Solanaceae hosts response to different PVY strains.

Preventive and Curative Effects of Salicylic and Methyl Salicylic Acid Having Antifungal Potential against Monilinia laxa and the Development of Phenolic Response in Apple Peel

The effects of salicylic acid (SA) and one of its better-known derivatives-methyl salicylic acid (MeSA)-on the infection of apple fruits with the fungus Monilinia laxa, which causes brown rot, were investigated. Since research to date has focused on preventive effects, we also focused on the curative use of SA and MeSA. Curative use of SA and MeSA slowed the progression of the infection. In contrast, preventive use was generally unsuccessful. HPLC-MS was used to analyze the content of phenolic compounds in apple peels in healthy and boundary peel tissues around lesions. The boundary tissue around the lesions of untreated infected apple peel had up to 2.2-times higher content of total analyzed phenolics (TAPs) than that in the control. Flavanols, hydroxycinnamic acids and dihydrochalcones were also higher in the boundary tissue. During the curative treatment with salicylates, the ratio of TAP content between healthy and boundary tissue was lower (SA up to 1.2-times higher and MeSA up to 1.3-times higher content of TAPs in boundary compared to those in healthy tissue) at the expense of also increasing the content in healthy tissues. The results confirm that salicylates and infection with the fungus M. laxa cause an increased content of phenolic compounds. Curative use of salicylates has a greater potential than preventive use in infection control.

Population Structure, Genetic Diversity and Candidate Genes for the Adaptation to Environmental Stress in Picea koraiensis

Picea koraiensis is major silvicultural and timber species in northeast China, and its distribution area is an important transition zone for genus spruce migration. The degree of intraspecific differentiation of P. koraiensis is high, but population structure and differentiation mechanisms are not clear. In this study, 523,761 single nucleotide polymorphisms (SNPs) were identified in 113 individuals from 9 populations of P. koraiensis by genotyping-by-sequencing (GBS). Population genomic analysis showed that P. koraiensis was divided into three geoclimatic regions: Great Khingan Mountains climatic region, Lesser Khingan Mountains climatic region, and Changbai Mountain climatic region. Mengkeshan (MKS) population on the northern edge of the distribution area and Wuyiling (WYL) population located in the mining area are two highly differentiated groups. Selective sweep analysis showed that MKS and WYL populations had 645 and 1126 selected genes, respectively. Genes selected in the MKS population were associated with flowering and photomorphogenesis, cellular response to water deficit, and glycerophospholipid metabolism; genes selected in the WYL population were associated with metal ion transport, biosynthesis of macromolecules, and DNA repair. Climatic factors and heavy metal stress drives divergence in MKS and WYL populations, respectively. Our findings provide insights into adaptive divergence mechanisms in Picea and will contribute to molecular breeding studies.

Detecting Grapevine Virus Infections in Red and White Winegrape Canopies Using Proximal Hyperspectral Sensing

Grapevine virus-associated disease such as grapevine leafroll disease (GLD) affects grapevine health worldwide. Current diagnostic methods are either highly costly (laboratory-based diagnostics) or can be unreliable (visual assessments). Hyperspectral sensing technology is capable of measuring leaf reflectance spectra that can be used for the non-destructive and rapid detection of plant diseases. The present study used proximal hyperspectral sensing to detect virus infection in Pinot Noir (red-berried winegrape cultivar) and Chardonnay (white-berried winegrape cultivar) grapevines. Spectral data were collected throughout the grape growing season at six timepoints per cultivar. Partial least squares-discriminant analysis (PLS-DA) was used to build a predictive model of the presence or absence of GLD. The temporal change of canopy spectral reflectance showed that the harvest timepoint had the best prediction result. Prediction accuracies of 96% and 76% were achieved for Pinot Noir and Chardonnay, respectively. Our results provide valuable information on the optimal time for GLD detection. This hyperspectral method can also be deployed on mobile platforms including ground-based vehicles and unmanned aerial vehicles (UAV) for large-scale disease surveillance in vineyards.

In Vivo Antiphytoviral and Aphid Repellency Activity of Essential Oils and Hydrosols from Mentha suaveolens and Foeniculum vulgare to Control Zucchini Yellow Mosaic Virus and Its Vector Aphis gossypii

In recent years, natural compounds have gained attention in many fields due to their wide-range biological activity. In particular, essential oils and their associated hydrosols are being screened to control plant pests, exerting antiviral, antimycotic and antiparasitic actions. They are more quickly and cheaply produced and are generally considered safer for the environment and non-target organisms than conventional pesticides. In this study, we report the evaluation of the biological activity of two essential oils and their corresponding hydrosols obtained from Mentha suaveolens and Foeniculum vulgare in the control of zucchini yellow mosaic virus and its vector, Aphis gossypii, in Cucurbita pepo plants. The control of the virus was ascertained with treatments applied either concurrently with or after virus infection; choice tests were performed to verify repellency activity against the aphid vector. The results indicated that treatments could decrease virus titer as measured using real-time RT-PCR, while the experiments on the vector showed that the compounds effectively repelled aphids. The extracts were also chemically characterized using gas chromatography-mass spectrometry. Mentha suaveolens and Foeniculum vulgare hydrosol extracts mainly comprised fenchone and decanenitrile, respectively, while essential oils analysis returned a more complex composition, as expected.

Holistic understanding of the response of grapevines to foliar application of seaweed extracts

Viticulture is highly dependent on phytochemicals to maintain good vineyard health. However, to reduce their accumulation in the environment, green regulations are driving the development of eco-friendly strategies. In this respect, seaweeds have proven to be one of the marine resources with the highest potential as plant protective agents, representing an environmentally-friendly alternative approach for sustainable wine production. The current work follows an interdisciplinary framework to evaluate the capacity of Ulva ohnoi and Rugulopteryx okamurae seaweeds to induce defense mechanisms in grapevine plants. To our knowledge, this is the first study to evaluate Rugulopteryx okamurae as a biostimulator . This macroalgae is relevant since it is an invasive species on the Atlantic and Mediterranean coast causing incalculable economic and environmental burdens. Four extracts (UL1, UL2, RU1 and RU2 developed from Ulva and Rugulopteryx, respectively) were foliar applied to Tempranillo plants cultivated under greenhouse conditions. UL1 and RU2 stood out for their capacity to induce defense genes, such as a PR10, PAL, STS48 and GST1, mainly 24 hours after the first application. The increased expression level of these genes agreed with i) an increase in trans-piceid and trans-resveratrol content, mainly in the RU2 treated leaves, and, ii) an increase in jasmonic acid and decrease in salicylic acid. Moreover, an induction of the activity of the antioxidant enzymes was observed at the end of the experiment, with an increase in superoxide dismutase and catalase in the RU2-treated leaves in particular. Interestingly, while foliar fungal diversity was not influenced by the treatments, alga extract amendment modified fungal composition, RU2 application enriching the content of various groups known for their biocontrol activity. Overall, the results evidenced the capacity of Rugulopteryx okamurae for grapevine biostimulation, inducing the activation of several secondary metabolite pathways and promoting the abundance of beneficial microbiota involved in grapevine protection. While further studies are needed to unravel the bioactive compound(s) involved, including conducting field experiments etc., the current findings are the first steps towards the inclusion of Rugulopteryx okamurae in a circular scheme that would reduce its accumulation on the coast and benefit the viticulture sector at the same time.

