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Host Cytoplasm (host + cytoplasm)
Selected AbstractsSerological detection and immunogold localization of cross-reactive antigens shared by Camellia sinensis and Exobasidium vexansJOURNAL OF APPLIED MICROBIOLOGY, Issue 5 2007B.N. Chakraborty Abstract Aims:, Pathogenicity of Exobasidium vexans, causal agent of blister blight of tea, was studied in 30 commercially cultivated tea varieties by analysing the antigenic patterns of host and pathogen using immunological techniques. Methods and Results:, Whole plant inoculation of tea varieties with E. vexans showed that T-78 and T-17/1/54 were most susceptible and most resistant respectively. Antigen preparations from tea varieties, pathogen, nonpathogen (Fusarium oxysporum) and of nonhosts (Glycine max, Leucaena leucocephala and Oryza sativa) were compared by indirect enzyme-linked immunosorbent assay and dot-immunobinding assay using polyclonal antibodies raised against the pathogen, nonpathogen, susceptible and resistant tea varieties. Cross-reactive antigens (CRA) were found among susceptible varieties and E. vexans isolates but not in resistant varieties, nonhosts or nonpathogen. Indirect staining of antibodies using fluorescein isothiocyanate indicated CRA were concentrated mainly around epidermal and mesophyll cells in compatible host (T-78). This was substantiated by ultrastructural studies using gold-labelled antibodies through transmission electron microscopy which showed specific localization in the chloroplasts and host cytoplasm. Conclusion:, Pathogenicity of E. vexans to different tea varieties is therefore related to the level of antigenic similarity between host and pathogen. Significance and Impact of the Study:, Immunological methods proved to be valuable in screening commercially cultivated tea varieties against E. vexans. [source] Viral appropriation of apoptotic and NF-,B signaling pathwaysJOURNAL OF CELLULAR BIOCHEMISTRY, Issue 6 2004Andrew G. Bowie Abstract Viruses utilize a variety of strategies to evade the host immune response and replicate in the cells they infect. The comparatively large genomes of the Orthopoxviruses and gammaherpesviruses encode several immunomodulatory proteins that are homologous to component of the innate immune system of host cells, which are reviewed here. However, the viral mechanisms used to survive host responses are quite distinct between these two virus families. Poxviruses undergo continuous lytic replication in the host cytoplasm while expressing many genes that inhibit innate immune responses. In contrast, herpesviruses persist in a latent state during much of their lifecycle while expressing only a limited number of relatively non-immunogenic viral proteins, thereby avoiding the adaptive immune response. Poxviruses suppress, whereas latent gammaherpesviruses activate, signaling by NF-,B, yet both viruses target similar host signaling pathways to suppress the apoptotic response. Here, modulation of apoptotic and NF-,B signal transduction pathways are examined as examples of common pathways appropriated in contrasting ways by herpesviruses and poxviruses. © 2004 Wiley-Liss, Inc. [source] Immunolocalization of 1,3-,-Glucanases Secreted by Gaeumannomyces graminis var. tritici in Infected Wheat RootsJOURNAL OF PHYTOPATHOLOGY, Issue 5 2010Yongting Yu Abstract The distribution of extracellular 1,3-,-glucanase secreted by Gaeumannomyces graminis var. tritici (Ggt) was investigated in situ in inoculated wheat roots by immunogold labelling and transmission electron microscopy. Antiserum was prepared by subcutaneously injecting rabbits with purified 1,3-,-glucanase secreted by the pathogenic fungus. A specific antibody of 1,3-,-glucanase, anti-GluGgt, was purified and characterized. Double immunodiffusion tests revealed that the antiserum was specific for 1,3-,-glucanase of Ggt, but not for 1,3-,-glucanase from wheat plants. Native polyacrylamide gel electrophoresis of the purified and crude enzyme extract and immunoblotting showed that the antibody was monospecific for 1,3-,-glucanase in fungal extracellular protein populations. After incubation of ultrathin sections of pathogen-infected wheat roots with anti-1,3-,-glucanase antibody and the secondary antibody, deposition of gold particles occurred over hyphal cells and the host tissue. Hyphal cell walls and septa as well as membranous structures showed regular labelling with gold particles, while few gold particles were detected over the cytoplasm and other organelles such as mitochondria and vacuoles. In host tissues, cell walls in contact with the hyphae usually exhibited a few gold particles, whereas host cytoplasm