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1.
Systemic Induction of Salicylic Acid Accumulation in Cucumber after Inoculation with Pseudomonas syringae pv syringae 总被引:25,自引:1,他引:24
Inoculation of one true leaf of cucumber (Cucumis sativus L.) plants with Pseudomonas syringae pathovar syringae results in the systemic appearance of salicylic acid in the phloem exudates from petioles above, below, and at the site of inoculation. Analysis of phloem exudates from the petioles of leaves 1 and 2 demonstrated that the earliest increases in salicylic acid occurred 8 hours after inoculation of leaf 1 in leaf 1 and 12 hours after inoculation of leaf 1 in leaf 2. Detaching leaf 1 at intervals after inoculation demonstrated that leaf 1 must remain attached for only 4 hours after inoculation to result in the systemic accumulation of salicylic acid. Because the levels of salicylic acid in phloem exudates from leaf 1 did not increase to detectable levels until at least 8 hours after inoculation with P. s. pathovar syringae, the induction of increased levels of salicylic acid throughout the plant are presumably the result of another chemical signal generated from leaf 1 within 4 hours after inoculation. Injection of salicylic acid into tissues at concentrations found in the exudates induced resistance to disease and increased peroxidase activity. Our results support a role for salicylic acid as an endogenous inducer of resistance, but our data also suggest that salicylic acid is not the primary systemic signal of induced resistance in cucumber. 相似文献
2.
Genes associated with meningococcal capsule complex are also found in Neisseria gonorrhoeae. 总被引:1,自引:0,他引:1
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H Petering S Hammerschmidt M Frosch J P van Putten C A Ison B D Robertson 《Journal of bacteriology》1996,178(11):3342-3345
A homolog of the meningococcal cps locus region E has been identified in Neisseria gonorrhoeae immediately upstream of the gonococcal region D locus. Region E has no detectable function in capsule biosynthesis in Neisseria meningitidis or in lipopolysaccharide biosynthesis in either organism. The open reading frame is homologous to proteins of unknown function in Escherichia coli and Haemophilus influenzae. Further analysis of the N. meningitidis cps cluster has identified a second copy of region D encoding three additional open reading frames, including homologs of DNA methyltransferases. The organization of the region D and E genes in N. gonorrhoeae and N. meningitidis in relation to the cps genes provides some insight into the evolutionary origin of encapsulation in N. meningitidis. 相似文献
3.
Episomal and integrated copies of Epstein-Barr virus coexist in Burkitt lymphoma cell lines. 总被引:8,自引:5,他引:3
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H J Delecluse S Bartnizke W Hammerschmidt J Bullerdiek G W Bornkamm 《Journal of virology》1993,67(3):1292-1299
The Epstein-Barr virus genome is present in more than 95% of the African cases of Burkitt lymphoma. In this tumor, the viral genome is usually maintained in multiple episomal copies. Viral integration has been described only for Namalwa, a cell line lacking episomes. In this study, we have addressed the question of whether integrated and episomal copies can coexist in Burkitt lymphoma cells. Gel electrophoresis was used to demonstrate the presence of episomal as well as free linear DNA in three Burkitt lymphoma cell lines. The numbers of episomal copies per cell were estimated to be 5 to 10 in BL36 and BL137 cells and below 1 in BL60 cells, indicating that BL60 does not represent a homogeneous cell population. Fluorescence in situ hybridization was combined with chromosomal banding to study the association of the viral DNA with metaphase chromosomes. A symmetrical pattern of signals at both chromatids located at the same chromosomal sites in many if not all metaphases was taken as evidence for viral integration. In each of the three cell lines, one site of integration was identified: at chromosome 11p15 in BL36 cells, at chromosome 1p34 in BL137 cells, and at the site of a reciprocal t(11;19) translocation in BL60 cells. Integrated, episomal and linear copies of Epstein-Barr virus DNA thus coexist in Burkitt lymphoma cells. The biological significance of viral integration in Burkitt lymphoma cells remains to be elucidated. 相似文献
4.
Hannah Maus Gerald Hinze Stefan Josef Hammerschmidt Thomas Basché Tanja Schirmeister 《Protein science : a publication of the Protein Society》2023,32(1):e4526
Ligand binding to proteins often is accompanied by conformational transitions. Here, we describe a competition assay based on single molecule Förster resonance energy transfer (smFRET) to investigate the ligand-induced conformational changes of the dengue virus (DENV) NS2B-NS3 protease, which can adopt at least two different conformations. First, a competitive ligand was used to stabilize the closed conformation of the protease. Subsequent addition of the allosteric inhibitor reduced the fraction of the closed conformation and simultaneously increased the fraction of the open conformation, demonstrating that the allosteric inhibitor stabilizes the open conformation. In addition, the proportions of open and closed conformations at different concentrations of the allosteric inhibitor were used to determine its binding affinity to the protease. The KD value observed is in accordance with the IC50 determined in the fluorometric assay. Our novel approach appears to be a valuable tool to study conformational transitions of other proteases and enzymes. 相似文献
5.
Shau-Ting Chiu Lori H. Anton Frank W. Ewers Raymond Hammerschmidt Kurt S. Pregitzer 《American journal of botany》1992,79(2):149-154
Fertilized stands of Pseudotsuga menziesii were found to have glaucous needles. We investigated the morphological and quantitative characteristics of the epicuticular waxes of needles of fertilized and control trees. Glaucousness was caused by ornate tubular epicuticular wax. Dipping needles in chloroform, which dissolves waxes, eliminated the glaucous appearance. Based on cryostage scanning electron microscopic observations, the epicuticular waxes in the nonstomatal region were much more ornate on the needles of the fertilized trees (experimental needles) than in unfertilized trees (control needles). The stomatal region in both experimental and control needles showed similarly ornate waxes. Quantities of waxes were similar in experimental and control needles. The glaucousness was not the result of greater quantities of wax; rather, fertilization altered wax morphology in the nonstomatal regions. 相似文献
6.