Transcriptome mapping related genes encoding PR1 protein involved in necrotic symptoms to soybean mosaic virus infection

Necrosis caused by soybean mosaic virus (SMV) has not been specifically distinguished from susceptible symptoms. The molecular mechanism for the occurrence of necrosis is largely overlooked in soybean genetic research. Field evaluation reveals that SMV disease seriously influences soybean production as indicated by decreasing 22.4% ~ 77.0% and 8.8% ~ 17.0% of yield and quality production, respectively. To expand molecular mechanism behind necrotic reactions, transcriptomic data obtained from the asymptomatic, mosaic, and necrotic pools were assessed. Compared between asymptomatic and mosaic plants, 1689 and 1752 up- and down-regulated differentially expressed genes (DEGs) were specifically found in necrotic plants. Interestingly, the top five enriched pathways with up-regulated DEGs were highly related to the process of the stress response, whereas the top three enriched pathways with down-regulated DEGs were highly related to the process of photosynthesis, demonstrating that defense systems are extensively activated, while the photosynthesis systems were severely destroyed. Further, results of the phylogenetic tree based on gene expression pattern and an amino acid sequence and validation experiments discovered three PR1 genes, Glyma.15G062400, Glyma.15G062500, and Glyma.15G062700, which were especially expressed in necrotic leaves. Meanwhile, exogenous salicylic acid (SA) but not methyl jasmonate (MeJA) could induce the three PR1 gene expressions on healthy leaves. Contrastingly, exogenous SA obviously decreased the expression level of Glyma.15G062400, Glyma.15G062500, and concentration of SMV, but increased Glyma.15G062700 expression in necrotic leaves. These results showed that GmPR1 is associated with the development of SMV-induced necrotic symptoms in soybean. Glyma.15G062400, Glyma.15G062500, and Glyma.15G062700 is up-regulated in necrotic leaves at the transcriptional levels, which will greatly facilitate a better understanding of the mechanism behind necrosis caused by SMV disease.

Supplementary information

The online version contains supplementary material available at 10.1007/s11032-022-01351-3.

Grapevine Leafroll-Associated Virus 3 Replication in Grapevine Hosts Changes through the Dormancy Stage

Grapevine leafroll-associated virus 3 (GLRaV-3) is a graft-transmissible virus present in every viticultural region of the world and poses a large threat to grapevine production. Frequent coinfections with other viruses, the large number of grapevine varieties, the complexity of processes involved in plant response to virus infection, and the lack of studies on GLRaV-3 replication limit our knowledge of GLRaV-3 damaging effects and their background. In this study, five different inocula, one containing GLRaV-3 and others containing GLRaV-3 in combination with different grapevine viruses were green grafted to 52 different grapevine plants of four varieties to analyze the influence of the phenological stage and virus composition on GLRaV-3 replication. Relative concentration analysis by quantitative PCR conducted over a 16-month period revealed that other viruses as well as plant stage had a significant effect on GLRaV-3 replication and symptoms expression. The replication was most pronounced in the deep dormancy stage at the beginning of the infection, and the least at the exit of the dormancy stage. This study brings new insight into GLRaV-3 replication and discusses about viral interactions in one of the most economically important perennial plants, the grapevine.

Investigating Grapevine Red Blotch Virus Infection in Vitis vinifera L. cv. Cabernet Sauvignon Grapes: A Multi-Omics Approach

Grapevine red blotch virus (GRBV) is a recently identified virus. Previous research indicates primarily a substantial impact on berry ripening in all varieties studied. The current study analyzed grapes’ primary and secondary metabolism across grapevine genotypes and seasons to reveal both conserved and variable impacts to GRBV infection. Vitis vinifera cv. Cabernet Sauvignon (CS) grapevines grafted on two different rootstocks (110R and 420A) were analyzed in 2016 and 2017. Metabolite profiling revealed a considerable impact on amino acid and malate acid levels, volatile aroma compounds derived from the lipoxygenase pathway, and anthocyanins synthesized in the phenylpropanoid pathway. Conserved transcriptional responses to GRBV showed induction of auxin-mediated pathways and photosynthesis with inhibition of transcription and translation processes mainly at harvest. There was an induction of plant-pathogen interactions at pre-veraison, for all genotypes and seasons, except for CS 110R in 2017. Lastly, differential co-expression analysis revealed a transcriptional shift from metabolic synthesis and energy metabolism to transcription and translation processes associated with a virus-induced gene silencing transcript. This plant-derived defense response transcript was only significantly upregulated at veraison for all genotypes and seasons, suggesting a phenological association with disease expression and plant immune responses.

Polyphenolic promiscuity, inflammation-coupled selectivity: Whether PAINs filters mask an antiviral asset

The Covid-19 pandemic has elicited much laboratory and clinical research attention on vaccines, mAbs, and certain small-molecule antivirals against SARS-CoV-2 infection. By contrast, there has been comparatively little attention on plant-derived compounds, especially those that are understood to be safely ingested at common doses and are frequently consumed in the diet in herbs, spices, fruits and vegetables. Examining plant secondary metabolites, we review recent elucidations into the pharmacological activity of flavonoids and other polyphenolic compounds and also survey their putative frequent-hitter behavior. Polyphenols, like many drugs, are glucuronidated post-ingestion. In an inflammatory milieu such as infection, a reversion back to the active aglycone by the release of β-glucuronidase from neutrophils and macrophages allows cellular entry of the aglycone. In the context of viral infection, virions and intracellular virus particles may be exposed to promiscuous binding by the polyphenol aglycones resulting in viral inhibition. As the mechanism's scope would apply to the diverse range of virus species that elicit inflammation in infected hosts, we highlight pre-clinical studies of polyphenol aglycones, such as luteolin, isoginkgetin, quercetin, quercetagetin, baicalein, curcumin, fisetin and hesperetin that reduce virion replication spanning multiple distinct virus genera. It is hoped that greater awareness of the potential spatial selectivity of polyphenolic activation to sites of pathogenic infection will spur renewed research and clinical attention for natural products antiviral assaying and trialing over a wide array of infectious viral diseases.

Mapping and functional characterization of the tomato spotted wilt virus resistance gene SlCHS3 in Solanum lycopersicum

Tomato spotted wilt virus (TSWV) poses a serious threat to tomato (Solanum lycopersicum) production. In this study, tomato inbred line YNAU335 was developed without the Sw-5 locus, which confers resistance or immunity to TSWV (absence of infection). Genetic analysis demonstrated that immunity to TSWV was controlled by a dominant nuclear gene. The candidate genes were mapped into a 20-kb region in the terminal of the long arm of chromosome 9 using bulk segregant analysis and linkage analysis. In this candidate region, a chalcone synthase-encoding gene (SlCHS3) was identified as a strong candidate gene for TSWV resistance. Silencing SlCHS3 reduced flavonoid synthesis, and SlCHS3 overexpression increased flavonoid content. The increase in flavonoids improved TSWV resistance in tomato. These findings indicate that SlCHS3 is indeed involved in the regulation of flavonoid synthesis and plays a significant role in TSWV resistance of YNAU335. This could provide new insights and lay the foundation for analyzing TSWV resistance mechanisms.

Supplementary information

The online version contains supplementary material available at 10.1007/s11032-022-01325-5.

