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71.
Veronika Deák Rita Lukács Zsuzsanna Buzás Adrienn Pálv?lgyi Péter P. Papp László Orosz Péter Putnoky 《Journal of bacteriology》2010,192(6):1617-1623
Genes encoding the tail proteins of the temperate phage 16-3 of the symbiotic nitrogen-fixing bacterium Sinorhizobium meliloti 41 have been identified. First, a new host range gene, designated hII, was localized by using missense mutations. The corresponding protein was shown to be identical to the 85-kDa tail protein by determining its N-terminal sequence. Electron microscopic analysis showed that phage 16-3 possesses an icosahedral head and a long, noncontractile tail characteristic of the Siphoviridae. By using a lysogenic S. meliloti 41 strain, mutants with insertions in the putative tail region of the genome were constructed and virion morphology was examined after induction of the lytic cycle. Insertions in ORF017, ORF018a, ORF020, ORF021, the previously described h gene, and hII resulted in uninfectious head particles lacking tail structures, suggesting that the majority of the genes in this region are essential for tail formation. By using different bacterial mutants, it was also shown that not only the RkpM and RkpY proteins but also the RkpZ protein of the host takes part in the formation of the phage receptor. Results for the host range phage mutants and the receptor mutant bacteria suggest that the HII tail protein interacts with the capsular polysaccharide of the host and that the tail protein encoded by the original h gene recognizes a proteinaceous receptor.The Sinorhizobium meliloti-Medicago symbiosis is an important model for endosymbiotic nitrogen fixation. The genome sequence of S. meliloti (strain 1021) has been established (14), and the Medicago truncatula genome is under intensive investigation (3). Phage 16-3 is a temperate, double-stranded DNA phage of S. meliloti strain 41. It is by far the best-studied rhizobiophage and serves as a tool in analyses of rhizobium genetics, in the isolation of some symbiotic mutants, and in the construction of special vectors. Genetic determinants and molecular mechanisms of many aspects of the 16-3 life cycle, such as phage integration and excision (8, 26, 38), regulation of the lytic/lysogenic switch (5, 6, 9, 24, 28), immunity to superinfection (4), phage DNA packaging (15), and the role of gene h in the host range (32), have been examined in detail. Moreover, the complete 60-kb phage genome sequence (accession no. ) has been determined recently (P. P. Papp et al., unpublished results). However, little is known about the genes and structural elements involved in the interaction between the phage and its host, and furthermore, only one study of the 16-3 virion proteins has been reported ( DQ50011811).The initial interaction between a tailed phage and its bacterial host cell is mediated by the distal part of the phage tail, which specifically binds to the phage receptor located on the host surface. Earlier results demonstrated that phage 16-3 adsorption is connected to the strain-specific capsular polysaccharide of S. meliloti 41, the KR5 antigen. So far, three bacterial gene clusters involved in KR5 antigen production, including the rkp-1, rkp-2, and rkp-3 regions, have been described. rkp mutants are defective in the invasion of the host plant for symbiosis. In addition, they cannot adsorb phage 16-3, suggesting that the KR5 antigen is required for both functions (19, 20, 30).In order to elucidate the molecular mechanism of phage 16-3 and S. meliloti 41 recognition, bacterial mutants carrying an altered phage receptor and host range phage mutants able to overcome the adsorption block have been characterized previously (32). It was shown that the RkpM protein, together with other yet uncharacterized elements, is a component of the phage receptor. With the use of rkpM mutants, host range mutations in phage gene h, which probably encodes the tail fiber protein, were identified. Interestingly, some mutations influencing phage-host recognition could not be localized in the rkpM and h genes, indicating that on both sides, additional components are important for bacteriophage-host recognition.The aim of this study was to identify additional genetic determinants involved in S. meliloti 41 and phage 16-3 recognition by characterizing new host range and receptor mutants. Furthermore, by using insertional mutagenesis, we examined a region of the phage chromosome supposed to be responsible for tail formation and identified six new genes essential for phage assembly. 相似文献
72.
73.