P. Haffter Jörg Odenthal M. C. Mullins Shuo Lin Michael J. Farrell E. Vogelsang F. Haas M. Brand Fredericus J. M. van Eeden Makoto Furutani-Seiki Michael Granato M. Hammerschmidt Carl-Philipp Heisenberg Yun-Jin Jiang D. A. Kane R. N. Kelsh Nancy Hopkins Christiane Nüsslein-Volhard 《Development genes and evolution》1996,206(4):260-276
Mutations causing a visible phenotype in the adult serve as valuable visible genetic markers in multicellular genetic model
organisms such as Drosophila melanogaster, Caenorhabditis elegans and Arabidopsis thaliana. In a large scale screen for mutations affecting early development of the zebrafish, we identified a number of mutations
that are homozygous viable or semiviable. Here we describe viable mutations which produce visible phenotypes in the adult
fish. These predominantly affect the fins and pigmentation, but also the eyes and body length of the adult. A number of dominant
mutations caused visible phenotypes in the adult fish. Mutations in three genes, long fin, another long fin and wanda affected fin formation in the adult. Four mutations were found to cause a dominant reduction of the overall body length in
the adult. The adult pigment pattern was found to be changed by dominant mutations in wanda, asterix, obelix, leopard, salz and pfeffer. Among the recessive mutations producing visible phenotypes in the homozygous adult, a group of mutations that failed to
produce melanin was assayed for tyrosinase activity. Mutations in sandy produced embryos that failed to express tyrosinase activity. These are potentially useful for using tyrosinase as a marker
for the generation of transgenic lines of zebrafish.
Received: 17 June 1996 / Accepted: 15 July 1996 相似文献
7.
8.
Hypochlorous acid HOCl/OCl- and other oxidants derived from stimulated polymorphonuclear leukocytes are involved in tissue damage during a number of pathological processes. In order to obtain more detailed information on possible reactions of HOCl/OCl- the effects of both NaOCl and PMN-derived hypochlorous acid on functional groups of amino acid solutions and human plasma are studied. In valine and lysine solutions NaOCl diminishes the number of amino groups in a molar ratio of 1:1 between NaOCl and amino groups. In cysteine and methionine samples the decrease of amino groups starts only after all sulfhydryl or thioether groups are oxidized by NaOCl. If freshly prepared human plasma is treated with increasing amounts of NaOCl all plasma SH groups are oxidized first, then probably the thioether groups and only after this the amino groups are affected. Furthermore, it was found, that the reactivity of luminol against NaOCl is similar to that of amino groups. Increasing amounts of SH groups of components of human plasma are oxidized by incubation with PMA-stimulated polymorphonuclear leukocytes dependent on the incubation time. Plasma amino groups are not affected under the same experimental conditions. The addition of plasma to FMLP-stimulated PMN in the presence of luminol decreases that part of chemiluminescence caused by extracellularly generated hypochlorous acid. Plasma samples pretreated with NaOCl cause a lower inhibition of light generation in FMLP-stimulated PMN only when more than 4.10(-8) mol NaOCl per mg protein are used to pretreat plasma. It is assumed that in the development of tissue injuries caused by infiltrated PMN the following sequence of damage occurs in accessible tissue regions. First, the sulfhydryl groups are oxidized, then the thioether groups, and only after this amino and other target groups are affected. 相似文献
9.
10.
Alfredo Seiiti Urashima Tatiane de Fátima Mistura Lis Natali Rodrigues Porto Paige Dariel Austin Renee Silvia Arias 《Journal of Phytopathology》2020,168(10):581-590
The use of resistant genotypes is the preferred method to control orange rust of sugarcane (Saccharum spp) caused by Puccinia kuehnii. This approach has been adopted in Brazil but outbreaks of the disease on previously resistant varieties showed that the efficacy of this method is limited and requires a better understanding of pathogen diversity. Nevertheless, adequate molecular markers for examining pathogen diversity at population level are not available, which limits the success of orange rust control by genetic resistance. Therefore, two independent investigations were conducted to examine genetic diversity of P. kuehnii from São Paulo state, the most important sugarcane growing state of Brazil. First, simple-sequence repeat (SSR) markers were developed in the present work and genotypic diversity of orange rust isolates from different locations investigated. Second, phenotypic diversity was examined by the single-pustule inoculation technique on P. kuehnii isolates retrieved from three susceptible commercial sugarcane cultivars. A total of 96 SSR markers were generated and tested for this species. Subsequently, 29 isolates of P. kuehnii were fingerprinted with nine SSR markers to estimate the genotypic diversity by neighbour-joining and 3D principal coordinates. The 29 isolates of the pathogen clustered into four main groups, which were identified by three SSR markers (NPRL_PK_108a, NPRL_PK_162_spka and NPRL_PK_221_spka). Phenotypic data at 21 days after the single-pustule inoculation showed that P. kuehnii from highly susceptible commercial cultivars harboured a small proportion of variants capable of causing disease on resistant cultivars. A differential reaction was demonstrated for the most virulent variant in a repeated experiment confirming the existence of races within P. kuehnii in Brazil. 相似文献