Transcriptomic Analyses of Grapevine Leafroll-Associated Virus 3 Infection in Leaves and Berries of 'Cabernet Franc'

Grapevine leafroll-associated virus 3 (GLRaV-3) is one of the most important viruses affecting global grape and wine production. GLRaV-3 is the chief agent associated with grapevine leafroll disease (GLRD), the most prevalent and economically destructive grapevine viral disease complex. Response of grapevine to GLRaV-3 infection at the gene expression level is poorly characterized, limiting the understanding of GLRaV-3 pathogenesis and viral-associated symptom development. In this research, we used RNA-Seq to profile the changes in global gene expression of Cabernet franc, a premium red wine grape, analyzing leaf and berry tissues at three key different developmental stages. We have identified 1457 differentially expressed genes (DEGs) in leaves and 1181 DEGs in berries. The expression profiles of a subset of DEGs were validated through RT-qPCR, including those involved in photosynthesis (VvPSBP1), carbohydrate partitioning (VvSUT2, VvHT5, VvGBSS1, and VvSUS), flavonoid biosynthesis (VvUFGT, VvLAR1, and VvFLS), defense response (VvPR-10.3, and VvPR-10.7), and mitochondrial activities (ETFB, TIM13, and NDUFA1). GLRaV-3 infection altered source-sink relationship between leaves and berries. Photosynthesis and photosynthate assimilation were inhibited in mature leaves while increased in young berries. The expression of genes involved in anthocyanin biosynthesis increased in GLRaV-3-infected leaves, correlating with interveinal tissue reddening, a hallmark of GLRD symptoms. Notably, we identified changes in gene expression that suggest a compromised sugar export and increased sugar retrieval in GLRaV-3-infected leaves. Genes associated with mitochondria were down-regulated in both leaves and berries of Cabernet franc infected with GLRaV-3. Results of the present study suggest that GLRaV-3 infection may disrupt mitochondrial function in grapevine leaves, leading to repressed sugar export and accumulation of sugar in mature leaf tissues. The excessive sugar accumulation in GLRaV-3-infected leaves may trigger downstream GLRD symptom development and negatively impact berry quality. We propose a working model to account for the molecular events underlying the pathogenesis of GLRaV-3 and symptom development.

Defense Responses and Metabolic Changes Involving Phenylpropanoid Pathway and PR Genes in Squash (Cucurbita pepo L.) following Cucumber mosaic virus Infection

The current study focuses on the effects of Cucumber mosaic virus (CMV) infection on phytochemical changes and pathogenesis- and phenylpropanoid pathway-associated gene activities in squash (Cucurbita pepo L.) plants during a time course of 2 to 12 days post inoculation (dpi). The identity of the CMV isolate was confirmed by DAS-ELISA, TEM, and coat protein gene sequence. The CMV infection initially boosts and then suppresses transcript levels of the defense-related genes PR-1, PR-2, PAL, HQT, and CHS during the investigated time course compared to controls. The expression profile during the time-course study indicated that early, transient induction of PR-1 occurs during CMV infection, while CMV induced the expression of PR-2 in systemically infected squash tissues at all time points and suppressed the expression of PAL and HQT at 8-12 dpi. CHS transcript levels fluctuated between up- and down-regulation, but by 12 dpi, CHS expression reached its peak. The HPLC and GC–MS analyses of CMV-infected squash extracts revealed that different phenolic, flavonoid, and fatty acid compounds could be induced or suppressed upon CMV infection. In particular, CMV could suppress the synthesis of most phenolic compounds, specifically chlorogenic acid, possibly leading to the virus’s rapid spread.

Grapevine Leafroll-Associated Virus 3 Genotype Influences Foliar Symptom Development in New Zealand Vineyards

Grapevine leafroll disease (GLD) constrains wine production worldwide. In New Zealand, the main causal agent of GLD is grapevine leafroll-associated virus 3 (GLRaV-3). To control GLD, an integrated management program is used and includes removing (roguing) GLRaV-3-infected vines from the vineyard. The classical foliar symptoms from virus-infected red-berry cultivars are leaves with dark red intervein, green veins, and downward rolling of margins. Growers use these phenotypic cues to undertake visual symptom identification (VSI) for GLD. However, the influence of the known large genetic variation among GLRaV-3 isolates on the foliar symptoms from different grapevine cultivars remains undescribed, especially in cool-climate growing environments, such as New Zealand. Over three vintages (2015, 2016, and 2017), VSI for GLD was undertaken at three field sites in New Zealand (Auckland, Hawke’s Bay, and Marlborough), each including four cultivars (Merlot, Pinot noir, Sauvignon blanc, and Pinot gris) infected with three GLRaV-3 genotypes (Groups I, VI, and X) or GLRaV-3-uninfected control plants. Throughout this study, no visual symptoms were observed on white-berry cultivars infected with GLRaV-3. For red-berry cultivars, the greatest variability in observed foliar symptoms among regional study sites, cultivars, and GLRaV-3 genotypes was observed early in the growing season. In particular, Group X had significantly delayed symptom expression across all three sites compared with Groups I and VI. As the newly infected, young vines matured in years 2 and 3, the GLRaV-3 genotype, cultivar, region, and environmental conditions had minimal influence on the accuracy of VSI, with consistently high (>95%) within-vintage identification by the end of each vintage. The results from this study strongly support the use of VSI for the GLD management of red-berry cultivar grapevines, Merlot and Pinot noir, as a reliable and cost-effective tool against GLD.

Potential effects of Grapevine leafroll-associated virus 3 (genus Ampelovirus; family Closteroviridae) or Grapevine red blotch virus (genus Grablovirus; family Geminiviridae) infection on foliar phenolic and amino acid levels

Objective

Grapevine (Vitis spp.) viral infections, including those by Grapevine leafroll-associated virus 3 (GLRaV-3) and Grapevine red blotch virus (GRBV), greatly reduce fruit yields and quality. Evidence exists that host chemistry shifts result in reductions in fruit quality. However, changes over the season in foliar chemistry has not been well examined. Therefore, phenolic and amino acid levels were examined in leaves collected in grapevines with different rootstocks that were healthy or were infected with GLRaV-3 or GRBV. This was part of an effort to assess changes that different pathogens cause in grapevine tissues.

Results

Month and year appeared to account for the greatest variability in grapevine foliar phenolic or amino acid levels, followed by differences in rootstock, and then differences in infection status. GLRaV-3 infection significantly lowered levels of total and individual hydroxycinnamic acid derivatives, and GRBV lowered total phenolic levels, total and individual hydroxycinnamic acids. Amino acid levels were increased over controls in vines infected by GLRaV-3, but not with GRBV. Overall, changes within grapevine leaves due to viral infection were likely too small to overcome variability due to sampling time or rootstock cultivar, and therefore such factors should be considered in determining infection effects on plant foliar chemistry.

