103 research outputs found
Comparative genomics yields insights into niche adaptation of plant vascular wilt pathogens
No full textThe vascular wilt fungi Verticillium dahliae and V. albo-atrum infect over 200 plant species, causing billions of dollars in
annual crop losses. The characteristic wilt symptoms are a result of colonization and proliferation of the pathogens in the
xylem vessels, which undergo fluctuations in osmolarity. To gain insights into the mechanisms that confer the organisms’
pathogenicity and enable them to proliferate in the unique ecological niche of the plant vascular system, we sequenced the
genomes of V. dahliae and V. albo-atrum and compared them to each other, and to the genome of Fusarium oxysporum,
another fungal wilt pathogen. Our analyses identified a set of proteins that are shared among all three wilt pathogens, and
present in few other fungal species. One of these is a homolog of a bacterial glucosyltransferase that synthesizes virulencerelated
osmoregulated periplasmic glucans in bacteria. Pathogenicity tests of the corresponding V. dahliae
glucosyltransferase gene deletion mutants indicate that the gene is required for full virulence in the Australian tobacco
species Nicotiana benthamiana. Compared to other fungi, the two sequenced Verticillium genomes encode more pectindegrading
enzymes and other carbohydrate-active enzymes, suggesting an extraordinary capacity to degrade plant pectin
barricades. The high level of synteny between the two Verticillium assemblies highlighted four flexible genomic islands in V.
dahliae that are enriched for transposable elements, and contain duplicated genes and genes that are important in
signaling/transcriptional regulation and iron/lipid metabolism. Coupled with an enhanced capacity to degrade plant
materials, these genomic islands may contribute to the expanded genetic diversity and virulence of V. dahliae, the primary
causal agent of Verticillium wilts. Significantly, our study reveals insights into the genetic mechanisms of niche adaptation of
fungal wilt pathogens, advances our understanding of the evolution and development of their pathogenesis, and sheds
light on potential avenues for the development of novel disease management strategies to combat destructive wilt
diseases
High-dose 5-Fluorouracil with uridine-diphosphoglucose rescue increases thymidylate synthase inhibition but not 5-Fluorouracil incorporation into RNA in murine tumors.
No full textComparison of continuous infusions and bolus injections of 5-fluorouracil with or without leucovorin; implications for inhibition of thymidylate synthase
No full text
The rhizosphere: a playground and battlefield for soilborne pathogens and beneficial microorganisms
No full textThe rhizosphere is a hot spot of microbial interactions as exudates released by plant roots are a main food source for microorganisms and a driving force of their population density and activities. The rhizosphere harbors many organisms that have a neutral effect on the plant, but also attracts organisms that exert deleterious or beneficial effects on the plant. Microorganisms that adversely affect plant growth and health are the pathogenic fungi, oomycetes, bacteria and nematodes. Most of the soilborne pathogens are adapted to grow and survive in the bulk soil, but the rhizosphere is the playground and infection court where the pathogen establishes a parasitic relationship with the plant. The rhizosphere is also a battlefield where the complex rhizosphere community, both microflora and microfauna, interact with pathogens and influence the outcome of pathogen infection. A wide range of microorganisms are beneficial to the plant and include nitrogen-fixing bacteria, endo- and ectomycorrhizal fungi, and plant growth-promoting bacteria and fungi. This review focuses on the population dynamics and activity of soilborne pathogens and beneficial microorganisms. Specific attention is given to mechanisms involved in the tripartite interactions between beneficial microorganisms, pathogens and the plant. We also discuss how agricultural practices affect pathogen and antagonist populations and how these practices can be adopted to promote plant growth and health
Mechanisms of action of the organophosphorus fungicide pyrazophos
