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Results for “host:pathogen interactions”

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PubMed1990

The development and application of ultrastructural research in mycology.

Electron microscopy has contributed a great deal to the field of mycology. Fungal ultrastructure has been, and continues to be, a key research element in the study of spore development and germination, host-pathogen interactions, nuclear behavior, and studies of subcellular organelles and organization linking structure and function. Since the earliest research in transmission electron microscopy in the 1950s, mycologists have kept pace with the developments in all areas of electron microscopy and have used them to great advantage in generating fine structural information on fungi. These recent developments include the use of scanning electron microscopy in the 1960s, X-ray microanalysis, cryopreservation and immunoelectron microscopy in the 1970s and 1980s. All of these techniques will continue to provide mycologists with the means to gain morphological and analytical data at the ultrastructural level.

Cryopreservation↗

PubMed1996

Green fluorescent protein (GFP) as a new vital marker in the phytopathogenic fungus Ustilago maydis.

Pathogenic development of Ustilago maydis, the causative agent of corn smut disease, is a multistep process. Compatible yeast-like cells fuse and this generates the infectious dikaryon which grows filamentously. Having entered the plant the dikaryon induces tumors in its host in which massive proliferation of fungal material, karyogamy and spore formation occur. In order to follow fungal development from the initial steps to the final stage we have expressed the green fluorescent protein (GFP) from Aequorea victoria as a vital marker in U. maydis and demonstrate that GFP-tagged strains can be used to study host-pathogen interactions in vivo.

Gene Expression Regulation, Fungal↗

PubMed1999

Production of stress-inducible form of heat-shock protein 70 in mouse peritoneal adherent cells after in vivo infection by Francisella tularensis.

Heat-shock proteins (hsp) are ubiquitously produced molecules which participate in the protection of cells from environmental perturbation. Moreover, the members of the heat-shock protein 60 (hsp60) and 70 (hsp70) families play an important role in pathogen-host interactions. We studied in vivo production of the 70-kDa heat-shock proteins in the extract of peritoneal exudate cells (PEC) from mice injected intraperitoneally with an attenuated vaccine strain (LVS) of Francisella tularensis. We found a differential production of a highly stress-inducible member of the hsp70 family, designated hsp72, in three inbred strains of mice exhibiting either resistance or susceptibility to F. tularensis LVS infection. Whereas in tularemia-resistant mice hsp72 was even expressed in PEC without injection of bacteria and its production further increased on day 3 and slowly declined on days 5 and 7 after injection, in susceptible mice hsp72 production was highly inducible and restricted only to day 3 after in vivo infection. Further analysis of hsp72 expression revealed intracellular hsp72 accumulation and its preferential production by peritoneal adherent cells.

Animals↗

PubMed1997

Structural and evolutionary relationships among chitinases of flowering plants.

The analysis of nuclear-encoded chitinase sequences from various angiosperms has allowed the categorization of the chitinases into discrete classes. Nucleotide sequences of their catalytic domains were compared in this study to investigate the evolutionary relationships between chitinase classes. The functionally distinct class III chitinases appear to be more closely related to fungal enzymes involved in morphogenesis than to other plant chitinases. The ordering of other plant chitinases into additional classes mainly relied on the presence of auxiliary domains-namely, a chitin-binding domain and a carboxy-terminal extension-flanking the main catalytic domain. The results of our phylogenetic analyses showed that classes I and IV form discrete and well-supported monophyletic groups derived from a common ancestral sequence that predates the divergence of dicots and monocots. In contrast, other sequences included in classes I* and II, lacking one or both types of auxiliary domains, were nested within class I sequences, indicating that they have a polyphyletic origin. According to phylogenetic analyses and the calculation of evolutionary rates, these chitinases probably arose from different class I lineages by relatively recent deletion events. The occurrence of such evolutionary trends in cultivated plants and their potential involvement in host-pathogen interactions are discussed.

Amino Acid Sequence↗

PubMed2005

A frequent toll-like receptor (TLR)-2 polymorphism is a risk factor for coronary restenosis.

