Systemic Resistance Response Research Articles

The lipopeptide surfactin triggers induced systemic resistance and priming state responses in Arachis hypogaea L.

Bioactive metabolites produced by multiple strains of Bacillus spp. stimulate plant defense responses. Among these, the cyclic lipopeptide surfactin was identified as an Induced Systemic Resistance (ISR) elicitor in different plant species. However, the underlying mechanisms involved in the ISR elicitation and the priming state costs in peanut plants (Arachis hypogaea L.) remain unknown. In this work, we demonstrated the ability of surfactin from B. subtilis to induce systemic resistance against Sclerotium rolfsii in peanut plants, and showed that this response involves key characteristics of priming-mediated resistance defense. Application of surfactin significantly reduced S. rolfsii disease incidence and severity on peanut plants, and an increased shoot and root dry weight was observed in surfactin pre-treated and pathogen challenged plants compared to non-treated challenged plants. In addition, peroxidase activity and phenolic compounds deposition underneath the fungal infection zone were significantly higher in surfactin pre-treated and challenged plants than in non-surfactin treated challenged plants. Collectively, results from this work indicate that ISR activity elicited by surfactin involves a priming defense state with low fitness-related costs, providing an enhanced protection against S. rolfsii in peanut plants.

MYB72-dependent coumarin exudation shapes root microbiome assembly to promote plant health

Plant roots nurture a tremendous diversity of microbes via exudation of photosynthetically fixed carbon sources. In turn, probiotic members of the root microbiome promote plant growth and protect the host plant against pathogens and pests. In the Arabidopsis thaliana-Pseudomonas simiae WCS417 model system the root-specific transcription factor MYB72 and the MYB72-controlled β-glucosidase BGLU42 emerged as important regulators of beneficial rhizobacteria-induced systemic resistance (ISR) and iron-uptake responses. MYB72 regulates the biosynthesis of iron-mobilizing fluorescent phenolic compounds, after which BGLU42 activity is required for their excretion into the rhizosphere. Metabolite fingerprinting revealed the antimicrobial coumarin scopoletin as a dominant metabolite that is produced in the roots and excreted into the rhizosphere in a MYB72- and BGLU42-dependent manner. Shotgun-metagenome sequencing of root-associated microbiota of Col-0, myb72, and the scopoletin biosynthesis mutant f6'h1 showed that scopoletin selectively impacts the assembly of the microbial community in the rhizosphere. We show that scopoletin selectively inhibits the soil-borne fungal pathogens Fusarium oxysporum and Verticillium dahliae, while the growth-promoting and ISR-inducing rhizobacteria P. simiae WCS417 and Pseudomonas capeferrum WCS358 are highly tolerant of the antimicrobial effect of scopoletin. Collectively, our results demonstrate a role for coumarins in microbiome assembly and point to a scenario in which plants and probiotic rhizobacteria join forces to trigger MYB72/BGLU42-dependent scopolin production and scopoletin excretion, resulting in improved niche establishment for the microbial partner and growth and immunity benefits for the host plant.

Serratia proteamaculans mediated alteration of tomato defense system and growth parameters in response to early blight pathogen Alternaria solani infection

Early blight caused by Alternaria solani is a devastating tomato plant disease affecting one of the most economically important vegetable crops worldwide. The plant growth promoting rhizobacteria are known to suppress plant pathogens and induce systemic resistance response in infected plants. The objectives of this study were to evaluate the efficacy of Serratia proteamaculans to induce the defense machinery and enhance tomato seedlings growth. Primary in vitro examination revealed a constant suppression of fungal growth. Under greenhouse conditions, bacterial suspensions at rate 50 ml/plant (108 cfu/ml) were incorporated once into pots containing tomato seedlings challenged or not with fungal spores. Results showed that S. proteamaculans was able to alleviate disease symptoms; severity reached 48.75% compared to control. Furthermore, the strain enhanced significantly tomato growth and chlorophyll content. In addition, bacterial treatment enhanced activity of plant defense enzymes and pathogenesis related proteins including guaiacol peroxidase (GPX), superoxide dismutase (SOD), phenylalanine ammonia-lyase (PAL) and β-1,3 glucanase reached 2, 7, 3,2 folds at days 5, 7, 6, 5 respectively. The obtained results suggested that application of S. proteamaculans as soil drench efficiently controlled tomato early blight disease and enhanced plant growth.