In vivo Antiphytoviral Activity of Essential Oils and Hydrosols From Origanum vulgare, Thymus vulgaris, and Rosmarinus officinalis to Control Zucchini Yellow Mosaic Virus and Tomato Leaf Curl New Delhi Virus in Cucurbita pepo L

In the last decades, the interest in biological activity of natural compounds has been growing. In plant protection, essential oils have been reported to exhibit antiviral, antimycotic, and antiparasitic activities, and are regarded as promising for the formulation of safe antimicrobial agents. Attention has also been focused on hydrosols, the by-products of hydro-distillation of essential oils. Their production is easy, fast, and cheap, and they seem to arise less concern for human health than essential oils. Plant viruses represent a major concern for agricultural crops since no treatment compound is available for virus control. This work was aimed at evaluating the antiphytoviral effectiveness of treatments with three essential oils and corresponding hydrosols extracted from Origanum vulgare, Thymus vulgaris, and Rosmarinus officinalis on Cucurbita pepo plants infected by zucchini yellow mosaic virus or tomato leaf curl New Delhi virus. Treatments were applied either concurrently or after virus inoculation to ascertain an inhibition or curative activity, respectively. Symptoms were observed and samplings were performed weekly. Virus titer and expression levels of phenylalanine ammonia lyase gene (PAL) were measured on treated and untreated infected plants by real-time PCR. PAL gene plays an important role in plant defense response as it is involved in tolerance/resistance to phytopathogens. Results indicated that treatments were effective against tomato leaf curl New Delhi virus whether applied simultaneously with the inoculation or after. A major inhibition was observed with O. vulgare essential oil and hydrosol, resulting in 10^–4-fold decrease of virus titer 3 weeks after treatment. Curative activity gave maximum results with all three essential oils and T. vulgaris and R. officinalis hydrosols, recording from 10^–2-fold decrease to virus not detected 4 weeks after treatment. An induction of PAL gene expression was recorded at 12 d.p.i. and then was restored to the levels of untreated control. This allows to hypothesize an early plant defense response to virus infection, possibly boosted by treatments. Plant extracts’ composition was characterized by gas chromatography-mass spectrometry. Phenols were largely main components of O. vulgare and T. vulgaris extracts (carvacrol and thymol, respectively), while extracts from R. officinalis were based on monoterpene hydrocarbons (essential oil) and oxygenated monoterpenes (hydrosol).

Plant Viral Disease Detection: From Molecular Diagnosis to Optical Sensing Technology—A Multidisciplinary Review

Plant viral diseases result in productivity and economic losses to agriculture, necessitating accurate detection for effective control. Lab-based molecular testing is the gold standard for providing reliable and accurate diagnostics; however, these tests are expensive, time-consuming, and labour-intensive, especially at the field-scale with a large number of samples. Recent advances in optical remote sensing offer tremendous potential for non-destructive diagnostics of plant viral diseases at large spatial scales. This review provides an overview of traditional diagnostic methods followed by a comprehensive description of optical sensing technology, including camera systems, platforms, and spectral data analysis to detect plant viral diseases. The paper is organized along six multidisciplinary sections: (1) Impact of plant viral disease on plant physiology and consequent phenotypic changes, (2) direct diagnostic methods, (3) traditional indirect detection methods, (4) optical sensing technologies, (5) data processing techniques and modelling for disease detection, and (6) comparison of the costs. Finally, the current challenges and novel ideas of optical sensing for detecting plant viruses are discussed.

Papaya Leaf Curl Virus (PaLCuV) Infection on Papaya (Carica papaya L.) Plants Alters Anatomical and Physiological Properties and Reduces Bioactive Components

Papaya leaves are used frequently for curing scores of ailments. The medicinal properties of papaya leaves are due to presence of certain bioactive/pharmacological compounds. However, the papaya leaf curl virus (PaLCuV), a geminivirus, is a major threat to papaya cultivation globally. During the present investigation, we observed that PaLCuV infection significantly altered the anatomy, physiology, and bioactive properties of papaya leaves. As compared to healthy leaves, the PaLCuV-infected leaves were found to have reduced stomatal density (76.83%), stomatal conductance (78.34%), photosynthesis rate (74.87%), water use efficiency (82.51%), chlorophyll (72.88%), carotenoid (46.63%), osmolality (48.55%), and soluble sugars (70.37%). We also found lower enzymatic activity (superoxide dismutase (SOD), ascorbate peroxidase (APX), and catalase (CAT)-56.88%, 85.27%, and 74.49%, respectively). It was found that the size of guard cells (50%), transpiration rate (45.05%), intercellular CO₂ concentration (47.81%), anthocyanin (27.47%), proline content (74.17%), malondialdehyde (MDA) (106.65%), and electrolyte leakage (75.38%) was elevated in PaLCuV-infected leaves. The chlorophyll fluorescence analysis showed that the infected plant leaves had a significantly lower value of maximal quantum yield of photosystem II (PSII (Fv/Fm), photochemical quantum yield of photosystem I (PSI (Y(I)), and effective quantum yield of PSII (Y(II)). However, in non-photochemical quenching mechanisms, the proportion of energy dissipated in heat form (Y(NPQ)) was found to be significantly higher. We also tested the bioactivity of infected and healthy papaya leaf extracts on a Caenorhabditis elegans (C. elegans) model system. It was found that the crude extract of papaya leaves significantly enhanced the life span of C. elegans (29.7%) in comparison to virus-infected leaves (18.4%) on application of 100 µg/mL dose of the crude extract. Our research indicates that the PaLCuV-infected leaves not only had anatomical and physiological losses, but that pharmacological potential was also significantly decreased.

Engineering CRISPR immune systems conferring GLRaV-3 resistance in grapevine

Grapevine leafroll-associated virus 3 (GLRaV-3) is one of the causal agents of grapevine leafroll disease (GLD), which severely impacts grapevine production in most viticultural regions of the world. The development of virus-resistant plants is a desirable strategy for the efficient control of viral diseases. However, natural resistant resources have not been reported in the genus Vitis, and anti-GLRaV-3 research has been quite limited in grapevine. In this study, by expressing FnCas9 and LshCas13a, we established a highly effective transgenic construct screening system via an optimized Agrobacterium-mediated transient delivery system in grapevine plantlets. Our study indicated that CRISPR/FnCas9 and LshCas13a caused GLRaV-3 inhibition. Moreover, three vectors-pCR01-CP, pCR11-Hsp70h and pCR11-CP-exhibited the most robust inhibition efficiency compared to those targeting other sites and could be further engineered to generate GLRaV-3-resistant grapevine. In addition, the viral interference efficiency of FnCas9 was dependent on its RNA binding activity. The efficiency of virus inhibition was positively correlated with the level of Cas gene expression. Importantly, we demonstrated that LshCas13a had better interference efficiency against viruses than FnCas9. In summary, this study confirmed that these two RNA-targeting CRISPR mechanisms can confer immunity against viruses in grapevine, providing new avenues to control GLRaV-3 or other RNA viruses in fruit crops.

Grapevine Red Blotch Disease Etiology and Its Impact on Grapevine Physiology and Berry and Wine Composition

Grapevine red blotch virus (GRBV) has become widespread in the United States since its identification in 2012. GRBV is the causative agent of grapevine red blotch disease (GRBD), which has caused detrimental economic impacts to the grape and wine industry. Understanding viral function, plant–pathogen interactions, and the effects of GRBV on grapevine performance remains essential to developing potential mitigation strategies. This comprehensive review examines the current body of knowledge regarding GRBV, to highlight gaps in the knowledge and potential mitigation strategies for grape growers and winemakers.