Restenosis is a major problem for patients undergoing percutaneous transluminal coronary angioplasty (PTCA). Inflammatory processes and genetic factors have been suggested to be involved in the pathogenesis of both atherosclerosis and restenosis. The recently discovered family of Toll-like receptors (TLRs) consists of molecules that initiate signaling after host-pathogen interactions. Recently it has been shown that the TLRs are involved in the development and progression of atherosclerosis by interfering with lipid metabolisms and by mediating inflammation. TLR-2 is a key innate immunity receptor for sensing both endogenous inflammatory mediators and ligands of several microbial pathogens postulated to be involved in atherosclerosis. A frequent single nucleotide polymorphism (SNP) for the TLR-2 gene, resulting in a non-functional receptor, has been described. By genotyping two independent groups of patients receiving PTCA, followed by stent implantation in one group, we found a significantly enhanced frequency of the TLR-2 Arg753Gln SNP in patients with restenosis as compared to those without restenosis (PTCA: 7.21 versus 2.45%, P = 0.014; PTCA/stent: 6.86 versus 1.53%, P = 0.013). In contrast, a common TLR-4 SNP was similarly distributed among the patient groups investigated. We furthermore compared the frequency of both SNPs in the patients with an age-matched group of individuals without atherosclerosis and found a trend towards a lower frequency of the TLR-4 SNP in the atherosclerotic group (PTCA: 5.58; PTCA/stent: 3.85 versus 7.14%). We conclude that in restenosis a functional TLR-2 is protective and potentially involved in a reaction pattern preventing restenosis. Screening for the TLR-2 Arg753Gln SNP may be of importance for stratifying a patient's risk and for preventive and therapeutic measures.

Coronary Restenosis↗

PubMed2025

Foliar disease resistance phenomics of fungal pathogens: image-based approaches for mapping quantitative resistance in cereal germplasm.

Host plant resistance is the most effective and environmentally sustainable means of reducing yield losses caused by fungal foliar pathogens of cereal species. Cereal genebank collections hold diverse pools of potentially underutilized disease resistance alleles, and cereal genomic resources are well advanced due to large-scale sequencing and genotyping efforts. Genome-Wide Association Studies (GWAS) have emerged as the predominant association genetics technique to initially discover novel disease resistance loci or alleles in these diverse collections. Traditional disease resistance phenotyping methods are reliant on visual estimation of disease symptom severity and have successfully supported genetic mapping studies either via GWAS or QTL mapping in biparental populations facilitating both marker development and gene cloning efforts. Due to foliar pathogens having a high capacity to evolve, there is a need to pyramid disease resistance genes with diverse mechanisms for durable control. Resistance expressed as a quantitative trait, known as quantitative resistance (QR), is hypothesized to be more durable, unlike major R-gene resistance that is race-specific and can be vulnerable to breaking down without gene stewardship. However, assessing QR visually is challenging, particularly when complicated by complex genotype × environment (G × E) effects in the field. High-throughput image-based phenotyping provides accurate and unbiased data that can support foliar disease resistance screening efforts of genebank collections using GWAS. In this review, we discuss image-based disease phenotyping based on macroscopic (visible symptoms) and microscopic features during the host-pathogen interaction. Quantitative image analysis approaches using conventional and artificial intelligence (AI) algorithms are also discussed.

Disease Resistance↗

PubMed2004

Characterization of two genes encoding leucine-rich repeat-containing proteins in grass carp Ctenopharyngodon idellus.

