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A Model of an Integrated Immune System Pathway in Homo sapiens and Its Interaction with Superantigen Producing Expression Regulatory Pathway in Staphylococcus aureus: Comparing Behavior of Pathogen Perturbed and Unperturbed Pathway  [PDF]
Namrata Tomar, Rajat K. De
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0080918
Abstract: Response of an immune system to a pathogen attack depends on the balance between the host immune defense and the virulence of the pathogen. Investigation of molecular interactions between the proteins of a host and a pathogen helps in identifying the pathogenic proteins. It is necessary to understand the dynamics of a normally behaved host system to evaluate the capacity of its immune system upon pathogen attack. In this study, we have compared the behavior of an unperturbed and pathogen perturbed host system. Moreover, we have developed a formalism under Flux Balance Analysis (FBA) for the optimization of conflicting objective functions. We have constructed an integrated pathway system, which includes Staphylococcal Superantigen (SAg) expression regulatory pathway and TCR signaling pathway of Homo sapiens. We have implemented the method on this pathway system and observed the behavior of host signaling molecules upon pathogen attack. The entire study has been divided into six different cases, based on the perturbed/unperturbed conditions. In other words, we have investigated unperturbed and pathogen perturbed human TCR signaling pathway, with different combinations of optimization of concentrations of regulatory and signaling molecules. One of these cases has aimed at finding out whether minimization of the toxin production in a pathogen leads to the change in the concentration levels of the proteins coded by TCR signaling pathway genes in the infected host. Based on the computed results, we have hypothesized that the balance between TCR signaling inhibitory and stimulatory molecules can keep TCR signaling system into resting/stimulating state, depending upon the perturbation. The proposed integrated host-pathogen interaction pathway model has accurately reflected the experimental evidences, which we have used for validation purpose. The significance of this kind of investigation lies in revealing the susceptible interaction points that can take back the Staphylococcal Enterotoxin (SE)-challenged system within the range of normal behavior.
The Signalling Pathway Involved in Plant-pathogen Interactions in Arabidopsis thaliana  [PDF]
K. Nadarajah
Pakistan Journal of Biological Sciences , 2001,
Abstract: The system of plant defence against fungi is complex. It encompasses several cross-talking pathways that respond to various signals. Methyl jasmonate, a plant growth regulator is one of the various signals that stimulate a defence response. In order to comprehend the involvement of jasmonate in the defence of Arabidopsis against Erysiphe cruciferarum, a mutant that is defective in jasmonate accumulation, was used (fad3-2fad7-2fad8). This mutant is susceptible to E.cruciferarum infection, which results in powdery mildew. The wild type plants were resistant towards powdery mildew. Mutant plants sprayed with methyl jasmonate received substantial protection against E.cruciferarum infections. The incidence of disease in methyl jasmonate treated mutants was reduced to levels observed in the wildtype. The coi1 mutant however was not protected through treatment with methyl jasmonate. This therefore indicates that methyl jasmonate induces the plants resistance through the activation of the plants defence system and not as an antifungal agent. One of the genes activated in the defence response is the AtVSP gene. The transcript in wildtype plants was induced when infected by E.cruciferarum. Transcript levels in mutants were comparable to the constitutive levels observed in the controls. Therefore it is apparent that jasmonate-signalling is essential in protection against E.cruciferarum infections of Arabidopsis.