Differential Triggering of the Phenylpropanoid Biosynthetic Pathway Key Genes Transcription upon Cold Stress and Viral Infection in Tomato Leaves

Plants develop a plethora of defense strategies during their acclimation and interactions with various environmental stresses. Secondary metabolites play a pivotal role in the processes during stress acclimation, therefore deciphering their relevant responses exchange the interpretation of the underlying molecular mechanisms that may contribute to improved adaptability and efficacy. In the current study, tomato plants were exposed to short-term cold stress (5 °C for 16 h) or inoculated (20 d) with either Cucumber Mosaic Virus (CMV) or Potato Virus Y (PVY). Responses were recorded via the assessments of leaf total phenolic (TP) content, total flavonoid (TF) levels, and phenylalanine ammonia-lyase (PAL) enzyme activity. The transcription of the gene families regulating the core phenylpropanoid biosynthetic pathway (PBP) at an early (PAL, cinnamic acid 4-hydroxylase, 4-coumarate-CoA ligase) or late (chalcone synthase and flavonol synthase) stage was also evaluated. The results showed that cold stress stimulated an increase in TP and TF contents, while PAL enzyme activity was also elevated compared to viral infection. Besides genes transcription of the enzymes involved in the core PBP was mostly induced by cold stress, whereas transcription of the genes regulating flavonoid biosynthesis was mainly triggered by viral infection. In conclusion, abiotic and biotic stressors induced differential regulation of the core PBP and flavonoid biosynthetic metabolism. Taking the above into consideration, our results highlight the complexity of tomato responses to diverse stimuli allowing for better elucidation of stress tolerance mechanisms at this crop.

Genome-wide screening of novel RT-qPCR reference genes for study of GLRaV-3 infection in wine grapes and refinement of an RNA isolation protocol for grape berries

BACKGROUND

Grapevine, as an essential fruit crop with high economic values, has been the focus of molecular studies in diverse areas. Two challenges exist in the grapevine research field: (i) the lack of a rapid, user-friendly and effective RNA isolation protocol for mature dark-skinned berries and, (ii) the lack of validated reference genes that are stable for quantification of gene expression across desired experimental conditions. Successful isolation of RNA with sufficient yield and quality is essential for downstream analyses involving nucleic acids. However, ripe berries of dark-skinned grape cultivars are notoriously challenging in RNA isolation due to high contents of polyphenolics, polysaccharides, RNase and water.

RESULTS

We have optimized an RNA isolation protocol through modulating two factors at the lysis step that could impact results of RNA isolation - 2-ME concentration and berry mass. By finding the optimal combination among the two factors, our refined protocol was highly effective in isolating total RNA with high yield and quality from whole mature berries of an array of dark-skinned wine grape cultivars. Our protocol takes a much shorter time to complete, is highly effective, and eliminates the requirement for hazardous organic solvents. We have also shown that the resulting RNA preps were suitable for multiple downstream analyses, including the detection of viruses and amplification of grapevine genes using reverse transcription-polymerase chain reaction (RT-PCR), gene expression analysis via quantitative reverse transcription PCR (RT-qPCR), and RNA Sequencing (RNA-Seq). By using RNA-Seq data derived from Cabernet Franc, we have identified seven novel reference gene candidates (CYSP, NDUFS8, YLS8, EIF5A2, Gluc, GDT1, and EF-Hand) with stable expression across two tissue types, three developmental stages and status of infection with grapevine leafroll-associated virus 3 (GLRaV-3). We evaluated the stability of these candidate genes together with two conventional reference genes (actin and NAD5) using geNorm, NormFinder and BestKeeper. We found that the novel reference gene candidates outperformed both actin and NAD5. The three most stable reference genes were CYSP, NDUFS8 and YSL8, whereas actin and NAD5 were among the least stable. We further tested if there would be a difference in RT-qPCR quantification results when the most stable (CYSP) and the least stable (actin and NAD5) genes were used for normalization. We concluded that both actin and NAD5 led to erroneous RT-qPCR results in determining the statistical significance and fold-change values of gene expressional change.

CONCLUSIONS

We have formulated a rapid, safe and highly effective protocol for isolating RNA from recalcitrant berry tissue of wine grapes. The resulting RNA is of high quality and suitable for RT-qPCR and RNA-Seq. We have identified and validated a set of novel reference genes based on RNA-Seq dataset. We have shown that these new reference genes are superior over actin and NAD5, two of the conventional reference genes commonly used in early studies.

Rootstock influences the effect of grapevine leafroll-associated viruses on berry development and metabolism via abscisic acid signalling

Grapevine leafroll-associated virus (GLRaV) infections are accompanied by symptoms influenced by host genotype, rootstock, environment, and which individual or combination of GLRaVs is present. Using a dedicated experimental vineyard, we studied the responses to GLRaVs in ripening berries from Cabernet Franc grapevines grafted to different rootstocks and with zero, one, or pairs of leafroll infection(s). RNA sequencing data were mapped to a high-quality Cabernet Franc genome reference assembled to carry out this study and integrated with hormone and metabolite abundance data. This study characterized conserved and condition-dependent responses to GLRaV infection(s). Common responses to GLRaVs were reproduced in two consecutive years and occurred in plants grafted to different rootstocks in more than one infection condition. Though different infections were inconsistently distinguishable from one another, the effects of infections in plants grafted to different rootstocks were distinct at each developmental stage. Conserved responses included the modulation of genes related to pathogen detection, abscisic acid (ABA) signalling, phenylpropanoid biosynthesis, and cytoskeleton remodelling. ABA, ABA glucose ester, ABA and hormone signalling-related gene expression, and the expression of genes in several transcription factor families differentiated the effects of GLRaVs in berries from Cabernet Franc grapevines grafted to different rootstocks. These results support that ABA participates in the shared responses to GLRaV infection and differentiates the responses observed in grapevines grafted to different rootstocks.

Assessment of Ionomic, Phenolic and Flavonoid Compounds for a Sustainable Management of Xylella fastidiosa in Morocco

Morocco belongs to the countries ranked at a high-risk level for entry, establishment, and spread of Xylella fastidiosa, which has recently re-emerged as a plant pathogen of global importance causing olive quick decline syndrome (OQDS). Symptomatic infection by X. fastidiosa leads to devastating diseases and important economic losses. To prevent such losses and damages, countries without current outbreaks like Morocco need to first understand their host plant responses to X. fastidiosa. The assessment of the macro and micro-elements content (ionome) in leaves can give basic and useful information along with being a powerful tool for the sustainable management of diseases caused by this devastating pathogen. Herein, we compare the leaf ionome of four important autochthonous Moroccan olive cultivars (‘Picholine Marocaine’, ‘Haouzia’, ‘Menara’, and ‘Meslalla’), and eight Mediterranean varieties introduced in Morocco (‘Arbequina’, ‘Arbosana’, ‘Leccino’, ‘Ogliarola salentina’, ‘Cellina di Nardo’, ‘Frantoio’, ‘Leucocarpa’, and ‘Picholine de Languedoc’), to develop hypotheses related to the resistance or susceptibility of the Moroccan olive trees to X. fastidiosa infection. Leaf ionomes, mainly Ca, Cu, Fe, Mg, Mn, Na, Zn, and P, were determined using inductively coupled plasma optical emission spectroscopy (ICP-OES). These varieties were also screened for their total phenolics and flavonoids content. Data were then involved in a comparative scheme to determine the plasticity of the pathogen. Our results showed that the varieties ‘Leccino’, ’Arbosana’, ‘Arbequina’ consistently contained higher Mn, Cu, and Zn and lower Ca and Na levels compared with the higher pathogen-sensitive ‘Ogliarola salentina’ and ‘Cellina di Nardò’. Our findings suggest that ‘Arbozana’, ‘Arbiquina’, ‘Menara’, and ‘Haouzia’ may tolerate the infection by X. fastidiosa to varying degrees, provides additional support for ‘Leccino’ having resistance to X. fastidiosa, and suggests that both ‘Ogliarola salentina’ and ‘Cellina di Nardö’ are likely sensitive to X. fastidiosa infection.

