Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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    Genomics spurs rapid advances in our understanding of the biology of vascular wilt pathogens in the genus Verticillium
    Klimes, A. ; Dobinson, K.F. ; Thomma, B. ; Klosterman, S.J. - \ 2015
    Annual Review of Phytopathology 53 (2015). - ISSN 0066-4286 - p. 181 - 198.
    protein-kinase gene - molecular characterization - functional-analysis - microsclerotia development - ethylene perception - hydrophobin gene - dahliae kleb - tomato ve1 - resistance - expression
    The availability of genomic sequences of several Verticillium species triggered an explosion of genome-scale investigations of mechanisms fundamental to the Verticillium life cycle and disease process. Comparative genomics studies have revealed evolutionary mechanisms, such as hybridization and interchromosomal rearrangements, that have shaped these genomes. Functional analyses of a diverse group of genes encoding virulence factors indicate that successful host xylem colonization relies on specific Verticillium responses to various stresses, including nutrient deficiency and host defense–derived oxidative stress. Regulatory pathways that control responses to changes in nutrient availability also appear to positively control resting structure development. Conversely, resting structure development seems to be repressed by pathways, such as those involving effector secretion, which promote responses to host defenses. The genomics-enabled functional characterization of responses to the challenges presented by the xylem environment, accompanied by identification of novel virulence factors, has rapidly expanded our understanding of niche adaptation in Verticillium species.
    Genome mining and metabolic profiling of the rhizosphere bacterium Pseudomonas sp. SH-C52 for antimicrobial compounds
    Voort, M. van der; Meijer, H.J.G. ; Schmidt, Y. ; Watrous, J. ; Dekkers, E. ; Mendes, R. ; Dorrestein, P.C. ; Gross, H. ; Raaijmakers, J.M. - \ 2015
    Frontiers in Microbiology 6 (2015). - ISSN 1664-302X - 14 p.
    ii secretion system - phytophthora-infestans - biological-activity - functional-analysis - mass-spectrometry - natural functions - phospholipase-d - corrugata - biocontrol - lipopeptides
    The plant microbiome represents an enormous untapped resource for discovering novel genes and bioactive compounds. Previously, we isolated Pseudomonas sp. SH-C52 from the rhizosphere of sugar beet plants grown in a soil suppressive to the fungal pathogen Rhizoctonia solani and showed that its antifungal activity is, in part, attributed to the production of the chlorinated 9-amino-acid lipopeptide thanamycin (Mendes et al., 2011). To get more insight into its biosynthetic repertoire, the genome of Pseudomonas sp. SH-C52 was sequenced and subjected to in silico, mutational and functional analyses. The sequencing revealed a genome size of 6.3 Mb and 5579 predicted ORFs. Phylogenetic analysis placed strain SH-C52 within the Pseudomonas corrugata clade. In silico analysis for secondary metabolites revealed a total of six non-ribosomal peptide synthetase (NRPS) gene clusters, including the two previously described NRPS clusters for thanamycin and the 2-amino acid antibacterial lipopeptide brabantamide. Here we show that thanamycin also has activity against an array of other fungi and that brabantamide A exhibits anti-oomycete activity and affects phospholipases of the late blight pathogen Phytophthora infestans. Most notably, mass spectrometry led to the discovery of a third lipopeptide, designated thanapeptin, with a 22-amino-acid peptide moiety. Seven structural variants of thanapeptin were found with varying degrees of activity against P. infestans. Of the remaining four NRPS clusters, one was predicted to encode for yet another and unknown lipopeptide with a predicted peptide moiety of 8-amino acids. Collectively, these results show an enormous metabolic potential for Pseudomonas sp. SH-C52, with at least three structurally diverse lipopeptides, each with a different antimicrobial activity spectrum.
    Catalytic and hydrodynamic properties of styrene monooxygenases from Rhocodoccus opacus 1CP are modulated by cofactor binding.
    Riedel, A. ; Heine, T. ; Westphal, A.H. ; Conrad, C. ; Rathsack, P. ; Berkel, W.J.H. van; Tischler, D. - \ 2015
    AMB Express 5 (2015). - ISSN 2191-0855 - 11 p.
    recombinant escherichia-coli - pseudomonas-fluorescens st - functional-analysis - crystal-structure - catabolism genes - strain vlb120 - putida ca-3 - degradation - mechanism - oxide
    Styrene monooxygenases (SMOs) are flavoenzymes catalyzing the epoxidation of styrene into styrene oxide. SMOs are composed of a monooxygenase (StyA) and a reductase (StyB). The latter delivers reduced FAD to StyA on the expense of NADH. We identified Rhodococcus opacus 1CP as the first microorganism to possess three different StyA isoforms occurring in two systems StyA1/StyA2B and StyA/StyB, respectively. The hydrodynamic properties of StyA isozymes were found to be modulated by the binding of the (reduced) FAD cofactor. StyA1 and SyA2B mainly occur as dimers in their active forms while StyA is a monomer. StyA1 showed the highest epoxidation activity and excellent enantioselectivity in aromatic sulfoxidation. The hydrodynamic and biocatalytic properties of SMOs from strain 1CP are of relevance for investigation of possible industrial applications.
