Phytoalexins In Plants Research Articles

Rhizosphere competent inoculants modulate the apple root-associated microbiome and plant phytoalexins.

Modulating the soil microbiome by applying microbial inoculants has gained increasing attention as eco-friendly option to improve soil disease suppressiveness. Currently, studies unraveling the interplay of inoculants, root-associated microbiome, and plant response are lacking for apple trees. Here, we provide insights into the ability of Bacillus velezensis FZB42 or Pseudomonas sp. RU47 to colonize apple root-associated microhabitats and to modulate their microbiome. We applied the two strains to apple plants grown in soils from the same site either affected by apple replant disease (ARD) or not (grass), screened their establishment by selective plating, and measured phytoalexins in roots 3, 16, and 28days post inoculation (dpi). Sequencing of 16S rRNA gene and ITS fragments amplified from DNA extracted 28 dpi from different microhabitat samples revealed significant inoculation effects on fungal β-diversity in root-affected soil and rhizoplane. Interestingly, only in ARD soil, most abundant bacterial amplicon sequence variants (ASVs) changed significantly in relative abundance. Relative abundances of ASVs affiliated with Enterobacteriaceae were higher in rhizoplane of apple grown in ARD soil and reduced by both inoculants. Bacterial communities in the root endosphere were not affected by the inoculants but their presence was indicated. Interestingly and previously unobserved, apple plants responded to the inoculants with increased phytoalexin content in roots, more pronounced in grass than ARD soil. Altogether, our results indicate that FZB42 and RU47 were rhizosphere competent, modulated the root-associated microbiome, and were perceived by the apple plants, which could make them interesting candidates for an eco-friendly mitigation strategy of ARD. KEY POINTS: • Rhizosphere competent inoculants modulated the microbiome (mainly fungi) • Inoculants reduced relative abundance of Enterobacteriaceae in the ARD rhizoplane • Inoculants increased phytoalexin content in roots, stronger in grass than ARD soil.

Trends in the Potential of Stilbenes to Improve Plant Stress Tolerance: Insights of Plant Defense Mechanisms in Response to Biotic and Abiotic Stressors.

Stilbenes belong to the naturally synthesized plant phytoalexins, produced de novo in response to various biotic and abiotic stressors. The importance of stilbenes in plant resistance to stress and disease is of increasing interest. However, the defense mechanisms and potential of stilbenes to improve plant stress tolerance have not been thoroughly reviewed. This work overviewed the pentose phosphate pathway, glycolysis pathway, shikimate pathway, and phenylalanine pathway occurred in the synthesis of stilbenes when plants are subjected to biotic and abiotic stresses. The positive implications and underlying mechanisms regarding defensive properties of stilbenes were demonstrated. Ten biomimetic chemosynthesis methods can underpin the potential of stilbenes to improve plant stress tolerance. The prospects for the application of stilbenes in agriculture, food, cosmetics, and pharmaceuticals industries are anticipated. It is hoped that some of the detailed ideas and practices may contribute to the development of stilbene-related products and improvement of plant resistance breeding.

Use of Elicitors and Beneficial Bacteria to Induce and Prime the Stilbene Phytoalexin Response: Applications to Grapevine Disease Resistance

Phytoalexins are naturally occurring molecules with antimicrobial activity deriving from the secondary metabolism of plants; they are synthesized in response to physical agents or stresses and phytopathogenic agents (fungi, bacteria and viruses), as well as numerous chemical compounds and biological control agents. Among these, grapevine phytoalexins, which belong to the chemical group of stilbenes, exhibit biocidal activity against a large number and variety of plant pathogens. It is important to investigate whether induction of stilbene phytoalexin production can serve to protect this plant against its pathogens. Quite a few chemical compounds, derivatives of phytohormones bio-elicitors as well as biocontrol agents, have been used to induce the synthesis of stilbene phytoalexins with the aim of conferring protection to grapevine against its main diseases (gray mold, downy mildew, powdery mildew and esca). This article reviews the experiments that have been carried out in this direction during the last 30 years and shows that the observed protective effects towards pathogens are generally linked to induction and priming of the grapevine phytoalexin response, confirming the interest in using, in a more general way, stimulation of the production of phytoalexins in plants as a basis for crop protection.