Arabidopsis thaliana: A model host plant to study plant-pathogen interaction using Chilean field isolates of Botrytis cinerea
GONZáLEZ,JUAN; REYES,FRANCISCA; SALAS,CARLOS; SANTIAG,MARGARITA; CODRIANSKY,YAEL; COLIHEUQUE,NELSON; SILVA,HERMAN;
Biological Research , 2006, DOI: 10.4067/S0716-97602006000200004
Abstract: one of the fungal pathogens that causes more agriculture damage is botrytis cinerea. botrytis is a constant threat to crops because the fungus infects a wide range of host species, both native and cultivated. furthermore, botrytis persists on plant debris in and on the soil. some of the most serious diseases caused by botrytis include gray mold on vegetables and fruits, such as grapes and strawberries. botrytis also causes secondary soft rot of fruits and vegetables during storage, transit and at the market. in many plant-pathogen interactions, resistance often is associated with the deposition of callose, accumulation of autofluorescent compounds, the synthesis and accumulation of salicylic acid as well as pathogenesis-related proteins. arabidopsis thaliana has been used as a plant model to study plant-pathogen interaction. the genome of arabidopsis has been completely sequenced and this plant serves as a good genetic and molecular model. in this study, we demonstrate that chilean field isolates infect arabidopsis thaliana and that arabidopsis subsequently activates several defense response mechanisms associated with a hypersensitive response. furthermore, we propose that arabidopsis may be used as a model host species to analyze the diversity associated with infectivity among populations of botrytis cinerea field isolates
Arabidopsis thaliana: A model host plant to study plant-pathogen interaction using Chilean field isolates of Botrytis cinerea  [cached]
JUAN GONZáLEZ,FRANCISCA REYES,CARLOS SALAS,MARGARITA SANTIAG
Biological Research , 2006,
Abstract: One of the fungal pathogens that causes more agriculture damage is Botrytis cinerea. Botrytis is a constant threat to crops because the fungus infects a wide range of host species, both native and cultivated. Furthermore, Botrytis persists on plant debris in and on the soil. Some of the most serious diseases caused by Botrytis include gray mold on vegetables and fruits, such as grapes and strawberries. Botrytis also causes secondary soft rot of fruits and vegetables during storage, transit and at the market. In many plant-pathogen interactions, resistance often is associated with the deposition of callose, accumulation of autofluorescent compounds, the synthesis and accumulation of salicylic acid as well as pathogenesis-related proteins. Arabidopsis thaliana has been used as a plant model to study plant-pathogen interaction. The genome of Arabidopsis has been completely sequenced and this plant serves as a good genetic and molecular model. In this study, we demonstrate that Chilean field isolates infect Arabidopsis thaliana and that Arabidopsis subsequently activates several defense response mechanisms associated with a hypersensitive response. Furthermore, we propose that Arabidopsis may be used as a model host species to analyze the diversity associated with infectivity among populations of Botrytis cinerea field isolates
The Relationship between Host Lifespan and Pathogen Reservoir Potential: An Analysis in the System Arabidopsis thaliana-Cucumber mosaic virus  [PDF]
Jean Michel Hily,Adrián García,Arancha Moreno,María Plaza,Mark D. Wilkinson,Alberto Fereres,Aurora Fraile,Fernando García-Arenal
PLOS Pathogens , 2014, DOI: doi/10.1371/journal.ppat.1004492
Abstract: Identification of the determinants of pathogen reservoir potential is central to understand disease emergence. It has been proposed that host lifespan is one such determinant: short-lived hosts will invest less in costly defenses against pathogens, so that they will be more susceptible to infection, more competent as sources of infection and/or will sustain larger vector populations, thus being effective reservoirs for the infection of long-lived hosts. This hypothesis is sustained by analyses of different hosts of multihost pathogens, but not of different genotypes of the same host species. Here we examined this hypothesis by comparing two genotypes of the plant Arabidopsis thaliana that differ largely both in life-span and in tolerance to its natural pathogen Cucumber mosaic virus (CMV). Experiments with the aphid vector Myzus persicae showed that both genotypes were similarly competent as sources for virus transmission, but the short-lived genotype was more susceptible to infection and was able to sustain larger vector populations. To explore how differences in defense against CMV and its vector relate to reservoir potential, we developed a model that was run for a set of experimentally-determined parameters, and for a realistic range of host plant and vector population densities. Model simulations showed that the less efficient defenses of the short-lived genotype resulted in higher reservoir potential, which in heterogeneous host populations may be balanced by the longer infectious period of the long-lived genotype. This balance was modulated by the demography of both host and vector populations, and by the genetic composition of the host population. Thus, within-species genetic diversity for lifespan and defenses against pathogens will result in polymorphisms for pathogen reservoir potential, which will condition within-population infection dynamics. These results are relevant for a better understanding of host-pathogen co-evolution, and of the dynamics of pathogen emergence.
