bluuebunny/crossref_metadata_2025_split huggingface dataset:
Differential regulation of the transcriptional repressor NRG1 accounts for altered host‐cell interactions in Candida albicans and Candida dubliniensis
Authors: Moran Gary P. , MacCallum Donna M. , Spiering Martin J. , Coleman David C. , Sullivan Derek J. 
Published: September 2007

Summary Candida dubliniensis is genetically closely related to Candida albicans, but causes fewer infections in humans and exhibits reduced virulence and filamentation in animal models of infection. We investigated the role of the C. dubliniensis transcriptional repressor‐encoding gene CdNRG1 in regulating this phenotype. Deletion of both copies of CdNRG1 increased the formation of true hyphae by C. dubliniensis in response to serum, exogenous cAMP and CO2. In addition, deletion of CdNRG1 greatly enhanced filamentation and survival of C. dubliniensis in co‐culture with murine macrophages. In the reconstituted human oral epithelium infection model, the nrg1Δ mutant caused increased tissue damage relative to the wild‐type strain. However, deletion of CdNRG1 did not change the virulence of C. dubliniensis in the systemic mouse model of infection. The increased rate of hypha formation in C. albicans relative to C. dubliniensis in response to phagocytosis by macrophages and serum was associated with rapid downregulation of NRG1 expression in C. albicans. This study demonstrates that the reduced virulence and host cell damage elicited by C. dubliniensis may in part be due to the inability of this species to modulate NRG1 expression in response to the same environmental signals that promote filamentation in C. albicans.
A novel relaxase homologue is involved in chromosomal DNA processing for type IV secretion in Neisseria gonorrhoeae
Authors: Salgado‐Pabón Wilmara , Jain Samta , Turner Nicholas , Van Der Does Chris , Dillard Joseph P. 
Published: September 2007

SummaryThe Neisseria gonorrhoeae type IV secretion system secretes chromosomal DNA that acts in natural transformation. To examine the mechanism of DNA processing for secretion, we made mutations in the putative relaxase gene traI and used nucleases to characterize the secreted DNA. The nuclease experiments demonstrated that the secreted DNA is single‐stranded and blocked at the 5′ end. Mutation of traI identified Tyr93 as required for DNA secretion, while substitution of Tyr201 resulted in intermediate levels of DNA secretion. TraI exhibits features of relaxases, but also has features that are absent in previously characterized relaxases, including an HD phosphohydrolase domain and an N‐terminal hydrophobic region. The HD domain residue Asp120 was required for wild‐type levels of DNA secretion. Subcellular localization studies demonstrated that the TraI N‐terminal region promotes membrane interaction. We propose that Tyr93 initiates DNA processing and Tyr201 is required for termination or acts in DNA binding. Disruption of an inverted‐repeat sequence eliminated DNA secretion, suggesting that this sequence may serve as the origin of transfer for chromosomal DNA secretion. The TraI domain architecture, although not previously described, is present in 53 uncharacterized proteins, suggesting that the mechanism of TraI function is a widespread process for DNA donation.
Interaction of Bacteroides fragilis pLV22a relaxase and transfer DNA with Escherichia coli RP4‐TraG coupling protein
Authors: Thomas Johnson , Hecht David W. 
Published: September 2007

SummaryMany Bacteroides transfer factors are mobilizable in Escherichia coli when coresident with the IncP conjugative plasmid RP4, but not F. To begin characterization and potential interaction between Bacteroides mobilizable transfer factors and the RP4 mating channel, both mutants and deletions of the DNA processing (dtr), mating pair formation (mpf) and traG coupling genes of RP4 were tested for mobilization of Bacteroides plasmid pLV22a. All 10 mpf but none of the four dtr genes were required for mobilization of pLV22a. The RP4 TraG coupling protein (CP) was also required for mobilization of pLV22a, but could be substituted by a C‐terminal deletion mutant of the F TraD CP. Potential interactions of the TraG CP with relaxase protein(s) and transfer DNA of both RP4 and pLV22a were assessed. Overlay assays identified productive interactions between TraG and the relaxase proteins of both MbpB and TraI from pLV22a and RP4 respectively. The Agrobacterium Transfer‐ImmunoPrecipitation (TrIP) assay also identified an interaction between TraG and both RP4 and pLV22a transfer DNA. Thus, mobilization of the Bacteroides pLV22a in E. coli utilizes both RP4 Mpf and CP functions including an interaction between the relaxosome and the RP4 CP similar to that of cognate RP4 plasmid.
Feeding by the tick, Ixodes scapularis, causes CD4+ T cells responding to cognate antigen to develop the capacity to express IL‐4
Authors: MÜLLER‐DOBLIES U. U. , MAXWELL S. S. , BOPPANA V. D. , MIHALYO M. A. , MCSORLEY S. J. , VELLA A. T. , ADLER A. J. , WIKEL S. K. 
Published: September 2007