    Oral administration of Lactobacillus plantarum 299v modulates gene expression in the ileum of pigs: prediction of crosstalk between intestinal immune cells and sub-mucosal adipocytes
    Hulst, M.M. ; Gross, G. ; Liu, Yapin ; Hoekman, A.J.W. ; Niewold, T. ; Meulen, J. van der; Smits, M.A. - \ 2015
    Genes & Nutrition 10 (2015)3. - ISSN 1555-8932 - 13 p.
    kappa-b - functional-analysis - in-vivo - inhibition - immunoglobulins - identification - adipogenesis - macrophages - metabolism - activation
    To study host–probiotic interactions in parts of the intestine only accessible in humans by surgery (jejunum, ileum and colon), pigs were used as model for humans. Groups of eight 6-week-old pigs were repeatedly orally administered with 5 × 1012 CFU Lactobacillus plantarum 299v (L. plantarum 299v) or PBS, starting with a single dose followed by three consecutive daily dosings 10 days later. Gene expression was assessed with pooled RNA samples isolated from jejunum, ileum and colon scrapings of the eight pigs per group using Affymetrix porcine microarrays. Comparison of gene expression profiles recorded from L. plantarum 299v-treated pigs with PBS-treated pigs indicated that L. plantarum 299v affected metabolic and immunological processes, particularly in the ileum. A higher expression level of several B cell-specific transcription factors/regulators was observed, suggesting that an influx of B cells from the periphery to the ileum and/or the proliferation of progenitor B cells to IgA-committed plasma cells in the Peyer’s patches of the ileum was stimulated. Genes coding for enzymes that metabolize leukotriene B4, 1,25-dihydroxyvitamin D3 and steroids were regulated in the ileum. Bioinformatics analysis predicted that these metabolites may play a role in the crosstalk between intestinal immune cells and sub-mucosal adipocytes. Together with regulation of genes that repress NFKB- and PPARG-mediated transcription, this crosstalk may contribute to tempering of inflammatory reactions. Furthermore, the enzyme adenosine deaminase, responsible for the breakdown of the anti-inflammatory mediator adenosine, was strongly down-regulated in response to L. plantarum 299v. This suggested that L. plantarum 299v-regulated production of adenosine by immune cells like regulatory T cells may also be a mechanism that tempers inflammation in the ileum, and perhaps also in other parts of the pig’s body.
    Identifying the core microbial community in the gut of fungus-growing termites
    Otani, S. ; Mikaelyan, A. ; Nobre, T. ; Hansen, L.H. ; Kone, N.A. ; Sorensen, S.J. ; Aanen, D.K. ; Boomsma, J.J. ; Brune, A. ; Poulsen, M. - \ 2014
    Molecular Ecology 23 (2014)18. - ISSN 0962-1083 - p. 4631 - 4644.
    feeding higher termite - bacterial community - phylogenetic analysis - functional-analysis - macrotermes-gilvus - lignin degradation - nasutitermes spp. - sp-nov. - diversity - hindgut
    Gut microbes play a crucial role in decomposing lignocellulose to fuel termite societies, with protists in the lower termites and prokaryotes in the higher termites providing these services. However, a single basal subfamily of the higher termites, the Macrotermitinae, also domesticated a plant biomass-degrading fungus (Termitomyces), and how this symbiont acquisition has affected the fungus-growing termite gut microbiota has remained unclear. The objective of our study was to compare the intestinal bacterial communities of five genera (nine species) of fungus-growing termites to establish whether or not an ancestral core microbiota has been maintained and characterizes extant lineages. Using 454-pyrosequencing of the 16S rRNA gene, we show that gut communities have representatives of 26 bacterial phyla and are dominated by Firmicutes, Bacteroidetes, Spirochaetes, Proteobacteria and Synergistetes. A set of 42 genus-level taxa was present in all termite species and accounted for 56–68% of the species-specific reads. Gut communities of termites from the same genus were more similar than distantly related species, suggesting that phylogenetic ancestry matters, possibly in connection with specific termite genus-level ecological niches. Finally, we show that gut communities of fungus-growing termites are similar to cockroaches, both at the bacterial phylum level and in a comparison of the core Macrotermitinae taxa abundances with representative cockroach, lower termite and higher nonfungus-growing termites. These results suggest that the obligate association with Termitomyces has forced the bacterial gut communities of the fungus-growing termites towards a relatively uniform composition with higher similarity to their omnivorous relatives than to more closely related termites
    Apoplastic Venom Allergen-like Proteins of Cyst Nematodes Modulate the Activation of Basal Plant Innate Immunity by Cell Surface Receptors
    Lozano Torres, J.L. ; Wilbers, R.H.P. ; Warmerdam, S. ; Finkers-Tomczak, A.M. ; Diaz Granados Muñoz, A. ; Schaik, C.C. van; Helder, J. ; Bakker, J. ; Goverse, A. ; Schots, A. ; Smant, G. - \ 2014
    PLoS Pathogens 10 (2014)12. - ISSN 1553-7366 - 18 p.
