Co-evolutionary interactions between host resistance and pathogen effector genes in flax rust disease

Plant-pathogen co-evolutionary selection processes are continuous, complex and occur across many spatial and temporal scales. Comprehensive studies of the flax-flax rust pathosystem have led to the postulation of the gene-for-gene model, a genetic paradigm describing recognition events between host disease resistance proteins and pathogen effector proteins. The identification of directly interacting fungal effector proteins and plant disease resistance proteins in this pathosystem has facilitated the study of both the physical nature of these interactions and the evolutionary forces that have resulted in a molecular arms race between these organisms. The flax-flax rust pathosystem has also been detailed on the scale of interacting populations, and the integration of molecular- and population-scale datasets represents a unique opportunity to further our understanding of many poorly understood facets of host-pathogen dynamics. In this article, we discuss recent developments and insights in the flax-flax rust pathosystem and their implications for both long-term co-evolutionary dynamics in natural settings, as well as short-term co-evolutionary dynamics in agro-ecosystems.     

Population Processes at Multiple Spatial Scales Maintain Diversity and Adaptation in the Linum marginale - Melampsora lini Association

Host-pathogen coevolution is a major driver of species diversity, with an essential role in the generation and maintenance of genetic variation in host resistance and pathogen infectivity. Little is known about how resistance and infectivity are structured across multiple geographic scales and what eco-evolutionary processes drive these patterns. Across southern Australia, the wild flax Linum marginale is frequently attacked by its rust fungus Melampsora lini. Here, we compare the genetic and phenotypic structure of resistance and infectivity among population pairs from two regions where environmental differences associate with specific life histories and mating systems. We find that both host and pathogen populations are genetically distinct between these regions. The region with outcrossing hosts and pathogens that go through asexual cycles followed by sexual reproduction showed greater diversity of resistance and infectivity phenotypes, higher levels of resistance and less clumped within-population spatial distribution of resistance. However, in the region where asexual pathogens infect selfing hosts, pathogens were more infective and better adapted to sympatric hosts. Our findings largely agree with expectations based on the distinctly different host mating systems in the two regions, with a likely advantage for hosts undergoing recombination. For the pathogen in this system, sexual reproduction may primarily be a survival mechanism in the region where it is observed. While it appears to potentially have adverse effects on local adaptation in the short term, it may be necessary for longer-term coevolution with outcrossing hosts.     

Biosorption of mercury from aqueous solution by Ulva lactuca biomass

The mercury biosorption onto non-living protonated biomass of Ulva lactuca, as an alternative method for mercury removal from aqueous solutions, was investigated. Batch equilibrium tests showed that at pH 3.5, 5.5 and 7 the maxima of mercury uptake values, according to Langmuir adsorption isotherm, were 27.24, 84.74 and 149.25 mg/g, respectively. The ability of Ulva lactuca biomass to adsorb mercury in fixed-bed column, was investigated as well. The influence of column bed height, flow rate and effluent initial concentration of metal was studied. The adsorbed metal ions were easily desorbed from the algal biomass with 0.3 N H₂SO₄ solution. After acid desorption and regeneration with distilled water, the biomass could be reused for other biosorption assays with similar performances.     

Enhanced dendritic cell-driven proliferation and anti-HIV activity of CD8(+) T cells by a new phenothiazine derivative, aminoperazine

T cell anergy, apoptosis, and chronic activation of T lymphocytes are prevailing features of HIV infection. The inability to develop an efficient natural antiviral activity in infected patients might be the consequence of a failure of the Ag presentation by dendritic cells (DCs) in chronically activated lymphoid tissues. We have identified a new phenothiazine derivative aminoperazine (APR; 2-amino-10-[3'-(1-methyl-4-piperazinyl)propyl]phenothiazine, C(20)H(26)N(4)S; m.w. 354.51) able to increase (effective dose from 0.1 to 100 nM) the Ag-specific DC-driven proliferation and differentiation of in vitro HIV-infected and uninfected normal donor T cells and of T cells from HIV-1-infected patients. The immunomodulatory effect of APR-sensitized DCs were ascribed to soluble factors derived from DCs. APR was also capable of increasing HIV gag-p24-specific proliferation and anti-HIV cytotoxic activity of patients' CD8(+) T cells against autologous B-lymphoblastoid cell lines expressing a HIV gag gene, resulting in the suppression of both proviral DNA and supernatant viral RNA in the HIV-1-infected patients' T cell culture. This new phenothiazine derivative (APR) might be used for boosting the immune response of vaccinated individuals and for restoring the immunity of immunocompromised patients.     