Artificial formation of flash-photoactive oligomeric protochlorophyllide complexes was found in etiolated pea (Pisum sativum L. cv. Zsuzsi) epicotyl homogenates containing glycerol (40% v/v) and sucrose (40% m/v). The 77 K fluorescence emission spectra indicated that the ratio of the 644 and 655 nm emitting forms to the 636 nm form increased during 3 to 5-day incubation in the dark at -14 degrees C. Electron micrographs showed the presence of well-organized prolamellar bodies in the homogenates. The same phenomena were found when the homogenates were frozen into liquid nitrogen and thawed to room temperature in several cycles. Similar treatments of intact epicotyl pieces caused significant membrane destructions. In homogenates, the in vitro produced 644 and 655 nm emitting protochlorophyllide forms were flash-photoactive; the extent of phototransformation increased compared to that in native epicotyls. The newly appeared 692 nm chlorophyllide band showed a blue shift (similar to the Shibata shift in leaves), however this process took place only partially due to the effect of the isolation medium. These results prove that the in vitro accumulated 644 and 655 nm protochlorophyllide forms were produced from the flash-photoactive 636 nm emitting monomeric NADPH:protochlorophyllide oxidoreductase units via aggregation, in connection with structure stabilization properties of glycerol and sucrose. 相似文献
74.
Agonist stimulation of G protein-coupled receptors causes receptor activation, phosphorylation, beta-arrestin binding and receptor internalization. Angiotensin II (AngII) causes rapid internalization of the AT1 receptors, whereas AngII-bound AT2 receptors do not internalize. Although the activation of the rat AT1A receptor with AngII causes translocation of beta-arrestin2 to the receptor, no association of this molecule with the AT2 receptor can be detected after AngII treatment with confocal microscopy or bioluminescence resonance energy transfer. These data demonstrate that the two subtypes of angiotensin receptors have different mechanisms of regulation. 相似文献
75.
Production of Trichoderma strains with pesticide-polyresistance by mutagenesis and protoplast fusion 总被引:1,自引:0,他引:1
Hatvani L Manczinger L Kredics L Szekeres A Antal Z Vágvölgyi C 《Antonie van Leeuwenhoek》2006,89(3-4):387-393
The sensitivity of two cold-tolerant Trichoderma strains belonging to the species T. harzianum and T.␣atroviride was determined to a series of pesticides widely used in agriculture. From the 16 pesticides tested, seven fungicides: copper sulfate, carbendazim, mancozeb, tebuconazole, imazalil, captan and thiram inhibited colony growth of the test strains significantly with minimal inhibitory concentrations of 300, 0.4, 50, 100, 100, 100 and 50 g/ml, respectively. Mutants resistant to carbendazim and tebuconazole were produced from both wild type strains by means of UV-mutagenesis. The cross-resistance capabilities and in␣vitro antagonistic properties of the mutants were determined. Carbendazim-resistant mutants showed total cross-resistance to benomyl and thiabendazole at a concentration of 20 g/ml. Intraspecific protoplast fusion was carried out between carbendazim- and tebuconazole-resistant mutants of both parental strains, and putative haploid recombinants with stable resistance to both pesticides were produced in the case of T.␣atroviride. These pesticide-polyresistant progenies are potential candidates for application in an integrated pest management system.This work was presented as an oral lecture in section ‘Agriculture, Soil, Forest Microbiology’ at the BioMicroWorld2005 conference. 相似文献
76.
In autoimmune (type 1) diabetes, autoreactive lymphocytes destroy pancreatic β-cells responsible for insulin synthesis. To
assess the feasibility of gene therapy for type 1 diabetes, recombinant vaccinia virus (rVV) vectors were constructed expressing
pancreatic islet autoantigens proinsulin (INS) and a 55-kDa immunogenic peptide from glutamic acid decarboxylase (GAD), and
the immunomodulatory cytokine interleukin (IL)-10. To augment the beneficial effects of recombinant virus therapy, the INS
and GAD genes were fused to the C terminus of the cholera toxin B subunit (CTB). Five-week-old non-obese diabetic (NOD) mice
were injected once with rVV. Humoral antibody immune responses and hyperglycemia in the infected mice were analyzed.
Only 20% of the mice inoculated with rVV expressing the CTB::INS fusion protein developed hyperglycemia, in comparison to
70% of the mice in the uninoculated animal group. Islets from pancreatic tissues isolated from euglycemic mice from this animal
group showed no sign of inflammatory lymphocyte invasion. Inoculation with rVV producing CTB::GAD or IL-10 was somewhat less
effective in reducing diabetes. Humoral antibody isotypes of hyperglycemic and euglycemic mice from all treated groups possessed
similar IgG1/IgG2c antibody titer ratios from 19 to 32 wk after virus inoculation. In comparison with uninoculated mice, 11-wk-old
NOD mice injected with virus expressing CTB::INS were delayed in diabetes onset by more than 4 wk. The experimental results
demonstrate the feasibility of using rVV expressing CTB::INS fusion protein to generate significant protection and therapy
against type 1 diabetes onset and progression. 相似文献
77.