    root-knot nematode - cf-2-dependent disease resistance - pamp-triggered immunity - arabidopsis-thaliana - globodera-rostochiensis - heterodera-schachtii - ancylostoma-caninum - parasitic nematodes - extracellular-matrix - functional-analysis
    Despite causing considerable damage to host tissue during the onset of parasitism, nematodes establish remarkably persistent infections in both animals and plants. It is thought that an elaborate repertoire of effector proteins in nematode secretions suppresses damage-triggered immune responses of the host. However, the nature and mode of action of most immunomodulatory compounds in nematode secretions are not well understood. Here, we show that venom allergen-like proteins of plant-parasitic nematodes selectively suppress host immunity mediated by surface-localized immune receptors. Venom allergen-like proteins are uniquely conserved in secretions of all animal- and plant-parasitic nematodes studied to date, but their role during the onset of parasitism has thus far remained elusive. Knocking-down the expression of the venom allergen-like protein Gr-VAP1 severely hampered the infectivity of the potato cyst nematode Globodera rostochiensis. By contrast, heterologous expression of Gr-VAP1 and two other venom allergen-like proteins from the beet cyst nematode Heterodera schachtii in plants resulted in the loss of basal immunity to multiple unrelated pathogens. The modulation of basal immunity by ectopic venom allergen-like proteins in Arabidopsis thaliana involved extracellular protease-based host defenses and non-photochemical quenching in chloroplasts. Non-photochemical quenching regulates the initiation of the defense-related programmed cell death, the onset of which was commonly suppressed by venom allergen-like proteins from G. rostochiensis, H. schachtii, and the root-knot nematode Meloidogyne incognita. Surprisingly, these venom allergen-like proteins only affected the programmed cell death mediated by surface-localized immune receptors. Furthermore, the delivery of venom allergen-like proteins into host tissue coincides with the enzymatic breakdown of plant cell walls by migratory nematodes. We, therefore, conclude that parasitic nematodes most likely utilize venom allergen-like proteins to suppress the activation of defenses by immunogenic breakdown products in damaged host tissue.
    Discovery of new regulatory genes of lipopeptide biosynthesis in Pseudomonas fluorescens
    Song, C. ; Aundy, K. ; Mortel, J.E. van de; Raaijmakers, J.M. - \ 2014
    FEMS Microbiology Letters 356 (2014). - ISSN 0378-1097 - p. 166 - 175.
    syringae pv.-syringae - biosurfactant production - functional-analysis - natural functions - putida pcl1445 - putisolvin-ii - diversity - cluster - identification - antibiotics
    Pseudomonas fluorescens SS101 produces the cyclic lipopeptide massetolide with diverse functions in antimicrobial activity, motility, and biofilm formation. To understand how massetolide biosynthesis is genetically regulated in SS101, c. 8000 random plasposon mutants were screened for reduced or loss of massetolide production. Of a total of 58 putative mutants, 45 had a mutation in one of the three massetolide biosynthesis genes massA, massB, or massC. For five mutants, the insertions were located in the known regulatory genes gacS, gacA, and clpP. For the remaining eight mutants, insertions were located in clpA, encoding the ClpP chaperone, in phgdh, encoding D-3-phosphoglycerate dehydrogenase, in the heat shock protein-encoding dnaK, or in the transmembrane regulatory gene prtR. Genetic, chemical, and phenotypic analyses showed that phgdh, dnaK, and prtR are indeed involved in the regulation of massetolide biosynthesis, most likely by transcriptional repression of the LuxR-type regulator genes massAR and massBCR. In addition to their role in massetolide biosynthesis, dnaK and prtR were found to affect siderophore and extracellular protease(s) production, respectively. The identification of new regulatory genes substantially extended insights into the signal transduction pathways of lipopeptide biosynthesis in P. fluorescens and into regulation of other traits that may contribute to its life-style in the rhizosphere.
