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Bhatnagar A, Burman N, Sharma E, Tyagi A, Khurana P, Khurana JP. Two splice forms of OsbZIP1, a homolog of AtHY5, function to regulate skotomorphogenesis and photomorphogenesis in rice. Plant Physiol 2023; 193:426-447. [PMID: 37300540 DOI: 10.1093/plphys/kiad334] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/24/2023] [Revised: 04/24/2023] [Accepted: 05/05/2023] [Indexed: 06/12/2023]
Abstract
Plants possess well-developed light sensing mechanisms and signal transduction systems for regulating photomorphogenesis. ELONGATED HYPOCOTYL5 (HY5), a basic leucine zipper (bZIP) transcription factor, has been extensively characterized in dicots. In this study, we show that OsbZIP1 is a functional homolog of Arabidopsis (Arabidopsis thaliana) HY5 (AtHY5) and is important for light-mediated regulation of seedling and mature plant development in rice (Oryza sativa). Ectopic expression of OsbZIP1 in rice reduced plant height and leaf length without affecting plant fertility, which contrasts with OsbZIP48, a previously characterized HY5 homolog. OsbZIP1 is alternatively spliced, and the OsbZIP1.2 isoform lacking the CONSTITUTIVELY PHOTOMORPHOGENIC1 (COP1)-binding domain regulated seedling development in the dark. Rice seedlings overexpressing OsbZIP1 were shorter than the vector control under white and monochromatic light conditions, whereas RNAi knockdown seedlings displayed the opposite phenotype. While OsbZIP1.1 was light-regulated, OsbZIP1.2 showed a similar expression profile in both light and dark conditions. Due to its interaction with OsCOP1, OsbZIP1.1 undergoes 26S proteasome-mediated degradation under dark conditions. Also, OsbZIP1.1 interacted with and was phosphorylated by CASEIN KINASE2 (OsCK2α3). In contrast, OsbZIP1.2 did not show any interaction with OsCOP1 or OsCK2α3. We propose that OsbZIP1.1 likely regulates seedling development in the light, while OsbZIP1.2 is the dominant player under dark conditions. The data presented in this study reveal that AtHY5 homologs in rice have undergone neofunctionalization, and alternative splicing of OsbZIP1 has increased the repertoire of its functions.
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Affiliation(s)
- Akanksha Bhatnagar
- Interdisciplinary Centre for Plant Genomics & Department of Plant Molecular Biology, University of Delhi South Campus, New Delhi 110021, India
| | - Naini Burman
- Interdisciplinary Centre for Plant Genomics & Department of Plant Molecular Biology, University of Delhi South Campus, New Delhi 110021, India
- Regional Centre for Biotechnology, Faridabad, Haryana 121001, India
| | - Eshan Sharma
- Interdisciplinary Centre for Plant Genomics & Department of Plant Molecular Biology, University of Delhi South Campus, New Delhi 110021, India
| | - Akhilesh Tyagi
- Interdisciplinary Centre for Plant Genomics & Department of Plant Molecular Biology, University of Delhi South Campus, New Delhi 110021, India
| | - Paramjit Khurana
- Interdisciplinary Centre for Plant Genomics & Department of Plant Molecular Biology, University of Delhi South Campus, New Delhi 110021, India
| | - Jitendra P Khurana
- Interdisciplinary Centre for Plant Genomics & Department of Plant Molecular Biology, University of Delhi South Campus, New Delhi 110021, India
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Sharma P, Mishra S, Burman N, Chatterjee M, Singh S, Pradhan AK, Khurana P, Khurana JP. Characterization of Cry2 genes (CRY2a and CRY2b) of B. napus and comparative analysis of BnCRY1 and BnCRY2a in regulating seedling photomorphogenesis. Plant Mol Biol 2022; 110:161-186. [PMID: 35831732 DOI: 10.1007/s11103-022-01293-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/21/2022] [Accepted: 06/02/2022] [Indexed: 06/15/2023]
Abstract
Cryptochrome 2 (CRY2) perceives blue/UV-A light and regulates photomorphogenesis in plants. However, besides Arabidopsis, CRY2 has been functionally characterized only in native species of japonica rice and tomato. In the present study, the BnCRY2a, generating a relatively longer cDNA and harboring an intron in its 5'UTR, has been characterized in detail. Western blot analysis revealed that BnCRY2a is light labile and degraded rapidly by 26S proteasome when seedlings are irradiated with blue light. For functional analysis, BnCRY2a was over-expressed in Brassica juncea, a related species more amenable to transformation. The BnCRY2a over-expression (BnCRY2aOE) transgenics developed short hypocotyl and expanded cotyledons, accumulated more anthocyanin in light-grown seedlings, and displayed early flowering on maturity. Early flowering in BnCRY2aOE transgenics was coupled with the up-regulation of many flowering-related genes such as FT. The present study also highlights the differential light sensitivity of cry1 and cry2 in controlling hypocotyl elongation growth in Brassica. BnCRY2aOE seedlings developed much shorter hypocotyl under the low-intensity of blue light, while BnCRY1OE seedling hypocotyls were shorter under the high-intensity blue light, compared to untransformed seedlings.
