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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    The Non-Legume Parasponia andersonii Mediates the Fitness of Nitrogen-Fixing Rhizobial Symbionts Under High Nitrogen Conditions
    Dupin, Simon E. ; Geurts, René ; Kiers, E.T. - \ 2020
    Frontiers in Plant Science 10 (2020). - ISSN 1664-462X
    host control - nitrogen fertilizer - nitrogen fixing bacteria - nodulation - non-legume - Parasponia - plant nutrition - rhizobium fitness

    Organisms rely on symbiotic associations for metabolism, protection, and energy. However, these intimate partnerships can be vulnerable to exploitation. What prevents microbial mutualists from parasitizing their hosts? In legumes, there is evidence that hosts have evolved sophisticated mechanisms to manage their symbiotic rhizobia, but the generality and evolutionary origins of these control mechanisms are under debate. Here, we focused on the symbiosis between Parasponia hosts and N2-fixing rhizobium bacteria. Parasponia is the only non-legume lineage to have evolved a rhizobial symbiosis and thus provides an evolutionary replicate to test how rhizobial exploitation is controlled. A key question is whether Parasponia hosts can prevent colonization of rhizobia under high nitrogen conditions, when the contribution of the symbiont becomes nonessential. We grew Parasponia andersonii inoculated with Bradyrhizobium elkanii under four ammonium nitrate concentrations in a controlled growth chamber. We measured shoot and root dry weight, nodule number, nodule fresh weight, nodule volume. To quantify viable rhizobial populations in planta, we crushed nodules and determined colony forming units (CFU), as a rhizobia fitness proxy. We show that, like legumes and actinorhizal plants, P. andersonii is able to control nodule symbiosis in response to exogenous nitrogen. While the relative host growth benefits of inoculation decreased with nitrogen fertilization, our highest ammonium nitrate concentration (3.75 mM) was sufficient to prevent nodule formation on inoculated roots. Rhizobial populations were highest in nitrogen free medium. While we do not yet know the mechanism, our results suggest that control mechanisms over rhizobia are not exclusive to the legume clade.

    Genetic Interaction Studies Reveal Superior Performance of Rhizobium tropici CIAT899 on a Range of Diverse East African Common Bean (Phaseolus vulgaris L.) Genotypes
    Gunnabo, A.H. ; Geurts, R. ; Wolde-Meskel, E. ; Degefu, T. ; Giller, K.E. ; Heerwaarden, J. van - \ 2019
    Applied and Environmental Microbiology 85 (2019)24. - ISSN 0099-2240
    bean genotypes - genotype-by-strain interaction - N2 fixation - nodulation - Rhizobium strains

    We studied symbiotic performance of factorial combinations of diverse rhizobial genotypes (GR) and East African common bean varieties (GL) that comprise Andean and Mesoamerican genetic groups. An initial wide screening in modified Leonard jars (LJ) was followed by evaluation of a subset of strains and genotypes in pots (contained the same, sterile medium) in which fixed nitrogen was also quantified. An additive main effect and multiplicative interaction (AMMI) model was used to identify the contribution of individual strains and plant genotypes to the GL × GR interaction. Strong and highly significant GL × GR interaction was found in the LJ experiment but with little evidence of a relation to genetic background or growth habits. The interaction was much weaker in the pot experiment, with all bean genotypes and Rhizobium strains having relatively stable performance. We found that R. etli strain CFN42 and R. tropici strains CIAT899 and NAK91 were effective across bean genotypes but with the latter showing evidence of positive interaction with two specific bean genotypes. This suggests that selection of bean varieties based on their response to inoculation is possible. On the other hand, we show that symbiotic performance is not predicted by any a priori grouping, limiting the scope for more general recommendations. The fact that the strength and pattern of GL × GR depended on growing conditions provides an important cautionary message for future studies.IMPORTANCE The existence of genotype-by-strain (GL × GR) interaction has implications for the expected stability of performance of legume inoculants and could represent both challenges and opportunities for improvement of nitrogen fixation. We find that significant genotype-by-strain interaction exists in common bean (Phaseolus vulgaris L.) but that the strength and direction of this interaction depends on the growing environment used to evaluate biomass. Strong genotype and strain main effects, combined with a lack of predictable patterns in GL × GR, suggests that at best individual bean genotypes and strains can be selected for superior additive performance. The observation that the screening environment may affect experimental outcome of GL × GR means that identified patterns should be corroborated under more realistic conditions.