and cell walls distant from the hyphae were free of labelling. Furthermore, over lignitubers in the infected host cells labelling with gold particles was detected. No gold particles were found over sections of non-inoculated wheat roots. The results indicate that 1,3-,-glucanase secreted by Ggt may be involved in pathogenesis of the take-all fungus through degradation of callose in postinfectionally formed cell wall appositions, such as lignitubers. [source] Light and Electron Microscopy of the Compatible Interaction Between Arabidopsis and the Downy Mildew Pathogen Peronospora parasiticaJOURNAL OF PHYTOPATHOLOGY, Issue 6 2003E. M. Soylu Abstract In this study, we focused on compatible interactions between Peronospora parasitica isolate Emoy-2 and wild-type (Oy-0) and mutant (Ws- eds1) Arabidopsis thaliana accessions by using light and transmission electron microscopy (TEM). Light microscopy of compatible interactions revealed that conidia germinated and penetrated through the anticlinal cell walls of two epidermal cells. Rapid spreading of the hyphal growth with formation of numerous haustoria within the mesophyll cells was subsequently followed by profuse sporulation in the absence of host cell necrosis on both wild-type and mutant accessions. TEM observations revealed that coenocytic intercellular hyphae ramified and spread intercellularly throughout the host tissue forming several haustoria in host mesophyll cells. Intracellular haustoria were lobed with the diameter of 6,7 ,m. Each haustorium was connected to intercellular hyphae in the absence of apparent haustorial neck. The cytoplasm of the haustorium included the organelles characteristic of the pathogen. Callose-like deposits were frequently observed at sites of penetration around the proximal region of the haustorial neck. Apart from a few callose ensheatments, no obvious response was observed in host cells following formation of haustoria. Most of mesophyll cells contained normal haustoria and the host cytoplasm displayed a high degree of structural integrity. Absence of host cell wall alteration and cell death in penetrated host cell of both accessions suggest that the pathogen exerts considerable control over basic cellular processes and in this respect, response to this biotroph oomycete differs considerably from responses to other pathogens such as necrotrophs. [source] Pathogen trafficking pathways and host phosphoinositide metabolismMOLECULAR MICROBIOLOGY, Issue 6 2009Stefan S. Weber Summary Phosphoinositide (PI) glycerolipids are key regulators of eukaryotic signal transduction, cytoskeleton architecture and membrane dynamics. The host cell PI metabolism is targeted by intracellular bacterial pathogens, which evolved intricate strategies to modulate uptake processes and vesicle trafficking pathways. Upon entering eukaryotic host cells, pathogenic bacteria replicate in distinct vacuoles or in the host cytoplasm. Vacuolar pathogens manipulate PI levels to mimic or modify membranes of subcellular compartments and thereby establish their replicative niche. Legionella pneumophila, Brucella abortus, Mycobacterium tuberculosis and Salmonella enterica translocate effector proteins into the host cell, some of which anchor to the vacuolar membrane via PIs or enzymatically turnover PIs. Cytoplasmic pathogens target PI metabolism at the plasma membrane, thus modulating their uptake and antiapoptotic signalling pathways. Employing this strategy, Shigella flexneri directly injects a PI-modifying effector protein, while Listeria monocytogenes exploits PI metabolism indirectly by binding to transmembrane receptors. Thus, regardless of the intracellular lifestyle of the pathogen, PI metabolism is critically involved in the interactions with host cells. [source] Folding kinetics and thermodynamics of Pseudomonas syringae effector protein AvrPto provide insight into translocation via the type III secretion systemPROTEIN SCIENCE, Issue 7 2008Jennifer E. Dawson Abstract In order to infect their hosts, many Gram-negative bacteria translocate agents of infection, called effector proteins, through the type III secretion system (TTSS) into the host cytoplasm. This process is thought to require at least partial unfolding of these agents, raising the question of how an effector protein might unfold to enable its translocation and then refold once it reaches the host cytoplasm. AvrPto is a well-studied effector protein of Pseudomonas syringae pv tomato. The presence of a readily observed unfolded population of AvrPto in aqueous solution and the lack of a known secretion chaperone make it ideal for studying the kinetic and thermodynamic characteristics that facilitate