Genetic and immunological comparison of the cladoceran parasite Pasteuria ramosa with the nematode parasite Pasteuria penetrans. (65/189)

Pasteuria penetrans, an obligate endospore-forming parasite of Meloidogyne spp. (root knot nematodes), has been identified as a promising agent for biocontrol of these destructive agricultural crop pests. Pasteuria ramosa, an obligate parasite of water fleas (Daphnia spp.), has been shown to modulate cladoceran populations in natural ecosystems. Selected sporulation genes and an epitope associated with the spore envelope of these related species were compared. The sigE and spoIIAA/spoIIAB genes differentiate the two species to a greater extent than 16S rRNA and may serve as probes to differentiate the species. Single-nucleotide variations were observed in several conserved genes of five distinct populations of P. ramosa, and while most of these variations are silent single-nucleotide polymorphisms, a few result in conservative amino acid substitutions. A monoclonal antibody directed against an adhesin epitope present on P. penetrans P20 endospores, previously determined to be specific for Pasteuria spp. associated with several phytopathogenic nematodes, also detects an epitope associated with P. ramosa endospores. Immunoblotting provided patterns that differentiate P. ramosa from other Pasteuria spp. This monoclonal antibody thus provides a probe with which to detect and discriminate endospores of different Pasteuria spp. The presence of a shared adhesin epitope in two species with such ecologically distant hosts suggests that there is an ancient and ecologically significant recognition process in these endospore-forming bacilli that contributes to the virulence of both species in their respective hosts.  (+info)

Characterisation of potential adhesins of the bacterium Pasteuria penetrans, and of putative receptors on the cuticle of Meloidogyne incognita, a nematode host. (66/189)

Pasteuria penetrans spores were fragmented by glass bead vortexing, producing exosporial membranes and spore fragments, which consisted of fibre bundles. Both exosporia and spore fragments are capable of host-specific attachment to the cuticle of Meloidogyne incognita, a root-knot nematode host. Putative M. incognita receptors appear to be soluble in beta-mercaptoethanol (BME) but not SDS, and are also sensitive to tryptic digestion and deglycosylation by endoglycosidase F. Polyclonal antibodies against intact spores and spore fragments of antispore antibodies produced 100% inhibition. The antibodies, however, did not show preferential staining of particular spore structures in thin section immunolabelling studies. Exposure of Pasteuria penetrans spores to HCl or urea-SDS-dithiothreitol renders them incapable of attachment to their host juveniles and extensively disrupts fibres that surround the spore core. Protein extracts from spore fragments or from exosporial membranes are identical, and urea-BME extracts from either structure, but not SDS extracts, can inhibit the attachment of spores to juveniles by 60-80%. An inhibitory BME extract from spore fragments was analysed by anion-exchange chromatography and adsorption onto host cuticle followed by immunoblotting. It appeared to contain six potential spore adhesins of approximate Mr 24-29, 38-47, 59, 89, 126, and 190 (x10(3)). Lectin affinity blotting with wheat germ agglutinin and concanavalin A showed that all of these proteins bear terminal N-acetylglucosamine residues and the 38-47 kDa band also bears terminal Glc/Man residues.(ABSTRACT TRUNCATED AT 250 WORDS)  (+info)

Histological characterization of root-knot nematode resistance in cowpea and its relation to reactive oxygen species modulation. (67/189)

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Analysis of a horizontally transferred pathway involved in vitamin B6 biosynthesis from the soybean cyst nematode Heterodera glycines. (68/189)

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A role for AtWRKY23 in feeding site establishment of plant-parasitic nematodes. (69/189)

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A novel negative regulatory factor for nematicidal Cry protein gene expression in Bacillus thuringiensis. (70/189)

A 3-kb HindIII fragment bearing the cry6Aa2 gene and the adjacent and intergenic regions was cloned from Bacillus thuringiensis strain YBT-1518. Two open reading frames (ORFs), namely, orf1 (termed cry6Aa2) and orf2 that were separated by an inverted-repeat sequence were identified. orf1 encoded a 54-kDa protein that exhibited high toxicity to the plant-parasitic nematode Meloidogyne hapla. The orf2 expression product was not detected by SDS-PAGE, but its mRNA was detected by RT-PCR. The orf2 coexpressed with orf1 at a high level in the absence of the inverted-repeat sequence, whereas, the expression level of orf1 was decreased. When orf2 was mutated, the level of orf1 expression was enhanced obviously. In conclusion, the inverted-repeat sequence disturbs orf2 expression, and the orf2 downregulates orf1 expression. This is an example of novel negative regulation in B. thuringiensis and a potential method for enhancing the expression level of cry genes.  (+info)

Genetic tests of ancient asexuality in root knot nematodes reveal recent hybrid origins. (71/189)

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Evaluation of the effect of ecologic on root knot nematode, Meloidogyne incognita, and tomato plant, Lycopersicon esculenum. (72/189)

Nonchemical methods and strategies for nematode management including cultural methods and engineered measures have been recommended as an alternative to methyl bromide (a major soil fumigant), due to its role in the depletion of the ozone layer. Hence, an international agreement has recently been reached calling for its reduced consumption and complete phasing out. This present research evaluates the potential of Ecologic, a biological, marine shell meal chitin material, as a soil amendment management agent for root knot nematode, Meloidogyne incognita, control, and its effect on the growth of Floradel tomato plant, Lycopersicon esculentum. To accomplish this goal, studies were conducted during which, experimental pots were set up in greenhouse environments using sterilized soil inoculated with 5,000 root-knot eggs per 1500 g soil. There were 4 treatments and 5 replications. Treatments were: No chitin; 50 g chitin; 100 g chitin; and 200 g chitin. A two-week wait period following Ecologic amendment preceded Floradel tomato planting to allow breakdown of the chitin material into the soil. Fresh and dry weights of shoot and root materials were taken as growth end-points. A statistically significant difference (p < or = 0.05) was obtained with regard to the growth rate of L. esculentum at 100 g chitin treatment compared to the control with no chitin. Mean fresh weights of Floradel tomato were 78.0 +/- 22.3 g, 81.0 +/- 20.3 g, 109.0 +/- 25.4 g and 102.0 +/- 33.3 g at 0, 50, 100 and 200 g chitin, respectively. The analysis of root knot nematode concentrations indicated a substantial effect on reproduction rate associated with chitin amendment. Study results showed a significant decrease in both root knot nematode eggs and juveniles (J2) at 100g and 200 g Ecologic chitin levels, however, an increase in nematode concentrations was recorded at the 50 g Ecologic chitin level (p < or = 0.05). The mean amounts of J2 population, as expressed per 1500 cm3 soil, were 49,933 +/- 38,819, 86,050 +/- 25248, 103 +/- 133 and 103 +/- 133 for 0, 50, 100 and 200 g chitin, respectively. Similarly, the mean numbers of root knot nematode eggs (per 1500 cm3 of soil) were 40,759 +/- 36,712, 66,048 +/- 39,730, 9,904 +/- 16,591 and 9,257 +/- 17,204. Root gall rating was also significantly lower (p < or = 0.05) at the 100 g and 200 g chitin levels compared to the control. Percent gall ratings were 3.3 +/- 1.0%, 3.2 +/- 1.0%, 1.0 +/- 0.5%, and 1.0% +/- 0.6% for amendment levels of 0, 50, 100, and 200 g chitin, respectively.  (+info)