A Role for Nonsense-Mediated mRNA Decay in Plants: Pathogen Responses Are Induced in Arabidopsis thaliana NMD Mutants  [PDF]
Samantha Rayson, Luis Arciga-Reyes, Lucie Wootton, Marta De Torres Zabala, William Truman, Neil Graham, Murray Grant, Brendan Davies
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0031917
Abstract: Nonsense-mediated mRNA decay (NMD) is a conserved mechanism that targets aberrant mRNAs for destruction. NMD has also been found to regulate the expression of large numbers of genes in diverse organisms, although the biological role for this is unclear and few evolutionarily conserved targets have been identified. Expression analyses of three Arabidopsis thaliana lines deficient in NMD reveal that the vast majority of NMD-targeted transcripts are associated with response to pathogens. Congruently, NMD mutants, in which these transcripts are elevated, confer partial resistance to Pseudomonas syringae. These findings suggest a biological rationale for the regulation of gene expression by NMD in plants and suggest that manipulation of NMD could offer a new approach for crop protection. Amongst the few non-pathogen responsive NMD-targeted genes, one potential NMD targeted signal, the evolutionarily conserved upstream open reading frame (CuORF), was found to be hugely over-represented, raising the possibility that this feature could be used to target specific physiological mRNAs for control by NMD.
Effects of 17β-Estradiol on Growth, Primary Metabolism, Phenylpropanoid-Flavonoid Pathways and Pathogen Resistance in Arabidopsis thaliana  [PDF]
Pallavi Upadhyay, Camelia Maier
American Journal of Plant Sciences (AJPS) , 2016, DOI: 10.4236/ajps.2016.713160
Abstract: Mammalian sex hormones are spread in the environment from natural and anthropogenic sources. In the present study, the effect of estradiol on Arabidopsis thaliana growth primary metabolism, phenylpropanoid and flavonoid pathways and pathogen resistance were investigated. Treatments of Arabidopsis plants with 10 and 100 nM 17β-estradiol resulted in enhanced root growth and shoot biomass. In addition, treated plants had an increased rate of photosynthesis with a concomitant increase in carbohydrate and protein accumulation. Plants exposed to higher concentrations of 17β-estradiol (10 μM) had significantly lower root growth, biomass, photosynthesis rate, primary metabolite and phenylpropanoid and flavonoid contents indicating a toxic effect of estradiol. Treatments with increasing estradiol concentrations (10 nM, 100 nM and 10 μM) resulted in the downregulation of phenylpropanoid-flavonoid pathway genes (PAL1, PAL4, CHI and ANS) and subsequent decreased accumulation of phenolics, flavonoids and anthocyanins. Estradiol-treated plants were inoculated with Pseudomonas syringae pv. Tomato DC3000 and basal resistance was determined. Estradiol treatments rendered plants susceptible to the pathogen, thus compromising the plant defense mechanisms. These results indicate that at low concentrations, estradiol functions as a biostimulant of growth, yield and primary metabolism of Arabidopsis. However, estradiol functions as a potential transcriptional regulator of the phenylpropanoid pathway genes in Arabidopsis, having a negative effect on
DEFINIENDO HOMO SAPIENS-SAPIENS: APROXIMACIóN ANTROPOLóGICA
Valdebenito,Carolina;
Acta bioethica , 2007, DOI: 10.4067/S1726-569X2007000100008
Abstract: this paper reflects on the similarities and differences between human beings and animals as members of systems in permanent interaction. the main goal is to define homo, reviewing his/her biological and cultural evolution and reflecting on the animal social behaviors that still remain in homo sapiens-sapiens. the paper reflect on the moral dilemmas present in humans as cultural beings, taking as example the ethical dilemmas of violence and incest