Probing into the Effects of Grapevine Leafroll-Associated Viruses on the Physiology, Fruit Quality and Gene Expression of Grapes

Grapevine leafroll is one of the most widespread and highly destructive grapevine diseases that is responsible for great economic losses to the grape and wine industries throughout the world. Six distinct viruses have been implicated in this disease complex. They belong to three genera, all in the family Closteroviridae. For the sake of convenience, these viruses are named as grapevine leafroll-associated viruses (GLRaV-1, -2, -3, -4, -7, and -13). However, their etiological role in the disease has yet to be established. Furthermore, how infections with each GLRaV induce the characteristic disease symptoms remains unresolved. Here, we first provide a brief overview on each of these GLRaVs with a focus on genome structure, expression strategies and gene functions, where available. We then provide a review on the effects of GLRaV infection on the physiology, fruit quality, fruit chemical composition, and gene expression of grapevine based on the limited information so far reported in the literature. We outline key methodologies that have been used to study how GLRaV infections alter gene expression in the grapevine host at the transcriptomic level. Finally, we present a working model as an initial attempt to explain how infections with GLRaVs lead to the characteristic symptoms of grapevine leafroll disease: leaf discoloration and downward rolling. It is our hope that this review will serve as a starting point for grapevine virology and the related research community to tackle this vastly important and yet virtually uncharted territory in virus-host interactions involving woody and perennial fruit crops.

Genome-wide characterization and analysis of bHLH transcription factors related to anthocyanin biosynthesis in spine grapes (Vitis davidii)

As one of the largest transcription factor family, basic helix-loop-helix (bHLH) transcription factor family plays an important role in plant metabolism, physiology and growth. Berry color is one of the important factors that determine grape quality. However, the bHLH transcription factor family's function in anthocyanin synthesis of grape berry has not been studied systematically. We identified 115 bHLH transcription factors in grape genome and phylogenetic analysis indicated that bHLH family could be classified into 25 subfamilies. First, we screened six candidate genes by bioinformatics analysis and expression analysis. We found one of the candidate genes VdbHLH037 belonged to III (f) subfamily and interacted with genes related to anthocyanin synthesis through phylogenetic analysis and interaction network prediction. Therefore, we speculated that VdbHLH037 participated in the anthocyanin synthesis process. To confirm this, we transiently expressed VdbHLH037 in grape and Arabidopsis transformation. Compared with the control, transgenic materials can accumulate more anthocyanins. These results provide a good base to study the function of the VdbHLH family in anthocyanin synthesis of grape berry.

Reference gene selection for miRNA and mRNA normalization in potato in response to potato virus Y

This was the first report on evaluating candidate reference genes for quantifying the expression profiles of both coding (e.g., mRNA) and non-coding (e.g., miRNA) genes in potato response to potato virus Y (PVY) inoculation. The reverse transcription-quantitative real-time polymerase chain reaction (RT-qPCR) method was employed to quantify the expression profiles of eight selected candidate reference genes; their expression stability was analyzed by four statistical algorithms, i.e., geNorm, BestKeeper, NormFinder and RefFinder. The most stable reference genes were sEF1a, sTUBb and seIF5 with a high stability. The least stable ones were sPP2A, sSUI1 and sGAPDH. The same reference gene allows for normalization of both miRNA and mRNA levels from a single RNA sample using cDNAs synthesized in a single RT reaction, in which a stem-loop primer was used for miRNAs and the oligo (dT) for mRNAs.

Bacillus licheniformis strain POT1 mediated polyphenol biosynthetic pathways genes activation and systemic resistance in potato plants against Alfalfa mosaic virus

Alfalfa mosaic virus (AMV) is a worldwide distributed virus that has a very wide host range and causes significant crop losses of many economically important crops, including potato (Solanum tuberosum L.). In this study, the antiviral activity of Bacillus licheniformis strain POT1 against AMV on potato plants was evaluated. The dual foliar application of culture filtrate (CF), 24 h before and after AMV-inoculation, was the most effective treatment that showed 86.79% reduction of the viral accumulation level and improvement of different growth parameters. Moreover, HPLC analysis showed that a 20 polyphenolic compound was accumulated with a total amount of 7,218.86 and 1606.49 mg/kg in POT1-treated and non-treated plants, respectively. Additionally, the transcriptional analysis of thirteen genes controlling the phenylpropanoid, chlorogenic acid and flavonoid biosynthetic pathways revealed that most of the studied genes were induced after POT1 treatments. The stronger expression level of F3H, the key enzyme in flavonoid biosynthesis in plants, (588.133-fold) and AN2, anthocyanin 2 transcription factor, (97.005-fold) suggested that the accumulation flavonoid, especially anthocyanin, might play significant roles in plant defense against viral infection. Gas chromatography-mass spectrometry (GC-MS) analysis showed that pyrrolo[1,2-a]pyrazine-1,4-dione is the major compound in CF ethyl acetate extract, that is suggesting it acts as elicitor molecules for induction of systemic acquired resistance in potato plants. To our knowledge, this is the first study of biological control of AMV mediated by PGPR in potato plants.

Water Deficits Do Not Improve Fruit Quality in Grapevine Red Blotch Virus-Infected Grapevines (Vitis vinifera L.)

Although deficit irrigation is used to improve fruit quality in healthy grapevines, it can potentially amplify negative effects of viral disease and reduce fruit quality in Grapevine Red Blotch Virus (GRBV) infected grapevines. Therefore, a 2-year field experiment was conducted to understand the interaction between GRBV infection and water deficits on disease development and vine physiology. Well-watered (WW) vines were irrigated at 100% of estimated crop evapotranspiration (ETc), while water deficit (WD) vines received water at 66 and 50% ETc in 2017 and 2018, respectively. Healthy (GRBV-) and infected (GRBV+) vines were confirmed by PCR assays. There were no significant effects of water deficits on foliar symptom onset in either year, but more severe water deficits in 2018 resulted in a more rapid symptom progression. GRBV+ vines had a higher Ψstem compared to GRBV- vines, but the effects of virus only appeared post-veraison and corresponded to decreased leaf gas exchange. In general, vine vegetative and reproductive growth were not reduced in GRBV+ vines. Yields were highest in WW/GRBV+ vines due to larger clusters containing larger berries. Consistent treatment effects on berry primary chemistry were limited to sugars, with no interactions between factors. Water deficits were able to somewhat increase berry anthocyanin concentration in GRBV+ fruit, but the effects were dependent on year. By comparison, virus status and water deficits interacted on skin tannins concentration such that they were decreased in WD/GRBV+ vines, but increased in WD/GRBV- vines. Water deficits had no effect on seed phenolics, with only virus status having a significant diminution. Although keeping GRBV+ vines well-watered may mitigate some of the negative effects of GRBD, these results suggest that water deficits will not improve overall fruit quality in GRBV+ vines. Ultimately, the control of fruit ripening imparted by GRBV infection seems to be stronger than abiotic control imparted by water deficits.

