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Evolution of GHF5 endoglucanase gene structure in plant-parasitic nematodes: no evidence for an early domain shuffling event
Tina Kyndt, Annelies Haegeman, Godelieve Gheysen
BMC Evolutionary Biology , 2008, DOI: 10.1186/1471-2148-8-305
Abstract: Two new endoglucanases from the migratory nematodes Pratylenchus coffeae and Ditylenchus africanus were included in this study. The latter one is the first gene isolated from a PPN of a different superfamily (Sphaerularioidea); all previously known nematode endoglucanases belong to the superfamily Tylenchoidea (order Rhabditida). Phylogenetic analyses were conducted with the PPN GHF5 endoglucanases and homologous endoglucanases from bacterial and other eukaryotic lineages such as beetles, fungi and plants. No statistical incongruence between the phylogenetic trees deduced from the catalytic domain and the CBM2 was found, which could suggest that both domains have evolved together. Furthermore, based on gene structure data, we inferred a model for the evolution of the GHF5 endoglucanase gene structure in plant-parasitic nematodes. Our data confirm a close relationship between Pratylenchus spp. and the root knot nematodes, while some Radopholus similis endoglucanases are more similar to cyst nematode genes.We conclude that the ancestral PPN GHF5 endoglucanase gene most probably consisted of the whole gene cassette, i.e. the GHF5 catalytic domain and the CBM2, rather than that it evolved by domain shuffling. Our evolutionary model for the gene structure in PPN GHF5 endoglucanases implies the occurrence of an early duplication event, and more recent gene duplications at genus or species level.Endo-1,4-beta-glucanases (EC 3.2.1.4), or endoglucanases, can degrade the beta-1,4-linkages of cellulose, the most abundant component of plant cell walls. The endoglucanases are classified in different glycosyl hydrolase families (GHF) on the basis of sequence similarity and hydrophobic cluster analysis [1]. Animal endoglucanases belong to three structurally and presumably phylogenetically unrelated families: GHF5, GHF9 and GHF45 [2]. GHF5 genes are found in various plant-parasitic bacteria and nematodes [3-6] from the order Rhabditida (infra-order Tylenchomorpha), which is part of
Parasitic Nematodes Modulate PIN-Mediated Auxin Transport to Facilitate Infection
Wim Grunewald ,Bernard Cannoot,Ji?í Friml,Godelieve Gheysen
PLOS Pathogens , 2009, DOI: 10.1371/journal.ppat.1000266
Abstract: Plant-parasitic nematodes are destructive plant pathogens that cause significant yield losses. They induce highly specialized feeding sites (NFS) in infected plant roots from which they withdraw nutrients. In order to establish these NFS, it is thought that the nematodes manipulate the molecular and physiological pathways of their hosts. Evidence is accumulating that the plant signalling molecule auxin is involved in the initiation and development of the feeding sites of sedentary plant-parasitic nematodes. Intercellular transport of auxin is essential for various aspects of plant growth and development. Here, we analysed the spatial and temporal expression of PIN auxin transporters during the early events of NFS establishment using promoter-GUS/GFP fusion lines. Additionally, single and double pin mutants were used in infection studies to analyse the role of the different PIN proteins during cyst nematode infection. Based on our results, we postulate a model in which PIN1-mediated auxin transport is needed to deliver auxin to the initial syncytial cell, whereas PIN3 and PIN4 distribute the accumulated auxin laterally and are involved in the radial expansion of the NFS. Our data demonstrate that cyst nematodes are able to hijack the auxin distribution network in order to facilitate the infection process.