Cardiotoxicity of sanguinarine via regulating apoptosis and MAPK pathways in zebrafish and HL1 cardiomyocytes

Sanguinarine, a plant phytoalexin, possesses extensive biological activities including antimicrobial, insecticidal, antitumor, anti-inflammatory and anti-angiogenesis effect. But its cardiotoxicity has rarely been studied. Here, we assess the cardiotoxicity of sanguinarine in vivo using larval zebrafish from 48 hpf to 96 hpf. The results show that sanguinarine caused severe malformation and the dysfunction of the heart including reductions of heart rate, red blood cell number, blood flow dynamics, stroke volume and increase of SV-BA distance, subintestinal venous congestion. Further studies showed that apoptosis in the zebrafish heart region was observed after sanguinarine exposure using TUNEL assay and AO staining method. In addition, the genes, such as sox9b, myl7, nkx2.5 and bmp10, which play crucial parts in the development and the function of the heart, were changed after sanguinarine treatment. caspase3, caspase9, bax and bcl2, apoptosis-related genes, were also altered by sanguinarine. Further studies were performed to study the cardiotoxicity in vitro using cardiomyocytes HL1 cell line. The results showed that remarkable increase of apoptosis and ROS level in HL1 cells were induced by sanguinarine. Moreover, the MAPK pathway (JNK and P38) were notably enhanced and involved in the cardiotoxicity induced by sanguinarine. Our findings will provide better understanding of sanguinarine in the toxic effect on heart.

Comparative Analysis of the Antitumor Activity of Cis- and Trans-Resveratrol in Human Cancer Cells with Different p53 Status.

Resveratrol, a natural plant phytoalexin, is produced in response to fungal infection or− UV irradiation. It exists as an isomeric pair with cis- and trans-conformation. Whereas multiple physiological effects of the trans-form, including a pronounced anti-tumoral activity, are nowadays elucidated, much less knowledge exists concerning the cis-isomer. In our work, we analyzed the antiproliferative and cytotoxic properties of cis-resveratrol in four different human tumor entities in direct comparison to trans-resveratrol. We used human cell lines as tumor models for hepatocellular carcinoma (HCC; HepG2, Hep3B), colon carcinoma (HCT-116, HCT-116/p53(−/−)), pancreatic carcinoma (Capan-2, MiaPaCa-2), and renal cell carcinoma (A498, SN12C). Increased cytotoxicity in all investigated tumor cells was observed for the trans-isomer. To verify possible effects of the tumor suppressor p53 on resveratrol-induced cell death, we used wild type and p53-deleted or -mutated cell lines for every tested tumor entity. Applying viability and cytotoxicity assays, we demonstrated a differential, dose-dependent sensitivity towards cis- or trans-resveratrol among the respective tumor types.

Stilbenes Can Impair Malolactic Fermentation with Strains ofOenococcus oeniandLactobacillus plantarum

Malolactic fermentation (MLF) is an important step in winemaking to improve wine quality by deacidification, increased microbial stability, and modified wine flavor. The phenolic composition of the wine influences the growth and metabolism of the lactic acid bacteria (LAB) used for MLF. Due to increased cultivation of fungus-resistant grape cultivars, the present study aimed to analyze the influence of stilbenes on MLF because stilbenes play an important role as phytoalexins in plants to counteract fungal pathogens. The analysis showed that the grapevine-shoot extract Vineatrol and the stilbenes e-viniferin, ampelopsin A, r2-viniferin, and r-viniferin, as well as mixtures of the five stilbenes, decelerated malic acid degradation. This can be partially attributed to a reduced number of viable cells. However, the direct impact of stilbenes on the malolactic enzyme must also play a role, as shown by the finding that the viability of LAB stabilized, while at the same time, malic acid degradation was reduced. These results show that wines made from stilbene-rich grapes, such as fungus-resistant cultivars, might have a higher risk for a sluggish or incomplete MLF.