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Affiliation(s)
- Pooja Sharma
- Department of Plant Molecular Biology & Interdisciplinary Centre for Plant Genomics, University of Delhi South Campus, New Delhi, 110021, India
- Proteus Genomics, 218 Summit Parkway, Birmingham, AL, 35209, USA
| | - Sushma Mishra
- Department of Plant Molecular Biology & Interdisciplinary Centre for Plant Genomics, University of Delhi South Campus, New Delhi, 110021, India
| | - Naini Burman
- Department of Plant Molecular Biology & Interdisciplinary Centre for Plant Genomics, University of Delhi South Campus, New Delhi, 110021, India
| | - Mithu Chatterjee
- Department of Plant Molecular Biology & Interdisciplinary Centre for Plant Genomics, University of Delhi South Campus, New Delhi, 110021, India
- AeroFarms, Newark, NJ, 07105, USA
| | - Shipra Singh
- Department of Plant Molecular Biology & Interdisciplinary Centre for Plant Genomics, University of Delhi South Campus, New Delhi, 110021, India
| | - Akshay K Pradhan
- Department of Genetics, University of Delhi South Campus, New Delhi, 110021, India
| | - Paramjit Khurana
- Department of Plant Molecular Biology & Interdisciplinary Centre for Plant Genomics, University of Delhi South Campus, New Delhi, 110021, India.
| | - Jitendra P Khurana
- Department of Plant Molecular Biology & Interdisciplinary Centre for Plant Genomics, University of Delhi South Campus, New Delhi, 110021, India
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Burman N, Chandran D, Khurana JP. A Rapid and Highly Efficient Method for Transient Gene Expression in Rice Plants. Front Plant Sci 2020; 11:584011. [PMID: 33178250 PMCID: PMC7593772 DOI: 10.3389/fpls.2020.584011] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/16/2020] [Accepted: 09/22/2020] [Indexed: 05/29/2023]
Abstract
Rice is the model plant system for monocots and the sequencing of its genome has led to the identification of a vast array of genes for characterization. The tedious and time-consuming effort of raising rice transgenics has significantly delayed the pace of rice research. The lack of highly efficient transient assay protocol for rice has only added to the woes which could have otherwise helped in rapid deciphering of the functions of genes. Here, we describe a technique for efficient transient gene expression in rice seedlings. It makes use of co-cultivation of 6-day-old rice seedlings with Agrobacterium in the presence of a medium containing Silwet® L-77, acetosyringone and glucose. Seedlings can be visualized 9 days after co-cultivation for transient expression. The use of young seedlings helps in significantly reducing the duration of the experiment and facilitates the visualization of rice cells under the microscope as young leaves are thinner than mature rice leaves. Further, growth of seedlings at low temperature, and the use of surfactant along with wounding and vacuum infiltration steps significantly increases the efficiency of this protocol and helps in bypassing the natural barriers in rice leaves, which hinders Agrobacterium-based transformation in this plant. This technique, therefore, provides a shorter, efficient and cost-effective way to study transient gene function in intact rice seedling without the need for a specialized device like particle gun.