translocation. Application of Nzz exchange spectroscopy revealed a global, two-state folding equilibrium with 16% unfolded population, a folding rate of 1.8 s,1, and an unfolding rate of 0.33 s,1 at pH 6.1. TrAvrPto stability increases with increasing pH, with only 2% unfolded population observed at pH 7.0. The R1 relaxation of TrAvrPto, which is sensitive to both the global anisotropy of folded TrAvrPto and slow exchange between folded and unfolded conformations, provided independent verification of the global kinetic rate constants. Given the acidic apoplast in which the pathogen resides and the more basic host cytoplasm, these results offer an intriguing mechanism by which the pH dependence of stability and slow folding kinetics of AvrPto would allow efficient translocation of the unfolded form through the TTSS and refolding into its functional folded form once inside the host. [source] Genetic Diversity of Parasitic Dinoflagellates in the Genus Amoebophrya and Its Relationship to Parasite Biology and BiogeographyTHE JOURNAL OF EUKARYOTIC MICROBIOLOGY, Issue 1 2008SUNJU KIM ABSTRACT. We determined 18S rRNA gene sequences of Amoebophrya strains infecting the thecate dinoflagellates Alexandrium affine and Gonyaulax polygramma from Korean coastal waters and compared those data with previously reported sequences of Amoebophrya from cultures, infected cells concentrated from field samples, and environmental 18S rRNA gene sequences obtained from a variety of marine environments. Further, we used these data to examine genetic diversity in Amoebophrya strains relative to geographic origin, host phylogeny, site of infection, and host specificity. In our analyses of known dinoflagellate taxa, the 13 available Amoebophrya sequences clustered together within the dinoflagellates as three groups forming a monophyletic group with high bootstrap support (maximum likelihood, ML: 100%) or a posterior probability (PP) of 1. When the Amoebophrya sequences were analyzed along with environmental sequences associated with Marine Alveolate Group II, nine subgroups formed a monophyletic group with high bootstrap support (ML: 100%) and PP of 1. Sequences known to be from Amoebophrya spp. infecting dinoflagellate hosts were distributed in seven of those subgroups. Despite differences in host species and geographic origin (Korea, United States, and Europe), Amoebophrya strains (Group II) from Gymnodinium instriatum, A. affine, Ceratium tripos (AY208892), Prorocentrum micans, and Ceratium lineatum grouped together by all of our tree construction methods, even after adding the environmental sequences. By contrast, strains within Groups I and III divided into several lineages following inclusion of environmental sequences. While Amoebophrya strains within Group II mostly developed within the host cytoplasm, strains in Groups I and III formed infections inside the host nucleus, a trait that appeared across several of the subgroups. Host specificity varied from moderately to extremely species-specific within groups, including Group II. Taken together, our results imply that genetic diversity in Amoebophrya strains does not always reflect parasite biology or biogeography. [source] Microreview: Type IV secretion in the obligatory intracellular bacterium Anaplasma phagocytophilumCELLULAR MICROBIOLOGY, Issue 9 2010Yasuko Rikihisa Summary Anaplasma phagocytophilum is an obligatory intracellular bacterium that infects neutrophils, the primary host defence cells. Consequent effects of infection on host cells result in a potentially fatal systemic disease called human granulocytic anaplasmosis. Despite ongoing reductive genome evolution and deletion of most genes for intermediary metabolism and amino acid biosynthesis, Anaplasma has also experienced expansion of genes encoding several components of the type IV secretion (T4S) apparatus. Two A. phagocytophilum T4S effector molecules are currently known; Anaplasma translocated substrate 1 (Ats-1) and ankyrin repeat domain-containing protein A (AnkA) have C-terminal positively charged amino acid residues that are recognized by the T4S coupling protein, VirD4. AnkA and Ats-1 contain eukaryotic protein motifs and are uniquely evolved in the family Anaplasmataceae; Ats-1 contains a mitochondria-targeting signal. They are abundantly produced and secreted into the host cytoplasm, are not toxic to host cells, and manipulate host cell processes to aid in the infection process. At the cellular level, the two effectors have distinct subcellular localization and signalling in host cells. Thus in this obligatory intracellular pathogen, the T4S system has evolved as a host-subversive survival factor. [source] | ||||||||||