    Dissecting hormonal pathways in nitrogen-fixing rhizobium symbioses
    Zeijl, Arjan van - \ 2017
    Wageningen University. Promotor(en): T. Bisseling, co-promotor(en): R. Geurts. - Wageningen : Wageningen University - ISBN 9789463436311 - 231
    plants - root nodules - rhizobium - symbiosis - cytokinins - plant-microbe interactions - biosynthesis - mutagenesis - genes - nodulation - planten - wortelknolletjes - rhizobium - symbiose - cytokininen - plant-microbe interacties - biosynthese - mutagenese - genen - knobbelvorming

    Nitrogen is a key element for plant growth. To meet nitrogen demands, some plants establish an endosymbiotic relationship with nitrogen-fixing rhizobium or Frankia bacteria. This involves formation of specialized root lateral organs, named nodules. These nodules are colonized intracellularly, which creates optimal physiological conditions for the fixation of atmospheric nitrogen by the microbial symbiont. Nitrogen-fixing endosymbioses are found among four related taxonomic orders that together form the nitrogen-fixation clade. Within this clade, nodulation is restricted to ten separate lineages that are scattered among mostly non-nodulating plant species. This limited distribution suggests that genetic adaptations that allowed nodulation to evolve occurred in a common ancestor.

    A major aim of the scientific community is to unravel the evolutionary trajectory towards a nitrogen-fixing nodule symbiosis. The formation of nitrogen-fixing root nodules is best studied in legumes (Fabaceae, order Fabales); especially in Lotus japonicus and Medicago truncatula, two species that serve as model. Legumes and Parasponia (Cannabaceae, order Rosales) represent the only two lineages that can form nodules with rhizobium bacteria. Studies on M. truncatula, L. japonicus and Parasponia showed, amongst others, that nodule formation is initiated upon perception of rhizobial secreted lipo-chitooligosaccharide (LCO) signals. These signals are structurally related to the symbiotic signals produced by arbuscular mycorrhizal fungi. These obligate biotropic fungi colonize roots of most land plants and form dense hyphal structures inside existing root cortical cells.

    Rhizobial and mycorrhizal LCOs are perceived by LysM-domain-containing receptor-like kinases. These activate a signaling pathway that is largely shared between both symbioses. Symbiotic LCO receptors are closely related to chitin innate immune receptors, and some receptors even function in symbiotic as well as innate immune signaling. In Chapter 2, I review the intertwining of symbiotic LCO perception and chitin-triggered immunity. Furthermore, I discuss how rhizobia and mycorrhiza might employ LCO signaling to modulate plant immunity. In a perspective, I speculate on a role for plant hormones in immune modulation, besides an important function in nodule organogenesis.

    In legumes, nodule organogenesis requires activation of cytokinin signaling. Mutants in the orthologous cytokinin receptor genes MtCRE1 and LjLHK1 in M. truncatula and L. japonicus, respectively, are severely affected in nodule formation. However, how cytokinin signaling is activated in response to rhizobium LCO perception and to what extent this contributes to rhizobium LCO-induced signaling remained elusive. In Chapter 3, I show that the majority of transcriptional changes induced in wild-type M. truncatula, upon application of rhizobium LCOs, are dependent on activation of MtCRE1-mediated cytokinin signaling. Among the genes induced in wild type are several involved in cytokinin biosynthesis. Consistently, cytokinin measurements indicate that cytokinins rapidly accumulate in M. truncatula roots upon treatment with rhizobium LCOs. This includes the bioactive cytokinins isopentenyl adenine and trans-zeatin. Therefore, I argue that cytokinin accumulation represents a key step in the pathway leading to legume root nodule organogenesis.

    Strigolactones are plant hormones of which biosynthesis is increased in response to nutrient limitation. In rice (Oryza sativa) and M. truncatula, this response requires the GRAS-type transcriptional regulators NSP1 and NSP2. Both proteins regulate expression of DWARF27 (D27), which encodes an enzyme that performs the first committed step in strigolactone biosynthesis. NSP1 and NSP2 are also essential components of the signaling cascade that controls legume root nodule formation. In line with this, I questioned whether the NSP1-NSP2-D27 regulatory module functions in rhizobium symbiosis. In Chapter 4, I show that in M. truncatula MtD27 expression is induced within hours after treatment with rhizobium LCOs. Spatiotemporal expression studies revealed that MtD27 is expressed in the dividing cells of the nodule primordium. At later stages, its expression becomes confined to the meristem and distal infection zone of the mature nodule. Analysis of the expression pattern of MtCCD7 and MtCCD8, two additional strigolactone biosynthesis genes, showed that these genes are co-expressed with MtD27 in nodule primordia and mature nodules. Additionally, I show that symbiotic expression of MtD27 requires MtNSP1 and MtNSP2. This suggests that the NSP1-NSP2-D27 regulatory module is co-opted in rhizobium symbiosis.