Photosensitizing Furocoumarins: Content in Plant Matrices and Kinetics of Supercritical Carbon Dioxide Extraction.

Furocoumarins are a group of plant phytoalexins exhibiting various bioactive properties; the most important of which are photosensitization and alteration of P450 cytochrome activity. Supercritical fluid extraction with carbon dioxide has been proposed as a green alternative for an organic solvent extraction of the furocoumarins. Four plant matrices rich in furocoumarins were extracted with CO2 at a temperature of 80 °C and pressure of 40 MPa, as these conditions were characterized by the highest solubility of furocoumarins. The extracts collected were analyzed using the HPLC method and the results obtained were used for the mathematical modeling of the observed phenomena. The total content of the furocoumarins in the matrices was 4.03–26.45 mg g−1 of dry weight. The impact of the process parameters on the solubility was consistent with the Chrastil equation. The broken plus intact cell model proved to be suitable to describe extraction curves obtained. The research proved the possibility of supercritical carbon dioxide utilization for the extraction of the furocoumarins from plant material and provided valuable data for prospective industrial-scale experiments.

Regulation of phytoalexin biosynthesis for agriculture and human health

Phytoalexins are diverse secondary metabolites of plants that are biosynthesized transiently and in relatively low amounts in response to pathogens and certain abiotic stresses. They commonly have potent antimicrobial and medicinal activities. As such, scientists have attempted to increase their accessibility by inventing diverse in vitro and in vivo approaches. Among these approaches, bioengineering plant transcription factors that directly regulate phytoalexin biosynthesis genes may be the most promising. Recent research has identified conserved transcription factors that directly regulate distinct phytoalexin biosynthesis pathways in different plant species. The intriguing results provide new insight into how conserved defense signaling pathways in plants result in lineage-specific biochemical defenses. These recent findings also suggest that a common transcription factor network could be engineered to enhance the biosynthesis of different phytoalexins in plants. However, the picture is far from complete since one or more transcription factors required to fully activate phytoalexin biosynthesis remain unidentified, and the exact mechanism of how the conserved factors regulate diverse phytoalexin pathways remains to be clarified. Here we review the agricultural and medicinal importance of phytoalexins, recent approaches to increase their accessibility, and the mechanisms that plants employ to activate and limit their biosynthesis. This review contributes to providing a systems level understanding of the regulation of phytoalexin biosynthesis so that effective bioengineering strategies can be developed to enhance phytoalexin biosynthesis for medicine and agriculture.

Optimization of extraction of total trans-resveratrol from peanut seeds and its determination by HPLC.

Resveratrol, a stilbene phytoalexin in plants, is believed to benefit human health. In this study, an optimized enzyme-assisted method was developed to extract the total content of trans-resveratrol (free or combined with glucose) in peanut seeds, followed by detection using high-performance liquid chromatography. The extraction process was optimized by Box-Behnken design and response surface methodology. The optimized enzyme concentration, digestion time, pH, and temperature were 3.02g/L, 57.06min, 5.88, and 51.05°C, respectively. Validation tests indicated that the experimental yield of trans-resveratrol was 0.183 ± 0.007 µg/g with a relative standard deviation of 3.87% (n=5) under the optimal condition, which was closely agreed with the predicted value (0.182 µg/g). The recoveries obtained from the spiked samples were varied from 89.4 to 103.9%. Therefore, this study will provide a useful method for quantification of total trans-resveratrol in peanut seeds.

Resveratrol as adjunctive therapy in treatment of irritability in children with autism: A double-blind and placebo-controlled randomized trial.

