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Salicylic acid (SA) is an important phytohormone, well‐known for its regulatory role in shaping plant immune responses. In recent years, significant progress has been made in unravelling the molecular mechanisms underlying SA biosynthesis, perception, and downstream signalling cascades. Through the concerted efforts employing genetic, biochemical, and omics approaches, our understanding of SA‐mediated defence responses has undergone remarkable expansion. In general, following SA biosynthesis through Avr effectors of the pathogens, newly synthesized SA undergoes various biochemical changes to achieve its active/inactive forms (e.g. methyl salicylate). The activated SA subsequently triggers signalling pathways associated with the perception of pathogen‐derived signals, expression of defence genes, and induction of systemic acquired resistance (SAR) to tailor the intricate regulatory networks that coordinate plant immune responses. Nonetheless, the mechanistic understanding of SA‐mediated plant immune regulation is currently limited because of its crosstalk with other signalling networks, which makes understanding this hormone signalling more challenging. This comprehensive review aims to provide an integrated overview of SA‐mediated plant immunity, deriving current knowledge from diverse research outcomes. Through the integration of case studies, experimental evidence, and emerging trends, this review offers insights into the regulatory mechanisms governing SA‐mediated immunity and signalling. Additionally, this review discusses the potential applications of SA‐mediated defence strategies in crop improvement, disease management, and sustainable agricultural practices. [ABSTRACT FROM AUTHOR]

Plants constantly perceive and process environmental signals and balance between the energetic demands of growth and defense. Growth arrest upon pathogen attack was previously suggested to result from a redirection of the plants' metabolic resources towards the activation of plant defense. The energy sensor Target of Rapamycin (TOR) kinase is a conserved master coordinator of growth and development in all eukaryotes. Although TOR is positioned at the interface between development and defense, little is known about the mechanisms by which TOR may potentially regulate the relationship between these two modalities. The plant hormones cytokinin (CK) and gibberellin (GA) execute various aspects of plant development and defense. The ratio between CK and GA was reported to determine the outcome of developmental programmes. Here, investigating the interplay between TOR‐mediated development and TOR‐mediated defense in tomato, we found that TOR silencing resulted in rescue of several different aberrant developmental phenotypes, demonstrating that TOR is required for the execution of developmental cues. In parallel, TOR inhibition enhanced immunity in genotypes with a low CK/GA ratio but not in genotypes with a high CK/GA ratio. TOR‐inhibition mediated disease resistance was found to depend on developmental status, and was abolished in strongly morphogenetic leaves, while being strongest in mature, differentiated leaves. CK repressed TOR activity, suggesting that CK‐mediated immunity may rely on TOR downregulation. At the same time, TOR activity was promoted by GA, and TOR silencing reduced GA sensitivity, indicating that GA signalling requires normal TOR activity. Our results demonstrate that TOR likely acts in concert with CK and GA signalling, executing signalling cues in both defense and development. Thus, differential regulation of TOR or TOR‐mediated processes could regulate the required outcome of development‐defense prioritisation. Summary Statement: Target of Rapamycin (TOR) is positioned at the interface between development and defense, but little is known about the mechanisms by which TOR may regulate shifts between them. Here, we demonstrate that TOR likely acts in concert with cytokinin and gibberellin to execute signalling cues in both defense and development. [ABSTRACT FROM AUTHOR]

SUMMARY: Bacterial fruit blotch, caused by Acidovorax citrulli, is a serious disease of melon and watermelon. The strains of the pathogen belong to two major genetic groups: group I strains are strongly associated with melon, while group II strains are more aggressive on watermelon. A. citrulli secretes many protein effectors to the host cell via the type III secretion system. Here we characterized AopW1, an effector that shares similarity to the actin cytoskeleton‐disrupting effector HopW1 of Pseudomonas syringae and with effectors from other plant‐pathogenic bacterial species. AopW1 has a highly variable region (HVR) within amino acid positions 147 to 192, showing 14 amino acid differences between group I and II variants. We show that group I AopW1 is more toxic to yeast and Nicotiana benthamiana cells than group II AopW1, having stronger actin filament disruption activity, and increased ability to induce cell death and reduce callose deposition. We further demonstrated the importance of some amino acid positions within the HVR for AopW1 cytotoxicity. Cellular analyses revealed that AopW1 also localizes to the endoplasmic reticulum, chloroplasts, and plant endosomes. We also show that overexpression of the endosome‐associated protein EHD1 attenuates AopW1‐induced cell death and increases defense responses. Finally, we show that sequence variation in AopW1 plays a significant role in the adaptation of group I and II strains to their preferred hosts, melon and watermelon, respectively. This study provides new insights into the HopW1 family of bacterial effectors and provides first evidence on the involvement of EHD1 in response to biotic stress. [ABSTRACT FROM AUTHOR]