    Comparative studies between legumes and nodulating non-legumes could identify shared genetic networks required for nodule formation. We recently adopted Parasponia, the only non-legume lineage able to engage in rhizobium symbiosis. However, to perform functional studies, powerful reverse genetic tools for Parasponia are essential. In Chapter 5, I describe the development of a fast and efficient protocol for CRISPR/Cas9-mediated mutagenesis in Agrobacterium tumefaciens-transformed Parasponia andersonii plants. Using this protocol, stable mutants can be obtained in a period of three months. These mutants can be effectively propagated in vitro, which allows phenotypic evaluation already in the T0 generation. As such, phenotypes can be obtained within six months after transformation. As proof-of-principle, we mutated PanHK4, PanEIN2, PanNSP1 and PanNSP2. These genes are putatively involved in cytokinin and ethylene signaling and regulation of strigolactone biosynthesis, respectively. Additionally, orthologues of these genes perform essential symbiotic functions in legumes. Panhk4 and Panein2 knockout mutants display developmental phenotypes associated with reduced cytokinin and ethylene signaling. Analysis of Pannsp1 and Pannsp2 mutants revealed a conserved role for NSP1 and NSP2 in regulation of the strigolactone biosynthesis genes D27 and MAX1 and root nodule organogenesis. In contrast, symbiotic mutant phenotypes of Panhk4 and Panein2 mutants are different from their legume counterparts. This illustrates the value of Parasponia as comparative model - besides legumes - to study the genetics underlying rhizobium symbiosis.

    Phylogenetic reconstruction showed that the Parasponia lineage is embedded in the non-nodulating Trema genus. This close relationship suggests that Parasponia and Trema only recently diverged in nodulation ability. In Chapter 6, I exploited this close relationship to question whether the nodulation trait is associated with gene expression differentiation. To this end, I sequenced root transcriptomes of two Parasponia and three Trema species. Principal component analysis separated all Parasponia samples from those of Trema along the first principal component. This component explains more than half of the observed variance, indicating that the root transcriptomes of two Parasponia species are distinct from that of the Trema sister species T. levigata, as well as the outgroup species T. orientalis and T. tomentosa. To determine, whether the transcriptional differences between Parasponia and Trema are relevant in a symbiotic context, I compared the list of differentially expressed genes to a list of genes that show nodule-enhanced expression in P. andersonii. This revealed significant enrichment of nodule-enhanced genes among genes that lower expressed in roots of Parasponia compared to Trema. Among the genes differentially expressed between Parasponia and Trema roots are several involved in mycorrhizal symbiosis as well as jasmonic acid biosynthesis. Measurements of hormone concentrations, showed that Parasponia and Trema roots harbor a difference in jasmonic acid/salicylic acid balance. However, mutants in jasmonic acid biosynthesis are unaffected in nodule development. Therefore, it remains a challenge to determine whether the difference in root transcriptomes between Parasponia and Trema are relevant in a symbiotic context.

    In Chapter 7, I review hormone function in nitrogen-fixing nodule symbioses in legumes, Parasponia and actinorhizal species. In this chapter, I question whether different nodulating lineages recruited the same hormonal networks to function in nodule formation. Additionally, I discuss whether nodulating species harbor genetic adaptations in hormonal pathways that correlate with nodulation capacity.

    Nod factor receptors form heteromeric complexes and are essential for intracellular infection in Medicago nodules
    Moling, S. ; Pietraszewska-Bogiel, A. ; Postma, M. ; Fedorova, E.E. ; Hink, M.A. ; Limpens, E.H.M. ; Gadella, T.W.J. ; Bisseling, T. - \ 2014
    The Plant Cell 26 (2014)10. - ISSN 1040-4651 - p. 4188 - 4199.
