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991.
Bennert HW Horn K Kauth M Fuchs J Jakobsen IS Ollgaard B Schnittler M Steinberg M Viane R 《Annals of botany》2011,108(5):867-876
Background and Aims
Interspecific Diphasiastrum hybrids have been assumed to be homoploid and to produce well-formed spores serving sexual reproduction. If this were the case, forms intermediate between hybrids and parents or hybrid swarms should be expected. The purpose of this study was: (1) to check whether homoploidy consistently applies to the three hybrids throughout their Central European range; (2) to examine whether their genome sizes confirm their parentage as assumed by morphology; and (3) to perform a screening for detection of ploidy levels other than diploid and variation in DNA content due to backcrossing.Methods
Flow cytometry was used first to measure the relative DNA values [with 4′,6-diamidino-2-phenylindole (DAPI) staining] and ploidy level as a general screening, and secondly to determine the absolute DNA 2C values [with propidium iodide (PI) staining] in a number of selected samples with the main focus on the hybrids.Key Results
A considerable variation of DNA 2C values (5·26–7·52 pg) was detected between the three European Diphasiastrum species. The values of the diploid hybrids are highly constant without significant variation between regions. They are also intermediate between their assumed parents and agree closely with those calculated from their putative parents. This confirms their hybrid origin, assumed parentage and homoploid status. Considerably higher DNA amounts (9·48–10·30 pg) were obtained for three populations, suggesting that these represent triploid hybrids, an interpretation that is strongly supported by their morphology.Conclusions
Diploid hybrids have retained their genetic and morphological identites throughout their Central European range, and thus no indications for diploid backcrossing were found. The triploid hybrids have probably originated from backcrossing between a diploid gametophyte of a hybrid (derived from a diplospore) and a haploid gametophyte of a diploid parental species. By repeated crossing events, reticulate evolution patterns arise that are similar to those known for a number of ferns. 相似文献992.
993.
Rania DagherShan Peng Sophie GioriaMarie Fève Maria ZeniouMichael Zimmermann Claire PigaultJacques Haiech Marie-Claude Kilhoffer 《Biochimica et Biophysica Acta (BBA)/Molecular Cell Research》2011,1813(5):1059-1067
Calmodulin (CaM) is a ubiquitous Ca2+ sensor regulating many biochemical processes in eukaryotic cells. Its interaction with a great variety of different target proteins has led to the fundamental question of its mechanism of action. CaM exhibits four “EF hand” type Ca2+ binding sites. One way to explain CaM functioning is to consider that the protein interacts differently with its target proteins depending on the number of Ca2+ ions bound to it. To test this hypothesis, the binding properties of three entities known to interact with CaM (a fluorescent probe and two peptide analogs to the CaM binding sites of death associated protein kinase (DAPK) and of EGFR) were investigated using a quantitative approach based on fluorescence polarization (FP). Probe and peptide interactions with CaM were studied using a titration matrix in which both CaM and calcium concentrations were varied. Experiments were performed with SynCaM, a hybrid CaM able to activate CaM dependent enzymes from mammalian and plant cells. Results show that the interaction between CaM and its targets is regulated by the number of calcium ions bound to the protein, namely one for the DAPK peptide, two for the probe and four for the EGFR peptide. The approach used provides a new tool to elaborate a typology of CaM-targets, based on their recognition by the various CaM-Can (n = 0-4) complexes. This article is part of a Special Issue entitled: 11th European Symposium on Calcium. 相似文献
994.
Prevalence of the pathogen Batrachochytrium dendrobatidis (Bd), implicated in amphibian population declines worldwide, is associated with habitat moisture and temperature, but few studies have varied these factors and measured the response to infection in amphibian hosts. We evaluated how varying humidity, contact with water, and temperature affected the manifestation of chytridiomycosis in boreal toads Anaxyrus (Bufo) boreas boreas and how prior exposure to Bd affects the likelihood of survival after re-exposure, such as may occur seasonally in long-lived species. Humidity did not affect survival or the degree of Bd infection, but a longer time in contact with water increased the likelihood of mortality. After exposure to approximately 10(6) Bd zoospores, all toads in continuous contact with water died within 30 d. Moreover, Bd-exposed toads that were disease-free after 64 d under dry conditions, developed lethal chytridiomycosis within 70 d of transfer to wet conditions. Toads in unheated aquaria (mean = 15 degrees C) survived less than 48 d, while those in moderately heated aquaria (mean = 18 degrees C) survived 115 d post-exposure and exhibited behavioral fever, selecting warmer sites across a temperature gradient. We also found benefits of prior Bd infection: previously exposed toads survived 3 times longer than Bd-na?ve toads after re-exposure to 106 zoospores (89 vs. 30 d), but only when dry microenvironments were available. This study illustrates how the outcome of Bd infection in boreal toads is environmentally dependent: when continuously wet, high reinfection rates may overwhelm defenses, but periodic drying, moderate warming, and previous infection may allow infected toads to extend their survival. 相似文献
995.