The cDNAs and genes of two different types of leucine-rich repeat-containing proteins from grass carp (Ctenopharyngodon idellus) were cloned. Homology search revealed that the two genes, designated as GC-GARP and GC-LRG, have 37% and 32% deduced amino-acid sequence similarities with human glycoprotein A repetitions predominant precursor (GARP) and leucine-rich alpha2-glycoprotein (LRG), respectively. The cDNAs of GC-GARP and GC-LRG encoded 664 and 339 amino acid residues, respectively. GC-GARP and GC-LRG contain many distinct structural and/or functional motifs of the leucine-rich repeat (LRR) subfamily, such as multiple conserved 11-residue segments with the consensus sequence LxxLxLxxN/CxL (x can be any amino acid). The genes GC-GARP and GC-LRG consist of two exons, with 4,782 bp and 2,119 bp in total length, respectively. The first exon of each gene contains a small 5'-untranslated region and partial open reading frame. The putative promoter region of GC-GARP was found to contain transcription factor binding sites for GATA-1, IRF4, Oct-1, IRF-7, IRF-1, AP1, GATA-box and NFAT, and the promoter region of GC-LRG for MYC-MAX, MEIS1, ISRE, IK3, HOXA9 and C/EBP alpha. Phylogenetic analysis showed that GC-GARP and mammalian GARPs were clustered into one branch, while GC-LRG and mammalian LRGs were in another branch. The GC-GARP gene was only detected in head kidney, and GC-LRG in the liver, spleen and heart in the copepod (Sinergasilus major)-infected grass carp, indicating the induction of gene expression by the parasite infection. The results obtained in the present study provide insight into the structure of fish LRR genes, and further study should be carried out to understand the importance of LRR proteins in host-pathogen interactions.

Amino Acid Sequence↗

PubMed2004

Genome-wide analysis of defense-responsive genes in bacterial blight resistance of rice mediated by the recessive R gene xa13.

Defense responses triggered by dominant and recessive disease resistance (R) genes are presumed to be regulated by different molecular mechanisms. In order to characterize the genes activated in defense responses against bacterial blight mediated by the recessive R gene xa13, two pathogen-induced subtraction cDNA libraries were constructed using the resistant rice line IRBB13--which carries xa13--and its susceptible, near-isogenic, parental line IR24. Clustering analysis of expressed sequence tags (ESTs) identified 702 unique expressed sequences as being involved in the defense responses triggered by xa13; 16% of these are new rice ESTs. These sequences define 702 genes, putatively encoding a wide range of products, including defense-responsive genes commonly involved in different host-pathogen interactions, genes that have not previously been reported to be associated with pathogen-induced defense responses, and genes (38%) with no homology to previously described functional genes. In addition, R-like genes putatively encoding nucleotide-binding site/leucine rich repeat (NBS-LRR) and LRR receptor kinase proteins were observed to be induced in the disease resistance activated by xa13. A total of 568 defense-responsive ESTs were mapped to 588 loci on the rice molecular linkage map through bioinformatic analysis. About 48% of the mapped ESTs co-localized with quantitative trait loci (QTLs) for resistance to various rice diseases, including bacterial blight, rice blast, sheath blight and yellow mottle virus. Furthermore, some defense-responsive sequences were conserved at similar locations on different chromosomes. These results reveal the complexity of xa13-mediated resistance. The information obtained in this study provides a large source of candidate genes for understanding the molecular bases of defense responses activated by recessive R genes and of quantitative disease resistance.

Chromosomes, Plant↗

PubMed2006

Molecular cloning and differential expression of an gamma-aminobutyrate transaminase gene, OsGABA-T, in rice (Oryza sativa) leaves infected with blast fungus.

gamma-Aminobutyrate transaminase (GABA-T) catalyzes the conversion of GABA to succinic semialdehyde. Using differential display PCR and cDNA library screening, a full-length GABA-T cDNA (OsGABA-T) was isolated from rice (Oryza sativa) leaves infected with an incompatible race of Magnaporthe grisea. The deduced amino acid sequence comprises 483 amino acid residues and shares 85-69% identity with GABA-T sequences from other plants. OsGABA-T expression is induced by blast fungus infection, mechanical wounding and ultraviolet radiation in rice leaves and is not detected in normal rice organs. This gene is also induced by defense signal molecules such as salicylic acid and abscisic acid, but not by jasmonic acid. Our data suggest that OsGABA-T (GABA shunt) may play a role in restricting the levels of cell death during the host-pathogen interaction.

4-Aminobutyrate Transaminase↗

PubMed2007

Transimmortalized proximal tubule and collecting duct cell lines derived from the kidneys of transgenic mice.

