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961.
In symbiotic systems, patterns of symbiont diversity and selectivity are crucial for the understanding of fundamental ecological processes such as dispersal and establishment. The lichen genus Nephroma (Peltigerales, Ascomycota) has a nearly cosmopolitan distribution and is thus an attractive model for the study of symbiotic interactions over a wide range of spatial scales. In this study, we analyze the genetic diversity of Nephroma mycobionts and their associated Nostoc photobionts within a global framework. The study is based on Internal Transcribed Spacer (ITS) sequences of fungal symbionts and tRNALeu (UAA) intron sequences of cyanobacterial symbionts. The full data set includes 271 Nephroma and 358 Nostoc sequences, with over 150 sequence pairs known to originate from the same lichen thalli. Our results show that all bipartite Nephroma species associate with one group of Nostoc different from Nostoc typically found in tripartite Nephroma species. This conserved association appears to have been inherited from the common ancestor of all extant species. While specific associations between some symbiont genotypes can be observed over vast distances, both symbionts tend to show genetic differentiation over wide geographic scales. Most bipartite Nephroma species share their Nostoc symbionts with one or more other fungal taxa, and no fungal species associates solely with a single Nostoc genotype, supporting the concept of functional lichen guilds. Symbiont selectivity patterns within these lichens are best described as a geographic mosaic, with higher selectivity locally than globally. This may reflect specific habitat preferences of particular symbiont combinations, but also the influence of founder effects. 相似文献
962.
963.
Katja Rateitschak Felix Winter Falko Lange Robert Jaster Olaf Wolkenhauer 《PLoS computational biology》2012,8(12)
The present work exemplifies how parameter identifiability analysis can be used to gain insights into differences in experimental systems and how uncertainty in parameter estimates can be handled. The case study, presented here, investigates interferon-gamma (IFNγ) induced STAT1 signalling in two cell types that play a key role in pancreatic cancer development: pancreatic stellate and cancer cells. IFNγ inhibits the growth for both types of cells and may be prototypic of agents that simultaneously hit cancer and stroma cells. We combined time-course experiments with mathematical modelling to focus on the common situation in which variations between profiles of experimental time series, from different cell types, are observed. To understand how biochemical reactions are causing the observed variations, we performed a parameter identifiability analysis. We successfully identified reactions that differ in pancreatic stellate cells and cancer cells, by comparing confidence intervals of parameter value estimates and the variability of model trajectories. Our analysis shows that useful information can also be obtained from nonidentifiable parameters. For the prediction of potential therapeutic targets we studied the consequences of uncertainty in the values of identifiable and nonidentifiable parameters. Interestingly, the sensitivity of model variables is robust against parameter variations and against differences between IFNγ induced STAT1 signalling in pancreatic stellate and cancer cells. This provides the basis for a prediction of therapeutic targets that are valid for both cell types. 相似文献
964.
Jacot Katja A. Lüscher Andreas Nösberger Josef Hartwig Ueli A. 《Plant and Soil》2000,225(1-2):201-211
The significance of symbiotic N2 fixation in legumes (Trifolium alpinum L., T. nivale Sieber, T. pratense L., T. badium Schreber, T. thalii Vill., T. repens L., Lotus alpinus [DC.] Schleicher, L. corniculatus L., Vicia sativa L.) and other N sources for the N budget of grassland ecosystems was studied along an altitudinal gradient in the Swiss Alps.
The total annual symbiotic N2 fixation was compared with other sources of N for plant growth of the total plant community (mineralisation and wet deposition).
The contribution of symbiotically fixed N to total above-ground N yield of the swards decreased from at least 16% to 9% with
increasing altitude where legumes were present. This decrease was due to a decrease in the yield proportion of legumes from
15% at 900 and 1380 m a.s.l. to 5% at 2100 and 2300 m a.s.l. (no legumes were found above 2750 m a.s.l.) and not to a decline
in the activity of symbiotic N2 fixation. With increasing altitude legumes are more patchily distributed. The high symbiotic N2 fixation of individual plants up to their altitudinal limit is not primarily the result of low mineral N availability since
an addition of NH4
+ or NO3
− fertiliser at 2300 m a.s.l. led either to no decrease or only to a minor decrease in symbiotic N2 fixation. At 1380 m a.s.l., N mineralisation (13.45 g N m−2 yr−1) appeared to be the main source of N for growth of the sward; N from symbiosis (at least 1.0 g to 2.6 g N m−2 yr−1) and wet deposition (0.4 g to 0.6 g m−2 yr−1) was not a significant N source for plant growth at this altitude. At 2100 m a.s.l., the combined amounts of N from symbiotic
N2 fixation (at least 0.1 g N m−2 yr−1) and wet deposition (0.3 g N m−2 yr−1) appeared to be similarly important for plant growth as soil N mineralisation (0.47 g N m−2 yr−1). At high altitudes, wet N deposition and symbiotic N2 fixation together represent a significant source of N for the grassland ecosystem while at low altitudes these N inputs appear
to be much less important.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
965.