The underlying pathophysiology of autism spectrum disorder (ASD) has been linked to immune dysregulation, oxidative stress and excitation-inhibition imbalance. Among associated symptoms of ASD, management of irritability has gained considerable attention as it complicates adjustment of ASD patients and thus necessitates its pharmacological treatment. Resveratrol is a plant phytoalexin, which has been demonstrated to have neuroprotective effects through its anti-inflammatory and antioxidant properties. This double-blind, placebo-controlled randomized trial was designed to assess the potential therapeutic effects of resveratrol plus risperidone on irritability of ASD patients. Sixty-two patients were assigned randomly into two groups of resveratrol and placebo. Both groups were treated with risperidone twice daily starting at a dose of 0.5mg with a dose increase of 0.5mg per week (for the first 3weeks). Resveratrol dosage was 250mg twice per day from the beginning of the study. Using the Aberrant Behavior Checklist-Community (ABC-C), patients were assessed for ASD-related behavioural symptoms at baseline, week 5 and week 10. The frequency of adverse events was recorded using a checklist containing 25 possible side effects, including general, gastrointestinal, neurological and cardiovascular complications. Improvements in primary outcome measure (irritability) and three secondary outcome measures (lethargy/social withdrawal, stereotypic behaviour and inappropriate speech subscales) in the resveratrol group were statistically similar to those in the placebo group. The repeated measures analysis showed no time×treatment interaction on these subscale scores. In contrast, patients in the resveratrol group showed greater decline in hyperactivity/non-compliance score as a secondary outcome measure (mean difference [CI=95%]=4.51 [0.10-8.92], t=2.04; P=.04), and repeated measures analysis showed significant effect for time×treatment effect on this subscale score (F=3.81; df=1.30; P=.043). There was no significant difference in number and severity of adverse events between the two groups. This clinical trial demonstrated no significant effect for adjunctive treatment with resveratrol on irritability of patients with ASD. However, it provided preliminary evidence indicating that resveratrol could improve hyperactivity/non-compliance of ASD patients.

Molecular Engineering of Phytoalexins in Plants: Benefits and Limitations for Food and Agriculture.

Molecular Engineering of Phytoalexins in Plants: Benefits and Limitations for Food and Agriculture.

A high-resolution genetic map of the cereal crown rot pathogen Fusarium pseudograminearum provides a near-complete genome assembly.

Fusarium pseudograminearum is an important pathogen of wheat and barley, particularly in semi-arid environments. Previous genome assemblies for this organism were based entirely on short read data and are highly fragmented. In this work, a genetic map of F. pseudograminearum has been constructed for the first time based on a mapping population of 178 individuals. The genetic map, together with long read scaffolding of a short read-based genome assembly, was used to give a near-complete assembly of the four F. pseudograminearum chromosomes. Large regions of synteny between F. pseudograminearum and F. graminearum, the related pathogen that is the primary causal agent of cereal head blight disease, were previously proposed in the core conserved genome, but the construction of a genetic map to order and orient contigs is critical to the validation of synteny and the placing of species-specific regions. Indeed, our comparative analyses of the genomes of these two related pathogens suggest that rearrangements in the F. pseudograminearum genome have occurred in the chromosome ends. One of these rearrangements includes the transposition of an entire gene cluster involved in the detoxification of the benzoxazolinone (BOA) class of plant phytoalexins. This work provides an important genomic and genetic resource for F. pseudograminearum, which is less well characterized than F. graminearum. In addition, this study provides new insights into a better understanding of the sexual reproduction process in F. pseudograminearum, which informs us of the potential of this pathogen to evolve.

Inhaled resveratrol treatments slow ageing-related degenerative changes in mouse lung.

Lung ageing, a significant risk factor for chronic human lung diseases such as COPD and emphysema, is characterised by airspace enlargement and decreasing lung function. Likewise, in prematurely ageing telomerase null (terc-/-) mice, p53 stabilisation within diminishing numbers of alveolar epithelial type 2 cells (AEC2) accompanies reduced lung function. Resveratrol (RSL) is a plant phytoalexin that has previously showed efficacy in enhancing invertebrate longevity and supporting mammalian muscle metabolism when delivered orally. Here, we tested whether inhaled RSL could protect young, terc-/- mice from accelerated ageing of the lung. terc-/- mice aged 2 months inhaled 1 mg/kg RSL that was instilled intratracheally once per month for 3 months. One month after the last inhalation, whole lung function, structure and cellular DNA damage were evaluated and AEC2 survival was assessed by western blotting for survival pathway gene expression. RSL treatments delayed the loss of lung compliance (p<0.05), maintained lung structure (p<0.001) and blocked parenchymal cell DNA damage as measured by TdT Nick-End Labeling (TUNEL). RSL, a known agonist of deacetylase SIRT1, supported AEC2 survival by stimulating SIRT1 expression, promoting p53 destabilisation and decreasing Bax expression and by maintaining expression levels of Peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α), activated p-Akt and p-Mdm2 and inactivated Phospho-Phosphatase and tensin homolog (p-PTEN). RSL prophylaxis by inhalation is a potential approach for slowing ageing-related deterioration of lung function and structure by maintaining AEC2 integrity.