    rhizobium-leguminosarum - n-2-fixing symbiosomes - root-nodules - kinase - truncatula - arabidopsis - lyk3 - phosphorylation - perception - nodulation
    Rhizobial Nod factors are the key signaling molecules in the legume-rhizobium nodule symbiosis. In this study, the role of the Nod factor receptors NOD FACTOR PERCEPTION (NFP) and LYSIN MOTIF RECEPTOR-LIKE KINASE3 (LYK3) in establishing the symbiotic interface in root nodules was investigated. It was found that inside Medicago truncatula nodules, NFP and LYK3 localize at the cell periphery in a narrow zone of about two cell layers at the nodule apex. This restricted accumulation is narrower than the region of promoter activity/mRNA accumulation and might serve to prevent the induction of defense-like responses and/or to restrict the rhizobium release to precise cell layers. The distal cell layer where the receptors accumulate at the cell periphery is part of the meristem, and the proximal layer is part of the infection zone. In these layers, the receptors can most likely perceive the bacterial Nod factors to regulate the formation of symbiotic interface. Furthermore, our Förster resonance energy transfer-fluorescence lifetime imaging microscopy analysis indicates that NFP and LYK3 form heteromeric complexes at the cell periphery in M. truncatula nodules.
    Nutrient computation for root architecture : Perspective
    Bisseling, T. ; Scheres, B. - \ 2014
    Science 346 (2014)6207. - ISSN 0036-8075 - p. 300 - 301.
    nodulation - peptide
    Evolution of a symbiotic receptor through gene duplications in the legume-rhizobium mutualism
    Mita, S. De; Streng, A. ; Bisseling, T. ; Geurts, R. - \ 2014
    New Phytologist 201 (2014)3. - ISSN 0028-646X - p. 961 - 972.
    amino-acid sites - medicago-truncatula - phylogenetic perspectives - mycorrhizal symbiosis - arbuscular mycorrhiza - populus-trichocarpa - maximum-likelihood - draft genome - land plants - nodulation
    •The symbiosis between legumes and nitrogen-fixing rhizobia co-opted pre-existing endomycorrhizal features. In particular, both symbionts release lipo-chitooligosaccharides (LCOs) that are recognized by LysM-type receptor kinases. We investigated the evolutionary history of rhizobial LCO receptor genes MtLYK3-LjNFR1 to gain insight into the evolutionary origin of the rhizobial symbiosis. •We performed a phylogenetic analysis integrating gene copies from nonlegumes and legumes, including the non-nodulating, phylogenetically basal legume Cercis chinensis. Signatures of differentiation between copies were investigated through patterns of molecular evolution. •We show that two rounds of duplication preceded the evolution of the rhizobial symbiosis in legumes. Molecular evolution patterns indicate that the resulting three paralogous gene copies experienced different selective constraints. In particular, one copy maintained the ancestral function, and another specialized into perception of rhizobial LCOs. It has been suggested that legume LCO receptors evolved from a putative ancestral defense-related chitin receptor through the acquisition of two kinase motifs. However, the phylogenetic analysis shows that these domains are actually ancestral, suggesting that this scenario is unlikely. •Our study underlines the evolutionary significance of gene duplication and subsequent neofunctionalization in MtLYK3-LjNFR1 genes. We hypothesize that their ancestor was more likely a mycorrhizal LCO receptor, than a defense-related receptor kinase.
    Comparative and functional analysis of NODULATION SIGNALING PATHWAY 1 (NSP1) and NSP2 in rice and Medicago
    Liu, W. - \ 2013
    Wageningen University. Promotor(en): Ton Bisseling, co-promotor(en): Rene Geurts. - S.l. : s.n. - ISBN 9789461736369 - 147
    oryza - medicago - knobbelvorming - symbiose - genen - rhizobium - wortelknolletjes - stikstoffixatie - oryza - medicago - nodulation - symbiosis - genes - rhizobium - root nodules - nitrogen fixation
    Efficiency of Agrobacterium rhizogenes-mediated root transformation of Parasponia and Trema is temperature dependent
    Cao, Q. ; Camp, R. Op den; Seifi Kalhor, M. ; Bisseling, T. ; Geurts, R. - \ 2012
    Plant Growth Regulation 68 (2012)3. - ISSN 0167-6903 - p. 459 - 465.