A unique genetic code change in the mitochondrial genome of the parasitic nematode Radopholus similis
Joachim EM Jacob, Bartel Vanholme, Thomas Van Leeuwen, Godelieve Gheysen
BMC Research Notes , 2009, DOI: 10.1186/1756-0500-2-192
Abstract: We present the complete mt genomic sequence (16,791 bp) of the plant-parasitic nematode Radopholus similis (class Chromadorea). Although it has a gene content similar to most other nematodes, many idiosyncrasies characterize the extremely AT-rich mt genome of R. similis (85.4% AT). The secondary structure of the large (16S) rRNA is further reduced, the gene order is unique, the large non-coding region contains two large repeats, and most interestingly, the UAA codon is reassigned from translation termination to tyrosine. In addition, 7 out of 12 protein-coding genes lack a canonical stop codon and analysis of transcriptional data showed the absence of polyadenylation. Northern blot analysis confirmed that only one strand is transcribed and processed. Furthermore, using nucleotide content bias methods, regions for the origin of replication are suggested.The extraordinary mt genome of R. similis with its unique genetic code appears to contain exceptional features correlated to DNA decoding. Therefore the genome may provide an incentive to further elucidate these barely understood processes in nematodes. This comprehension may eventually lead to parasitic nematode-specific control targets as healthy mitochondria are imperative for organism survival. In addition, the presented genome is an interesting exceptional event in genetic code evolution.Nematodes are one of the largest phyla of multicellular animals on earth with over 20,000 described species. The burrowing nematode Radopholus similis infects numerous (sub)tropical crops and is considered as one of the most damaging pests on banana. Recently transcriptomic sequence data of this parasite were studied and several 'expressed sequence tags' (ESTs) originated from genes of the mitochondrial (mt) genome [1]. Mitochondria are found in all eukaryotic cells and provide the cell with energy through the process of oxidative phosphorylation. Originating from an ancestral endosymbiotic α-proteobacterial species [2], they sti
Silencing of Mg-pat-10 and Mg-unc-87 in the Plant Parasitic Nematode Meloidogyne graminicola Using siRNAs
Joseph Nsengimana,Lander Bauters,Annelies Haegeman,Godelieve Gheysen
Agriculture , 2013, DOI: 10.3390/agriculture3030567
Abstract: Until recently, the standard method for RNA interference (RNAi)-based reverse genetics in plant parasitic nematodes (PPNs) was based on the use of long double-stranded RNA (dsRNA). This increased the chance of off-target gene silencing through interactions between different short interfering RNAs (siRNAs) and non-cognate mRNA targets. In this work, we applied gene-specific knockdown of Mg-pat-10 and Mg-unc-87 of the root knot nematode Meloidogyne graminicola, using discrete 21 bp siRNAs. The homologue of Mg-pat-10 in C. elegans encodes body wall troponin C, which is essential for muscle contraction, whereas the homologue of Mg-unc-87 encodes two proteins involved in maintenance of the structure of myofilaments in the body wall muscle of C. elegans. The knockdown at the transcript level, as seen by semi-quantitative RT-PCR analysis, indicates that the Mg-pat-10 gene was silenced after soaking the nematodes in a specific siRNA for 48 h. At 72 h post-soaking, the Mg-pat-10 mRNA level was similar to the control, indicating the recovery of expression between 48 h and 72 h post-soaking. For Mg-unc-87 the nematodes started to recover from siRNA silencing 24 h after thorough washing. A migration assay showed that for the nematodes that were soaked in the control (siRNA of β-1,4-endoglucanase), 77% of the nematodes completed migration through the column in a 12 h period. By comparison with the control, nematodes incubated in the siRNA of pat-10 or unc-87 were significantly inhibited in their motility. After 12 h, only 6.3% of the juveniles incubated in the Mg-pat-10 siRNA and 9.3% of those incubated in Mg-unc-87 siRNA had migrated through the column, representing 91.8% and 87.9% inhibition respectively compared to the control. In the present work, we demonstrated that M. graminicola is readily susceptible to siRNAs of two genes involved in nematode motility. This is an important contribution to the progressive use of siRNA for functional analysis. Moreover, the application of RNAi in PPNs opens the way for environmentally friendly control of M. graminicola.