Transcript Profiling and Gene Identification Involved in the Ethylene Signal Transduction Pathways of Creeping Bentgrass (Agrostis stolonifera) during ISR Response Induced by Butanediol.

Creeping bentgrass (Agrostis stolonifera) is the preferred green lawn grass, with excellent turf characteristics but poor disease resistance. At present, the mechanisms of disease resistance in creeping bentgrass are poorly understood, especially the ethylene signal transduction pathway under the induced systemic resistance (ISR) response. In this study, butanediol (BDO), as a new type of disease-resistance compound, was applied to creeping bentgrass seedlings to induce the ISR response. Then, we measured ethylene production and related enzyme activities. Additionally, transcript profiling and gene identification were performed in association to ethylene signal transduction pathways. The changes of ethylene production and related enzyme 1-aminocyclopropane-1-carboxylic acid oxidase (ACO) and 1-aminocyclopropane-1-carboxylic acid synthases (ACS) activities showed significant difference at 24 h after Rhizoctonia solani inoculation among five treatments of various BDO concentrations. After 100 µmol L−1 BDO treatment, ethylene production and related enzyme activities reached their peak levels. Additionally, 208,672 unigenes of creeping bentgrass were obtained by de novo assembly. In total, 15,903 annotated unigenes were grouped into 33 canonical pathways in the KEGG (Kyoto Encyclopedia of Genes and Genomes) analysis. Among those, 1803 unigenes were classified as ‘signal transduction’. There were 6766 differentially expressed genes (DEGs) among B24 (inoculated-rhizobacteria in MS medium with 100 µmol L−1 BDO for 24 h), NB24, B72 and NB24 (no rhizobacteria in MS medium with 100 µmol L−1 BDO for 24 h) libraries, and 4,639 DEGs between B24 and B72 (inoculated-rhizobacteria in MS medium with 100 µmol L−1 BDO for 72 h) libraries, with 4489 DEGs in all three libraries. As suggested by the RT-PCR assay, the expression levels of ethylene-responsive and defense-related genes were variable among treated samples during the BDO-induced ISR responses. The expression levels of EIN, ERF, NPR1, PR3 and PR4 genes increased and reached their peaks in the first 24 h after R. solani infection in the BDO-induced ISR reaction compared with NB24 treatments. This results is consistent with the changes of important ethylene biosynthetic enzymes and ethylene concentrations during the BDO-induced ISR responses. We further found the intermediate substances for the signaling pathway, and the relationships between the expression levels of BDO-induced ISR disease-resistance genes and those of the response genes for ethylene signal pathway. Our findings present a genetic basis for systemic resistance of creeping bentgrass through transcriptomic analysis and our study provides a theoretical and practical basis for the improvement of turfgrass disease resistance and quality.

Salicylic Acid Regulates Systemic Defense Signaling in Chickpea During Fusarium oxysporum f. sp. ciceri Race 1 Infection

Annual loss of productivity of the important crop legume chickpea has received prime scientific concern at recent times. Vascular wilt caused by fungal pathogen Fusarium oxysporum f. sp. ciceris race 1 (Foc1) accounts for major share of yield loss of chickpea. Control of this disease remains a challenge due to the lack of appropriate breeding programs to manage fast pathogen mutability. Previous studies with this pathogen have highlighted the role of reactive oxygen species (ROS) as chemical signal in enkindling downstream systemic resistance response instead of activating site specific defense. But the role of salicylic acid in modulating resistance is still unexplored. Present study explains the probable function of salicylic acid (SA) in coordination with ROS. The external SA application reveals the restoration of relative water content of infected susceptible chickpea plants. The qRT-PCR based expression study of key SA biosynthetic genes indicate that the SA biogenesis takes place by the activity of phenylalanine ammonia lyase (PAL) that activates other SA responsive genes and TGA transcription factors to induce an active defense against Foc1. Finally, detection of SA by LC MS/MS along with the accumulation of transcripts of SA marker genes, PR1 and PR5, strengthens the involvement of SA in translocation of distant systemic signals in chickpea-Foc1 interaction.