All organisms need to sense and process information about the availability of nutrients, energy status, and environmental cues to determine the best time for growth and development. The conserved target of rapamycin (TOR) protein kinase has a central role in sensing and perceiving nutritional information. TOR connects environmental information about nutrient availability to developmental and metabolic processes to maintain cellular homeostasis. Under favourable energy conditions, TOR is activated and promotes anabolic processes such as cell division, while suppressing catabolic processes. Conversely, when nutrients are limited or environmental stresses are present, TOR is inactivated, and catabolic processes are promoted. Given the central role of TOR in regulating metabolism, several previous works have examined whether TOR is wired to plant defence. To date, the mechanisms by which TOR influences plant defence are not entirely clear. Here, we addressed this question by testing the effect of inhibiting TOR on immunity and pathogen resistance in tomato. Examining which hormonal defence pathways are influenced by TOR, we show that tomato immune responses and disease resistance to several pathogens increase on TOR inhibition, and that TOR inhibition‐mediated resistance probably requires a functional salicylic acid, but not jasmonic acid, pathway. Our results support the notion that TOR is a master regulator of the development–defence switch in plants. [ABSTRACT FROM AUTHOR]

Plants employ systemic‐induced resistance as part of their defence arsenal against pathogens. In recent years, the application of mild heating has been found to induce resistance against several pathogens. In the present study, we investigated the effect of root zone warming (RZW) in promoting tomato's resistance against the necrotrophic fungus Botrytis cinerea (Bc), the hemibiotrophic bacterium Xanthomonas campestris pv. vesicatoria (Xcv) and the biotrophic fungus Oidium neolycopersici (On). We demonstrate that RZW enhances tomato's resistance to Bc, On and Xcv through a process that is dependent on salicylic acid and ethylene. RZW induced tomato immunity, resulting in increased defence gene expression, reactive oxygen species (ROS) and ethylene output when plants were challenged, even in the absence of pathogens. Overall, the results provide novel insights into the underlying mechanisms of warming‐induced immune responses against phytopathogens with different lifestyles in tomato. Plants are often exposed to several stresses simultaneously, particularly in agricultural settings; here, we investigate the relationships between heat and pathogen stresses. We demonstrate that root zone warming induces systemic immunity and promotes resistance to several tomato pathogens, through a process that is dependent on salicylic acid and ethylene. [ABSTRACT FROM AUTHOR]

Phytohormones are involved in the regulation of plant responses to biotic stress. How a limited number of hormones differentially regulate defence responses and influence the outcome of plant–biotic interactions is not fully understood. In recent years, cytokinin (CK) was shown to induce plant resistance against several pathogens. In the present study, we investigated the effect of CK in inducing tomato resistance against the hemibiotrophic pathogenic bacteria Xanthomonas campestris pv. vesicatoria (Xcv) and Pseudomonas syringae pv. tomato (Pst). We demonstrate that CK enhances tomato resistance to Xcv and Pst through a process that relies on salicylic acid and ethylene signalling. CK did not directly affect the growth or biofilm formation ability of these pathogens in vitro. Overall, our work provides insight into the underlying mechanisms of CK‐induced immune responses against bacterial pathogens in tomato. [ABSTRACT FROM AUTHOR]

Plant immunity is often defined by the immunity hormones: salicylic acid (SA), jasmonic acid (JA), and ethylene (ET). These hormones are well known for differentially regulating defence responses against pathogens. In recent years, the involvement of other plant growth hormones such as auxin, gibberellic acid, abscisic acid, and cytokinins (CKs) in biotic stresses has been recognized. Previous reports have indicated that endogenous and exogenous CK treatment can result in pathogen resistance. We show here that CK induces systemic immunity in tomato (Solanum lycopersicum), modulating cellular trafficking of the pattern recognition receptor (PRR) LeEIX2, which mediates immune responses to Xyn11 family xylanases, and promoting resistance to Botrytis cinerea and Oidium neolycopersici in an SA‐ and ET‐dependent mechanism. CK perception within the host underlies its protective effect. Our results support the notion that CK promotes pathogen resistance by inducing immunity in the host. [ABSTRACT FROM AUTHOR]