    medicago-truncatula - gene-transfer - non-legume - plants - nitrogen - andersonii - nodulation - rhizobium - phaseolus - sequences
    Parasponia trees are the only non-legume species that form nitrogen-fixing root nodules with rhizobium. Based on its taxonomic position in relation to legumes (Fabaceae), it is most likely that both lineages have gained this symbiotic capacity independently. Therefore, Parasponia forms a bridging species to understand the evolutionary constraints underlying this symbiosis. However, absence of key technologies to genetically modify Parasponia seriously impeded studies on these species. We employed Agrobacterium rhizogenes to create composite Parasponia andersonii plants that harbour transgenic roots. Here, we provide an optimized protocol to infect P. andersonii as well as its non-symbiotic sister species Trema tomentosa with A. rhizogenes. We show that the transformation efficiency is temperature dependent. Whereas the optimal growth temperature for both these species is 28 °C, the transformation is most efficient when co-cultivation with A. rhizogenes occurs at 21 °C. Using this optimized protocol up to 80 % transformation efficiency can be obtained. These robust transformation platforms will provide a strong tool to unravel the Parasponia–rhizobium symbiosis
    Rhizobium-legume symbiosis shares an exocytotic pathway required for arbuscle formation
    Ivanov, S. ; Fedorova, E.E. ; Limpens, E.H.M. ; Mita, S. De; Genre, A. ; Bonfante, P. ; Bisseling, T. - \ 2012
    Proceedings of the National Academy of Sciences of the United States of America 109 (2012)21. - ISSN 0027-8424 - p. 8316 - 8321.
    medicago-truncatula - root-nodules - intracellular accommodation - n-2-fixing symbiosomes - mycorrhizal symbiosis - infection threads - cell wall - membrane - genes - nodulation
    Endosymbiotic interactions are characterized by the formation of specialized membrane compartments, by the host in which the microbes are hosted, in an intracellular manner. Two well-studied examples, which are of major agricultural and ecological importance, are the widespread arbuscular mycorrhizal symbiosis and the Rhizobium–legume symbiosis. In both symbioses, the specialized host membrane that surrounds the microbes forms a symbiotic interface, which facilitates the exchange of, for example, nutrients in a controlled manner and, therefore, forms the heart of endosymbiosis. Despite their key importance, the molecular and cellular mechanisms underlying the formation of these membrane interfaces are largely unknown. Recent studies strongly suggest that the Rhizobium–legume symbiosis coopted a signaling pathway, including receptor, from the more ancient arbuscular mycorrhizal symbiosis to form a symbiotic interface. Here, we show that two highly homologous exocytotic vesicle-associated membrane proteins (VAMPs) are required for formation of the symbiotic membrane interface in both interactions. Silencing of these Medicago VAMP72 genes has a minor effect on nonsymbiotic plant development and nodule formation. However, it blocks symbiosome as well as arbuscule formation, whereas root colonization by the microbes is not affected. Identification of these VAMP72s as common symbiotic regulators in exocytotic vesicle trafficking suggests that the ancient exocytotic pathway forming the periarbuscular membrane compartment has also been coopted in the Rhizobium–legume symbiosis.
    A phylogenetic strategy based on a legume-specific whole genome duplication yields symbiotic cytokinin type-A Response Regulators
    Camp, R. Op den; Mita, S. De; Lillo, A. ; Cao, Q. ; Limpens, E.H.M. ; Bisseling, T. ; Geurts, R. - \ 2011
    Plant Physiology 157 (2011)4. - ISSN 0032-0889 - p. 2013 - 2022.
    lateral root-formation - nodule organogenesis - medicago-truncatula - lotus-japonicus - signal-transduction - diverse roles - white clover - gene family - arabidopsis - nodulation
    Legumes host their rhizobium symbiont in novel root organs, called nodules. Nodules originate from differentiated root cortical cells that de-differentiate and subsequently form nodule primordia, a process controlled by cytokinin. A whole genome duplication (WGD) has occurred at the root of the legume Papilionoideae subfamily. We hypothesize that gene pairs originating from this duplication event and are conserved in distinct Papilionoideae lineages have evolved symbiotic functions. A phylogenetic strategy was applied to search for such gene pairs in order to identify novel regulators of nodulation, using the cytokinin phosphorelay pathway as a test case. In this way two paralogous type-A cytokinin Response Regulators were identified that are involved in root nodule symbiosis. MtRR9 and MtRR11 in Medicago truncatula, and an ortholog in Lotus japonicus, are rapidly induced upon rhizobium Nod factor signaling. Constitutive expression of MtRR9 results in arrested primordia that have emerged from cortical, endodermal and pericycle cells. In legumes lateral root primordia are not exclusively formed from pericycle cells, but also involves the root cortical cell layer. Therefore, the MtRR9 induced foci of cell divisions show a strong resemblance to lateral root primordia, suggesting an ancestral function of MtRR9 in this process. Together, these findings provide a proof of principle for the applied phylogenetic strategy to identify genes with a symbiotic function in legumes.