    Genomic Characterization of Non-Mucus Adherent Derivatives of Lactobacillus rhamnosus GG Reveals Genes Affecting Pilus Biogenesis
    Rasinkangas, P. ; Reunanen, J. ; Douillard, F.P. ; Ritari, J. ; Uotinen, V. ; Palva, A. ; Vos, W.M. de - \ 2014
    Applied and Environmental Microbiology 80 (2014)22. - ISSN 0099-2240 - p. 7001 - 7009.
    intestinal epithelial-cells - placebo-controlled trial - gram-positive bacteria - functional-analysis - atopic disease - strain gg - adhesion - probiotics - surface - prevention
    Lactobacillus rhamnosus GG is one of the best-characterized lactic acid bacteria and can be considered a probiotic paradigm. Comparative and functional genome analysis showed that L. rhamnosus GG harbors a genomic island including the spaCBA-srtC1 gene cluster, encoding the cell surface-decorating host-interacting pili. Here, induced mutagenesis was used to study pilus biogenesis in L. rhamnosus GG. A combination of two powerful approaches, mutation selection and next-generation sequencing, was applied to L. rhamnosus GG for the selection of pilus-deficient mutants from an enriched population. The isolated mutants were first screened by immuno-dot blot analysis using antiserum against pilin proteins. Relevant mutants were selected, and the lack of pili was confirmed by immunoelectron microscopy. The pilosotype of 10 mutant strains was further characterized by analyzing pilin expression using Western blot, dot blot, and immunofluorescence methods. A mucus binding assay showed that the mutants did not adhere to porcine intestinal mucus. Comparative genome sequence analysis using the Illumina MiSeq platform allowed us to determine the nature of the mutations in the obtained pilus-deficient derivatives. Three major classes of mutants with unique genotypes were observed: class I, with mutations in the srtC1 gene; class II, with a deletion containing the spaCBA-srtC1 gene cluster; and class III, with mutations in the spaA gene. Only a limited number of collateral mutations were observed, and one of the pilus-deficient derivatives with a deficient srtC1 gene contained 24 other mutations. This strain, PB12, can be considered a candidate for human trials addressing the impact of the absence of pili.
    Metabolomic engineering for the microbial production of cartenoids and related products with a focus on the rare C50 carotenoids
    Heider, S.A.E. ; Peters-Wendisch, P. ; Wendisch, V.F. ; Beekwilder, M.J. - \ 2014
    Applied Microbiology and Biotechnology 98 (2014)10. - ISSN 0175-7598 - p. 4355 - 4368.
    alga haematococcus-pluvialis - blue-light photoreception - escherichia-coli - bacterial carotenoids - biosynthetic-pathway - bacillus-subtilis - astaxanthin biosynthesis - functional-analysis - beta-carotene - corynebacterium-glutamicum
    Carotenoids, a subfamily of terpenoids, are yellowtored-colored pigments synthesized by plants, fungi, algae, and bacteria. They are ubiquitous in nature and take over crucial roles in many biological processes as for example photosynthesis, vision, and the quenching of free radicals and singlet oxygen. Due to their color and their potential beneficial effects on human health, carotenoids receive increasing attention. Carotenoids can be classified due to the length of their carbon backbone. Most carotenoids have a C40 backbone, but also C30 and C50 carotenoids are known. All carotenoids are derived fromisopentenyl pyrophosphate (IPP) as a common precursor. Pathways leading to IPP as well as metabolic engineering of IPP synthesis and C40 carotenoid production have been reviewed expertly elsewhere. Since C50 carotenoids are synthesized from the C40 carotenoid lycopene, we will summarize common strategies for optimizing lycopene production and we will focus our review on the characteristics, biosynthesis, glycosylation, and overproduction of C50 carotenoids.
    Modelling cell division and endoreduplication in tomato fruit pericarp
    Apri, M. ; Kromdijk, J. ; Visser, P.H.B. de; Gee, M. de; Molenaar, J. - \ 2014
    Journal of Theoretical Biology 349 (2014). - ISSN 0022-5193 - p. 32 - 43.