SUMMARY Effects of tick feeding on an early antigen‐specific T cell response were studied by monitoring a clonotypic population of adoptively transferred T cell receptor (TCR) transgenic CD4 cells responding to a tick‐associated antigen. When recipient mice were infested with pathogen‐free Ixodes scapularis nymphs several days prior to T cell transfer and intradermal injection of soluble cognate antigen at the feeding site, the clonotypic CD4 cells gained the ability to express the Th2 effector cytokine IL‐4. Notably, this effect was not only observed in BALB/c mice predisposed towards developing Th2 responses but also in B10.D2 mice predisposed towards Th1 responsiveness. Furthermore, tick feeding was able to superimpose IL‐4 expression potential onto a strong Th1 response (indicated by robust IFN‐γ expression potential) elicited by immunization with a vaccinia virus expressing the cognate antigen. The magnitude to which tick feeding was able to programme IL‐4 expression potential in CD4 cells was partially reduced in mice that had been previously exposed to pathogen‐free tick nymphs 6 weeks earlier, as well as when the nymphs were infected with Borrelia burgdorferi. Intradermal injection of salivary gland extract programmed IL‐4 expression potential similar to that of tick infestation, suggesting that IL‐4 programming activity is contained within tick saliva.
Wound healing response is a major contributor to the severity of cutaneous leishmaniasis in the ear model of infection
Authors: BALDWIN T. , SAKTHIANANDESWAREN A. , CURTIS J. M. , KUMAR B. , SMYTH G. K. , FOOTE S. J. , HANDMAN E. 
Published: September 2007

SUMMARY In the conventional mouse model for cutaneous leishmaniasis involving infection with stationary phase Leishmania major promastigotes at the base of the tail, mice congenic for leishmaniasis resistance loci designated lmr1,2,3 cured their lesions more rapidly and laid down more ordered collagen fibres than the susceptible parental BALB/c mice, while the opposite was the case for the congenic mice carrying the susceptibility loci on the resistant C57BL/6 background. In that model, we showed that wound healing and not T cell responses played a major role in determining the resolution of skin infection. Here, we show a similar disease phenotype in the mouse model that mimics more closely the situation in humans, that is, strictly intradermal infection in the ear pinna with small numbers of metacyclic promastigotes. The data show that at the site of infection the innate and adaptive immune responses act in concert to clear parasites, and induce tissue repair and wound healing. Importantly, the data show that the host responses controlled by the lmr loci, which act locally to control infection in the skin, are distinct from the host responses operating systemically in the draining lymph node.
Inhibition of groups 1 and 2 CD1 molecules on human dendritic cells by Leishmania species
Authors: DONOVAN M. J. , JAYAKUMAR A. , McDOWELL M. A. 
Published: September 2007

SUMMARY Dendritic cells are potent immune‐activating cells, which traditionally are thought of as presenters of protein antigen to lymphocytes to initiate an immune response. Recently, another mechanism of immune surveillance, the detection of lipid antigens, has been found to be mediated by the nonpolymorphic family of CD1 molecules. There are two different CD1 families, Group 1 consisting of CD1a, CD1b and CD1c, and Group 2 consisting only of CD1d. Leishmania donovani‐infected dendritic cells have previously been demonstrated to exhibit decreased surface levels of Group 1 CD1 molecules and are no longer able to initiate a CD1b‐restricted T cell response. In contrast to L. donovani, which disseminates to the visceral organs, L. major remains localized, forming a cutaneous lesion. We investigate here whether L. major, the aetiological agent of cutaneous leishmaniasis, also inhibits CD1 expression. We demonstrate that infection of human monocyte‐derived dendritic cells with either L. major or L. donovani results in transcriptional down‐regulation of both Groups 1 and 2 CD1 molecules. Furthermore, infection of monocytes during differentiation results in a cell phenotype similar to undifferentiated monocytes. Finally, we demonstrate that this down‐regulation is not mediated by lipophosphoglycan or other phosphoglycans.
Immunogenicity in rhesus of the Plasmodium vivax mosquito stage antigen Pvs25H with Alhydrogel and Montanide ISA 720
Authors: SAUL A. , HENSMANN M. , SATTABONGKOT J. , COLLINS W. E. , BARNWELL J. W. , LANGERMANS J. A. M. , WU Y. , LONG C. A. , DUBOVSKY F. , THOMAS A. W. 
Published: September 2007