    LysM-Type Mycorrhizal Receptor Recruited for Rhizobium Symbiosis in Nonlegume Parasponia
    Camp, R.H.M. Op den; Streng, A.J. ; Mita, S. De; Cao, Q. ; Polone, E. ; Liu, W. ; Ammiraju, J.S.S. ; Kudrna, D. ; Wing, R. ; Untergasser, A. ; Bisseling, T. ; Geurts, R. - \ 2011
    Science 331 (2011)6019. - ISSN 0036-8075 - p. 909 - 912.
    medicago-truncatula - gene family - nodulation - evolution - kinases - legume - endosymbiosis - bacteria - nodules - plants
    Rhizobium root nodule symbiosis is generally considered to be unique for legumes. However, there is one exception and that is Parasponia. In this nonlegume, the rhizobial nodule symbiosis evolved independently and is, like in legumes, induced by rhizobium Nod factors. We used Parasponia to identify genetic constrains underlying evolution of Nod factor signalling. Part of the signalling cascade, downstream of Nod factor perception, has been recruited from the more ancient arbuscular endomycorrhizal symbiosis. However, legume Nod factor receptors that activate this common signalling pathway are not essential for arbuscular endomycorrhizae. Here, we show that in Parasponia a single Nod factor-like receptor is indispensable for both symbiotic interactions. Therefore we conclude that also the Nod factor perception mechanism is recruited from the widespread endomycorrhizal symbiosis
    Boomaantastingen meer dan alleen een estetisch probleem?
    Lammeren, Andre van - \ 2009
    trees - infestation - abnormalities - plant diseases - nodulation - bark - forest nurseries - plant protection - tree care - public green areas - municipalities
    Rapportage onderzoek aantasting van de bast bij laanbomen
    Lammeren, A.A.M. van; Ruiter, N.C.A. ; Kieft, H. - \ 2009
    Wageningen : Wageningen UR, Leerstoelgroep Plantencelbiologie
    straatbomen - afwijkingen, planten - deformiteiten - knobbelvorming - schors - korstmossen - schimmels - landbouwkundig onderzoek - boomverzorging - openbaar groen - street trees - plant disorders - deformities - nodulation - cortex - lichens - fungi - agricultural research - tree care - public green areas
    In dit verslag zijn aantastingen op de stam onderzocht van Carpinus betulus ‘Frans Fontaine’, Fagus sylvatica “ Atropurpurea”, Fraxinus excelsior ‘Atlas’, Quercus palustris, Quercus robur, Sorbus latifolia “Henk Vink” en Ulmus ‘Clusius’ Daarbij is aandacht besteed aan het voorkomen en de aard en ontwikkeling van bastknobbels, baststrepen, bastscheuren, verkleuringen en het effect van epifyten zoals schimmels en korstmossen
    Rapportage onderzoek aan bastknobbels en aantasting van bast door korstmossen aantasting van bast door korstmossen
    Lammeren, A.A.M. van; Kieft, H. ; Donkers, J. - \ 2008
    Wageningen : Wageningen Universiteit en Research Centrum
    bomen - fraxinus - afwijkingen - deformiteiten - korstmossen - knobbelvorming - schors, bomen - cedrus - straatbomen - landbouwkundig onderzoek - boomkwekerijen - gemeenten - openbaar groen - trees - fraxinus - abnormalities - deformities - lichens - nodulation - bark - cedrus - street trees - agricultural research - forest nurseries - municipalities - public green areas
    In het hier beschreven onderzoek is nagegaan wat de aard en oorzaak is van het pokdalig uiterlijk van de stam van de es, wat het effect is van korstmosbegroeiing op de essenbast en hoe de reeds eerder beschreven bastknobbels ontstaan. Het is een voortgangsrapportage van een grotere studie naar oorzaak en gevolg van boomaantastingen. Hier worden verschijnselen beschreven maar er is vooralsnog geen uitspraak over hoe de aantastingen zoals bastknobbels zijn veroorzaakt
    Oriënterend onderzoek naar de oorzaak van het ontstaan van bastknobbels in laanbomen op de kwekerij
    Doorn, J. van; Sluis, B.J. van der - \ 2008
    [S.l.] : PPO Bomen - 5
    straatbomen - afwijkingen, planten - deformiteiten - knobbelvorming - schors, bomen - boomkwekerijen - boomverzorging - openbaar groen - street trees - plant disorders - deformities - nodulation - bark - forest nurseries - tree care - public green areas
    Bastknobbels op de stam van laanbomen komen niet alleen in het stedelijk groen voor, maar ook op de boomkwekerij in jongere bomen. In een consultancy opdracht is gekeken in hoeverre er een relatie kan worden gevonden met een infectie van fytoplasma’s. Dit is in 30 gevallen onderzocht bij Fagus, Fraxinus, Aesculus en Tilia met behulp van PCR technieken. Er konden geen fytoplasma’s worden aangetoond. De oorzaak van bastknobbels blijft vooralsnog onduidelijk
    Bastknobbels op straatbomen
    Lammeren, A.A.M. van; Kuik, A.J. van - \ 2007
    Bomen, het vakblad voor de boomverzorging 2007 (2007)1. - p. 4 - 7.