    cyclin-dependent kinase - transcriptional adapter protein - arabidopsis-thaliana trichomes - anaphase-promoting complex - f-box protein - solanum-lycopersicon - fission yeast - functional-analysis - endocycle onset - auxin
    In many developing plant tissues and organs, differentiating cells switch from the classical cell cycle to an alternative partial cycle. This partial cycle bypasses mitosis and allows for multiple rounds of genome duplication without cell division, giving rise to cells with high ploidy numbers. This partial cycle is referred to as endoreduplication. Cell division and endoreduplication are important processes for biomass allocation and yield in tomato. Quantitative trait loci for tomato fruit size or weight are frequently associated with variations in the pericarp cell number, and due to the tight connection between endoreduplication and cell expansion and the prevalence of polyploidy in storage tissues, a functional correlation between nuclear ploidy number and cell growth has also been implicated (karyoplasmic ratio theory). In this paper, we assess the applicability of putative mechanisms for the onset of endoreduplication in tomato pericarp cells via development of a mathematical model for the cell cycle gene regulatory network. We focus on targets for regulation of the transition to endoreduplication by the phytohormone auxin, which is known to play a vital role in the onset of cell expansion and differentiation in developing tomato fruit. We show that several putative mechanisms are capable of inducing the onset of endoreduplication. This redundancy in explanatory mechanisms is explained by analysing system behaviour as a function of their combined action. Namely, when all these routes to endoreduplication are used in a combined fashion, robustness of the regulation of the transition to endoreduplication is greatly improved
    Fragmentation of an aflatoxin-like gene cluster in a forest pathogen
    Bradshaw, R.E. ; Slot, J.C. ; Moore, G.G. ; Chettri, P. ; Wit, P.J.G.M. de; Ehrlich, K.C. ; Ganley, A.R.D. ; Olson, M.A. ; Rokas, A. ; Carbone, I. ; Cox, M.P. - \ 2013
    New Phytologist 198 (2013)2. - ISSN 0028-646X - p. 525 - 535.
    aspergillus-parasiticus - dothistroma-septosporum - phylogenetic analyses - biosynthetic-pathway - recombination events - secondary metabolism - functional-analysis - horizontal transfer - filamentous fungi - evolution
    Plant pathogens use a complex arsenal of weapons, such as toxic secondary metabolites, to invade and destroy their hosts. Knowledge of how secondary metabolite pathways evolved is central to understanding the evolution of host specificity. The secondary metabolite dothistromin is structurally similar to aflatoxins and is produced by the fungal pine pathogen Dothistroma septosporum. Our study focused on dothistromin genes, which are widely dispersed across one chromosome, to determine whether this unusual distributed arrangement evolved from an ancestral cluster. We combined comparative genomics and population genetics approaches to elucidate the origins of the dispersed arrangement of dothistromin genes over a broad evolutionary time-scale at the phylum, class and species levels. Orthologs of dothistromin genes were found in two major classes of fungi. Their organization is consistent with clustering of core pathway genes in a common ancestor, but with intermediate cluster fragmentation states in the Dothideomycetes fungi. Recombination hotspots in a D.septosporum population matched sites of gene acquisition and cluster fragmentation at higher evolutionary levels. The results suggest that fragmentation of a larger ancestral cluster gave rise to the arrangement seen in D.septosporum. We propose that cluster fragmentation may facilitate metabolic retooling and subsequent host adaptation of plant pathogens.
    Genetic Analysis of Health-Related Secondary Metabolites in a Brassica rapa Recombinant Inbred Line Population
    Bagheri, H. ; Soda, M. El; Kim, H.K. ; Fritsche, S. ; Jung, C. ; Aarts, M.G.M. - \ 2013
    International Journal of Molecular Sciences 14 (2013)8. - ISSN 1661-6596 - p. 15561 - 15577.
    synechocystis sp pcc-6803 - quantitative trait loci - vitamin-e content - arabidopsis-thaliana - hydroxyphenylpyruvate dioxygenase - tocopherol biosynthesis - plastoquinone synthesis - functional-analysis - natural variation - alpha-tocopherol
    The genetic basis of the wide variation for nutritional traits in Brassica rapa is largely unknown. A new Recombinant Inbred Line (RIL) population was profiled using High Performance Liquid Chromatography (HPLC) and Nuclear Magnetic Resonance (NMR) analysis to detect quantitative trait loci (QTLs) controlling seed tocopherol and seedling metabolite concentrations. RIL population parent L58 had a higher level of glucosinolates and phenylpropanoids, whereas levels of sucrose, glucose and glutamate were higher in the other RIL population parent, R-o-18. QTL related to seed tocopherol (-, -, -, -, -/- and total tocopherol) concentrations were detected on chromosomes A3, A6, A9 and A10, explaining 11%-35% of the respective variation. The locus on A3 co-locates with the BrVTE1gene, encoding tocopherol cyclase. NMR spectroscopy identified the presence of organic/amino acid, sugar/glucosinolate and aromatic compounds in seedlings. QTL positions were obtained for most of the identified compounds. Compared to previous studies, novel loci were found for glucosinolate concentrations. This work can be used to design markers for marker-assisted selection of nutritional compounds in B. rapa.
