114 research outputs found

    Nematodes

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    Plant-parasitic nematodes (PPNs) represent an important constraint for plant production worldwide. They are widely distributed around the world and are able to parasitize every plant species. Furthermore, the current restrictions on the use of chemical nematicides have increased the problems caused by PPNs, irrespec-tive of the production system. Intensive vegetable production under protected culti-vation is the system most vulnerable to PPN, especially to root-knot nematodes.Postprint (published version

    Parthenogenesis in insects: the centriole renaissance

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    Building a new organism usually requires the contribution of two differently shaped haploid cells, the male and female gametes, each providing its genetic material to restore diploidy of the new born zygote. The successful execution of this process requires defined sequential steps that must be completed in space and time. Otherwise, development fails. Relevant among the earlier steps are pronuclear migration and formation of the first mitotic spindle that promote the mixing of parental chromosomes and the formation of the zygotic nucleus. A complex microtubule network ensures the proper execution of these processes. Instrumental to microtubule organization and bipolar spindle assembly is a distinct non-membranous organelle, the centrosome. Centrosome inheritance during fertilization is biparental, since both gametes provide essential components to build a functional centrosome. This model does not explain, however, centrosome formation during parthenogenetic development, a special mode of sexual reproduction in which the unfertilized egg develops without the contribution of the male gamete. Moreover, whereas fertilization is a relevant example in which the cells actively check the presence of only one centrosome, to avoid multipolar spindle formation, the development of parthenogenetic eggs is ensured, at least in insects, by the de novo assembly of multiple centrosomes. Here, we will focus our attention on the assembly of functional centrosomes following fertilization and during parthenogenetic development in insects. Parthenogenetic development in which unfertilized eggs are naturally depleted of centrosomes would provide a useful experimental system to investigate centriole assembly and duplication together with centrosome formation and maturation

    Arabidopsis leucine-rich repeat receptor–like kinase NILR1 is required for induction of innate immunity to parasitic nematodes

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    Plant-parasitic nematodes are destructive pests causing losses of billions of dollars annually. An effective plant defence against pathogens relies on the recognition of pathogen-associated molecular patterns (PAMPs) by surface-localised receptors leading to the activation of PAMP-triggered immunity (PTI). Extensive studies have been conducted to characterise the role of PTI in various models of plant-pathogen interactions. However, far less is known about the role of PTI in roots in general and in plant-nematode interactions in particular. Here we show that nematode-derived proteinaceous elicitor/s is/are capable of inducing PTI in Arabidopsis in a manner dependent on the common immune co-receptor BAK1. Consistent with the role played by BAK1, we identified a leucine-rich repeat receptor-like kinase, termed NILR1 that is specifically regulated upon infection by nematodes. We show that NILR1 is essential for PTI responses initiated by nematodes and nilr1 loss-of-function mutants are hypersusceptible to a broad category of nematodes. To our knowledge, NILR1 is the first example of an immune receptor that is involved in induction of basal immunity (PTI) in plants or in animals in response to nematodes. Manipulation of NILR1 will provide new options for nematode control in crop plants in future

    The feeding tube of cyst nematodes: characterisation of protein exclusion

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    Plant parasitic nematodes comprise several groups; the most economically damaging of these are the sedentary endoparasites. Sedentary endoparasitic nematodes are obligate biotrophs and modify host root tissue, using a suite of effector proteins, to create a feeding site that is their sole source of nutrition. They feed by withdrawing host cell assimilate from the feeding site though a structure known as the feeding tube. The function, composition and molecular characteristics of feeding tubes are poorly characterised. It is hypothesised that the feeding tube facilitates uptake of host cell assimilate by acting as a molecular sieve. Several studies, using molecular mass as the sole indicator of protein size, have given contradictory results about the exclusion limits of the cyst nematode feeding tube. In this study we propose a method to predict protein size, based on protein database coordinates in silico. We tested the validity of these predictions using travelling wave ion mobility spectrometry--mass spectrometry, where predictions and measured values were within approximately 6%. We used the predictions, coupled with mass spectrometry, analytical ultracentrifugation and protein electrophoresis, to resolve previous conflicts and define the exclusion characteristics of the cyst nematode feeding tube. Heterogeneity was tested in the liquid, solid and gas phase to provide a comprehensive evaluation of three proteins of particular interest to feeding tube size exclusion, GFP, mRFP and Dual PI. The data and procedures described here could be applied to the design of plant expressed defence compounds intended for uptake into cyst nematodes. We also highlight the need to assess protein heterogeneity when creating novel fusion proteins