OP.7B.01] MASKED HYPERTENSIVES EXHIBIT AN EXAGGERATED BLOOD PRESSURE RESPONSE DURING HANDGRIP EXERCISE SIMILAR TO THAT IN HYPERTENSIVE INDIVIDUALS

Objective: Masked hypertension has been associated with increased risk for target organ damage and cardiovascular disease. Recent evidence indicate that hypertensive individuals exhibit exaggerated blood pressure (BP) response during exercise and delayed recovery, linked to excessive sympathetic stimulation and an overactive exercise pressor reflex. Whether individuals with masked hypertension (masked-HYP) also exhibit exaggerated BP and systemic vascular resistance (SVR) responses as true hypertensives (true-HYP) during exercise has not been investigated. Therefore, the aim of this study was to evaluate the cardiovascular responses during handgrip exercise and recovery in masked-HYP, true-HYP, and normotensive (NORMO) individuals. Design and method: Eighty six individuals participated in the present study: healthy-NORMO (n = 28), masked-HYP (n = 27), and true-HYP (n = 31). All hypertensive participants were newly diagnosed, untreated, with no other known cardiovascular disease. Following a complete history, physical examination, and blood testing, office and ambulatory BP were measured in order to determine their hypertensive status. All participants underwent an exercise protocol, consisting of a 3-min rest (baseline), a 3-min handgrip exercise at 30% maximal voluntary contraction (MVC), and a 3-min recovery. Beat-by-beat BP and heart rate (HR) were continuously assessed via photoplethysmography (Finapress) throughout the protocol and SVR was calculated. Results: There were no differences among the three groups in age, smoking status, body mass index, fasting blood glucose, lipid profile, and MVC. Masked-HYP exhibited similar baseline BP to NORMO, however, during HG-exercise, masked-HYP exhibited a markedly greater (p < 0.05) systolic/diastolic BP response compared with NORMO (174.8 ± 13.5/98.5 ± 7.0 vs. 159.2 ± 15.7/91.3 ± 9.2 mmHg, respectively) and similar BP responses to true-HYP (181.4 ± 14.5/101.8 ± 9.5 mmHg). In addition, during exercise, masked-HYP exhibited a significant increase in SVR (p < 0.05), similar to that observed in true-HYP, whereas no significant increase in SVR was observed in NORMO. During the 3-min post-exercise period, BP in masked-HYP declined and returned to values comparable to those in NORMO (p = 0.32). Conclusions: This is the first study to show that during isometric exercise, masked-HYP exhibit exaggerated BP and SVR responses, suggesting an overactive exercise pressor reflex in masked hypertension. The cardiovascular responses during exercise in masked-HYP are similar to those in true-HYP.

The cyclic lipopeptide orfamide induces systemic resistance in rice to Cochliobolus miyabeanus but not to Magnaporthe oryzae.

The Pseudomonas- derived cyclic lipopeptide orfamide can induce resistance to Cochliobolus miyabeanus but not to Magnaporthe oryzae in rice. Abscisic acid signaling is involved in the induced systemic resistance response triggered by orfamide. Diverse natural products produced by beneficial Pseudomonas species have the potential to trigger induced systemic resistance (ISR) in plants, and thus may contribute to control of diseases in crops. Some beneficial Pseudomonas spp. can produce cyclic lipopeptides (CLPs), amphiphilic molecules composed of a fatty acid tail linked to an oligopeptide which is cyclized. CLPs can have versatile biological functions, but the capacity of Pseudomonas-derived CLPs in triggering ISR responses has barely been studied. Pseudomonas protegens and related species can produce orfamide-type CLPs. Here we show that in rice, orfamides can act as ISR elicitors against the necrotrophic fungus Cochliobolus miyabeanus, the causal agent of brown spot disease, but are not active against the blast fungus Magnaporthe oryzae. Orfamide A can trigger early defensive events and activate transcripts of defense-related genes in rice cell suspension cultures, but does not cause cell death. Further testing in rice cell suspension cultures and rice plants showed that abscisic acid signaling, the transcriptional activator OsWRKY4 and pathogenesis-related protein PR1b are triggered by orfamide A and may play a role in the ISR response against C. miyabeanus.