This review summarizes the strategy of cellular immortalization based on the principle of targeted oncogenesis in transgenic mice, used to establish models of transimmortalized renal proximal tubule cells, referred to as PKSV-PCT and PKSV-PR-cells, and collecting duct principal cells, referred to as mpkCCD(cl4) cells. These cell lines have maintained for long-term passages the main biochemical and functional properties of the parental cells from which they were derived. Proximal tubule PKSV-PCT and PKSV-PR cells have been proved to be suitable cell systems for toxicological and pharmacological studies. They also permitted the establishment of a model of multidrug-resistant (MDR) renal epithelial tubule cells, PKSV-PR(col50), which have served for the study of both MDR-dependent extrusion of chemotherapeutic drugs and inappropriate accumulation of weak base anthracyclines in intracellular acidic organelles. The novel collecting duct cell line mpkCCD(cl4), which has maintained the characteristics of tight epithelial cells, in particular Na(+) absorption stimulated by aldosterone, has been extensively used for pharmacological studies related to the regulation of ion transport. These cells have permitted the identification of several aldosterone-induced proteins playing a key role in the regulation of Na(+) absorption mediated by the epithelial Na(+) channel ENaC. Recent studies have also provided evidence that these cell lines represent valuable cell systems for the study of host-pathogen interactions and the analysis of the role of renal tubule epithelial cells in the induction of inflammatory response caused by uropathogens that may lead to severe renal damage.

Absorption↗

PubMed2007

In vivo functions of mitogen-activated protein kinases: conclusions from knock-in and knock-out mice.

Multicellular organisms achieve intercellular communication by means of signalling molecules whose effect on the target cell is mediated by signal transduction pathways. Such pathways relay, amplify and integrate signals to elicit appropriate biological responses. Protein kinases form crucial intermediate components of numerous signalling pathways. One group of protein kinases, the mitogen-activated protein kinases (MAP kinases) are kinases involved in signalling pathways that respond primarily to mitogens and stress stimuli. In vitro studies revealed that the MAP kinases are implicated in several cellular processes, including cell division, differentiation, cell survival/apoptosis, gene expression, motility and metabolism. As such, dysfunction of specific MAP kinases is associated with diseases such as cancer and immunological disorders. However, the genuine in vivo functions of many MAP kinases remain elusive. Genetically modified mouse models deficient in a specific MAP kinase or expressing a constitutive active or a dominant negative variant of a particular MAP kinase offer valuable tools for elucidating the biological role of these protein kinases. In this review, we focus on the current status of MAP kinase knock-in and knock-out mouse models and their phenotypes. Moreover, examples of the application of MAP kinase transgenic mice for validating therapeutic properties of specific MAP kinase inhibitors, and for investigating the role of MAP kinase in pathogen-host interactions will be discussed.

Animals↗

PubMed1995

Major allergen Phl p Vb in timothy grass is a novel pollen RNase.

A cDNA coding for the major group V allergen Phl p Vb was isolated from a timothy grass pollen cDNA library by immunoscreening with a specific monoclonal antibody. It was discovered for the first time that the recombinant Phl p Vb pollen allergen after expression and purification has ribonuclease activity. High homology of Phl p Vb to other group V allergens in grass pollen indicates similar function. By RNase activity gel of natural pollen extract of timothy grass and consecutive Western blot analysis of the excised proteins, the RNase active bands were shown to be group V allergens. Additionally it was demonstrated that an homologous protein to Phl p Vb in the mother plant could be induced by salicylic acid. This indicates that group Vb allergens may be involved in host-pathogen interactions because in pollen they are quickly exported RNases and in the mother plant they depend on a hormone which is related to expression of plant resistance genes.

Allergens↗

PubMed1985

Exposure of bovine cornea to different strains of Moraxella bovis and to other bacterial species in vitro.