966.
Hannes Vo?feldt Malte Butzlaff Katja Prü?ing Róisín-Ana Ní Chárthaigh Peter Karsten Anne Lankes Sabine Hamm Mikael Simons Boris Adryan J?rg B. Schulz Aaron Voigt 《PloS one》2012,7(11)
Polyglutamine (polyQ) diseases represent a neuropathologically heterogeneous group of disorders. The common theme of these disorders is an elongated polyQ tract in otherwise unrelated proteins. So far, only symptomatic treatment can be applied to patients suffering from polyQ diseases. Despite extensive research, the molecular mechanisms underlying polyQ-induced toxicity are largely unknown. To gain insight into polyQ pathology, we performed a large-scale RNAi screen in Drosophila to identify modifiers of toxicity induced by expression of truncated Ataxin-3 containing a disease-causing polyQ expansion. We identified various unknown modifiers of polyQ toxicity. Large-scale analysis indicated a dissociation of polyQ aggregation and toxicity. 相似文献
967.
Plinio C. Casarotto Mykhailo Girych Senem M. Fred Vera Kovaleva Rafael Moliner Giray Enkavi Caroline Biojone Cecilia Cannarozzo Madhusmita Pryiadrashini Sahu Katja Kaurinkoski Cecilia A. Brunello Anna Steinzeig Frederike Winkel Sudarshan Patil Stefan Vestring Tsvetan Serchov Cassiano R.A.F. Diniz Liina Laukkanen Eero Castrén 《Cell》2021,184(5):1299-1313.e19
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968.
Fusarium oxysporum is an important plant pathogen and an opportunistic pathogen of humans. Here we investigated phagocytosis of F. oxysporum by J774.1 murine cell line macrophages using live cell video microscopy. Macrophages avidly migrated towards F. oxysporum germlings and were rapidly engulfed after cell-cell contact was established. F. oxysporum germlings continued hyphal growth after engulfment by macrophages, leading to associated macrophage lysis and escape. Macrophage killing depended on the multiplicity of infection. After engulfment, F. oxysporum inhibited macrophages from completing mitosis, resulting in large daughter cells fused together by means of a F. oxysporum hypha. These results shed new light on the initial stages of Fusarium infection and the innate immune response of the mammalian host. 相似文献
969.
Allopurinol is a purine analogue that inhibits xanthine oxidase. It is mainly used for the treatment of hyperuricemia in patients with gout or tumor lysis syndrome. Experience with allopurinol in pregnancy is scarce. In 2011, Kozenko et al. reported on a child with multiple malformations after maternal treatment with allopurinol throughout pregnancy. Possible teratogenicity of allopurinol was proposed due to the similarity of the pattern of malformations in children with mycophenolate embryopathy. A possible common mechanism of both drugs, i.e. disruption of purine synthesis, was discussed. We report on the outcome of 31 prospectively ascertained pregnancies with allopurinol exposure at least during first trimester. Pregnancy outcomes were 2 spontaneous abortions, 2 elective terminations of pregnancy and 27 live born children. The overall rate of major malformations (3.7%) and of spontaneous abortions (cumulative incidence 11%, 95%-CI 3–40) were both within the normal range. However, there was one child with severe malformations including microphthalmia, cleft lip and palate, renal hypoplasia, low-set ears, hearing deficit, bilateral cryptorchidism, and micropenis. The striking similarity of the anomalies in this child and the case described by Kozenko et al. might be considered as a signal for teratogenicity. Thus, we would recommend caution with allopurinol treatment in the first trimester, until further data are available. 相似文献
970.