Effect of Artificial Light Conditions on Local and Systemic Resistance Response of Tobacco to TMV Infection

Systemic acquired resistance (SAR) is effectively inducible in greenhouse and certain artificial light sources cause non-optimal growth of tobacco plants. Therefore, the morphological characteristics, local and systemic resistance response of N. tabacum cv. ‘Xanthi’ nc plants (harbouring NN resistance genes) to tobacco mosaic virus (TMV) infection under three artificial light sources with different spectral distribution were compared with greenhouse conditions. Statistical analysis of data was carried out by R package (R Core Team, 2015). Generally, artificial light sources (especially fluorescent tube, and halogen lamp) decreased the local resistance response and caused substantial morphological and developmental differences as compared to greenhouse conditions when plants were kept during their entire life (lifelong experimental regime) under these conditions. On the contrary, no or much less differences were found when plants were transferred from greenhouse to artificial light sources only at six leaf stage (short experimental regime). While induction of systemic acquired resistance (SAR) frequently decreased TMV lesion size by about 50-60% under greenhouse conditions, two of the three artificial light sources, fluorescent tube and halogen lamp were substantially and significantly less effective under short experimental regime conditions (25-35%). A metal halide light source with similarity to sunshine’s spectral distribution, however, partially mimicked the effect of greenhouse conditions indicating the importance of light spectrum among other factors in SAR induction and prevention of distorted growth of plants. Consequently, the optimization of the effect of artificial light sources is an important factor in experimental design studying signal transduction and biochemistry of SAR.

A split-root system to assess biocontrol effectiveness and defense-related genetic responses in above-ground tissues during the tripartite interaction Verticillium dahliae-olive-Pseudomonas fluorescens PICF7 in roots

The olive root endophyte Pseudomonas fluorescens PICF7 is an effective biocontrol agent of Verticillium wilt of olive (VWO). Colonization of olive roots either by strain PICF7 or by Verticillium dahliae triggers differential systemic transcriptomic responses, many of them related with defense-related genes. The aims were to develop an olive split-root system for assessing VWO development and biocontrol effectiveness of strain PICF7 in plants with a divided root architecture, and for evaluating systemic defense responses during this tripartite interaction when strain PICF7 and V. dahliae are spatially separated. An olive split-root system was generated and disease development, biocontrol effectiveness and systemic genetic responses in these plants upon strain PICF7 and V. dahliae colonization were compared to those reported and observed in olive plants grown under standard conditions (single pots). Specific defense-related genes, previously identified during PICF7- and/or V. dahliae-olive root interactions were selected and their expression patterns assessed in above-ground tissues by real-time qPCR analyses. Symptoms of VWO developed similarly both in split-root and single-root plants. However, even though PICF7 triggered systemic defense responses in aerial tissues prior to the infection by V. dahliae, effective biocontrol was not observed under these experimental conditions. While most of studied genes showed similar expression patterns along time in both systems (i.e. split root and single pot), some of them (e.g. the caffeoyl-O-methyltransferase coding gene) varied depending on whether strain PICF7 and V. dahliae were spatially separated or shared the same compartment. A successful split-root system was generated to investigate genetic events taking place during the tripartite interaction olive-V. dahliae-P. fluorescens PICF7. VWO biocontrol by strain PICF7 must rely on mechanisms other than induction of systemic resistance responses. The expression pattern of specific defense-related olive genes depended on whether or not the biocontrol agent and the pathogen share the same root/soil region.