A collection of strains of Moraxella bovis, some pathogenic and some non-pathogenic in cattle, together with other M. bovis preparations, Neisseria ovis, Staphylococcus aureus and Moraxella non-liquefaciens were studied by scanning electron microscopy for their affinity to bovine corneal preparations in vitro. The in vitro procedure provides a convenient method for studies on host-pathogen interactions at the early stage of pathogenesis. The results corresponded well with the pathogenicity of the respective strains and species in cattle. It is considered that the pathogenicity of M. bovis is associated with at least two factors, piliation and the ability to produce pit-like depressions in corneal epithelial cells. The other bacterial species, which are not thought to play an important role in infectious bovine keratoconjunctivitis, had the ability to adhere to the bovine cornea but did not produce pits. The pitting factor of M. bovis is of interest in relation to studies on vaccination against infectious bovine keratoconjunctivitis.

Animals↗

PubMed1993

Ethylene is a selective ribosomal cistron regulator in Allium cepa epidermal cells.

In Allium cepa L. (onion) the number, size, and morphology of visible nucleoli per nucleus varies during cell division, growth, differentiation, storage, activation of quiescent tissue, senescence, wounding, and disease (host-pathogen interactions). Since there are two types (differentiated visually by size) of ribosomal cistrons in onion (major and minor nucleoli differ in the external spacer nucleotide sequences), we inferred that they function separately. In controls, major nucleolar organizer regions (NORs) were visible in epidermal cell nuclei as nucleoli. After exposure of the tissue to ambient conditions, these nucleoli enlarged and changed morphology. Minor NORs (when in the genome) required more than 6 h to become developed as visible nucleoli. In the ethylene treatments, the major NORs (visible nucleoli in quiescent epidermal cells) increased in size a (activation of a greater number of tandem rRNA genes) as in the controls. The minor, quiescent NORs became active and visible (activation of quiescent, inactive NORs) within 3 h. Actinomycin D, and cycloheximide, with or without ethylene, inhibited the increase in size of the major NORs, and prevented activation of the minor NORs (i.e. they did not become visible). Silver nitrate and cobalt chloride had no effect on major NORs but inhibited the appearance of minor nucleoli when combined with ethylene treatments. We infer: ethylene acts to regulate the expression of the minor NORs (selective ribosomal cistron regulation); and, other hormone(s) are involved in the regulation of the major NORs. Yellow and white sweet Spanish onions we studied had two major NORs and two minor NORs. Red sweet Spanish onions we studied had only the two major NORs.

Allium↗

PubMed1996

Nuclear degeneration in epidermal cells of drying onion bulb leaf bases.

We tested the null hypothesis 'that activated nuclei and nucleoli in outer-epidermal cells of newly exposed equatorial tissue of the turgid leaf bases of white onions (exposed to the ambient atmosphere by removal of two dry and two turgid leaf bases) remained in that state as the tissue dried' by following nuclear macromolecules (total nucleic acid, DNA, RNA, total protein, histone, and non-histone protein; compared with T0 = 100%) and nucleolar morphologies over a 5-day period. The nuclei became activated within 6 h and remained in that state for 2-3 days [increases in RNA, non-histone protein, and volume of major nucleoli occurred by T12 (about 191, 177, and 289%, respectively) and appearance of the minor nucleoli between T12 and T24 (activation of silent rRNA cistrons)]. Combined nucleolar (major and minor) volumes decreased to 228% by T24 and to 150% by T48. Minor nucleoli were visible at T24 and T48. DNA (DAPI) remained unchanged over that period of time. At the T96 sampling, all nuclear indices had decreased to levels below those obtained at the time of exposure to the ambient atmosphere; minor rRNA cistrons had became silent genes; nuclear volume was about 89% of the original volume; and, nucleolar volume (major nucleoli) was about 93%. The percentages for nuclear indices at T120 were DNA, 85% of T0; RNA, 35%; histone, 87%; non-histone protein, 47%; nuclear volume, 81%; and nucleolar volume, 67%. Of interest is the lack of change in major nucleolar morphologies between T96 and T120 although they decreased in volume during that period. We infer that the karyoskeleton (nuclear matrix) had undergone irreversible degeneration after T48 and that the cells had passed the point-of-no-return in the senescence pathway by T120. We propose that this model for cell senescence and death (drying of turgid leaf bases to form the dry, dead outer covering of the bulbs) simulates post-harvest storage conditions and will prove helpful to those studying cellular senescence mechanisms and associated host-pathogen interactions in plants.