    Comparative genome analysis of Lactobacillus casei strains isolated from Actimel and Yakult products reveals marked similarities and points to a common origin
    Douillard, F.P. ; Kant, R. ; Ritari, J. ; Paulin, L. ; Palva, A. ; Vos, W.M. de - \ 2013
    Microbial Biotechnology 6 (2013)5. - ISSN 1751-7907 - p. 576 - 587.
    lactic-acid bacteria - gram-positive bacteria - rhamnosus gg - functional-analysis - cell-wall - surface-proteins - staphylococcus-aureus - controlled-trial - binding-protein - sequence
    The members of the Lactobacillus genus are widely used in the food and feed industry and show a remarkable ecological adaptability. Several Lactobacillus strains have been marketed as probiotics as they possess health-promoting properties for the host. In the present study, we used two complementary next-generation sequencing technologies to deduce the genome sequences of two Lactobacillus casei strains LcA and LcY, which were isolated from the products Actimel and Yakult, commercialized as probiotics. The LcA and LcY draft genomes have, respectively, an estimated size of 3067 and 3082 Mb and a G+ C content of 46.3%. Both strains are close to identical to each other and differ by no more than minor chromosomal re-arrangements, substitutions, insertions and deletions, as evident from the verified presence of one insertion-deletion (InDel) and only 29 single-nucleotide polymorphisms (SNPs). In terms of coding capacity, LcA and LcY are predicted to encode a comparable exoproteome, indicating that LcA and LcY are likely to establish similar interactions with human intestinal cells. Moreover, both L. casei LcA and LcY harboured a 59.6 kb plasmid that shared high similarities with plasmids found in other L. casei strains, such as W56 and BD-II. Further analysis revealed that the L. casei plasmids constitute a good evolution marker within the L. casei species. The plasmids of the LcA and LcY strains are almost identical, as testified by the presence of only three verified SNPs, and share a 3.5 kb region encoding a remnant of a lactose PTS system that is absent from the plasmids of W56 and BD-II but conserved in another smaller L. casei plasmid (pLC2W). Our observations imply that the results obtained in animal and human experiments performed with the Actimel and Yakult strains can be compared with each other as these strains share a very recent common ancestor.
    Dendritic cells and their role in tumor immunosurveillance
    Strioga, M.M. ; Schijns, V.E.J.C. ; Powell, D.J. ; Pasukoniene, V. ; Dobrovolskiene, N.T. ; Michalek, J. - \ 2013
    Innate Immunity 19 (2013)1. - ISSN 1753-4259 - p. 98 - 111.
    regulatory t-cells - epidermal langerhans cells - ovarian-cancer progression - antigen-presenting cells - in-vivo - peripheral tolerance - adaptive immunity - functional-analysis - colorectal-cancer - apoptotic cells
    Dendritic cells (DCs) comprise a heterogeneous population of cells that play a key role in initiating, directing and regulating adaptive immune responses, including those critically involved in tumor immunosurveillance. As a riposte to the central role of DCs in the generation of antitumor immune responses, tumors have developed various mechanisms which impair the immunostimulatory functions of DCs or even instruct them to actively contribute to tumor growth and progression. In the first part of this review we discuss general aspects of DC biology, including their origin, subtypes, immature and mature states, and functional plasticity which ensures a delicate balance between active immune response and immune tolerance. In the second part of the review we discuss the complex interactions between DCs and the tumor microenvironment, and point out the challenges faced by DCs during the recognition of tumor Ags. We also discuss the role of DCs in tumor angiogenesis and vasculogenesis.
    Ve1-mediated resistance against Verticillium does not involve a hypersensitive response in Arabidopsis
    Zhang, Z. ; Esse, H.P. van; Damme, M. van; Fradin, E.F. ; Liu, Chun-Ming ; Thomma, B.P.H.J. - \ 2013
    Molecular Plant Pathology 14 (2013)7. - ISSN 1464-6722 - p. 719 - 727.
    ethylene-inducing xylanase - receptor-like proteins - gated ion-channel - disease resistance - rhynchosporium-secalis - functional-analysis - defense responses - gene family - tomato ve1 - cell-death
    The recognition of pathogen effectors by plant immune receptors leads to the activation of immune responses that often include a hypersensitive response (HR): rapid and localized host cell death surrounding the site of attempted pathogen ingress. We have demonstrated previously that the recognition of the Verticillium dahliae effector protein Ave1 by the tomato immune receptor Ve1 triggers an HR in tomato and tobacco. Furthermore, we have demonstrated that tomato Ve1 provides Verticillium resistance in Arabidopsis upon Ave1 recognition. In this study, we investigated whether the co-expression of Ve1 and Ave1 in Arabidopsis results in an HR, which could facilitate a forward genetics screen. Surprisingly, we found that the co-expression of Ve1 and Ave1 does not induce an HR in Arabidopsis. These results suggest that an HR may occur as a consequence of Ve1/Ave1-induced immune signalling in tomato and tobacco, but is not absolutely required for Verticillium resistance.