Enhancing the Defensive Mechanism of Lead Affected Barley (Hordeum vulgare L.) Genotypes by Exogenously Applied Salicylic Acid

Lead is a non-essential element reduced plant growth and development that may cause multifarious disturbance in physiological, biochemical and structural integrity of plants. SA is an efficient signal molecule induces systemic resistance responses that control local defense reactions in plants. To evaluate the effect of SA on photosynthetic activity of Pb affected plants therefore a pot experiment was conducted on barley genotype Juo- 93 and Juo- 87 in the Old Botanical Garden, University Of Agriculture, Faisalabad, Pakistan. Three treatment levels (0, 100 and 200 µM) of lead sulphate (PbSO4) were applied in thrice replication with or without SA (0.5 mM) along half strength of Hoagland’s solution till the termination of experiment. The experiment was arranged in a completely randomized design. During course of study growth and pigments modulations were recorded. The result indicated that growth parameters such as root and shoot length, leaf area, fresh weight of shoot and root, dry weight of shoot and root were reduced under lead toxicity. Pb stress damaged the photosynthetic pigments such as Chlorophyll a, chlorophyll b, total chlorophyll and carotenoids but chlorophyll a/b was increased under Pb stress whereas exogenous application of SA alleviated the negative effect of lead toxicity. Juo- 93 showed more tolerance to Pb toxicity as compared to Juo-87.

Effects of Six Months Training on Physical Capacity and Metaboreflex Activity in Patients with Multiple Sclerosis.

Patients with multiple sclerosis (MS) have an increased systemic vascular resistance (SVR) response during the metaboreflex. It has been hypothesized that this is the consequence of a sedentary lifestyle secondary to MS. The purpose of this study was to discover whether a 6-month training program could reverse this hemodynamic dysregulation. Patients were randomly assigned to one of the following two groups: the intervention group (MSIT, n = 11), who followed an adapted training program; and the control group (MSCTL, n = 10), who continued with their sedentary lifestyle. Cardiovascular response during the metaboreflex was evaluated using the post-exercise muscle ischemia (PEMI) method and during a control exercise recovery (CER) test. The difference in hemodynamic variables such as stroke volume (SV), cardiac output (CO), and SVR between the PEMI and the CER tests was calculated to assess the metaboreflex response. Moreover, physical capacity was measured during a cardiopulmonary test till exhaustion. All tests were repeated after 3 and 6 months (T3 and T6, respectively) from the beginning of the study. The main result was that the MSIT group substantially improved parameters related to physical capacity (+5.31 ± 5.12 ml·min−1/kg in maximal oxygen uptake at T6) in comparison with the MSCTL group (−0.97 ± 4.89 ml·min−1/kg at T6; group effect: p = 0.0004). However, none of the hemodynamic variables changed in response to the metaboreflex activation. It was concluded that a 6-month period of adapted physical training was unable to reverse the hemodynamic dys-regulation in response to metaboreflex activation in these patients.

Cardiac remodeling after reduction of high-flow arteriovenous fistulas in end-stage renal disease.

In patients with end-stage renal disease, excessive blood flow through an arteriovenous fistula (AVF) may lead to volume overload-induced cardiac remodeling and heart failure. It is unclear which patients with hyperfunctional AVF may benefit from AVF reduction or ligation. The indication for the procedure is often based on AVF flow. Because cardiac remodeling is driven by increased venous return, which is equivalent to cardiac output, we hypothesized that an elevated cardiac index (CI) might better identify subjects with reverse remodeling after AVF reduction. Thirty patients (age 52±12 years, 73% male) with AVF flow ⩾1.5 l min(-1) underwent comprehensive echocardiographic evaluations before and after AVF reduction. At baseline, 16 patients had a normal CI (2.5-3.8 l min(-1) m(-2)) and 14 had a high CI (4.0-6.0 l min(-1) m(-2)). A left ventricular end-diastolic diameter decrease after operation was predicted by elevated baseline CI (P<0.01), but not elevated AVF flow (P=0.07). There was a significant decrease in CI, left ventricular mass, left atrial and right ventricular diameter and pulmonary systolic pressure in the high CI group but not in the normal CI group. After AVF reduction, systemic vascular resistance decreased in the normal CI group, whereas it did not change in the high CI group. In conclusion, reduction of high-flow AVF leads to reverse cardiac remodeling but only in patients with elevated CI. The variability of the response of systemic vascular resistance to AVF flow may explain this observation. Increased CI but not increased AVF flow may better determine candidates for AVF reduction.