Student supervision as educational method in faculties of social work. A study in seven European countries
Godelieve van Hees
Journal of Social Intervention : Theory and Practice , 2011,
Abstract: Student supervision as educational method in faculties of social work. A study in seven European countries Supervision Meets Education (Van Hees & Geiβler-Piltz, 2010) is the title of a comparative study on the use of supervision in training social workers as part of the Bachelor degree programmes at seven European universities and universities of applied sciences. It is the first research project to be carried out by the Supervision in Social Work Education in Europe (SSWEE) network. Supervision is seen as an educational method and to indicate this specific form of supervision, the term “student supervision” has been used. The results of the study are based on seven case studies and a comparative analysis to answer the question: how is supervision integrated into the curriculum and why is it done in this way? The second part of the study concerns a comparative analysis of the case studies. This article details the main results of the differences and similarities not only regarding the way that “supervision” is understood in various settings but also the variety of organizational approaches to supervision within the study programmes themselves. In conclusion, we can say that this description of “the current state of play” provides common ground from which one go on to develop student supervision methodology in the context of European Higher Education and the challenges of a changing profession. Opleidingssupervisie als didactische methode in opleidingen Sociaal Werk. Een zoektocht in zeven Europese landen Dit artikel doet verslag van een vergelijkende studie naar de praktijk van supervisie in de Bachelor Social Work aan zeven verschillende Europese universiteiten en hogescholen, genaamd Supervision Meets Education (Van Hees & Geiβler-Piltz, 2010). Het betreft een onderzoeksproject van het “Network Supervision in Social Work Education in Europe (SSWEE)”. Supervisie wordt hier besproken als een didactische methode waarvoor in Nederland de term opleidingssupervisie wordt gebruikt en in de context van deze internationale studie de term student supervision. Het onderzoek bestaat uit zeven casestudies en een vergelijkende analyse om een antwoord te geven op de vraag hoe supervisie als leermethode ingebed is in het curriculum en waarom dat zo gedaan is. In dit artikel worden de resultaten van de studie besproken met betrekking tot verschillende opvattingen over supervisie en supervisiemodellen en komen overeenkomsten en verschillen in de uitvoering van de supervisiemethode aan bod. Een van de belangrijkste uitkomsten van het onderzoek is de algemene opvatting
Validation d’un dispositif en ligne d’aide à la persévérance aux études postsecondaires
Louise Sauvé,Godelieve Debeurme,Alan Wright,Nicole Racette
Revue Internationale des Technologies en Pédagogie Universitaire , 2009,
Abstract: [Fran ais] De plus en plus d’universités mettent en place des dispositifs de soutien à la persévérance aux études universitaires. Ce texte fait état du contexte de recherche justifiant la mise en ligne d’un dispositif d’aide à la persévérance aux études. SAMI-Persévérance signifie : système d’aide multimédia interactif à la persévérance aux études postsecondaires. Les difficultés éprouvées par les étudiants universitaires auxquelles SAMI-Persévérance répond, la méthodologie pour valider le dispositif auprès de 103 étudiants et les résultats sur les plans de la convivialité, de la pertinence et de l’utilité du dispositif également présentés. [English] An increasing number of universities are creating instruments to support student perseverance. This paper describes the context which leads to the creation of an online system supporting student perseverance. SAMI-Perseverance is an interactive, multi-media system supporting student perseverance in post-secondary education. The results of an instrument validation study undertaken with a sample of 103 individuals from the target population are presented. This article describes the nature of the student difficulties addressed, as well as the methodology used in the validation study. The study’s findings with regard to measures of userfriendliness, relevance, and usefulness of the instrument are described.
Soutenir la persévérance des étudiants (sur campus et à distance) dans leur première session d’études universitaires : constats de recherche et recommandations
Louise Sauvé,Godelieve Debeurme,Virginie Martel,Alan Wright
Revue Internationale des Technologies en Pédagogie Universitaire , 2007,
Abstract: [Fran ais] Quelles sont les mesures mises en place pour contrer le phénomène d’abandon des études universitaires ? Comment des outils d’aide et de soutien à la persévérance aux études, accessibles en ligne, sont-ils utilisés par des étudiants nouvellement inscrits en première session d’études universitaires ? Une étude auprès de 216 étudiants (sur campus et à distance) dans trois universités québécoises montre qu’ils ont des difficultés sur le plan des compétences et connaissances préalables, des stratégies d’apprentissage et d’autorégulation ainsi que de la lecture de l’anglais et du fran ais, et que les mesures de soutien mises en ligne (S@MI-Persévérance) ont été utilisées pour résoudre ces difficultés. [English] What are the measures that have been put into place to counter the phenomenon of abandonment in university studies ? How are online perseverance support tools used by undergraduate students experiencing their first semester of university studies ? A study of 216 students from three Quebec universities shows that students have difficulties in the following areas : prior knowledge and competences, strategies related to learning and self-regulation, reading English and French. The study also shows that the online support measures (S@MI-Persévérance) have helped the students to resolve these difficulties.