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Affiliation(s)
- Naini Burman
- Regional Centre for Biotechnology, Faridabad, India
| | | | - Jitendra P. Khurana
- Department of Plant Molecular Biology, University of Delhi, New Delhi, India
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Burman N, Bhatnagar A, Khurana JP. OsbZIP48, a HY5 Transcription Factor Ortholog, Exerts Pleiotropic Effects in Light-Regulated Development. Plant Physiol 2018; 176:1262-1285. [PMID: 28775143 PMCID: PMC5813549 DOI: 10.1104/pp.17.00478] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/06/2017] [Accepted: 07/27/2017] [Indexed: 05/04/2023]
Abstract
Plants have evolved an intricate network of sensory photoreceptors and signaling components to regulate their development. Among the light signaling components identified to date, HY5, a basic leucine zipper (bZIP) transcription factor, has been investigated extensively. However, most of the work on HY5 has been carried out in Arabidopsis (Arabidopsis thaliana), a dicot. In this study, based on homology search and phylogenetic analysis, we identified three homologs of AtHY5 in monocots; however, AtHYH (HY5 homolog) homologs are absent in the monocots analyzed. Out of the three homologs identified in rice (Oryza sativa), we have functionally characterized OsbZIP48OsbZIP48 was able to complement the Athy5 mutant. OsbZIP48 protein levels are developmentally regulated in rice. Moreover, the OsbZIP48 protein does not degrade in dark-grown rice and Athy5 seedlings complemented with OsbZIP48, which is in striking contrast to AtHY5. In comparison with AtHY5, which does not cause any change in hypocotyl length when overexpressed in Arabidopsis, the overexpression of full-length OsbZIP48 in rice transgenics reduced the plant height considerably. Microarray analysis revealed that OsKO2, which encodes ent-kaurene oxidase 2 of the gibberellin biosynthesis pathway, is down-regulated in OsbZIP48OE and up-regulated in OsbZIP48KD transgenics as compared with the wild type. Electrophoretic mobility shift assay showed that OsbZIP48 binds directly to the OsKO2 promoter. The RNA interference lines and the T-DNA insertional mutant of OsbZIP48 showed seedling-lethal phenotypes despite the fact that roots were more proliferative during early stages of development in the T-DNA insertional mutant. These data provide credible evidence that OsbZIP48 performs more diverse functions in a monocot system like rice in comparison with its Arabidopsis ortholog, HY5.
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Affiliation(s)
- Naini Burman
- Interdisciplinary Centre for Plant Genomics and Department of Plant Molecular Biology, University of Delhi, South Campus, New Delhi-110021, India
| | - Akanksha Bhatnagar
- Interdisciplinary Centre for Plant Genomics and Department of Plant Molecular Biology, University of Delhi, South Campus, New Delhi-110021, India
| | - Jitendra P Khurana
- Interdisciplinary Centre for Plant Genomics and Department of Plant Molecular Biology, University of Delhi, South Campus, New Delhi-110021, India
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Sharma P, Chatterjee M, Burman N, Khurana JP. Cryptochrome 1 regulates growth and development in Brassica through alteration in the expression of genes involved in light, phytohormone and stress signalling. Plant Cell Environ 2014; 37:961-77. [PMID: 24117455 DOI: 10.1111/pce.12212] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/27/2012] [Accepted: 10/01/2013] [Indexed: 05/19/2023]
Abstract
The blue light photoreceptors cryptochromes are ubiquitous in higher plants and are vital for regulating plant growth and development. In spite of being involved in controlling agronomically important traits like plant height and flowering time, cryptochromes have not been extensively characterized from agriculturally important crops. Here we show that overexpression of CRY1 from Brassica napus (BnCRY1), an oilseed crop, results in short-statured Brassica transgenics, likely to be less prone to wind and water lodging. The overexpression of BnCRY1 accentuates the inhibition of cell elongation in hypocotyls of transgenic seedlings. The analysis of hypocotyl growth inhibition and anthocyanin accumulation responses in BnCRY1 overexpressors substantiates that regulation of seedling photomorphogenesis by cry1 is dependent on light intensity. This study highlights that the photoactivated cry1 acts through coordinated induction and suppression of specific downstream genes involved in phytohormone synthesis or signalling, and those involved in cell wall modification, during de-etiolation of Brassica seedlings. The microarray-based transcriptome profiling also suggests that the overexpression of BnCRY1 alters abiotic/biotic stress signalling pathways; the transgenic seedlings were apparently oversensitive to abscisic acid (ABA) and mannitol.