SUMMARY Pvs25 is an ookinete surface protein from Plasmodium vivax that is the target of transmission‐blocking antibodies. Two immunogenicity trials in rhesus monkeys with a recombinant form of the protein, Pvs25H, were undertaken. Monkeys were vaccinated with Pvs25H adsorbed to Alhydrogel or emulsified in Montanide ISA 720 at 0, 4 and 27 weeks (study 1) or in Montanide ISA 720 at 0 and 18 weeks (study 2) with 1·5 or 15 µg Pvs25H in 0·1 or 0·5 mL of emulsion (four combinations). Immunogenicity was assessed by ELISA and by membrane‐feeding experiments using P. vivax‐infected blood from human volunteers (studies 1 and 2) or from chimpanzees (study 1). Both vaccine trials generated antibodies that blocked transmission of P. vivax to mosquitoes. Antibody titres and transmission blocking were higher with Montanide ISA 720 than with Alhydrogel in the first trial and with the 15 µg Pvs25H/0·5 mL ISA 720 combination in the second trial.
Parasite‐specific IL‐4 responses inAscaris suumandTrichuris suis‐infected pigs evaluated by ELISPOT
Authors: STEENHARD N. R. , KRINGEL H. , ROEPSTORFF A. , THAMSBORG S. M. , JUNGERSEN G. 
Published: September 2007

SUMMARYThe objective of the present study was to develop an ELISPOT method to measure parasite‐specific IL‐4 producing cells during experimentalAscaris suumandTrichuris suisinfections in pigs. In many experimental settings it is useful to be able to measure changes in specifically induced cytokines over time at post‐mRNA level; in particular, specific measurement of IL‐4 is important for studies on nematodes due to the key function of IL‐4 in driving the Th2 response. Two separate experiments were carried out, one withA. suumand other withT. suisinfection in which we were able to measure statistically significant increases in specific IL‐4 production in peripheral blood mononuclear cells over time in parallel to an increase in blood eosinophils. Furthermore, IL‐4 was measured in the colon lymph node ofT. suis‐infected pigs. Egg excretion and worm burdens at necropsy were measured. The ELISPOT method is a valuable tool for future experimental settings as it enables repeated and parasite‐specific measurement of IL‐4 at protein level when investigating, for example, immunomodulatory properties of helminths. Furthermore, the method could be used to identify specific parasite antigens inducing IL‐4 production.
Development and application of a PCR‐based ‘molecular tool box’ for the identification of Phytophthora species damaging forests and natural ecosystems
Authors: Schena L. , Duncan J. M. , Cooke D. E. L. 
Published: September 2007

A PCR‐based ‘molecular tool box’, based on a region of the ras‐related protein gene Ypt1, was developed for the identification of 15 Phytophthora species that damage forests and trees: P. cactorum, P. cambivora, P. cinnamomi, P. citricola, P. europaea, P. inundata, P. lateralis, P. megasperma, P. nemorosa, P. kernoviae, P. pseudosyringae, P. psychrophila, P. quercina, P. ramorum and P. ilicis. Most primers proved highly specific in blast analyses and in tests with DNA from 72 isolates of 35 species of Phytophthora and nine species representative of Pythium. Exceptions were primers designed for P. cactorum and P. ilicis, which cross‐reacted with P. idaei and P. nemorosa, respectively. Amplification with Phytophthora‐genus‐specific primers before amplification with the various species‐specific primers (nested PCR) increased the sensitivity of detection over amplification with species‐specific primers only: detection limits ranged between 100 and 10 pg target DNA µL−1 in the latter, compared with 100 fg µL−1 in nested PCR. Using existing methods for rapid extraction and purification of DNA, single‐round amplification was appropriate for detection of target Phytophthora species in leaves, but nested PCR was required for soil and water samples. The quarantine pathogens P. ramorum and P. kernoviae were detected in a number of naturally infected leaves collected in England and Wales, whereas P. citricola was commonest in water and soil samples from natural Scottish ecosystems.
Dynamics of soilborne Rhizoctonia solani in the presence of Trichoderma harzianum: effects on stem canker, black scurf and progeny tubers of potato
Authors: Wilson P. S. , Ketola E. O. , Ahvenniemi P. M. , Lehtonen M. J. , Valkonen J. P. T. 
Published: September 2007