Functional inhibition by cyclosporin A of the lymphocyte receptor for the AIDS virus (HIV)

The Human Immunodeficiency Virus (HIV) displays a selective tropism for cells expressing the CD4 molecule which, by itself, represents at least part of the specific receptor for this virus. However, modification of the activation state of each individual cell seems critical not only for virus replication but also for its binding and subsequent penetration into its target. We demonstrate here that Cyclosporin-A (CSA), a drug which inhibits IL-2 dependent T-lymphocyte proliferation and differentiation and which is known for its immunosuppressive activity, can prevent subsequent virus binding to cells otherwise susceptible to HIV. Normal T-lymphocytes were preincubated in vitro with CSA at concentrations that were in the same range than those reached in the serum of treated patients. This resulted in the complete disappearance of HIV receptors (HIV-R), as assessed by the direct measure of specific binding of fluoresceinated HIV (HIV-FITC), and in the subsequent inhibition of HIV replication in cultured cells. Moreover CSA pretreatment of IL-2 independent transformed cells derived from the CEM line, before their infection, strongly inhibited HIV adsorption as well as further virus replication. These results provide a new experimental basis for the potential application of CSA in the treatment of HIV-related diseases.     

A Comprehensive Characterisation of Rosemary tea Obtained from Rosmarinus officinalis L. Collected in a sub‐Humid Area of Tunisia

Introduction

Rosemary (Rosmarinus officinalis L.) is an aromatic plant common in Tunisia and it is widely consumed as a tea in traditional cuisine and in folk medicine to treat various illnesses. Currently, most research efforts have been focused on rosemary essential oil, alcoholic and aqueous extracts, however, little is reported on rosemary infusion composition.

Objective

To investigate compounds present in rosemary tea obtained from Rosmarinus officinalis L. collected in a sub‐humid area of Tunisia in order to assess whether the traditional rosemary tea preparation method could be considered as a reference method for rosemary's compounds extraction.

Methodology

Qualitative characterisation of Rosmarinus officinalis tea obtained after rosemary infusion in boiled water was determined by high performance liquid chromatography coupled with electrospray ionisation quadrupole time‐of‐flight mass spectrometry (HPLC‐ESI‐QTOF‐MS). Quantitative analysis relies on high performance liquid chromatography with diode array detector (HPLC‐DAD).

Results

Forty‐nine compounds belonging to six families, namely flavonoids, phenolic acids, phenolic terpenes, jasmonate, phenolic glycosides, and lignans were identified. To the best of the authors' knowledge eucommin A is characterised for the first time in rosemary. Rosmarinic acid (158.13 μg/g dried rosemary) was the main compound followed then by feruloylnepitrin (100.87 μg/g) and luteolin‐3′‐O‐(2″‐O‐acetyl)‐β‐d ‐glucuronide (44.04 μg/g). Among quantified compounds, luteolin‐7‐O‐rutinoside was the compound with the lowest concentration.

Conclusion

The infusion method allows several polyphenols present in rosemary tea to be extracted, therefore it could be a reference method for rosemary's compounds extraction. Moreover, traditional Tunisian Rosmarinus officinalis tea consumption is of interest for its rich phenolic content. Copyright © 2017 John Wiley & Sons, Ltd.     

Effect of myocardial infarction and ischemia on induction of cardiac reentries and ventricular fibrillation

The present work is aimed at investigating the effects of myocardial infarction and ischemia on induction of ventricular fibrillation. Electrophysiologic effects of global and local ischemia (variation of the dispersion of refractory periods as well as conduction velocity) on initiation of reentry mechanisms was studied by means of computer simulations based on a cellular automata model of propagation of activation wave through a ventricular surface element. A local area of ischemia where effects of the dispersion of refractory periods are investigated is then simulated. This is made using a Gaussian distribution characterized by its mean and standard deviation. These simulations show that ischemia is capable of initiating reentry phenomena which propagate through the whole ventricle; they are responsible for ventricular fibrillation which causes sudden cardiac death, even when ischemia only involves limited parts of the myocardium. Statistical study of the probability of reentries as a function of both of the size of ischemic zones and the rate of dispersion of refractory periods shows that the latter parameter is of primary importance in triggering cardiac reentries.     

Are CD4 and Fas peptide identities of gp120 relevant to the molecular basis of AIDS pathogenesis?

The release of virions from HIV-1-infected CD4 cells, although occurring readily as a result of immune activation, does not appear to be the only mechanism mediating T-cell loss in AIDS. Three other interacting HIV-1-induced immune disorders in association with viral release (the source of gp120 molecules) may also account for the constitutive T-cell depletion and functional immune suppression: 1. gp120-induced CD4(+) cell anergy, which can be reproduced in cultures of immune activated normal T-cells in the presence of gp120 or gp120 peptide containing the SLWDQ sequence identity to the CD4 molecule; 2. overproduction of IFNalpha and gamma, 3. activation-driven apoptosis of non infected T-cells. Apoptosis of T-cells could also be: 1. induced by effector components - particularly CTL and lymphotoxins produced by helper T-cells of the anti-Fas autoimmune reaction triggered by gp120 epitopes shared with the Fas/APO-1 molecule; 2. enhanced by IFN overproduction. These molecular mechanisms stress the importance in the progression to AIDS of both the viral load and HIV-induced cytokine dysregulation, including overproduction of IFNalpha, which should be considered as targets in the development of strategies for AIDS prophylaxis and immunotherapy.