    straatbomen - aantasting - knobbelvorming - plantenziekten - afwijkingen - boomverzorging - street trees - infestation - nodulation - plant diseases - abnormalities - tree care
    Onlangs bleken in Alphen aan den Rijn diverse straatbomen eigenaardige knobbels op de stam te vertonen. De knobbels kunnen zich betrekkelijk snel tot grote uitwassen ontwikkelen, met voorlopig nog geen gevolgen voor de boomgroei. De gemeente gaf opdracht tot een onderzoek naar de ontwikkeling en aard van de knobbels. Dit artikel vormt de neerslag van dat onderzoek.
    Bastknobbels op bomen trekken aandacht
    Lammeren, A. van; Kuik, A.J. van - \ 2007
    Tuin en Landschap 29 (2007)7. - ISSN 0165-3350 - p. 38 - 39.
    straatbomen - houtachtige planten als sierplanten - afwijkingen - deformiteiten - knobbelvorming - fraxinus - gleditsia - acer - street trees - ornamental woody plants - abnormalities - deformities - nodulation - fraxinus - gleditsia - acer
    In Alphen aan den Rijn ontwikkelen zich in rap tempo opmerkelijke knobbels op de stammen van diverse soorten straatbomen. Op verzoek van de gemeenten doen PPO en Wageningen Universiteit onderzoek. Gekeken is naar de opbouw van de uitwassen. Wat de gevolgen zijn voor de bomen, die op het oog vitaal zijn, is nog een open vraag
    Analysis of nodule meristem persistence and ENOD40 functioning in Medicago truncatula nodule formation
    Wan Xi, - \ 2007
    Wageningen University. Promotor(en): Ton Bisseling, co-promotor(en): Henk Franssen. - [S.l.] : S.n. - ISBN 9789085048343 - 108
    medicago truncatula - wortelknolletjes - genen - bacteriën - knobbelvorming - messenger rna - wortelmeristemen - medicago truncatula - root nodules - genes - bacteria - nodulation - messenger rna - root meristems
    Medicago root nodules are formed as a result of the interaction of the plant with the soil-borne bacterium Sinorhizobium meliloti. Several plant genes are induced during nodule formation and MtENOD40 is one of the earliest genes activated. The precise function as well as the molecule harboring the biological activity of ENOD40, however, remains unknown. In this thesis, we conducted experiments aiming at filling this gap in knowledge concerning ENOD40. As two copies of ENOD40 are present in the genome of Medicago, we used gene-specific knock-down of the two genes to determine whether both genes are involved in nodule formation. This is described in chapter 2. We showed that the number of nodules per root, in case expression of both genes was reduced, was lower than the number of nodules per root in case either of the two genes was reduced. This showed that both genes are involved in initiation of nodule formation and the two genes work in an additive manner in nodule initiation. Furthermore, we showed that reduced expression of either MtENOD40 gene induced premature nodule senescence and that both genes are essential for the development of the bacterium into the nitrogen-fixing bacteroid. Whereas the vast majority of eukaryotic mRNAs code for proteins, a common feature of ENOD40 genes is the absence of a long open reading frame (ORF). Instead, ENOD40s share at the nucleotide level two highly conserved regions, box1 and box2, of which box1, in almost all ENOD40 genes, contains an ORF for a peptide of 10-13 amino acids. In chapter 3, we showed that over-expression of MtENOD40, as well as box1 or box2 only, induced premature nodule senescence. We showed that the box1 activity was mediated by the 13 amino acid peptide encoded within box1, while the box2 activity is not peptide mediated. Using transgenic Medicago lines containing the marker gene coding for RED FLUORESCENT PROTEIN (RFP) with or without box2 sequences in its 3’UTR, we showed that the translation of the mRNA with box2 yielded less RFP than the mRNA lacking box2. This showed that box2 is involved in the regulation of translation of RFP and suggests that box2 functions in a similar way in the regulation of the translation of the peptide encoded by box1 in MtENOD40. Thus our data as described in chapters 2 and 3 propose a role of the peptide in nodule initiation and at a later stage in nodule development, most likely in avoiding senescence. In this latter process the concentration of the peptide is critical as over-expression and reduction in expression of