Impact of Grapevine Red Blotch Disease on Cabernet Sauvignon and Merlot Wine Composition and Sensory Attributes

Grapevine red blotch disease (GRBD) is a recently identified viral disease that affects grapevines. GRBD has been shown to impact grapevine physiology and grape composition by altering specific ripening events. However, no studies have been reported on the impact of GRBD on wine composition and its sensory attributes. This study evaluated the impact of GRBD on wine primary and secondary metabolites, in addition to its sensory properties, when making wines from Cabernet Sauvignon and Merlot grapes during two seasons. Wines made with GRBD-impacted fruit were lower in ethanol content when compared to wines made with grapes from healthy grapevines. This was attributed to the lower total soluble sugar (TSS) levels of diseased grapes due to delayed ripening at harvest. GRBD impacted wine phenolic composition by decreasing anthocyanin concentrations and increasing flavonol concentrations in some instances. Additionally, proanthocyanidin concentrations were also consistently higher in GRBD wines compared to wines made from healthy fruit. Descriptive analysis demonstrated that GRBD can impact wine style by altering aroma, flavor, and mouthfeel attributes. However, the extent of GRBD impact on wine composition and sensory properties were site and season dependent.

Hydrogen peroxide generated by over-expression of cytosolic superoxide dismutase in transgenic plums enhances bacterial canker resistance and modulates plant defence responses

H₂O₂ generated during the oxidative burst, plays important roles in plant defenses responses against pathogens. In this study we examined the role of H₂O₂ on bacterial canker resistance in transgenic plums over-expressing cytosolic superoxide dismutase. Three transgenic lines (C64, C66 and F12) with elevated levels of H₂O₂ accumulation showed enhanced resistance against bacterial canker disease caused by Pseudomonas syringae pv. syringae, when compared to the non-transformed control. Analysis of the expression of several genes involved in the plant-pathogen interaction showed that the expression of those involved in SA pathway (pr1 and npr1) and JA (lox3) were activated earlier and transiently in transgenic lines C66 and F12 when compared to the wild type. However, the expression of genes involved in anthocyanin synthesis (chi, chs, f3h, dfr, atcs, myb10) and ethylene (acs) was induced at very low levels whereas it was activated by the pathogen at exaggerated levels in the non-transformed line. These results suggest that resistance observed in transgenic lines over-producing H₂O₂ is correlated with an early and transient induction of defense genes associated with the SA and JA pathways and inhibition of gene expression associated with ethylene and anthocyanin biosynthesis.

Detection of Grapevine Leafroll-Associated Virus 1 and 3 in White and Red Grapevine Cultivars Using Hyperspectral Imaging

Grapevine leafroll disease (GLD) is considered one of the most widespread grapevine virus diseases, causing severe economic losses worldwide. To date, six grapevine leafroll-associated viruses (GLRaVs) are known as causal agents of the disease, of which GLRaV-1 and -3 induce the strongest symptoms. Due to the lack of efficient curative treatments in the vineyard, identification of infected plants and subsequent uprooting is crucial to reduce the spread of this disease. Ground-based hyperspectral imaging (400–2500 nm) was used in this study in order to identify white and red grapevine plants infected with GLRaV-1 or -3. Disease detection models have been successfully developed for greenhouse plants discriminating symptomatic, asymptomatic, and healthy plants. Furthermore, field tests conducted over three consecutive years showed high detection rates for symptomatic white and red cultivars, respectively. The most important detection wavelengths were used to simulate a multispectral system that achieved classification accuracies comparable to the hyperspectral approach. Although differentiation of asymptomatic and healthy field-grown grapevines showed promising results further investigations are needed to improve classification accuracy. Symptoms caused by GLRaV-1 and -3 could be differentiated.

R2R3-MYB Transcription Factors Regulate Anthocyanin Biosynthesis in Grapevine Vegetative Tissues

Anthocyanins with important physiological functions mainly accumulate in grape berry, but teinturier grape cultivars can accumulate anthocyanins in both reproductive and vegetative tissues. The molecular regulatory mechanisms of anthocyanin biosynthesis in grapevine reproductive and vegetative tissues are different. Therefore, teinturier grapevine cultivar provides opportunities to investigate transcriptional regulation of vegetative anthocyanins, and to compare with mechanisms that regulate grape berry anthocyanins. Yan73 is a teinturier Vitis vinifera variety with vegetative tissues able to accumulate anthocyanins, but the anthocyanin pattern and the molecular mechanism regulating anthocyanin biosynthesis in these tissues remain uncharacterized. We analyzed the anthocyanin metabolic and transcriptome profiles of the vegetative tissues of Yan73 and its male parent with HPLC-ESI-MS/MS and RNA-sequencing technologies. Yan73 vegetative tissues had relatively high 3'-OH, acylated, and methoxylated anthocyanins. Furthermore, peonidin-3-O-(trans-6-coumaryl)-glucoside is the most abundant anthocyanin in Yan73 grapevine vegetative tissues. A total of 30,17 and 10 anthocyanin biosynthesis genes showed up-regulated expression in Yan73 leaf, stem and tendril, respectively, indicating anthocyanin biosynthesis in Yan73 vegetative tissues is regulated by transcription factors. The up-regulated expression of VvMYBA1 on chromosome 2 and VvMYBA5, VvMYBA6, and VvMYBA7 on chromosome 14 are responsible for the anthocyanin patterns of Yan73 vegetative tissues. The expression of a set of R2R3-MYB C2 repressor genes is activated and may negatively regulate anthocyanin biosynthesis in Yan73 vegetative tissues. These findings enhance our understanding of anthocyanin biosynthesis in grapevine.

Biochemical Changes in Leaves of Vitis vinifera cv. Sangiovese Infected by Bois Noir Phytoplasma

Bois noir is a disease associated with the presence of phytoplasma 'Candidatus Phytoplasma solani' belonging to the Stolbur group (subgroup 16SrXII-A), which has a heavy economic impact on grapevines. This study focused on the changes induced by phytoplasma in terms of the profile and amount of secondary metabolites synthesized in the phenylpropanoid pathway in leaves of Vitis vinifera L. red-berried cultivar Sangiovese. Metabolic alterations were assessed according to the disease progression through measurements of soluble sugars, chlorophyll, and phenolic compounds produced by plant hosts, in response to disease on symptomatic and asymptomatic Bois noir-positive plants. Significant differences were revealed in the amount of soluble sugars, chlorophyll, and accumulation/reduction of some compounds synthesized in the phenylpropanoid pathway of Bois noir-positive and negative grapevine leaves. Our results showed a marked increase in phenolic and flavonoid production and a parallel decrease in lignin content in Bois noir-positive compared to negative leaves. Interestingly, some parameters (chlorophyll a, soluble sugars, total phenolic or flavonoids content, proanthocyanidins, quercetin) differed between Bois noir-positive and negative leaves regardless of symptoms, indicating measurable biochemical changes in asymptomatic leaves. Our grapevine cultivar Sangiovese results highlighted an extensive modulation of the phenylpropanoid biosynthetic pathway as a defense mechanism activated by the host plant in response to Bois noir disease.

Influence of pruning time and viral infection on stilbenoid levels in Pinot noir grape canes

BACKGROUND

Grapevine canes represent a large source of waste derived from grape cultivation. In the present study, the effect of different processes of storage and different pruning times on the stilbene accumulation on Pinot noir canes was analyzed. Whether the alteration of the secondary metabolism accompanying leafroll symptom expressions could affect the stilbenoid accumulation in canes harvested at pruning time was also investigated.