Allium↗

PubMed1996

Intracellular, genetic or congenital immunisation--transgenic approaches to increase disease resistance of farm animals.

Novel approaches to modify disease resistance or susceptibility in livestock are justified not only by economical reasons and with respect to animal welfare but also by recent advancements in molecular genetics. The control or elimination of infectious pathogens in farm animals is historically achieved by the use of vaccines and drugs and by quarantine safeguards and eradication. Currently, research on the improvement of disease resistance based on nucleic acid technology focuses on two main issues: additive gene transfer and the development of nucleic acid vaccines. The strategies aim at the stable or transient expression of components known to influence non-specific or specific host defence mechanisms against infectious pathogens. Thus, candidates for gene transfer experiments include all genes inducing or conferring innate and acquired immunity as well as specific disease resistance genes. Referring to the site and mode of action and the source of the effective agent the strategies are termed 'intracellular', 'genetic' and 'congenital' immunisation. The targeted disruption (deletive gene transfer) of disease susceptibility genes awaits the establishment of totipotential embryonic cell lineages in farm animals. The cytokine network regulates cellular viability, growth and differentiation in physiological and pathophysiological states. The identification of the JAK-STAT pathway used by many cytokines for their intracellular signal propagation has provided not only new target molecules for modulating the immune response but will also permit the further elucidation of host-pathogen interactions and resistance mechanisms.

Animal Diseases↗

PubMed2004

Rafts and related glycosphingolipid-enriched microdomains in the intestinal epithelium: bacterial targets linked to nutrient absorption.

Plasma membrane microdomains such as lipid rafts or caveolae play a major role in host-pathogen interactions. Although this field of research has been extensively studied, two important points have been poorly addressed: (i) the molecular basis of raft-pathogen interactions, and (ii) the effect of such interactions on nutrient absorption. The aim of this review was to propose a biochemical analysis of bacterial adhesion to lipid raft components exposed on the mucosal surface of the intestinal epithelium. A special attention has been given to CH-pi interactions that allow the sugar rings of glycosphingolipids (GSL) to stack against aromatic side chains of bacterial adhesins and toxins. These interactions are controlled by cholesterol molecules intercalated between membrane GSL and/or by the presence of an alpha-OH group in the acyl chain of the ceramide backbone of GSL. In the second part of the review, we analysed the experimental data suggesting the involvement of lipid rafts in the intestinal absorption of nutrients, the mechanisms by which bacteria could impair intestinal functions, and possible therapeutic strategies based on the biochemistry of raft-pathogen interactions.

Animals↗

PubMed2004

A hepatocellular carcinoma cell line producing mature hepatitis B viral particles.

Current in vitro models for hepatitis B virus (HBV) are based on human hepatoblastoma cell lines transfected with HBV genome. The objective of this work was to develop an in vitro, hepatocellular carcinoma (HCC)-based system supporting HBV full replication and producing mature viral particles. The FLC4 human HCC cell line was stably transfected with a plasmid carrying a head-to-tail dimer of the adwHBV genome. One of the clones, FLC4A10II, exhibited prolonged expression of HBV, as was demonstrated by secreted levels of HBsAg, HBeAg, and HBV DNA in the culture medium of the growing cells. Furthermore, the cells produced HBV particles that were detected by a cesium chloride density gradient performed on the culture medium. Analysis by Southern blot revealed that HBV DNA has integrated into the FLC4A10II cell genome. The presence of HBV in the FLC4A10II cells did not cause alterations in cell morphology and the cells continued to resemble mature hepatocytes. They do exhibit a high mitotic activity. The new HBV stably transfected cell line, FLC4A10II, can serve as an important tool for further exploration of HBV host-pathogen interaction, viral life cycle, and for assessing new antiviral agents.

Carcinoma, Hepatocellular↗