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Affiliation(s)
- Pooja Sharma
- Interdisciplinary Centre for Plant Genomics and Department of Plant Molecular Biology, University of Delhi South Campus, New Delhi, 110021, India
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Shamaei-Tousi A, Martin P, Bergh A, Burman N, Brännström T, Bergström S. Erythrocyte-aggregating relapsing fever spirochete Borrelia crocidurae induces formation of microemboli. J Infect Dis 1999; 180:1929-38. [PMID: 10558950 DOI: 10.1086/315118] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Abstract
The African relapsing fever spirochete Borrelia crocidurae forms aggregates with erythrocytes, resulting in a delayed immune response. Mice were infected with B. crocidurae and monitored during 50 days after infection. Spirochetes were observed extravascularly at day 2 after infection. Two days later, inflammatory responses, cell death, and tissue damage were evident. The pathologic responses in lungs and kidneys were similar, whereas the symptoms in the brains were delayed, with a less pronounced inflammatory response. Microemboli were found in the blood vessels, possibly a result of the erythrocyte aggregation. The B. crocidurae invasion emerged more rapidly than has been described for Lyme disease-causing Borrelia species. In addition to erythrocyte rosetting, the presence of extravascular B. crocidurae indicates a novel route for these bacteria to propagate and cause damage in the mammalian host. The histopathologic findings in this study may explain the clinical manifestations of human relapsing fever.
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Abstract
A number of mechanisms have been described by which African trypanosomes undergo the genetic switches that differentially activate their variant surface glycoprotein genes (VSGs) and bring about antigenic variation. These mechanisms have been observed mainly in trypanosome lines adapted, by rapid syringe passaging, to laboratory conditions. Such "monomorphic" lines, which routinely yield only the proliferative bloodstream form and do not develop through their life cycle, have VSG switch rates up to 4 or 5 orders of magnitude lower than those of nonadapted lines. We have proposed that nonadapted, or pleomorphic, trypanosomes normally have an active VSG switch mechanism, involving gene duplication, that is depressed, or from which a component is absent, in monomorphic lines. We have characterized 88 trypanosome clones from the first two relapse peaks of a single rabbit infection with pleomorphic trypanosomes and shown that they represent 11 different variable antigen types (VATs). The pattern of appearance in the first relapse peak was generally reproducible in three more rabbit infections. Nine of these VATs had activated VSGs by gene duplication, the tenth possibly also had done so, and only one had activated a VSG by the transcriptional switch mechanism that predominates in monomorphic lines. At least 10 of the donor genes have telomeric silent copies, and many reside on minichromosomes. It appears that trypanosome antigenic variation is dominated by one, relatively highly active, mechanism rather than by the plethora of pathways described before.
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Affiliation(s)
- N P Robinson
- Wellcome Centre for Molecular Parasitology, University of Glasgow, Anderson College, Glasgow G11 6NU, Scotland
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Abstract
Several species of the genus Borrelia exhibit antigenic variation of variable major proteins on their surface during relapsing fever. We have investigated the African relapsing fever species Borrelia crocidurae during infections in mice and compared it with the thoroughly studied North American species Borrelia hermsii. A major difference between the two species is that B. crocidurae can bind and become completely covered with erythrocytes. In addition, B. crocidurae causes a prolonged spirochetemia which coincides with a delayed appearance of antiborrelial antibodies. We show that the antibody response against an unrelated antigen is not delayed and that antibiotic treatment, which dissociates rosettes and inhibits the spirochetes, also leads to an early antibody response. Taken together, the erythrocyte aggregation and prolonged spirochetemia hint at a new mode of immune evasion where erythrocyte-covered spirochetes may avoid contact with the phagocytic cells and B cells of the immune system, thereby delaying the onset of a specific immune response.
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Affiliation(s)
- N Burman
- Department of Microbiology, Umeå University, Sweden
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Noppa L, Burman N, Sadziene A, Barbour AG, Bergström S. Expression of the flagellin gene in Borrelia is controlled by an alternative sigma factor. Microbiology (Reading) 1995; 141 ( Pt 1):85-93. [PMID: 7894724 DOI: 10.1099/00221287-141-1-85] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The flagellin genes from six Borrelia species were cloned, sequenced and characterized at the molecular level. The flagellin genes of two relapsing fever Borrelia species, B. hermsii and B. crocidurae, three Lyme disease genomic species, B. burgdorferi, B. afzelii and B. garinii, and the avian borreliosis agent, B. anserina, were compared and showed an 85-93% sequence identity to each other. Comparison of the fla genes from the different Lyme borreliosis spirochaetes revealed that they were 94-99% identical. Nucleotide sequencing of the fla gene and primer extension on isolated mRNA from both B. hermsii (as transcribed in Escherichia coli) and B. burgdorferi (as transcribed in the natural host) identified the putative transcriptional start points, the ribosomebinding sites and the promoter regions of these genes. The deduced promoter of the Borrelia flagellin gene resembled neither the sigma 70 promoter of prokaryotes, as seen for the genes for the outer-surface proteins A and B in Lyme disease Borrelia and the genes for the variable major proteins 7 and 21 of B. hermsii, nor the sigma 28 consensus promoter region of motility genes from other bacteria. Instead, the promoter of the fla gene in Borrelia has most similarity to the bacteriophage SP01 sigma gp33-34 promoter sequence of Bacillus subtilis.
