Striga hermonthica is a root hemiparasitic angiosperm nativeto the African semi-arid tropics. It is a major weed of C4 cerealsbut locally it is also an important weed of the C3 plant, rice[Oryza sativa). Infected rice plants produced 17% and 42% ofthe total biomass of uninfected plants when grown at two differentammonium nitrate concentrations, 1 and 3 mol m3, respectively.S. hermonthica prevented grain production at both concentrationsof nitrogen. At the lower concentration no heads were produced.At the higher concentration head weight was only 6% of uninfectedcontrols. S. hermonthica also altered the partitioning of drymatter between plant parts, such that shoot growth was reducedto a greater extent than root growth. As a consequence the root-to-shootratio of infected plants was approximately five times greaterthan that of uninfected control plants. Light saturated ratesof photosynthesis In infected plants were 56% and 70% of thoseof uninfected controls, at low and high nitrogen, respectively.Infection also led to lower values of stomatal conductance althoughthe substom-atal CO2 concentration was unaffected. Analysisof the response of photosynthesis to substomatal CO2 concentration(A/CI curves) demonstrated that lower rates of photosynthesiscould not be solely attributed to lower stomatal conductances.Lower initial slopes and asymptotic rates suggest that bothcarboxylation and processes controlling regeneration of ribulose-1,5-bisphosphate are reduced by infection. The data are discussedwith respect to the influence of S. hermonthica on the growthand photosynthesis of C4 hosts, where in contrast to the situationwith rice, nitrogen feeding results in a marked alleviationof the effects of the parasite on the host. Key words: Rice, Striga, growth, photosynthesis, nitrogen 相似文献
Because of their importance as target antigens in scleroderma and since all other major autoantigens in scleroderma can be localized to the interphase nucleolus, we were interested in a further investigation of the potential relationship between interphase centromeres and the nucleolus. Using human anticentromere autoantibodies (ACA) from patients with the CREST form of scleroderma as probes in indirect immunofluorescence microscopy, we observed nonrandom interphase "clumping" of centromeres in a distribution suggestive of nucleoli. By double-label immunofluorescence comparing the localization of centromeres to nucleolar proteins Ki-67, fibrillarin, or protein B23 (nucleophosmin), interphase centromeres appeared to be localized around and within nucleoli. A number of different ACA sera were tested on HEp-2, HeLa, PtK2, Indian muntjac, 3T3, and NRK cells, all with identical results indicating colocalization between centromeres and nucleoli. Immunoelectron microscopy revealed that interphase centromeres were distributed free in the nucleoplasm, in contact with the nuclear envelope, in contact with and on the periphery of nucleoli, and totally embedded within the confines of the nucleolus itself. Interestingly, actinomycin D treatment dissociated centromeres from localization within the segregated nucleolus. To determine if interphase centromeres were integral components of nucleoli, nucleoli were isolated according to classical methods. By double-label immunofluorescence, immunoelectron microscopy, and Western blotting, it was demonstrated that centromere autoantigens copurified with isolated nucleoli. These studies offer proof that some interphase centromeres can be associated with, and may even be considered part of, the interphase nucleolus. Furthermore, all of the major autoantigens in scleroderma can now be localized to the nucleolus. 相似文献
Mitochondria contribute to redox and calcium balance, and apoptosis thus regulating cellular fate. In the present study, mitochondrial staining applying a novel dye, V07‐07059, was performed in human embryonic kidney cells, a human vascular endothelial cell line and primary human mononuclear cells. The new fluorescent mega Stokes dye (peak excitation: 488 nm, peak emission: 554 nm) showed superior fluorescent properties and stability. V07‐07059 stains mitochondria dependent on their membrane potential and is safe to use in vitro and in vivo. Unlike other dyes applied in this context (e.g. Tetramethylrhodamine methyl ester), V07‐07059 only marginally inhibits mitochondrial respiration and function. V07‐07059 enables real time imaging of mitochondrial trafficking and remodeling. Prolonged staining with V07‐07059 demonstrated the dyes suitability as a novel probe to track cells. In comparison to the widely used standard for cell proliferation and tracking studies 5(6)‐diacetate N‐succinimidyl ester, V07‐07059 proved superior regarding toxicity and photostability.
Genome-wide association studies have been successful in identifying common genetic variants for human diseases. However, much of the heritable variation associated with diseases such as Parkinson’s disease remains unknown suggesting that many more risk loci are yet to be identified. Rare variants have become important in disease association studies for explaining missing heritability. Methods for detecting this type of association require prior knowledge on candidate genes and combining variants within the region. These methods may suffer from power loss in situations with many neutral variants or causal variants with opposite effects.
Results
We propose a method capable of scanning genetic variants to identify the region most likely harbouring disease gene with rare and/or common causal variants. Our method assigns a score at each individual variant based on our scoring system. It uses aggregate scores to identify the region with disease association. We evaluate performance by simulation based on 1000 Genomes sequencing data and compare with three commonly used methods. We use a Parkinson’s disease case–control dataset as a model to demonstrate the application of our method.Our method has better power than CMC and WSS and similar power to SKAT-O with well-controlled type I error under simulation based on 1000 Genomes sequencing data. In real data analysis, we confirm the association of α-synuclein gene (SNCA) with Parkinson’s disease (p = 0.005). We further identify association with hyaluronan synthase 2 (HAS2, p = 0.028) and kringle containing transmembrane protein 1 (KREMEN1, p = 0.006). KREMEN1 is associated with Wnt signalling pathway which has been shown to play an important role for neurodegeneration in Parkinson’s disease.
Conclusions
Our method is time efficient and less sensitive to inclusion of neutral variants and direction effect of causal variants. It can narrow down a genomic region or a chromosome to a disease associated region. Using Parkinson’s disease as a model, our method not only confirms association for a known gene but also identifies two genes previously found by other studies. In spite of many existing methods, we conclude that our method serves as an efficient alternative for exploring genomic data containing both rare and common variants.
Electronic supplementary material
The online version of this article (doi:10.1186/s12929-014-0088-9) contains supplementary material, which is available to authorized users. 相似文献
The Merkel cell-neurite (MCN) complex generates slowly adapting type 1 (SA1) response when mechanically stimulated. Both serotonin (5-HT) and glutamate have been implicated in the generation of normal SA1 responses, but previous studies have been inconclusive as to what their roles are or how synaptic transmission occurs. In this study, excised dorsal skin patches from common water frogs (Rana ridibunda) were stimulated by von Frey hairs during perfusion in a tissue bath, and single-unit spike activity was recorded from SA1 fibres. Serotonin had no significant effect on the SA1 response at low (10?μM) concentration, significantly increased activity in a force-independent manner at 100?μM, but decreased activity with reduced responsiveness to force at 1?mM. Glutamate showed no effect on the responsiveness to force at 100?μM. MDL 72222 (100?μM), an ionotropic 5-HT3 receptor antagonist, completely abolished the responsiveness to force, suggesting that serotonin is released from Merkel cells as a result of mechanical stimulation, and activated 5-HT3 receptors on the neurite. The metabotropic 5-HT2 receptor antagonist, ketanserin, greatly reduced the SA1 fibre's responsiveness to force, as did the non-specific glutamate receptor antagonist, kynurenic acid. This supports a role for serotonin and glutamate as neuromodulators in the MCN complex, possibly by activation and/or inhibition of signalling cascades in the Merkel cell associated with vesicle release. Additionally, it was observed that SA1 responses contained a force-independent component, similar to a dynamic response observed during mechanical vibrations. 相似文献