Stem canker and black scurf are diseases of potato caused by the fungus Rhizoctonia solani. Spatiotemporal experimentation and empirical modelling were applied for the first time to investigate the effect of antagonistic Trichoderma harzianum on the dynamics of soilborne R. solani on individual potato plants. Trichoderma harzianum reduced the severity of symptoms, expressed as ‘rhizoctonia stem lesion index’ (RSI), during the first 7 days post‐inoculation when the inoculum of R. solani was placed at certain distances (30–60 mm) from the host. For example, with inoculum at 40 mm from the host, RSI was 6 and 40 with and without T. harzianum, respectively. At later observation times, the antagonistic effect was overcome. Trichoderma harzianum reduced the severity of black scurf on progeny tubers. Furthermore, the mean number of progeny tubers per potato plant was reduced by the biocontrol treatment (means of 6·5 ± 1·1 and 9·9 ± 2·7 tubers per plant with and without T. harzianum, respectively), as was the proportion of small (0·1–20·0 g) tubers (48% and 66% with and without T. harzianum, respectively). Additionally, there were fewer malformed and green‐coloured tubers in pots treated with T. harzianum than in those without T. harzianum.
Mechanisms of Regulatory T‐cell Induction by Antigen‐IgG‐transduced Splenocytes
Authors: Wang R. , Song L. , Han G. , Wang J. , Chen G. , Xu R. , Yu M. , Qian J. , Shen B. , Li Y. 
Published: September 2007

AbstractOur previous studies have demonstrated that splenocytes, transduced with glutamate decarboxylate 65 (GAD) and IgG fusion construct, protect non‐obese diabetes (NOD) mice from diabetes. However, the mechanism by which this strategy prevents diabetes is not well understood. Here, we found that CD4+Foxp3+Treg cells, in vitro induced by GAD‐IgG‐transduced splenocytes, after transfer, were responsible for prevention of diabetes in NOD mice. Further studies suggested that GAD‐IgG‐transduced B cells could secrete high level of TGF‐β and stimulated CD4+T cells to secrete high level of IFN‐γ. Finally, we found that when TGF‐β and/or IFN‐γ were blocked, CD4+Foxp3−T cells were not converted into CD4+Foxp3+Treg cells. The results suggest that GAD‐IgG‐transduced B cells via TGF‐β and IFN‐γin vitro induce the CD4+Foxp3+Treg cells which are responsible for prevention of diabetes in NOD mice by GAD‐IgG‐gene transfer.
A hydraulic signal in root‐to‐shoot signalling of water shortage
Authors: Christmann Alexander , Weiler Elmar W. , Steudle Ernst , Grill Erwin 
Published: September 2007

SummaryPhotosynthesis and biomass production of plants are controlled by the water status of the soil. Upon soil drying, plants can reduce water consumption by minimizing transpiration through stomata, the closable pores of the leaf. The phytohormone abscisic acid (ABA) mediates stomatal closure, and is the assigned signal for communicating water deficit from the root to the shoot. However, our study does not support ABA as the proposed long‐distance signal. The shoot response to limited soil water supply is not affected by the capacity to generate ABA in the root; however, the response does require ABA biosynthesis and signalling in the shoot. Soil water stress elicits a hydraulic response in the shoot, which precedes ABA signalling and stomatal closure. Attenuation of the hydraulic response in various plants prevented long‐distance signalling of water stress, consistent with root‐to‐shoot communication by a hydraulic signal.
The identification of a gene (Cwp1), silenced during Solanum evolution, which causes cuticle microfissuring and dehydration when expressed in tomato fruit
Authors: Hovav Ran , Chehanovsky Noam , Moy Michal , Jetter Reinhard , Schaffer Arthur A. 
Published: September 2007