Pokeweed antiviral protein (PAP) increases plant systemic resistance to Tobacco mosaic virus infection in Nicotiana benthamiana

Pokeweed antiviral protein (PAP) isoforms are members of the type I ribosome inactivating proteins (RIPs) that are isolated from the extracts of pokeweed plant leaves (Phytolacca americana) and show many biological activities. However, the antiviral potential of the PAP in plants and its potential role in plant systemic resistance has been rarely reported. Therefore, in this report, we investigated the role of PAP in plant systemic resistance response against virus infection in Nicotiana benthamiana. N. benthamiana plants pre-treated with 0.1 mg/mL PAP three days before inoculation with green fluorescent protein (GFP)-tagged tobacco mosaic virus (TMV) showed less symptoms and less reactive oxygen species (ROS) accumulation compared to PBS-treated plants inoculated with TMV-GFP. Exogenous application of PAP yielded a significant reduction in GFP fluorescence in non-inoculated upper leaves. Furthermore, quantitative real-time PCR analysis revealed that the accumulation levels of TMV were significantly reduced in the systemic leaves of PAP-treated N. benthamiana plants compared with the levels observed in PBS-treated plants. In addition, some antioxidant enzymes including superoxide dismutase (SOD), catalase (CAT), peroxidase (POD) were activated after PAP treatment. Taken together, our results suggest that exogenous application of PAP enhances N. benthamiana systemic resistance to TMV infection by regulating ROS levels. Furthermore, we concluded that PAP might be acting as a strong antioxidant that does not allow the induction/accumulation of harmful ROS on virus infection.

The influences of nitric oxide, epinephrine, and dopamine on vascular tone: dose-response modeling and simulations.

Sodium Nitroprusside has successfully been an excellent choice when considering a decrease in systemic vascular resistance in the critical care setting. However, reflex tachycardia and ventilation-perfusion mismatch are possible side effects of this agent. To maintaining cardiac output, cerebral perfusion pressure, and concurrently drop SVR, low-dose epinephrine or dopamine are viable options. The aim of this paper is to conduct dose-response simulations to identify the equivalent dopamine, epinephrine, and nitroprusside infusion doses to decrease the systemic vascular resistance by 20% and by 40% from baseline resting values. Three studies were identified in the literature with reported epinephrine, dopamine, and sodium nitroprusside infusion doses with corresponding systemic vascular resistance responses. Infusion doses were normalized to mcg/kg/min and SVR values were normalized and scaled to the percent decrease (%SVR) in SVR from baseline resting values. The original published studies were mathematically modeled and the Hill equation parameters used for further dose-response simulations of a virtual population. One-hundred patients were simulated various doses resulting in corresponding %SVR responses for each of the three drugs. Equivalent infusion doses achieving in an approximate 20-25% decrease in SVR, from baseline, were identified for epinephrine, dopamine, and sodium nitroprusside. Moreover, equivalent infusion doses were identified for epinephrine and nitroprusside to decrease the SVR by 40% from baseline. Even though sodium nitroprusside is traditionally used in decreasing SVR, low doses of dopamine or epinephrine are viable alternatives to patients with contraindications to nitroprusside infusions or who will require prolonged infusions to avoid toxicity. The multiple comparisons procedure-modeling approach is an excellent methodology for dose-finding exercises and has enabled identification of equivalent pharmacodynamic responses for epinephrine, dopamine, and sodium nitroprusside through mathematic simulations.

The systemic vascular resistance response: a cardiovascular response modulating blood viscosity with implications for primary hypertension and certain anemias.

Without an active regulatory feedback loop, increased blood viscosity could lead to a vicious cycle of ischemia, increased erythropoiesis, further increases of blood viscosity, decreased tissue perfusion with worsened ischemia, further increases in red cell mass, etc. We suggest that an increase in blood viscosity is detected by mechanoreceptors in the left ventricle which upregulate expression of cardiac natriuretic peptides and soluble erythropoietin receptor. This response normalizes systemic vascular resistance and blood viscosity at the cost of producing 'anemia of chronic disease or inflammation' or 'hemolytic anemia' both of which are better described as states of compensated hyperviscosity. Besides its role in disease, this response is also active in the physiologic adaptation to chronic exercise. Malfunction of this response may cause primary hypertension.