Modelling the orbital modulation of ultraviolet resonance lines in high-mass X-ray binaries
Jacco Th. van Loon,Lex Kaper,Godelieve Hammerschlag-Hensberge
Physics , 2001, DOI: 10.1051/0004-6361:20010856
Abstract: The stellar-wind structure in high-mass X-ray binaries (HMXBs) is investigated through modelling of their ultraviolet (UV) resonance lines. For the OB supergiants in two systems, Vela X-1 and 4U1700-37, high-resolution UV spectra are available; for Cyg X-1, SMC X-1, and LMC X-4 low-resolution spectra are used. In order to account for the non-monotonic velocity structure of the stellar wind, a modified version of the Sobolev Exact Integration (SEI) method by Lamers et al. (1987) is applied. The orbital modulation of the UV resonance lines provides information on the size of the Stroemgren zone surrounding the X-ray source. The amplitude of the observed orbital modulation (known as the Hatchett-McCray effect), however, also depends on the density- and velocity structure of the ambient wind. Model profiles are presented that illustrate the effect on the appearance of the HM effect by varying stellar-wind parameters. The q parameter of Hatchett & McCray (1977), as well as other parameters describing the supergiant's wind structure, are derived for the 5 systems. The X-ray luminosity needed to create the observed size of the Stroemgren zone is consistent with the observed X-ray flux. The derived wind parameters are compared to those determined in single OB supergiants of similar spectral type. Our models naturally explain the observed absence of the HM effect in 4U1700-37. The orbital modulation in Vela X-1 indicates that besides the Stroemgren zone other structures are present in the stellar wind (such as a photo-ionization wake). The ratio of the wind velocity and the escape velocity is found to be lower in OB supergiants in HMXBs than in single OB supergiants of the same effective temperature.
Composite Phaseolus vulgaris plants with transgenic roots as research tool
N Colpaert, S Tilleman, M van Montagu, G Gheysen, N Terryn
African Journal of Biotechnology , 2008,
Abstract: Large seeded grain legumes such as the common bean (Phaseolus vulgaris) and cowpea (Vigna unguiculata) are very important crops with seeds that are major protein source for people in developing countries, but their yields and improvement lag behind the economically more important cereals. For research purposes, genetic transformation is a powerful tool to obtain valuable information on gene expression and putative gene functions. In addition, through genetic transformation, candidate genes can be evaluated for their potential in agricultural biotechnology applications, such as resistance against biotic stresses. However, it remains difficult to stable genetically transform large seeded grain legumes such as Phaseolus and cowpea using Agrobacterium tumefaciens. In this paper a system is described to obtain so-called transgenic composite plants from P. vulgaris. These have a transgenic root system, obtained through Agrobacterium rhizogenes transformation of de-rooted seedlings. Their potentials for studies on important processes in the root system will be discussed.
Pregnancy Close to the Edge: An Immunosuppressive Infiltrate in the Chorionic Plate of Placentas from Uncomplicated Egg Cell Donation
Dorrith Schonkeren, Godelieve Swings, Drucilla Roberts, Frans Claas, Emile de Heer, Sicco Scherjon
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0032347
Abstract: In pregnancies achieved after egg donation (ED) tolerance towards a completely allogeneic fetus is mediated by several complex immunoregulatory mechanisms, of which numerous aspects are still unknown. A distinct lesion not described previously in the literature, was repeatedly found in the chorionic plate in a substantial portion of placentas from ED pregnancies, but never in placentas from normal term pregnancies. The aim of this study was to assess its origin and its cellular composition. The relation between the lesion, the clinical and histological parameters were assessed. In addition we investigated the relation with the number of HLA-mismatches and KIR genotype of mother and child. In ten out of twenty-six (38.5%) placentas from ED pregnancies an inflammatory lesion was present in the chorionic plate. A significantly lower incidence of pre-eclampsia was found in the group with the lesion; 0% versus 45.5%. A significant relation was found between this lesion and the presence of intervillositis, chronic deciduitis, presence of plasma cells and fibrin deposition in the decidua. Fluorescent in situ hybridisation with X/Y-chromosome probes showed that the majority of cells present in the lesion are of maternal origin. The expression of the macrophage marker CD14+ and of the type 2 macrophage (M2) marker CD163+ was significantly higher in the lesion. The incidence of a fetal HLA-C2 genotype was significantly higher in cases with a lesion compared to the group without the lesion. In conclusion, a striking relationship was observed between the presence of a not previously described inflammatory lesion in the chorionic plate and the absence of pre-eclampsia in ED pregnancies. The lesion consists of mainly maternal cells with a higher expression of the macrophage marker CD14+ and the M2 marker CD163+. These findings suggest a protective immune mechanism which might contribute to the prevention of severe clinical complications like pre-eclampsia.
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