DEFINIENDO HOMO SAPIENS-SAPIENS: APROXIMACIóN ANTROPOLóGICA DEFININDO HOMO SAPIENS-SAPIENS: APROXIMA O ANTROPOLóGICA DEFINING HOMO SAPIENS-SAPIENS: ANTHROPOLOGICAL APPROACH  [cached]
Carolina Valdebenito
Acta Bioethica , 2007,
Abstract: Este artículo reflexiona sobre los encuentros y desencuentros entre el ser humano y el resto de los animales, en tanto miembros de sistemas en permanente interacción(1). Abordar la definición de Homo, repasar su evolución biológica y cultural y reflexionar sobre los resabios de animalidad que quedan en el comportamiento social del Homo sapiens-sapiens es su objetivo principal. Se busca reflexionar sobre los dilemas morales que acompa an al hombre en tanto ser cultural; para ello se analizan dos dilemas éticos: la violencia y el incesto Este artigo reflete sobre os encontros e desencontros entre o ser humano e os demais animais, enquanto membros de sistemas em permanente intera o(1). Seu principal objetivo é abordar a defini o de Homo, tra ar um panorama de sua evolu o biológica e cultural e refletir sobre os resquícios da animalidade que permanecem no comportamento social do Homo sapiens-sapiens. Busca-se refletir sobre os dilemas morais que acompanham o homem enquanto ser cultural, o que para isso s o considerados como dilemas éticos: a violência e o incesto This paper reflects on the similarities and differences between human beings and animals as members of systems in permanent interaction. The main goal is to define Homo, reviewing his/her biological and cultural evolution and reflecting on the animal social behaviors that still remain in Homo sapiens-sapiens. The paper reflect on the moral dilemmas present in humans as cultural beings, taking as example the ethical dilemmas of violence and incest
Gene Gain and Loss during Evolution of Obligate Parasitism in the White Rust Pathogen of Arabidopsis thaliana  [PDF]
Eric Kemen,Anastasia Gardiner,Torsten Schultz-Larsen,Ariane C. Kemen,Alexi L. Balmuth,Alexandre Robert-Seilaniantz,Kate Bailey,Eric Holub,David J. Studholme,Dan MacLean,Jonathan D. G. Jones
PLOS Biology , 2012, DOI: 10.1371/journal.pbio.1001094
Abstract: Biotrophic eukaryotic plant pathogens require a living host for their growth and form an intimate haustorial interface with parasitized cells. Evolution to biotrophy occurred independently in fungal rusts and powdery mildews, and in oomycete white rusts and downy mildews. Biotroph evolution and molecular mechanisms of biotrophy are poorly understood. It has been proposed, but not shown, that obligate biotrophy results from (i) reduced selection for maintenance of biosynthetic pathways and (ii) gain of mechanisms to evade host recognition or suppress host defence. Here we use Illumina sequencing to define the genome, transcriptome, and gene models for the obligate biotroph oomycete and Arabidopsis parasite, Albugo laibachii. A. laibachii is a member of the Chromalveolata, which incorporates Heterokonts (containing the oomycetes), Apicomplexa (which includes human parasites like Plasmodium falciparum and Toxoplasma gondii), and four other taxa. From comparisons with other oomycete plant pathogens and other chromalveolates, we reveal independent loss of molybdenum-cofactor-requiring enzymes in downy mildews, white rusts, and the malaria parasite P. falciparum. Biotrophy also requires “effectors” to suppress host defence; we reveal RXLR and Crinkler effectors shared with other oomycetes, and also discover and verify a novel class of effectors, the “CHXCs”, by showing effector delivery and effector functionality. Our findings suggest that evolution to progressively more intimate association between host and parasite results in reduced selection for retention of certain biosynthetic pathways, and particularly reduced selection for retention of molybdopterin-requiring biosynthetic pathways. These mechanisms are not only relevant to plant pathogenic oomycetes but also to human pathogens within the Chromalveolata.
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