No full textIn plant protection organophosphorus compounds are well-known for their insecticidal and acaricidal action. Since 1960, a number of organophosphorus fungicides have also been introduced. In an in vivo screening of these and some related insecticidal compounds against Sphaerotheca fuliginea on cucumber, pyrazophos (O,O-diethyl O-(5-methyl-6-ethoxycarbonylpyrazolo[1,5-a]pyrimidin-2-yl) phosphorothioate) proved to be most active. The chemical displayed both a protective and curative action against the disease; in addition, considerable toxicity to Pyricularia oryzae on barley was also found. Pyrazophos proved to be rather selective because hardly any other fungi sensitive to the chemical were found in a study on the in vitro spectrum of antifungal activity.The organophosphorus fungicides Hinosan (O-ethyl S,S-diphenyl phosphorodithioate) and Kitazin (O,O-diethyl S-benzyl phosphorothioate) were about as toxic as pyrazophos to P. oryzae, but were much less toxic than pyrazophos to S. fuliginea. In view of these results, investigations on mechanisms of fungitoxic action of orianophosphorus fungicides were mainly focused on pyrazophos.Both pyrazophos and its phosphate analogue (PO-pyrazophos) were found to inhibit the activity of carboxylesterases of S.fuliginea. However, because no correlation could be established between in vivo inhibition of the activity of these enzymes by pyrazophos and PO-pyrazophos, and their fungitoxicity, this effect probably does not account for the mechanism of action of pyrazophos.Neither could the toxicity of pyrazophos, in all other experiments studied with P. oryzae, be attributed to an effect on cell membrane permeability, as was shown to be present upon incubation of mycelium of the fungus with Hinosan and Kitazin. In addition, pyrazophos hardly affected nucleic acid and protein synthesis, and only slightly inhibited oxygen uptake.In short-term experiments, using an incubation time of 2 hours, pyrazophos was 100-1000 x less toxic to fungal growth in mycelial suspensions than to radial growth on agar and growth in liquid media inoculated with conidia. In the latter tests, growth was assayed after I week of incubation. These results can be partly ascribed to the fact that pyrazophos is metabolically converted in the fungus into two fungitoxic breakdown products, PO-pyrazophos and 2-hydroxy-5-methyl-6-ethoxycarbonylpyrazolo(1,5-a)pyrimidine (PP). In short-term experiments the toxicity of PP for mycelial growth in suspensions buffered at pH 4.0 even proved to be considerably higher than that of pyrazophos and PO-pyrazophos. PP might, therefore, be regarded as the actual fungitoxic principle of pyrazophos. This hypothesis is supported by the finding that PP, in contrast to pyrazophos, also displayed an inhibitory activity towards nucleic acid and protein synthesis and towards oxygen uptake of the fungus. The weak effects of pyrazophos on these processes and on mycelial growth in short-term experiments can probably be ascribed to an insufficient conversion of pyrazophos into PP under these conditions.Regarding the site of fungitoxic action of PP in P. oryzae, two hypotheses could be suggested. First, PP could inhibit specifically oxygen uptake and hence indirectly cellular synthetic processes like nucleic acid and protein synthesis. Secondly, PP might react aspecifically with cellular components and hence, directly affect both oxygen uptake and biosynthetic processes.Pythium debaryanum and Saccharomyces cerevisiae are practically insensitive to pyrazophos. Upon incubation of these fungi with the fungicide no breakdown products could be detected. Therefore, sensitivity of fungi for pyrazophos seems to be the result of a selective uptake of pyrazophos and/or of its conversion into PO pyrazophos and PP as has been demonstrated for P.oryzae.</em
The use of green waste compost in peat-based potting mixtures: Fertilization and suppressiveness against soilborne diseases
No full textTwelve commercially produced Dutch green waste composts were evaluated for their suitability to replace 20% (v/v) peat substrate in the cultivation of ornamentals. Salt concentrations were determined in water extracts of the composts and disease suppressive effects were assessed against various soilborne diseases. The Cl-concentration of the compost extract appeared to be the limiting factor for use of the composts in potting mixtures. The Cl-concentrations in 7 and 1 composts, respectively, were too high to replace 20% of peat for growing salt sensitive and moderately salt sensitive plants, according to guidelines set for these groups of plants. The suppressive effects of the composts were tested in peat-based potting mixtures using three bioassays: Phytophthora cinnamomi¿lupin, Cylindrocladium spathiphylli¿Spathiphyllum and Rhizoctonia solani AG2-1¿cauliflower. Disease levels in compost-amended mixtures were compared with the non-amended controls. None of the composts induced suppressiveness against P. cinnamomi; 3 and 9 composts significantly induced suppressiveness against C. spathiphylli and R. solani, respectively. No significant disease enhancement was observed in any of the bioassays. The pH of the potting mixture showed a negative correlation with suppression of the Rhizoctonia disease (R2 = 0.56). The effect of pH (pH 4¿6) on suppression of R. solani and