    Структура вірусних діарей у дітей на Сумщині

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    Гострі кишкові інфекції (ГКІ) стійко посідають одне з провідних місць серед усіх інфекційних захворювань, характеризуються широкою поширеністю, високою частотою розвитку тяжких форм і ускладнень. Прогрес у галузі лабораторних методів діагностики дозволив істотно розширити уявлення про етіологічні чинники хвороби: у країнах, що розвиваються, домінують діарейні інфекції бактерійної етіології, а в економічно розвинених країнах - вірусної. При цитуванні документа, використовуйте посилання http://essuir.sumdu.edu.ua/handle/123456789/3228

    Inheritance of resistance to root-lesion nematodes (Pratylenchus thornei and P. neglectus) in five doubled-haploid populations of wheat

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    Nematode species Pratylenchus thornei and P. neglectus are the two most important root-lesion nematodes affecting wheat (Triticum aestivum L.) and other grain crops in Australia. For practical plant breeding, it will be valuable to know the mode of inheritance of resistance and whether the same set of genes confer resistance to both species. We evaluated reactions to P. thornei and P. neglectus of glasshouse-inoculated plants of five doubled-haploid populations derived from five resistant synthetic hexpaloid wheat lines, each crossed to the susceptible Australian wheat cultivar Janz. For each cross we determined genetic variance, heritability and minimum number of effective resistance genes for each nematode species. Distributions of nematode numbers for both species were continuous for all doubled-haploid populations. Heritabilities were high and the resistances were controlled by 4-7 genes. There was no genetic correlation between resistance to P. thornei and to P. neglectus in four of the populations and a significant but low correlation in one. Therefore, resistances to P. thornei and to P. neglectus are probably inherited quantitatively and independently in four of these synthetic hexaploid wheat populations, with the possibility of at least one genetic factor contributing to resistance to both species in one of the populations. Parents with the greatest level of resistance will be the best to use as donor parents to adapted cultivars, and selection of resistance to both species in early generations will be optimal to carry resistance through successive cycles of inbreeding to produce resistant cultivars for release

    Interactions between nematodes and their microbial enemies in coastal sand dunes

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    European foredunes are almost exclusively colonised by Ammophila arenaria, and both the natural succession and the die-out of this plant have been linked to populations of plant-parasitic nematodes (PPN). The overarching aim of this study was to investigate top-down control processes of PPN in these natural ecosystems through comparative analyses of the diversity and dynamics of PPN and their microbial enemies. Our specific aims were, first, to identify and quantify PPN microbial enemies in European sand dunes; second, to assess their life history traits, their spatial and temporal variation in these ecosystems, and third, to evaluate their control potential of PPN populations. This was done by seasonal sampling of a range of sites and making observations on both the nematode and the microbial enemy communities in rhizosphere sand. Nine different nematode microbial enemies belonging to different functional groups were detected in European sand dunes. Their high diversity in these low productivity ecosystems could both result from or lead to the lack of dominance of a particular nematode genus. The distribution of microbial enemies was spatially and temporally variable, both among and within sampling sites. Obligate parasites, either with low host-specificity or having the ability to form an environmentally resistant propagule, are favoured in these ecosystems and are more frequent and abundant than facultative parasites. Three microbial enemies correlated, either positively or negatively, with PPN population size: Catenaria spp., Hirsutella rhossiliensis and Pasteuria penetrans. Microbial-enemy supported links in the food-web may be involved in the control of PPN populations through indirect effects. The endospore-forming P. penetrans was the most successful top-down control agent, and was implicated in the direct control of Meloidogyne spp. and indirect facilitation of Pratylenchus spp. Overall, our findings suggest strong and diverse top-down control effects on the nematode community in these natural ecosystems.Peer reviewe

    The map-1 Gene Family in Root-Knot Nematodes, Meloidogyne spp.: A Set of Taxonomically Restricted Genes Specific to Clonal Species