SummaryOne of the most intriguing phenomena of fleshy fruit is the ability to maintain high water content at maturity, even following harvest. This is accomplished by a fruit cuticle that is highly impermeable to water diffusion. In this paper, we report on a novel genotype of tomato, developed via introgression from the wild species Solanum habrochaites, which is characterized by microfissuring of the fruit cuticle and dehydration of the mature fruit. The microfissure/dehydration phenotype is inherited as a single gene, termed Cwp1 (cuticular water permeability). The gene was fine mapped, and its identity was determined by map‐based cloning and differential expression analysis in near‐isogenic lines. Causality of the Cwp1 gene was shown by the heterologous transgenic expression of the gene in the cultivated tomato, which caused a microfissured fruit cuticle leading to dehydrated fruit. Cwp1 encodes for a protein of unidentified function in the DUF833 domain family. The gene is expressed in the fruit epidermis of the dehydrating genotype harbouring the wild‐species introgression, but not in the cultivated tomato. It is expressed only in the primitive green‐fruited wild tomato species, but is not expressed in the cultivated Solanum lycopersicum and the closely related Solanum cheesmaniae and Solanum pimpinellifolium, indicating a pre‐adaptive role for Cwp1 silencing in the evolution and domestication of the cultivated tomato.
Nuclear–mitochondrial cross‐talk during heat shock in Arabidopsis cell culture
Authors: Rikhvanov Eugene G. , Gamburg Kim Z. , Varakina Nina N. , Rusaleva Tatyana M. , Fedoseeva Irina V. , Tauson Elena L. , Stupnikova Irina V. , Stepanov Alexey V. , Borovskii Genadii B. , Voinikov Victor K. 
Published: September 2007

SummaryApart from energy generation, mitochondria perform a signalling function determining the life and death of a cell under stress exposure. In the present study we have explored patterns of heat‐induced synthesis of Hsp101, Hsp70, Hsp17.6 (class I), Hsp17.6 (class II) and Hsp60, and the development of induced thermotolerance in Arabidopsis thaliana cell culture under conditions of mitochondrial dysfunction. It was shown that treatment by mitochondrial inhibitors and uncouplers at the time of mild heat shock downregulates HSP synthesis, which is important for induced thermotolerance in plants. The exposure to elevated temperature induced an increase in cell oxygen consumption and hyperpolarization of the inner mitochondrial membrane. Taken together, these facts suggest that mitochondrial functions are essential for heat‐induced HSP synthesis and development of induced thermotolerance in A. thaliana cell culture, suggesting that mitochondrial–nuclear cross‐talk is activated under stress conditions. Treatment of Arabidopsis cell culture at 50°C initiates a programmed cell death determined by the time course of viability decrease, DNA fragmentation and cytochrome c release from mitochondria. As treatment at 37°C protected Arabidopsis cells from heat‐induced cell death, it may be suggested that Hsp101, Hsp70 and small heat‐shock proteins, the synthesis of which is induced under these conditions, are playing an anti‐apoptotic role in the plant cell. On the other hand, drastic heat shock upregulated mitochondrial Hsp60 synthesis and induced its release from mitochondria to the cytosol, indicating a pro‐apoptotic role of plant Hsp60.
Mitochondrial type‐I prohibitins of Arabidopsis thaliana are required for supporting proficient meristem development
Authors: Van Aken Olivier , Pečenková Tamara , Van De Cotte Brigitte , De Rycke Riet , Eeckhout Dominique , Fromm Hillel , De Jaeger Geert , Witters Erwin , Beemster Gerrit T. S. , Inzé Dirk , Van Breusegem Frank 
Published: September 2007

SummaryThe Arabidopsis thaliana genome expresses five evolutionarily conserved prohibitin (PHB) genes that are divided into type‐I (AtPHB3 and AtPHB4) and type‐II (AtPHB1, AtPHB2 and AtPHB6) classes, based on their phylogenetic relationships with yeast PHB1 and PHB2, respectively. Yeast and animal PHBs are reported to have diverse roles in the cell cycle, mitochondrial electron transport, aging and apoptosis. All transcribed Arabidopsis PHB genes are primarily expressed in both shoot and root proliferative tissues, where they are present in mitochondrial multimeric complexes. Loss of function of the type‐I AtPHB4 had no phenotypic effects, while loss of function of the homologous AtPHB3 caused mitochondrial swelling, decreased meristematic cell production, increased cell division time and reduced cell expansion rates, leading to severe growth retardation. Double knockout atphb3 atphb4 plants were not viable, but transgenic lines overexpressing AtPHB3 or AtPHB4 showed leaf shape aberrations and an increased shoot branching phenotype. Genome‐wide microarray analysis revealed that both knockout and overexpression perturbations of AtPHB3 and AtPHB4 provoked an altered abundance of mitochondrial and stress‐related transcripts. We propose that plant type‐I PHBs take part in protein complexes that are necessary for proficient mitochondrial function or biogenesis, thereby supporting cell division and differentiation in apical tissues.