A composite film of nickel hexacyanoferrate (NiHCF) and bentonite (Bt) clay (abbreviated as NiHCF−Bt) is synthesized by an in situ electrochemical method. For this synthesis, nickel ions are immobilized on Bt clay by an ion‐exchange process, equilibrating Bt clay with nickel nitrate. On a glassy carbon electrode (GCE), the nickel ion‐exchanged Bt clay (Ni2+−Bt) is coated to get the modified electrode which is represented as GCE/Ni2+−Bt. The NiHCF−Bt composite film is prepared on the GCE surface using the GCE/Ni2+−Bt and scanning the electrode potentials between −0.10 to 1.00 V continuously in an aqueous solution containing potassium hexacyanoferrate and potassium chloride. This NiHCF−Bt modified GCE (GCE/NiHCF−Bt) exhibits redox peaks due to the oxidation and reduction of the central metal ion, Fe2+. The electro‐generated Fe3+ present in the GCE/NiHCF−Bt, electrocatalytically oxidizes a range of drugs like acetaminophen (AC), dopamine (DA), and tyrosine (TY) at decreased overpotentials with high current. This property is advantageously used for the precise quantification of AC, DA, and TY. Sensitivity, limit of detection, and linear calibration range for the determination of AC are found to be 0.20 μA μM−1 cm−2, 1.5 μM, and 25.0–1000.0 μM, respectively. Further, the amount of AC present in pharmaceutical products is satisfactorily quantified which demonstrated the use of the NiHCF−Bt composite film in electroanalysis. [ABSTRACT FROM AUTHOR]

Single‐walled carbon nanotubes (SWCNTs) were immobilized on glassy carbon (GC) electrode by drop casting The resulting modified electrode (represented as GC/SWCNTs) efficiently oxidizes acetaminophen (AC), dopamine (DA) and pyridoxine (PY) by decreasing the respective oxidation potentials and increasing peak currents in comparison to bare GC electrode. The extent of lowering of overpotentials is in the order of AC>PY>DA, in agreement with the order of decrease in the HOMO‐LUMO energy gap (ΔE) of these analytes, as determined from Density Functional Theory (DFT) calculations. DFT calculations further reveal that due to the interaction of the analytes on the SWCNT(10,10) there is a negative charge density transfer (higher probability of electron transfer, lower ΔE value) to the frontier molecular orbitals of the analytes, which eases their oxidation. Since AC, DA and PY oxidize distinctly at distinct potential values, the present SWCNTs modified electrodes could be used to simultaneously determine them. Cyclic voltammetry, differential pulse voltammetry and amperometry techniques are utilized to understand the electrochemical characteristics of the analytes (AC, DA and PY) and subsequent sensing of them at the GC/SWCNTs electrode. The electrode is then applied to the determination of AC as a case study. Sensitivity, detection limit and linear calibration range for the AC are found to be 7.9 μA μM−1 cm−2, 1.1 μM and 2.0–100.0 μM, respectively. The increased electroactive surface area of the GC/SWCNTs increases the oxidation peak currents and hence increases the sensitivity of the determination. [ABSTRACT FROM AUTHOR]

MnO2 nanorods incorporated MCM‐41 nanocomposite (MnO2@MCM‐41) is synthesized and employed as an electrode modifier for individual as well as simultaneous detection of purine bases, guanine (GU) and adenine (AD). For this purpose MnO2 nanorods are encapsulated within MCM‐41 by simple one pot synthetic approach. FT‐IR, UV‐vis absorption spectroscopy, scanning electron microscopy, energy dispersive X‐ray spectroscopy, X‐ray diffraction, X‐ray photoelectron spectroscopy and electrochemical methods are employed to characterize the nanocomposite and other materials. The electrochemical attributes of glassy carbon electrode (GCE) modified with the MnO2@MCM‐41 (represented as GCE/MnO2@MCM‐41) towards the determination of GU and AD is studied in detail. Upon incorporation of MnO2 nanorods on MCM‐41, noticeable upsurge in anodic peak current with a decline in peak potential is observed for both GU and AD oxidations in cyclic voltammetry studies. Individual as well as simultaneous determination of GU and AD are performed using differential pulse voltammetry (DPV) technique which offered a linear range of 100 nM to 100 μM for GU and AD with respective limit of detections, 44 and 66 nM. The practical applicability of the GCE/MnO2@MCM‐41 for real world samples analysis is satisfactorily demonstrated with certain DNA samples by DPV. [ABSTRACT FROM AUTHOR]