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    Taxonomically restricted genes (TRGs), i.e., genes that are restricted to a limited subset of phylogenetically related organisms, may be important in adaptation. In parasitic organisms, TRG-encoded proteins are possible determinants of the specificity of host-parasite interactions. In the root-knot nematode (RKN) Meloidogyne incognita, the map-1 gene family encodes expansin-like proteins that are secreted into plant tissues during parasitism, thought to act as effectors to promote successful root infection. MAP-1 proteins exhibit a modular architecture, with variable number and arrangement of 58 and 13-aa domains in their central part. Here, we address the evolutionary origins of this gene family using a combination of bioinformatics and molecular biology approaches. Map-1 genes were solely identified in one single member of the phylum Nematoda, i.e., the genus Meloidogyne, and not detected in any other nematode, thus indicating that the map-1 gene family is indeed a TRG family. A phylogenetic analysis of the distribution of map-1 genes in RKNs further showed that these genes are specifically present in species that reproduce by mitotic parthenogenesis, with the exception of M. floridensis, and could not be detected in RKNs reproducing by either meiotic parthenogenesis or amphimixis. These results highlight the divergence between mitotic and meiotic RKN species as a critical transition in the evolutionary history of these parasites. Analysis of the sequence conservation and organization of repeated domains in map-1 genes suggests that gene duplication(s) together with domain loss/duplication have contributed to the evolution of the map-1 family, and that some strong selection mechanism may be acting upon these genes to maintain their functional role(s) in the specificity of the plant-RKN interactions

    Transgenic Potatoes for Potato Cyst Nematode Control Can Replace Pesticide Use without Impact on Soil Quality

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    Current and future global crop yields depend upon soil quality to which soil organisms make an important contribution. The European Union seeks to protect European soils and their biodiversity for instance by amending its Directive on pesticide usage. This poses a challenge for control of Globodera pallida (a potato cyst nematode) for which both natural resistance and rotational control are inadequate. One approach of high potential is transgenically based resistance. This work demonstrates the potential in the field of a new transgenic trait for control of G. pallida that suppresses root invasion. It also investigates its impact and that of a second transgenic trait on the non-target soil nematode community. We establish that a peptide that disrupts chemoreception of nematodes without a lethal effect provides resistance to G. pallida in both a containment and a field trial when precisely targeted under control of a root tip-specific promoter. In addition we combine DNA barcoding and quantitative PCR to recognise nematode genera from soil samples without microscope-based observation and use the method for nematode faunal analysis. This approach establishes that the peptide and a cysteine proteinase inhibitor that offer distinct bases for transgenic plant resistance to G. pallida do so without impact on the non-target nematode soil community

    Hybridisation of Australian chickpea cultivars with wild Cicer spp. increases resistance to root-lesion nematodes (Pratylenchus thornei and P. neglectus)

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    Australian and international chickpea (Cicer arietinum) cultivars and germplasm accessions, and wild annual Cicer spp. in the primary and secondary gene pools, were assessed in glasshouse experiments for levels of resistance to the root-lesion nematodes Pratylenchus thornei and P. neglectus. Lines were grown in replicated experiments in pasteurised soil inoculated with a pure culture of either P. thornei or P. neglectus and the population density of the nematodes in the soil plus roots after 16 weeks growth was used as a measure of resistance. Combined statistical analyses of experiments (nine for P. thornei and four for P. neglectus) were conducted and genotypes were assessed using best linear unbiased predictions. Australian and international chickpea cultivars possessed a similar range of susceptibilities through to partial resistance. Wild relatives from both the primary (C. reticulatum and C. echinospermum) and secondary (C. bijugum) gene pools of chickpea were generally more resistant than commercial chickpea cultivars to either P. thornei or P. neglectus or both. Wild relatives of chickpea have probably evolved to have resistance to endemic root-lesion nematodes whereas modern chickpea cultivars constitute a narrower gene pool with respect to nematode resistance. Resistant accessions of C. reticulatum and C. echinospermum were crossed and topcrossed with desi chickpea cultivars and resistant F 4 lines were obtained. Development of commercial cultivars with the high levels of resistance to P. thornei and P. neglectus in these hybrids will be most valuable for areas of the Australian grain region and other parts of the world where alternating chickpea and wheat crops are the preferred rotatio
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