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Affiliation(s)
- L Noppa
- Department of Microbiology, Umeå University, Sweden
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Wilske B, Barbour AG, Bergström S, Burman N, Restrepo BI, Rosa PA, Schwan T, Soutschek E, Wallich R. Antigenic variation and strain heterogeneity in Borrelia spp. Res Microbiol 1992; 143:583-96. [PMID: 1475519 DOI: 10.1016/0923-2508(92)90116-6] [Citation(s) in RCA: 78] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Antigenic variation and strain heterogeneity have been demonstrated for the pathogenic Borrelia species, i.e. B. burgdorferi and the relapsing fever borreliae. In relapsing fever, new borrelia serotypes emerge at a high rate spontaneously, a mechanism that is caused by DNA rearrangements on linear plasmid translocating genes coding for variable major proteins from previous silent to expression sites (i.e. from inner sites to telomeric sites of the plasmid). As a result of this variation, the borreliae escape the immune response of the host, thus leading to the relapse phenomenon. In B. burgdorferi, which is the causative agent of the multisystem disorder Lyme borreliosis, there is also a growing body of findings that antigenic variation is involved in pathogenesis of the disease. Phenotypic variation of strains in vitro concerns the size and the amount of surface-associated proteins (OspA, OspB and pC). There are indications that OspA and OspB truncations are due to deletions within the ospAB operon caused by recombination events, and that OspA/OspB-less mutants lack the 49-kb plasmid that bears the ospAB operon. With the increasing number of isolates obtained from various geographic and biological sources, it became apparent that B. burgdorferi is immunologically and genetically more heterogeneous, as previously believed. The major outer surface proteins OspA and OspB (which have been efficient antigens in vaccine studies) are heterogeneous at a genetic level. The same degree of genetic non-identity was observed for the pC protein. Other proteins like flagellin and the highly specific immunodominant p100 range protein show a lower degree of non-identity. Recombinant OspA, pC, p100 range protein and flagellin have been hyperexpressed in E. coli and these proteins are immunologically reactive. This allows further research for development of vaccines and diagnostic tools. B. burgdorferi isolates have been investigated with genotyping (DNA hybridization, PCR and 16S rRNA analysis) as well as serotyping by various authors. Comparison of the different methods has shown good agreement when the same strains have been investigated. No correlation could be found between different phenotypic and genotypic groups with respect to the ability to cause arthritis in SCID mice. A serotyping system based on immunological differences in OspA detected by a panel of monoclonal antibodies has been proposed. Serotyping a large number of B. burgdorferi isolates has shown a striking predominance of the OspA serotype 2 among European isolates from human skin, in contrast to isolates from ticks or CSF.(ABSTRACT TRUNCATED AT 400 WORDS)
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Affiliation(s)
- B Wilske
- Max von Pettenkofer Institut für Hygiene and Medizinische Mikrobiologie, Universität München, Germany
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Bergström S, Olsén B, Burman N, Gothefors L, Jaenson TG, Jonsson M, Mejlon HA. Molecular characterization of Borrelia burgdorferi isolated from Ixodes ricinus in northern Sweden. Scand J Infect Dis 1992; 24:181-8. [PMID: 1641595 DOI: 10.3109/00365549209052610] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Ixodes ricinus ticks, harbouring Borrelia burgdorferi, were found in an area in northern Sweden, not thought to be endemic for Lyme borreliosis. This investigation took place at Norrbyskär, an island situated in the Bothnian Gulf, 63 degrees 33'N/19 degrees 52'E. One of 42 nymphal and 8/43 adult I. ricinus ticks collected carried spirochetes as seen by phase contrast microscopy. Pure bacterial cultures were obtained from 2 of the ticks. Western blot analysis using species-specific monoclonal antibodies showed that the isolated spirochetes were B. burgdorferi. The identity of the isolated spirochetes was confirmed by DNA amplification using B. burgdorferi OspA and flagellin gene specific oligonucleotides as well as partial DNA sequencing of the respective OspA and flagellin genes. The 2 isolated spirochaete populations were different as shown by their protein profiles in sodium dodecyl sulphate polyacrylamide gels. Moreover, the demonstration of Lyme borreliosis in a patient from the island of Norrbyskär indicates the need for clinical consideration of this disease in northern Sweden.