Abstract: Successful synthesis of gold nanoparticles incorporated in a zinc‐based metal‐organic framework (Au@Zn‐MOF) is reported in this paper. The synthesis of Au@Zn‐MOF is confirmed by UV‐Vis, FT‐IR and X‐ray photoelectron spectroscopy (XPS) studies. The Au@Zn‐MOF catalyst demonstrates electrocatalytic activity towards the oxygen reduction reaction (ORR) and the hydrogen evolution reaction (HER). The relative catalytic performance of Au@Zn‐MOF towards ORR and HER has been studied under acidic condition. ORR proceeds via a two electron and two proton mechanism with hydrogen peroxide as the end product, while HER follows the Volmer mechanism i. e., adsorption of H+ on the catalyst's active sites. Au@Zn‐MOF exhibits an ORR onset potential of 0.45 V (vs. RHE) with two different Tafel slopes, −93 and −103.6 mV in acidic solution. Further, an excellent catalytic activity is observed for HER with an onset potential of 0.02 V (vs. RHE) and a Tafel slope of 87 mV in N2 saturated 0.1 M HClO4 solution. However, in O2 saturated 0.1 M HClO4 solution, a HER onset potential of 0.04 V (vs. RHE) is observed with two different Tafel slopes, 610 and 220 mV. The value of Tafel slopes in the presence of O2 advocates the diminution of the ORR activity because of the HER. Thus, Tafel slope values of HER and ORR suggest that protons and O2 compete to reach the electrode surface for getting reduced. [ABSTRACT FROM AUTHOR]

Layered double hydroxides (LDHs) have recently attracted intense research attention because of their applications in the development of highly active and cost-effective electrocatalysts for the oxygen evolution reaction and in the fields of drug delivery, energy storage, for example. In this work, we report a cheap and simple route for the synthesis of nickel-iron LDH (Ni−Fe LDH) using an iron-based metal−organic framework, Fe-MIL-88 as a template. The prepared Ni−Fe LDH is characterized by scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy and X-ray diffraction techniques. Ni−Fe LDH is found to be highly active and stable for water oxidation in alkaline solution as compared to commercial Pt/C. The concept of using a metal−organic framework as a structure-directing agent to synthesize Ni−Fe LDH and the use of the material for the oxygen evolution reaction is explored for the first time. [ABSTRACT FROM AUTHOR]

BACKGROUND Despite the vast exploration of microbes for plant health, there is a lack of knowledge about the synergistic effects of specific microorganisms in sustainable agriculture, especially in medicinal plants such as Pelargonium graveolens L'Hér. The aim of this study was to evaluate how synergistic microbes Trichoderma harzianum ThU, Glomus intraradices and Bacillus subtilis CIM affected crop productivity, secondary metabolites and glandular trichome number in P. graveolens. RESULTS The results demonstrated a significant ( P < 0.05) increase in plant growth, secondary metabolites, total chlorophyll, carotenoids, carbohydrates, total phenolics, total flavonoids, free radical-scavenging activity and total antioxidant capacity of P. graveolens treated with synergistic bioinoculants as compared with the control. Most interestingly, an increase in essential oil by 32% in the treatment with all three microbes was observed. Furthermore, the principal aroma compounds citronellol and geraniol also increased in the same treatment. A positive and direct correlation was observed between essential oil content and number of glandular trichomes in all treatments. CONCLUSION The present study highlights an explicit amalgamation of prospective microbes showing potential for synergism that act as biostimulants in enhancing plant production and improving the antioxidant and aroma profile of P. graveolens. © 2016 Society of Chemical Industry [ABSTRACT FROM AUTHOR]