Induced systemic resistance responses in perennial ryegrass against Magnaporthe oryzae elicited by semi-purified surfactin lipopeptides and live cells of Bacillus amyloliquefaciens.

The suppressive ability of several strains of cyclic lipopeptide-producing Bacillus rhizobacteria to grey leaf spot disease caused by Magnaporthe oryzae has been documented previously; however, the underlying mechanism(s) involved in the induced systemic resistance (ISR) activity in perennial ryegrass (Lolium perenne L.) remains unknown. Root-drench application of solid-phase extraction (SPE)-enriched surfactin and live cells of mutant Bacillus amyloliquefaciens strain FZB42-AK3 (produces surfactin, but not bacillomycin D and fengycin) significantly reduced disease incidence and severity on perennial ryegrass. The application of the treatments revealed a pronounced multilayered ISR defence response activation via timely and enhanced accumulation of hydrogen peroxide (H2O2), elevated cell wall/apoplastic peroxidase activity, and deposition of callose and phenolic/polyphenolic compounds underneath the fungal appressoria in naïve leaves, which was significantly more intense in treated plants than in mock-treated controls. Moreover, a hypersensitive response (HR)-type reaction and enhanced expression of LpPrx (Prx, peroxidase), LpOXO4 (OXO, oxalate oxidase), LpPAL (PAL, phenylalanine ammonia lyase), LpLOXa (LOX, lipoxygenase), LpTHb (putative defensin) and LpDEFa (DEFa, putative defensin) in perennial ryegrass were associated with SPE-enriched surfactin and live AK3 cell treatments, acting as a second layer of defence when pre-invasive defence responses failed. The results indicate that ISR activity following surfactin perception may sensitize H2O2 -mediated defence responses, thereby providing perennial ryegrass with enhanced protection against M. oryzae.

Long-Term Induction of Defense Gene Expression in Potato by Pseudomonas sp. LBUM223 and Streptomyces scabies

Streptomyces scabies is a causal agent of common scab of potato, which generates necrotic tuber lesions. We have previously demonstrated that inoculation of potato plants with phenazine-1-carboxylic acid (PCA)- producing Pseudomonas sp. LBUM223 could significantly reduce common scab symptoms. In the present study, we investigated whether LBUM223 or an isogenic phzC- mutant not producing PCA could elicit an induced systemic resistance response in potato. The expression of eight defense-related genes (salicylic acid [SA]-related ChtA, PR-1b, PR-2, and PR-5; and jasmonic acid and ethylene-related LOX, PIN2, PAL-2, and ERF3) was quantified using newly developed TaqMan reverse-transcription quantitative polymerase chain reaction assays in 5- and 10-week-old potted potato plants. Although only wild-type LBUM223 was capable of significantly reducing common scab symptoms, the presence of both LBUM223 and its PCA-deficient mutant were equally able to upregulate the expression of LOX and PR-5. The presence of S. scabies overexpressed all SA-related genes. This indicates that (i) upregulation of potato defense-related genes by LBUM223 is unlikely to contribute to common scab's control and (ii) LBUM223's capacity to produce PCA is not involved in this upregulation. These results suggest that a direct interaction occurring between S. scabies and PCA-producing LBUM223 is more likely involved in controlling common scab development.

Essential oil compositions of summer savory under foliar application of jasmonic acid and salicylic acid

Jasmonic acid (JA) and its volatile methyl ester (MJ) are regarded as endogenous regulators that play important roles in regulating stress responses, plant growth and development. Salicylic acid (SA) has been identified as an important signaling element involved in establishing the local and systemic disease resistance response of plants after pathogen attack. Growth, oil yield and chemical components of Satureja hortensis L. grown in greenhouse conditions were investigated. Experimental treatments, included (i) water foliar application, (ii) water + ethanol foliar application, (iii–v) 50, 100, and 200 μL JA and (vi–ix) 50, 100, and 200 M SA. The hydro-distilled oil yields of studied treatments ranged between 0.74 and 0.91 mL/100 g dry matter. The major components of the oil were carvacrol, γ-terpinene, (Z)-β-ocimene, α-pinene, and α-terpinene. The result indicated that different levels of JA and SA had significant impacts on chemical components of S. hortensis oils, whereas they had no significant effects on oil yield and dry herbage. Foliar application of 50 μL SA increased monoterpene hydrocarbons in S. hortensis oil, whereas oxygenated monoterpenes and sesquiterpenes decreased. Finally, some of secondary metabolites in S. hortensis could be partially changed by supplementation of different elicitors.