    System-Wide Hypersensitive Response-Associated Transcriptome and Metabolome Reprogramming in Tomato
    Etalo, D.W. ; Stulemeijer, I.J.E. ; Esse, H.P. van; Vos, R.C.H. de; Bouwmeester, H.J. ; Joosten, M.H.A.J. - \ 2013
    Plant Physiology 162 (2013)3. - ISSN 0032-0889 - p. 1599 - 1617.
    programmed cell-death - pathogen pseudomonas-syringae - campestris pv. vesicatoria - glutathione s-transferases - amino-acid catabolism - leaf rust resistance - higher-plant cells - mass-spectrometry - cladosporium-fulvum - functional-analysis
    The hypersensitive response (HR) is considered to be the hallmark of the resistance response of plants to pathogens. To study HR-associated transcriptome and metabolome reprogramming in tomato (Solanum lycopersicum), we used plants that express both a resistance gene to Cladosporium fulvum and the matching avirulence gene of this pathogen. In these plants, massive reprogramming occurred, and we found that the HR and associated processes are highly energy demanding. Ubiquitin-dependent protein degradation, hydrolysis of sugars, and lipid catabolism are used as alternative sources of amino acids, energy, and carbon skeletons, respectively. We observed strong accumulation of secondary metabolites, such as hydroxycinnamic acid amides. Coregulated expression of WRKY transcription factors and genes known to be involved in the HR, in addition to a strong enrichment of the W-box WRKY-binding motif in the promoter sequences of the coregulated genes, point to WRKYs as the most prominent orchestrators of the HR. Our study has revealed several novel HR-related genes, and reverse genetics tools will allow us to understand the role of each individual component in the HR.
    Temperature-dependent regulation of flowering by antagonistic FLM variants
    Posé, D. ; Verhage, D.S.L. ; Ott, F. ; Yant, L. ; Mathieu, J. ; Angenent, G.C. ; Immink, G.H. ; Schmid, M. - \ 2013
    Nature 503 (2013)7476. - ISSN 0028-0836 - p. 414 - 417.
    mads-box gene - arabidopsis-thaliana - transcription factor - circadian clock - functional-analysis - floral transition - identification - repressor - time - vernalization
    The appropriate timing of flowering is crucial for plant reproductive success. It is therefore not surprising that intricate genetic networks have evolved to perceive and integrate both endogenous and environmental signals, such as carbohydrate and hormonal status, photoperiod and temperature1,2. In contrast to our detailed understanding of the vernalization pathway, little is known about how flowering time is controlled in response to changes in the ambient growth temperature. In Arabidopsis thaliana, the MADSbox transcription factor genesFLOWERING LOCUSM (FLM) and SHORTVEGETATIVEPHASE (SVP)have key roles in this process3,4. FLM is subject to temperature-dependent alternative splicing3. Here we report that the two mainFLMprotein splice variants,FLM-b and FLM-d, compete for interaction with the floral repressor SVP. The SVP–FLM-b complex is predominately formed at low temperatures and prevents precocious flowering. By contrast, the competingSVP–FLM-d complex is impaired in DNA binding and acts as a dominant-negative activator of flowering at higher temperatures. Our results show a new mechanism that controls the timing of the floral transition in response to changes in ambient temperature. A better understanding of how temperature controls the molecular mechanismsof flowering will be important to cope with current changes in global climate5,6.
    Regulation of intestinal homeostasis and immunity with probiotic lactobacilli
    Baarlen, P. van; Wells, J. ; Kleerebezem, M. - \ 2013
    Trends in Immunology 34 (2013)5. - ISSN 1471-4906 - p. 208 - 215.
    wall teichoic-acid - gut microbiota - rhamnosus gg - t-cells - lipoteichoic acid - functional-analysis - epithelial barrier - controlled-trials - dendritic cell - in-vivo
    The gut microbiota provide important stimuli to the human innate and adaptive immune system and co-mediate metabolic and immune homeostasis. Probiotic bacteria can be regarded as part of the natural human microbiota, and have been associated with improving homeostasis, albeit with different levels of success. Composition of microbiota, probiotic strain identity, and host genetic differences may account for differential modulation of immune responses by probiotics. Here, we review the mechanisms of immunomodulating capacities of specific probiotic strains, the responses they can induce in the host, and how microbiota and genetic differences between individuals may co-influence host responses and immune homeostasis.