RESULTS

The maximum accumulation of trans-resveratrol and trans-piceatannol was obtained in canes harvested in October and dried at 40 °C. Even in grape canes harvested in October, November, and December and stored for different times at room temperature (20 ± 2 °C) a marked increase in trans-resveratrol and trans-piceatannol was evident, which reached a maximum at around 8 weeks of storage. A significant higher accumulation of trans-resveratrol and trans-piceatannol was also found in canes harvested from symptomatic plants compared to those harvested from asymptomatic plants for all the pruning times.

CONCLUSION

This study confirms that the biosynthetic enzyme activities and, particularly, those involved in the stilbene pathway, persist during Pinot noir cane storage at different harvest times, with different storage times and conditions, and different sanitary status. © 2019 Society of Chemical Industry.

The impact of grapevine red blotch disease on Vitis vinifera L. Chardonnay grape and wine composition and sensory attributes over three seasons

BACKGROUND

Grapevine red blotch virus (GRBV) is a recently discovered DNA virus, which was demonstrated to be responsible for grapevine red blotch disease (GRBD). Its presence has been confirmed in the United States, Canada, Mexico, and South Korea in white and red Vitis vinifera cultivars, including Chardonnay. It has been shown that the three-cornered alfalfa treehopper (Spissistilus festinus) was able to both acquire the GRBV from a grapevine infected and transmit it to healthy grapevines in glasshouse conditions. Studies found that GRBD impacts fruit price, grapevine physiology, and grape berry composition and metabolism in red cultivars. This study evaluated the impact of GRBD on V. vinifera L. Chardonnay grape and wine composition and sensory properties from one vineyard during the 2014, 2015 and 2016 seasons.

RESULTS

Grapes from symptomatic red blotch diseased grapevines were lower in total soluble solids, flavan-3-ol, and total phenolic content, and higher in flavonol content when compared to grapes from healthy grapevines. Wines made with grapes from symptomatic grapevines resulted mostly in lower ethanol content and higher pH when compared to wines made from healthy grapevines. Analysis of volatile compounds and descriptive analysis demonstrated that GRBD can impact wine style by altering aroma, flavor, and mouthfeel attributes.

CONCLUSIONS

The impacts of GRBD on grape composition directly influenced wine chemistry. The decreased ethanol content impacted not only the levels of volatile compounds but the sensory perception during descriptive analysis. The extent of GRBD impact on the grape composition and wine composition and sensory attributes varied between seasons. © 2019 Society of Chemical Industry.

Mixed infecting of grapevine with viruses in the commercial vineyards of the Crimean Peninsula

Viral infections cause the reduction of yields and efficiency of vine cultivation in all viticultural regions of the world. Simultaneous infecting with several viruses, the so-called mixed infection, can significantly increase the severity of symptoms. The article presents the results of study of mixed infecting of grapevine with viruses in the vineyards of the Crimean Peninsula during 2011-2020. More than 800 grapevine samples of 153 varieties selected in 23 vineyards of the Crimea were analyzed over the entire period of study. Presence of phytopathogenic viruses in the samples was determined by RT-PCR using virus specific primers. The share of 25.5 % of all the samples tested gave positive result for one or more of the following viruses: GFLV, GLRaV-1, GLRV-2, GLRaV-3, GFkV, GVA, GRSPaV, ArMV, GFLV. During the process of studyno vines affected by GVB virus were identified. Single-agent infection was found in 20% of the examined vines. The amount of vines affected by mixed infection was 5.48 % of all tested. In a mixed viral infection more common combinations are: GRSPaV/GFkV; GVA/GRSPaV; GVA/GLRaV-1/GRSPaV; GVA/GLRaV-3/GRSPaV. Vines were infected the most with GRSPaV and GFkV viruses, which is visually manifested in the form of mosaic leaf variegation, leaf chlorosis and the appearance of necrotic spots.

Divergent molecular and growth responses of young "Cabernet Sauvignon" (Vitis vinifera) plants to simple and mixed infections with Grapevine rupestris stem pitting-associated virus

Grapevine rupestris stem pitting associated virus (GRSPaV) is one of the most widely distributed viruses; even so, little is known about its effect on Vitis vinifera. To provide new insights, the effects of single and mixed GRSPaV infections on the V. vinifera cultivar "Cabernet Sauvignon" were studied by evaluating growth parameters, such as measurements of the total plant length, the number and distance of internodes and the number of leaves per shoot. In addition, parameters relating to gas exchange, i.e., the stomatal conductance, net photosynthetic rate, internal CO2 concentration and leaf transpiration, were also assessed. All the measurements were performed in one- and two-year-old plants with a single GRSPaV infection or mixed infections of GRSPaV and Grapevine fanleaf virus (GFLV). The results show that the plant phytosanitary status did not significantly alter the growth and gas exchange parameters in one-year-old plants. However, in two-year-old plants, single GRSPaV infections increased shoot elongation, which was accompanied by the overexpression of genes associated with the gibberellic acid response pathway. The gas exchange parameters of these plants were negatively affected, despite exhibiting higher LHCII gene expression. Plants with mixed infections did not have modified growth parameters, although they presented a greater reduction in the primary photosynthetic parameters evaluated with no change in LHCII expression. The results presented here confirm the co-evolution hypothesis for V. vinifera and GRSPaV during the early stages of plant development, and they provide new evidence about the effects of GRSPaV and GFLV co-infections on the "Cabernet Sauvignon" cultivar.

Comparative Transcriptome Analysis and Expression of Genes Reveal the Biosynthesis and Accumulation Patterns of Key Flavonoids in Different Varieties of Zanthoxylum bungeanum Leaves

Zanthoxylum bungeanum (Rutaceae), a popular food flavoring and traditional Chinese medicine ingredient, is an important cash crop. Its leaves are rich in flavonoids with multiple bioactivities. However, the transcriptional sequencing has not been investigated, and the molecular basis for the flavonoid biosynthesis remains unclear in this plant. This paper, the key flavonoids (epicatechin, rutin, hyperoside, trifolin, quercitrin, and afzelin) contents were determined in the leaves of 10 Z. bungeanum varieties from a common garden. Results show the leaves of Z. bungeanum mainly contained hyperoside (11.410-21.721 mg/g) and quercitrin (9.401-18.016 mg/g). The total content of these key components was the highest in Fengxian Dahongpao (66.012 mg/g) and the lowest in Fugu (32.223 mg/g). Three varieties (Hancheng stingless, Fugu, and Fengxian Dahongpao) with significant differences in the total content of key flavonoids were selected for transcriptome analysis to obtain flavonoid biosynthesis-related genes. In total, 83 522 unigenes were obtained, 40 668 (48.69%) unigenes were annotated, and 6656 differentially expressed genes (DEGs) were identified. Comparison of the other two varieties, Fugu had many differentially expressed genes indicating the particularity of its variety. Flavonoid-related DEGs of 22 structural genes, including three PALs, one CYP73A, three 4CLs, six CHSs, one CHI, one F3H, one DFR, two ANSs, one ANR, one FLS, and two CYP75B1s, as well as nine MYBs were obtained. These structural genes had different expression patterns in different Z. bungeanum varieties. It is worth noting that the genes expressing the flavonoid 3'5' hydroxylase are absent in Z. bungeanum. Furthermore, quantitative real-time PCR experiment showed consistent results in transcriptome analysis. The RNA-Seq data set of this study sheds lights on the molecular mechanism of flavonoid biosynthesis in Z. bungeanum, provides valuable information for the metabolic regulation of flavonoids, and may serve as a guide for future breeding programs.