Salicylic Acid and Jasmonic Acid Are Essential for Systemic Resistance Against Tobacco mosaic virus in Nicotiana benthamiana

Systemic resistance is induced by pathogens and confers protection against a broad range of pathogens. Recent studies have indicated that salicylic acid (SA) derivative methyl salicylate (MeSA) serves as a long-distance phloem-mobile systemic resistance signal in tobacco, Arabidopsis, and potato. However, other experiments indicate that jasmonic acid (JA) is a critical mobile signal. Here, we present evidence suggesting both MeSA and methyl jasmonate (MeJA) are essential for systemic resistance against Tobacco mosaic virus (TMV), possibly acting as the initiating signals for systemic resistance. Foliar application of JA followed by SA triggered the strongest systemic resistance against TMV. Furthermore, we use a virus-induced gene-silencing-based genetics approach to investigate the function of JA and SA biosynthesis or signaling genes in systemic response against TMV infection. Silencing of SA or JA biosynthetic and signaling genes in Nicotiana benthamiana plants increased susceptibility to TMV. Genetic experiments also proved the irreplaceable roles of MeSA and MeJA in systemic resistance response. Systemic resistance was compromised when SA methyl transferase or JA carboxyl methyltransferase, which are required for MeSA and MeJA formation, respectively, were silenced. Moreover, high-performance liquid chromatography-mass spectrometry analysis indicated that JA and MeJA accumulated in phloem exudates of leaves at early stages and SA and MeSA accumulated at later stages, after TMV infection. Our data also indicated that JA and MeJA could regulate MeSA and SA production. Taken together, our results demonstrate that (Me)JA and (Me)SA are required for systemic resistance response against TMV.

Ocular Inflammation and Endoplasmic Reticulum Stress Are Attenuated by Supplementation with Grape Polyphenols in Human Retinal Pigmented Epithelium Cells and in C57BL/6 Mice

Inflammation and endoplasmic reticulum (ER) stress are common denominators for vision-threatening diseases such as diabetic retinopathy and age-related macular degeneration. Based on our previous study, supplementation with muscadine grape polyphenols (MGPs) alleviated systemic insulin resistance and proinflammatory responses. In this study, we hypothesized that MGPs would also be effective in attenuating ocular inflammation and ER stress. We tested this hypothesis using the human retinal pigmented epithelium (ARPE-19) cells and C57BL/6 mice. In ARPE-19 cells, tumor necrosis factor-α–induced proinflammatory gene expression of interleukin (IL)-1β, IL-6, and monocyte chemotactic protein-1 was decreased by 35.0%, 68.8%, and 62.5%, respectively, with MGP pretreatment, which was primarily due to the diminished mitogen-activated protein kinase activation and subsequent reduction of nuclear factor κ-B activation. Consistently, acute ocular inflammation and leukocyte infiltration were almost completely dampened (>95%) by MGP supplementation (100–200 mg/kg body weight) in C57BL/6 mice. Moreover, MGPs reduced inflammation-mediated loss of tight junctions and retinal permeability. To further investigate the protective roles of MGPs against ER stress, ARPE-19 cells were stimulated with thapsigargin. Pretreatment with MGPs significantly decreased the following: 1) ER stress-mediated vascular endothelial growth factor secretion (3.47 ± 0.06 vs. 1.58 ± 0.02 μ g/L, P < 0.0001), 2) unfolded protein response, and 3) early apoptotic cell death (64.4 ± 6.85 vs. 33.7 ± 4.32%, P = 0.0003). Collectively, we have demonstrated that MGP is effective in attenuating ocular inflammation and ER stress. Our work also suggests that MGP may provide a novel dietary strategy to prevent vision-threatening retinal diseases.