P. cinnamomi was further studied in non-amended peat. Disease suppression of R. solani in cauliflower decreased with increasing pH in two different kinds of peat, while there was no effect on P. cinnamomi. The suppressive effect of 3 composts was assessed in two experiments against Fusarium wilt in Cyclamen persicum (caused by F. oxysporum f. sp. cyclamini) and Begonia eliator (caused by F. foetens) under near-commercial conditions. None of the composts had a significant effect on Fusarium wilt in Cyclamen. Two and 3 composts significantly induced suppressiveness against Fusarium wilt in Begonia in the first and second experiments, respectively. No significant differences were observed in growth characteristics between Begonia plants grown in compost-amended and non-amended potting mixture in both experiments. In the second experiment, Cyclamen plants grown in compost-amended potting mixture had significant lower number of flowers than plants grown in non-amended potting mixture, which may have been due to lower concentrations of N in the compost-amended potting mixtures. In conclusion, most composts of the origin and composition tested can replace 20% peat in potting mixtures for moderately salt sensitive and salt tolerant plants. Amendment of these composts can contribute to control of Fusarium wilt in Begonia plants
In vitro antitumour activity of cis- and trans-5-fluoro-5,6-dihydro-6-alkoxy-uracils; effects on thymidylate synthesis
No full textA randomised controlled trial into the effects of food on ADHD.
No full textContains fulltext :
79797.pdf (Publisher’s version ) (Open Access)The aim of this study is to assess the efficacy of a restricted elimination diet in reducing symptoms in an unselected group of children with Attention deficit/hyperactivity disorder (ADHD). Dietary studies have already shown evidence of efficacy in selected subgroups. Twenty-seven children (mean age 6.2) who all met the DSM-IV criteria for ADHD, were assigned randomly to either an intervention group (15/27) or a waiting-list control group (12/27). Primary endpoint was the clinical response, i.e. a decrease in the symptom scores by 50% or more, at week 9 based on parent and teacher ratings on the abbreviated ten-item Conners Scale and the ADHD-DSM-IV Rating Scale. The intention-to-treat analysis showed that the number of clinical responders in the intervention group was significantly larger than that in the control group [parent ratings 11/15 (73%) versus 0/12 (0%); teacher ratings, 7/10 (70%) versus 0/7 (0%)]. The Number of ADHD criteria on the ADHD Rating Scale showed an effect size of 2.1 (cohen's d) and a scale reduction of 69.4%. Comorbid symptoms of oppositional defiant disorder also showed a significantly greater decrease in the intervention group than it did in the control group (cohens's d 1.1, scale reduction 45.3%). A strictly supervised elimination diet may be a valuable instrument in testing young children with ADHD on whether dietary factors may contribute to the manifestation of the disorder and may have a beneficial effect on the children's behaviour
Long-term effects of hemostatic variables on fatal coronary heart disease: 30-year results from the first prospective Northwick Park Heart Study (NPHS-I)
No full textBackground: The long-term associations of established risk factors for coronary heart disease (CHD), for example cholesterol, are well known, but not for the less familiar hemostatic variables. Objectives: To establish whether associations between hemostatic variables and CHD first identified nearly three decades ago have persisted long-term. Methods: The first Northwick Park Heart Study (NPHS-I) recruited 2167 white men and 941 white women, average age at entry 48 years, on whom measures of factor (F) VII activity (VIIc) and plasma fibrinogen were carried out, both at entry and at follow-up approximately 6 years later. Results: During a median follow-up of 29 years, 231 male and 36 female CHD deaths were recorded from notifications by the Office for National Statistics. VIIc at recruitment was significantly related to CHD mortality, corrected rate ratio, RR, per 1 SD increase 1.56 (95% CI 1.29, 1.88) in men and RR 1.78 (95% CI 1.17, 2.72) in women. Recruitment fibrinogen was also strongly related to CHD mortality in men, RR 1.63 (95% CI 1.33, 1.99) but not in women, RR 0.75 (95% CI 0.40, 1.43). The associations persisted after controlling for confounders and were confirmed using 6-year follow-up measurements and in analyses omitting deaths within 10 years of recruitment. Conclusions: The hemostatic system contributes to CHD mortality, and its effect is stable over time. For VIIc, the effect was similar in men and women, while for fibrinogen it appeared to be present only in men
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