Expression of the stilbene synthase genes in the needles of spruce Picea jezoensis

Stilbenes are valuable plant phytoalexins, the biosynthesis of which is characteristic of different groups of phylogenetically unrelated plants. It is believed that all the stilbenes are the derivatives of resveratrol (3,5,4'-trihydroxy-trans-stilbene) or compounds close to it (pinosylvin or piceatannol). The last stage of the resveratrol biosynthesis takes place with the involvement of stilbene synthase or resveratrol synthase (STS). The family Pinaceae is characterized by the presence of the derivatives of pinosylvin (genus Pinus) and piceatannol (genus Picea), the biosynthetic pathways of which are scarcely examined. Previously, in different species of the genus Picea, only two stilbene synthase genes were described. On the basis of RNA isolated from the needles of spruce Picea jezoensis, the full-length cDNAs of the four stilbene synthase genes, PjSTS1a, PjSTS1b, PjSTS2, and PjSTS3, were obtained. Then, using the clone frequency analysis and real-time PCR, expression of the PjSTS1a, PjSTS1b, PjSTS2, and PjSTS3 genes was examined in the needles of P. jezoensis accessions of different age and sampled in different seasons (spring, summer, autumn, winter). Among the analyzed transcripts, the PjSTS1a and PjSTS1b genes were the most frequent, indicating their higher level of expression compared to other STS genes. The highest level of PjSTS1a and PjSTS1b expression was observed in autumn, while the level of PjSTS2 and PjSTS3 expression was the highest in spring and winter. Moreover, the highest PjSTS expression was detected in the young tissues of P. jezoensis in autumn, which may indicate a higher level of stilbene biosynthesis in these tissues.

Changes in Plant Metabolism and Accumulation of Fungal Metabolites in Response to Esca Proper and Apoplexy Expression in the Whole Grapevine.

Trunk diseases have become among the most important grapevine diseases worldwide. They are caused by fungal pathogens that attack the permanent woody structure of the vines and cause various symptoms in woody and annual organs. This study examined modifications of plant responses in green stem, cordon, and trunk of grapevines expressing Esca proper (E) or apoplexy (A) event, which are the most frequent grapevine trunk disease symptoms observed in Europe. Transcript expression of a set of plant defense- and stress-related genes was monitored by quantitative reverse-transcription polymerase chain reaction while plant phytoalexins and fungal metabolites were quantified by high-performance liquid chromatography-mass spectrometry in order to characterize the interaction between the grapevine and trunk disease agents. Expression of genes encoding enzymes of the phenylpropanoid pathway and trans-resveratrol content were altered in the three organs of diseased plants, especially in the young tissues of A plants. Pathogenesis-related proteins and the antioxidant system were severely modulated in A plants, which indicates a drastic stress effect. In the meantime, fungal polyketides 6-MSA, (R)-mellein, and (3R,4R)-4-hydroxymellein, were accumulated in A plants, which suggests their potential effect on plant metabolism during the appearance of foliar symptoms.

An approach on phytoalexins: function, characterization and biosynthesis in plants of the family Poaceae

ABSTRACT: Phytoalexins are compounds that have been studied a few years ago, which present mainly antimicrobial activity. The plants of the family Poaceae are the most geographically widespread and stand out for their economic importance, once they are cereals used as staple food. This family stands out for having a variety of phytoalexins, which can be synthesized via the shikimic acid (the phenylpropanoids), or mevalonic acid, being considered terpenoid phytoalexins. The characterization of these compounds with antimicrobial activity is carried out using chromatographic techniques, and the high-performance liquid chromatography (HPLC) coupled with mass spectrometry are the most efficient methods in this process. This research aimed to present an approach of the function, characterization and biosynthesis of phytoalexins in plants of the family Poaceae.