    Adhesion and Nanomechanics of Pili from the Probiotic Lactobacillus rhamnosus GG
    Tripathi, P. ; Beaussart, A. ; Alsteens, D. ; Dupres, V. ; Claes, I. ; Ossowski, I. von; Vos, W.M. de; Palva, A. ; Lebeer, S. ; Vanderleyden, J. ; Dufrene, Y.F. - \ 2013
    ACS Nano 7 (2013)4. - ISSN 1936-0851 - p. 3685 - 3697.
    atomic-force-microscopy - coli p-pili - functional-analysis - escherichia-coli - stabilizing isopeptide - streptococcus-pyogenes - gastrointestinal-tract - mechanical force - binding-protein - antigen-i/ii
    Knowledge of the mechanisms by which bacterial pili adhere to host cells and withstand external forces is critical to our understanding of their functional roles and offers exciting avenues in biomedicine for controlling the adhesion of bacterial pathogens and probiotics. While much progress has been made in the nanoscale characterization of pili from Gram-negative bacteria, the adhesive and mechanical properties of Gram-positive bacterial pili remain largely unknown. Here, we use single-molecule atomic force microscopy to unravel the binding mechanism of pili from the probiotic Gram-positive bacterium Lactobacillus rhamnosus GG (LGG). First, we show that SpaC, the key adhesion protein of the LGG pilus, is a multifunctional adhesin with broad specificity. SpaC forms homophilic trans-interactions engaged in bacterial aggregation and specifically binds mucin and collagen, two major extracellular components of host epithelial layers. Homophilic and heterophilic interactions display similar binding strengths and dissociation rates. Next, pulling experiments on living bacteria demonstrate that LGG pili exhibit two unique mechanical responses, that is, zipper-like adhesion involving multiple SpaC molecules distributed along the pilus length and nanospring properties enabling pili to resist high force. These mechanical properties may represent a generic mechanism among Gram-positive bacterial pili for strengthening adhesion and withstanding shear stresses in the natural environment. The single-molecule experiments presented here may help us to design molecules capable of promoting or inhibiting bacterial-host interactions
    Using recombinant Lactococci as an approach to dissect the immunomodulating capacity of surface piliation in probiotic Lactobacillus rhamnosus GG
    Ossowski, I. von; Pietilä, T.E. ; Rintahaka, J. ; Nummenmaa, E. ; Mäkinen, V.M. ; Reunanen, J. ; Satokari, R.M. ; Vos, W.M. de; Palva, I. ; Palva, A. - \ 2013
    PLoS ONE 8 (2013)5. - ISSN 1932-6203
    lactic-acid bacteria - intestinal epithelial-cells - functional-analysis - dendritic cells - gastrointestinal-tract - dependent mechanism - protein-production - oral consumption - adhesion - pili
    Primarily arising from their well understood beneficial health effects, many lactobacilli strains are considered good candidates for use as probiotics in humans and animals. Lactobacillar probiosis can itself be best typified by the Lactobacillus rhamnosus GG strain, which, with its well-documented clinical benefits, has emerged as one of the most widely used probiotics in the food and health-supplement industries. Even so, many facets of its molecular mechanisms and limitations as a beneficial commensal bacterium still remain to be thoroughly explored and dissected. Because L. rhamnosus GG is one of only a few such strains exhibiting surface piliation (called SpaCBA), we sought to examine whether this particular type of cell-surface appendage has a discernible immunomodulating capacity and is able to trigger targeted responses in human immune-related cells. Thus, presented herein for this study, we recombinantly engineered Lactococcus lactis to produce native (and pilin-deleted) SpaCBA pili that were assembled in a structurally authentic form and anchored to the cell surface, and which had retained mucus-binding functionality. By using these recombinant lactococcal constructs, we were able to demonstrate that the SpaCBA pilus can be a contributory factor in the activation of Toll-like receptor 2-dependent signaling in HEK cells as well as in the modulation of pro- and anti-inflammatory cytokine (TNF-a, IL-6, IL-10, and IL-12) production in human monocyte-derived dendritic cells. From these data, we suggest that the recombinant-expressed and surface-anchored SpaCBA pilus, given its projected functioning in the gut environment, might be viewed as a new microbe-associated molecular pattern (MAMP)-like modulator of innate immunity. Accordingly, our study has brought some new insight to the molecular immunogenicity of the SpaCBA pilus, thus opening the way to a better understanding of its possible role in the multifaceted nature of L. rhamnosus GG probiosis within the human gut
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