The airborne dispersal of the anamorphs of the Gibberella fujikuroi species complex was studied under pre- and postharvest maize (corn) production conditions using a 3-stage Andersen sampler.
The aim of this study was to identify and analyse the size distribution of such species in air samples. Differences were observed
between the concentration of large- and small-sized propagules (identified as aggregates and single microconidia, respectively),
but the difference was only significant during a high concentration period (October 2007, P = 0.009). No correlation was found between the concentration of fusaria found at different sampling heights (10 and 150 cm
above ground level). Fusarium isolates were collected and identified based on morphological characters and using species-specific PCR assays. The PCR analysis
confirmed morphological identification of F. verticillioides, F. proliferatum and F. subglutinans. High concentrations were found during the maize harvest, loading and corn shelling. Our results showed that the monitoring
of F. verticillioides should be performed at a single sampling height. 相似文献
78.
Mukhopadhyay P Horváth B Zsengellér Z Zielonka J Tanchian G Holovac E Kechrid M Patel V Stillman IE Parikh SM Joseph J Kalyanaraman B Pacher P 《Free radical biology & medicine》2012,52(2):497-506
Cisplatin is a widely used antineoplastic agent; however, its major limitation is the development of dose-dependent nephrotoxicity whose precise mechanisms are poorly understood. Here we show not only that mitochondrial dysfunction is a feature of cisplatin nephrotoxicity, but also that targeted delivery of superoxide dismutase mimetics to mitochondria largely prevents the renal effects of cisplatin. Cisplatin induced renal oxidative stress, deterioration of mitochondrial structure and function, an intense inflammatory response, histopathological injury, and renal dysfunction. A single systemic dose of mitochondrially targeted antioxidants, MitoQ or Mito-CP, dose-dependently prevented cisplatin-induced renal dysfunction. Mito-CP also prevented mitochondrial injury and dysfunction, renal inflammation, and tubular injury and apoptosis. Despite being broadly renoprotective against cisplatin, Mito-CP did not diminish cisplatin's antineoplastic effect in a human bladder cancer cell line. Our results highlight the central role of mitochondrially generated oxidants in the pathogenesis of cisplatin nephrotoxicity. Because similar compounds seem to be safe in humans, mitochondrially targeted antioxidants may represent a novel therapeutic approach against cisplatin nephrotoxicity. 相似文献
79.
Mukhopadhyay P Horváth B Zsengellėr Z Bátkai S Cao Z Kechrid M Holovac E Erdėlyi K Tanchian G Liaudet L Stillman IE Joseph J Kalyanaraman B Pacher P 《Free radical biology & medicine》2012,53(5):1123-1138
Mitochondrial reactive oxygen species generation has been implicated in the pathophysiology of ischemia-reperfusion (I/R) injury; however, its exact role and its spatial-temporal relationship with inflammation are elusive. Herein we explore the spatial-temporal relationship of oxidative/nitrative stress and inflammatory response during the course of hepatic I/R and the possible therapeutic potential of mitochondrial-targeted antioxidants, using a mouse model of segmental hepatic ischemia-reperfusion injury. Hepatic I/R was characterized by early (at 2h of reperfusion) mitochondrial injury, decreased complex I activity, increased oxidant generation in the liver or liver mitochondria, and profound hepatocellular injury/dysfunction with acute proinflammatory response (TNF-α, MIP-1α/CCL3, MIP-2/CXCL2) without inflammatory cell infiltration, followed by marked neutrophil infiltration and a more pronounced secondary wave of oxidative/nitrative stress in the liver (starting from 6h of reperfusion and peaking at 24h). Mitochondrially targeted antioxidants, MitoQ or Mito-CP, dose-dependently attenuated I/R-induced liver dysfunction, the early and delayed oxidative and nitrative stress response (HNE/carbonyl adducts, malondialdehyde, 8-OHdG, and 3-nitrotyrosine formation), and mitochondrial and histopathological injury/dysfunction, as well as delayed inflammatory cell infiltration and cell death. Mitochondrially generated oxidants play a central role in triggering the deleterious cascade of events associated with hepatic I/R, which may be targeted by novel antioxidants for therapeutic advantage. 相似文献