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Affiliation(s)
- S Bergström
- Department of Microbiology, University of Umeå, Sweden
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Barbour AG, Burman N, Carter CJ, Kitten T, Bergström S. Variable antigen genes of the relapsing fever agent Borrelia hermsii are activated by promoter addition. Mol Microbiol 1991; 5:489-93. [PMID: 2041480 DOI: 10.1111/j.1365-2958.1991.tb02132.x] [Citation(s) in RCA: 77] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Borrelia hermsii, an agent of relapsing fever, avoids the host's immune response by means of multiphasic antigenic variation. Serotype specificity is determined by variable antigens called the Vmp lipoproteins. Through recombination between linear plasmids a formerly silent vmp gene replaces another vmp gene at a telomeric expression locus. We examined strain HS1 borreliae before and after a switch from serotype 7 to serotype 21. The nucleotide sequences of 5' regions of silent and expressed vmp7 and vmp21 were determined. Silent and active vmp7 and vmp21 genes shared a block of homologous sequences surrounding their 5' ends. Sequences upstream of silent vmp7 and vmp21 genes lacked the promoter and substantially differed from each other. In this antigenic switch a vmp gene was activated by a recombination that placed it downstream of a promoter.
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Affiliation(s)
- A G Barbour
- Department of Microbiology, University of Texas Health Science Center, San Antonio 78284
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Burman N, Bergström S, Restrepo BI, Barbour AG. The variable antigens Vmp7 and Vmp21 of the relapsing fever bacterium Borrelia hermsii are structurally analogous to the VSG proteins of the African trypanosome. Mol Microbiol 1990; 4:1715-26. [PMID: 1706456 DOI: 10.1111/j.1365-2958.1990.tb00549.x] [Citation(s) in RCA: 56] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The relapsing fever agent Borrelia hermsii avoids the host's immune response by the strategy of multiphasic antigenic variation. A given Borrelia cell can express one of a number of alleles for polymorphic outer-membrane proteins, known as Vmp proteins. The genes for the variant-specific Vmp proteins of serotypes 7 and 21 of B. hermsii strain HS1 were sequenced. The genes, which were designated vmp7 and vmp21, were obtained from populations of borreliae before and after a switch in serotypes from 7 to 21. The analysis showed that vmp7 and vmp21 are 77% identical in terms of their coding sequence. The deduced translation products of vmp7 and vmp21 are polypeptides of 369 (37.2 kD) and 364 amino acids (37.1 kD), respectively. Vmp7 and Vmp21 have sequence features of prokaryotic lipoproteins and are processed as such during expression in E. coli. The secondary structure predictions of the Vmp proteins reveals analogous structures to the VSG proteins of the African trypanosome.
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Affiliation(s)
- N Burman
- Department of Microbiology, University of Umeå, Sweden
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Jaenson TG, Bergström S, Burman N, Chirico J, Jonsson M. [Spirochete infected ticks (Ixodes ricinus)--risks even in Norrland]. Lakartidningen 1989; 86:2584. [PMID: 2779322] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
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Burman N. Acute rhabdomyolysis. S Afr Med J 1988; 74:592. [PMID: 3194813] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
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Abstract
A patient with hemodialysis-related porphyria cutanea tarda was treated with plasma exchange. A rapid clinical response occurred coincidentally with a significant fall in the plasma porphyrin level. The level fell further over the following few months without additional therapeutic intervention, whereafter a slow rise occurred without recurrence of skin disease. We suggest that this form of treatment may be ideal for the patient with porphyria cutanea tarda and chronic renal failure in whom no alternative therapy is available for the cutaneous problem.
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