Physiological evaluation of drought stress tolerance and recovery in Verbascum sinuatum plants treated with methyl jasmonate,salicylic acid and titanium dioxide nanoparticles

Abstract

The genus Verbascum L. (Scrophulariaceae) includes medicinal plants, which have several bioactive compounds especially saponins. The possible recovery ability of Verbascum sinuatum from drought stress conditions was assessed by using salicylic acid (SA), methyl jasmonate (MJA) and titanium dioxide nanoparticles (TiO₂NPs) as plant growth regulators (PGRs) in liquid culture media. Thirty days-old plants were exposed to different concentrations of polyethylene glycol (PEG-6000) for creating artificial drought conditions (0, ?0.3, and ?0.6?MPa osmotic potential) and also treated with 200?µM methyl jasmonate (MJA), 100?µM salicylic acid (SA) and 20?ppm TiO₂ nanoparticles (TiO₂NPs). Results showed that the growth parameters and the content of photosynthetic pigments decreased at higher drought level (?0.6?MPa). However, SA and TiO₂NPs alleviated the adverse effects of drought stress by increasing water stress tolerance through promotion of enzymatic and nonenzymatic antioxidant defense systems. MJA negatively affected the growth parameters and increased the content of malondialdehyde (MDA), hydrogen peroxide (H₂O₂) and total saponin and also the activity of peroxidase (POD) and polyphenol oxidase (PPO). Based on the results obtained from this study, the recovery treatments mainly affected the defense-related metabolism in Verbasum sinuatum plants.     

Matched sizes of activating and inhibitory receptor/ligand pairs are required for optimal signal integration by human natural killer cells

It has been suggested that receptor-ligand complexes segregate or co-localise within immune synapses according to their size, and this is important for receptor signaling. Here, we set out to test the importance of receptor-ligand complex dimensions for immune surveillance of target cells by human Natural Killer (NK) cells. NK cell activation is regulated by integrating signals from activating receptors, such as NKG2D, and inhibitory receptors, such as KIR2DL1. Elongating the NKG2D ligand MICA reduced its ability to trigger NK cell activation. Conversely, elongation of KIR2DL1 ligand HLA-C reduced its ability to inhibit NK cells. Whereas normal-sized HLA-C was most effective at inhibiting activation by normal-length MICA, only elongated HLA-C could inhibit activation by elongated MICA. Moreover, HLA-C and MICA that were matched in size co-localised, whereas HLA-C and MICA that were different in size were segregated. These results demonstrate that receptor-ligand dimensions are important in NK cell recognition, and suggest that optimal integration of activating and inhibitory receptor signals requires the receptor-ligand complexes to have similar dimensions.     

A ditopic receptor for cation binding and facilitated transport through a supported liquid membrane

The binding properties of an artificial receptor towards a series of cations including Li⁺, Na⁺, K⁺, Mg²⁺, Ca²⁺, Ba²⁺, Fe²⁺ and Al³⁺ in acetonitrile are described. The receptor comprises a photo-responsive pyrene unit connected via a short spacer to a 2,2′:6′,2″-terpyridine metal ion binding site. Interaction of cations with the receptor was monitored by changes in absorption profile and the association constants calculated for 1:1 and 1:2 cation:ligand binding fall within the range log β = 3-12. The receptor is highly fluorescent and quenching of the emission is observed upon cation binding. The potassium picrate transport properties of the membrane-bound receptor are also described. This receptor when immobilised in a polymer support, which separates two aqueous solutions, has been shown to transport potassium ions in the dark with a flux rate of 1.5 × 10⁸ mol/s m². In contrast, when the membrane-bound receptor is selectively illuminated with light (λ > 400 nm), the flux increases to 2.0 × 10⁸ mol/s m². The transport efficiency depends on the nature of the trap used in the receiver phase.     

Toxic effects of pyriproxyfen,neemarin, acetamiprid and Ferula assafoetida essential oil on the common pistachio psylla,Agonoscena pistaciae

The common pistachio psylla, Agonoscena pistaciae, Burckhardt and Lauterer (Hemiptera: Psyllidae) is the key pest of pistachio orchards in Iran. Chemical control is the common method for the control of this pest. In this study, the effects of pyriproxyfen (an insect growth regulator), neemarin (a botanical insecticide), acetamiprid (a neonicotinoid) and Ferula assafoetida essential oil were investigated on the fifth instar nymphs of A. pistaciae. Probit analysis of concentration-mortality data was conducted to estimate the LC₅₀ values. The LC₅₀ values for neemarin, pyriproxyfen, acetamiprid and F. assafoetida essential oil were estimated to be 0.22, 0.52, 290 and 5.62 ppm, respectively. Our results showed that the fifth instar nymphs of A. pistaciae are very sensitive to neemarin and pyriproxyfen.     