Overexpression of Soybean Isoflavone Reductase (GmIFR) Enhances Resistance to Phytophthora sojae in Soybean.

Isoflavone reductase (IFR) is an enzyme involved in the biosynthetic pathway of isoflavonoid phytoalexin in plants. IFRs are unique to the plant kingdom and are considered to have crucial roles in plant response to various biotic and abiotic environmental stresses. Here, we report the characterization of a novel member of the soybean isoflavone reductase gene family GmIFR. Overexpression of GmIFR transgenic soybean exhibited enhanced resistance to Phytophthora sojae. Following stress treatments, GmIFR was significantly induced by P. sojae, ethephon (ET), abscisic acid (placeCityABA), salicylic acid (SA). It is located in the cytoplasm when transiently expressed in soybean protoplasts. The daidzein levels reduced greatly for the seeds of transgenic plants, while the relative content of glyceollins in transgenic plants was significantly higher than that of non-transgenic plants. Furthermore, we found that the relative expression levels of reactive oxygen species (ROS) of transgenic soybean plants were significantly lower than those of non-transgenic plants after incubation with P. sojae, suggesting an important role of GmIFR might function as an antioxidant to reduce ROS in soybean. The enzyme activity assay suggested that GmIFR has isoflavone reductase activity.

The quorum-sensing inhibiting effects of stilbenoids and their potential structure-activity relationship.

Stilbenoids, known an important phytoalexins in plants, were renowned for their beneficial effects on cardiovascular, neurological and hepatic systems. In the present study, quorum sensing inhibition activity of ten stilbenoids were tested using Chromobacterium violaceum CV026 as the bio-indicator strain and the structure-activity relationship was also investigated. Among them, resveratrol (1), piceatannol (2) and oxyresveratrol (3) showed potential anti-QS activities. At the sub-MIC concentrations, 1-3 demonstrated a statistically significant reduction of violacein in C. violaceum CV026 in a concentration dependent manner. Furthermore, the effects of 1-3 on QS regulated virulence factors in Pseudomonas aeruginosa PAO1 were also evaluated. Our results showed that the stilbenoids 1-3 can markedly decreased the production of pyocyanin and swarming motility of P. aeruginosa PAO1. Further transcriptome analyses showed that 1-3 suppressed the expression of QS-induced genes: lasR, lasI, rhlR and rhlI.

Relevant Enzymes, Genes and Regulation Mechanisms in Biosynthesis Pathway of Stilbenes

Stilbenes are natural phenolic compounds which function as antimicrobial phytoalexins in plants and affect human health as cardioprotective, antibaceteria, antioxidative and antineoplastic agents. In this review, the progresses of study on relevant enzymes, genes, and regulation mechanism in biosynthesis pathway of stilbenes are described. Here we introduce a holistic and systematic method of researching relevant enzymes, genes and other regulatory factors in biosynthesis pathway of stilbenes—Systems biology. The application of knowledge of relative enzymes, genes and regulation mechanisms in stilbenes biosynthesis in metabolic engineering which is used as a tool of improving the disease resistance of plants and health caring quality of crops is also discussed.

Relevant Enzymes,Genes and Regulation Mechanisms in Biosynthesis Pathway of Stilbenes

Stilbenes are natural phenolic compounds which function as antimicrobial phytoalexins in plants and affect human health as cardioprotective, antibaceteria, antioxidative and antineoplastic agents . In this review, the progresses of study on relevant enzymes, genes and regulation mechanism in biosynthesis pathway of stilbenes are described. Here we introduce a holistic and systematic method of researching relevant enzymes, genes and other regulatory factors in biosynthesis pathway of stilbenes - Systems biology. The application of knowledge of relative enzymes, genes and regulation mechanisms in stilbenes biosynthesis in metabolic engineering which is used as a tool of improving the disease resistance of plants and health caring quality of crops is also discussed.