MtENOD40 induces premature nodule senescence. Medicago nodules have a persistent meristem, like roots. In the root meristem the persistence of the meristematic activity is maintained by a group of stem cells that surround the so-called quiescent center cells (QC). These maintain stem cell identity in the surrounding cells and are mitotically inactive themselves. However, it is not known whether a similar mechanism controls the persistence of a nodule meristem. As nodules are root-borne organs, we studied whether promoters of QC and stem cell-specific genes of Arabidopsis were activated in the nodule meristem of Medicago. Our data, as described in chapter 4, showed that three out of the five tested markers for QC and stem cell-specific genes are activated in cells that form a ring at the periphery of the nodule meristem. The activity of the other two markers was restricted to cells that are part of this ring of cells, but only were active in cells abutting on nodule vascular bundles. These data suggest that the nodule meristem contains two different stem cell domains and that the cells in which QC markers are activated may act as organizers and share properties with the QC of the root. As the cells expressing the tested stem cell marker are at the periphery of the nodule meristem, we propose that these cells form the stem cells for nodule peripheral and vascular tissues. Strikingly, none of the tested promoters was activated in cells in the central part of the nodule meristem. This part of the meristem adds cells to the central tissue of the nodule. However, it remains to be determined whether or not the mitotic activity of cells in the nodule meristem is maintained by the QC cells identified at the periphery of the meristem.
    Medicago truncatula ENOD40-1 and ENOD40-2 are both involved in nodule initiation and bacteroid development
    Wan, X. ; Hontelez, J. ; Lillo, A. ; Guarnerio, C. ; Peut, D. van de; Fedorova, E. ; Bisseling, T. ; Franssen, H. - \ 2007
    Journal of Experimental Botany 58 (2007)8. - ISSN 0022-0957 - p. 2033 - 2041.
    legume root-nodules - gene enod40 - alfalfa nodules - lotus-japonicus - expression - rna - nodulation - induction - growth - organogenesis
    The establishment of a nitrogen-fixing root nodule on legumes requires the induction of mitotic activity of cortical cells leading to the formation of the nodule primordium and the infection process by which the bacteria enter this primordium. Several genes are up-regulated during these processes, among them ENOD40. Here it is shown, by using gene-specific knock-down of the two Medicago truncatula ENOD40 genes, that both genes are involved in nodule initiation. Further, during nodule development, both genes are essential for bacteroid development.
    Anatomisch onderzoek naar het ontstaan en de opbouw van bastknobbels in straatbomen: Het onderzoek is uitgevoerd bij Fraxinus excelsior 'Atlas' en 'Westhofs Glorie', Gelditsia triacanthos 'Inermis' en Acer saccharinum 'Pyramidale'
    Kuik, A.J. van; Lammeren, A.A.M. van - \ 2006
    Lisse : PPO Bloembollen, Boomkwekerij en Fruit (PPO rapport 3234032400) - 38
    afwijkingen, planten - knobbelvorming - straatbomen - bosbomen - fraxinus excelsior - gleditsia triacanthos - acer saccharinum - bemonsteren - celbiologie - zuid-holland - plant disorders - nodulation - street trees - forest trees - fraxinus excelsior - gleditsia triacanthos - acer saccharinum - sampling - cellular biology - zuid-holland
    In opdracht van de gemeente Alphen aan den Rijn is een onderzoek opgezet naar de ontwikkeling en opbouw van bastknobbels in een aantal boomsoorten. Deze bastknobbels zijn de laatste jaren in aantal sterk toegenomen en komen op verschillende boomsoorten voor, zowel dicht bij het maaiveld, midden op de stam als ook net onder de kroon. Voor het onderzoek zijn op 7 september 2006 op 5 locaties in Alphen aan den Rijn monsters genomen van vijf verschillende bomen: Fraxinus excelsior ‘Atlas’, Fraxinus excelsior ‘Westhofs Glorie’, 2 x Gleditsia triacanthos ‘Inermis’ en Acer saccharinum ‘Pyramidale’. Het blijkt dat de knobbels bij Fraxinus excelsior en Gleditsia triacanthos op eenzelfde wijze ontstaan: dicht bij het stamoppervlak. De ontstaanswijze van de knobbels bij Acer is anders
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