Increased Expression and Activation of Absent in Melanoma 2 Inflammasome Components in Lymphocytic Infiltrates of Abdominal Aortic Aneurysms

Chronic vascular inflammation is a key hallmark in the pathogenesis of abdominal aortic aneurysm (AAA). Recent investigations have suggested that the inflammasome, a cytosolic multiprotein complex that recognizes pathogen-associated molecular patterns, plays a role in atherosclerosis. However, its role in AAA inflammation has not yet been investigated. This pilot study analyzed inflammasome activation and its intramural localization in 24 biopsy samples from 11 patients with asymptomatic AAA versus 12 aortic samples from apparently healthy controls. Using a histological inflammation scale, we identified grade 2/3 inflammatory changes with lymphoid aggregates/tertiary lymphoid organs in 21 out of 24 AAA samples, whereas only 7 of the 12 control samples exhibited local grade 1 inflammatory changes. Strong expression levels of “apoptosis-associated speck-like protein with a caspase recruitment domain” (ASC), caspase-1, caspase-5 and “absent in melanoma 2” (AIM2) were detected by immunohistochemistry in both sporadic infiltrating lymphoid cells and lymphoid aggregates located in the outer media and adventitia of AAA samples. In contrast, inflammasome-positive cells were restricted to cholesterol plaque–associated areas and to single infiltrating cells in control aortas. Analysis of gene expression using real-time polymerase chain reaction (PCR) revealed significantly increased median mRNA levels of the inflammasome core components PYCARD (ASC), CASP1 (Caspase-1) and IL1B (IL-1β) in AAA tissue compared with normal aorta. Moreover, significantly increased median amounts of AIM2 protein and mature caspase-5 (p20) were found in samples associated with high rupture risk compared with paired low rupture risk samples of the same AAA patient. We conclude from our data that AAA-associated lymphoid cells are capable of inflammasome signaling, suggesting that inflammasome activation is involved in the chronic inflammatory process driving AAA progression.     

Role of hydrogen peroxide during the interaction between the hemibiotrophic fungal pathogen Septoria tritici and wheat

Hydrogen peroxide (H(2)O(2)) is reported to inhibit biotrophic but benefit necrotrophic pathogens. Infection by necrotrophs can result in a massive accumulation of H(2)O(2) in hosts. Little is known of how pathogens with both growth types are affected (hemibiotrophs). The hemibiotroph, Septoria tritici, infecting wheat (Triticum aestivum) is inhibited by H(2)O(2) during the biotrophic phase, but a large H(2)O(2) accumulation occurs in the host during reproduction. Here, we infiltrated catalase, H(2)O(2) or water into wheat during the biotrophic or the necrotrophic phase of S. tritici and studied the effect of infection on host physiology to get an understanding of the survival strategy of the pathogen. H(2)O(2) removal by catalase at both early and late stages made plants more susceptible, whereas H(2)O(2) made them more resistant. H(2)O(2) is harmful to S. tritici throughout its life cycle, but it can be tolerated. The late accumulation of H(2)O(2) is unlikely to result from down-regulation of photosynthesis, but probably originates from damage to the peroxisomes during the general tissue collapse, which is accompanied by release of soluble sugars in a susceptible cultivar.     

Effector discovery in the fungal wheat pathogen Zymoseptoria tritici

Fungal plant pathogens, such as Zymoseptoria tritici (formerly known as Mycosphaerella graminicola), secrete repertoires of effectors to facilitate infection or trigger host defence mechanisms. The discovery and functional characterization of effectors provides valuable knowledge that can contribute to the design of new and effective disease management strategies. Here, we combined bioinformatics approaches with expression profiling during pathogenesis to identify candidate effectors of Z. tritici. In addition, a genetic approach was conducted to map quantitative trait loci (QTLs) carrying putative effectors, enabling the validation of both complementary strategies for effector discovery. In planta expression profiling revealed that candidate effectors were up‐regulated in successive waves corresponding to consecutive stages of pathogenesis, contrary to candidates identified by QTL mapping that were, overall, expressed at low levels. Functional analyses of two top candidate effectors (SSP15 and SSP18) showed their dispensability for Z. tritici pathogenesis. These analyses reveal that generally adopted criteria, such as protein size, cysteine residues and expression during pathogenesis, may preclude an unbiased effector discovery. Indeed, genetic mapping of genomic regions involved in specificity render alternative effector candidates that do not match the aforementioned criteria, but should nevertheless be considered as promising new leads for effectors that are crucial for the Z. tritici–wheat pathosystem.     

Accumulation of Glucosylceramide in the Absence of the Beta-Glucosidase GBA2 Alters Cytoskeletal Dynamics

Glycosphingolipids are key elements of cellular membranes, thereby, controlling a variety of cellular functions. Accumulation of the simple glycosphingolipid glucosylceramide results in life-threatening lipid storage-diseases or in male infertility. How glucosylceramide regulates cellular processes is ill defined. Here, we reveal that glucosylceramide accumulation in GBA2 knockout-mice alters cytoskeletal dynamics due to a more ordered lipid organization in the plasma membrane. In dermal fibroblasts, accumulation of glucosylceramide augments actin polymerization and promotes microtubules persistence, resulting in a higher number of filopodia and lamellipodia and longer microtubules. Similar cytoskeletal defects were observed in male germ and Sertoli cells from GBA2 knockout-mice. In particular, the organization of F-actin structures in the ectoplasmic specialization and microtubules in the sperm manchette is affected. Thus, glucosylceramide regulates cytoskeletal dynamics, providing mechanistic insights into how glucosylceramide controls signaling pathways not only during sperm development, but also in other cell types.