Philippa Parsons Sophie J. Gilbert Anne Vaughan-Thomas David A. Sorrell Rebecca Notman Mark Bishop Anthony J. Hayes Deborah J. Mason Victor C. Duance 《The Journal of biological chemistry》2011,286(40):34986-34997
Type IX collagen is covalently bound to the surface of type II collagen fibrils within the cartilage extracellular matrix. The N-terminal, globular noncollagenous domain (NC4) of the α1(IX) chain protrudes away from the surface of the fibrils into the surrounding matrix and is available for molecular interactions. To define these interactions, we used the NC4 domain in a yeast two-hybrid screen of a human chondrocyte cDNA library. 73% of the interacting clones encoded fibronectin. The interaction was confirmed using in vitro immunoprecipitation and was further characterized by surface plasmon resonance. Using whole and pepsin-derived preparations of type IX collagen, the interaction was shown to be specific for the NC4 domain with no interaction with the triple helical collagenous domains. The interaction was shown to be of high affinity with nanomolar Kd values. Analysis of the fibronectin-interacting clones indicates that the constant domain is the likely site of interaction. Type IX collagen and fibronectin were shown to co-localize in cartilage. This novel interaction between the NC4 domain of type IX collagen and fibronectin may represent an in vivo interaction in cartilage that could contribute to the matrix integrity of the tissue. 相似文献
996.
Woldt E Matz RL Terrand J Mlih M Gracia C Foppolo S Martin S Bruban V Ji J Velot E Herz J Boucher P 《The Journal of biological chemistry》2011,286(19):16775-16782
The low density lipoprotein receptor-related protein (LRP1) is a transmembrane receptor that integrates multiple signaling pathways. Its cytoplasmic domain serves as docking sites for several adaptor proteins such as the Src homology 2/α-collagen (ShcA), which also binds to several tyrosine kinase receptors such as the insulin-like growth factor 1 (IGF-1) receptor. However, the physiological significance of the physical interaction between LRP1 and ShcA, and whether this interaction modifies tyrosine kinase receptor signaling, are still unknown. Here we report that LRP1 forms a complex with the IGF-1 receptor, and that LRP1 is required for ShcA to become sensitive to IGF-1 stimulation. Upon IGF-1 treatment, ShcA is tyrosine phosphorylated and translocates to the plasma membrane only in the presence of LRP1. This leads to the recruitment of the growth factor receptor-bound protein 2 (Grb2) to ShcA, and activation of the Ras/MAP kinase pathway. Conversely, in the absence of ShcA, IGF-1 signaling bifurcates toward the Akt/mammalian target of rapamycin pathway and accelerates adipocyte differentiation when cells are stimulated for adipogenesis. These results establish the LRP1-ShcA complex as an essential component in the IGF-1-regulated pathway for MAP kinase and Akt/mammalian target of rapamycin activation, and may help to understand the IGF-1 signaling shift from clonal expansion to growth-arrested cells and differentiation during adipogenesis. 相似文献
997.
Tosiek MJ Gruber AD Bader SR Mauel S Hoymann HG Prettin S Tschernig T Buer J Gereke M Bruder D 《Journal of immunology (Baltimore, Md. : 1950)》2011,186(11):6106-6118
Every person harbors a population of potentially self-reactive lymphocytes controlled by tightly balanced tolerance mechanisms. Failures in this balance evoke immune activation and autoimmunity. In this study, we investigated the contribution of self-reactive CD8(+) T lymphocytes to chronic pulmonary inflammation and a possible role for naturally occurring CD4(+)CD25(+)Foxp3(+) regulatory T cells (nTregs) in counterbalancing this process. Using a transgenic murine model for autoimmune-mediated lung disease, we demonstrated that despite pulmonary inflammation, lung-specific CD8(+) T cells can reside quiescently in close proximity to self-antigen. Whereas self-reactive CD8(+) T cells in the inflamed lung and lung-draining lymph nodes downregulated the expression of effector molecules, those located in the spleen appeared to be partly Ag-experienced and displayed a memory-like phenotype. Because ex vivo-reisolated self-reactive CD8(+) T cells were very well capable of responding to the Ag in vitro, we investigated a possible contribution of nTregs to the immune control over autoaggressive CD8(+) T cells in the lung. Notably, CD8(+) T cell tolerance established in the lung depends only partially on the function of nTregs, because self-reactive CD8(+) T cells underwent only biased activation and did not acquire effector function after nTreg depletion. However, although transient ablation of nTregs did not expand the population of self-reactive CD8(+) T cells or exacerbate the disease, it provoked rapid accumulation of activated CD103(+)CD62L(lo) Tregs in bronchial lymph nodes, a finding suggesting an adaptive phenotypic switch in the nTreg population that acts in concert with other yet-undefined mechanisms to prevent the detrimental activation of self-reactive CD8(+) T cells. 相似文献
998.
Duchez S Rodrigues M Bertrand F Valitutti S 《Journal of immunology (Baltimore, Md. : 1950)》2011,187(9):4571-4580
Cognate interactions between T and B lymphocytes lead to the formation of the immunological synapse (IS) where bidirectional activation signals are exchanged. Although the molecular architecture and the function of the IS have been studied extensively on the T cell side, little is known about events occurring during synapse formation in Ag-presenting B cells. We investigated the impact of BCR and TLR signaling on human B cell activation and on the T and B cell side of the IS. On the T cell side, we observed that T cells polarized toward both naive and previously activated B cells. Nevertheless, when T cells interacted with different B cells simultaneously, T cells selectively polarized their secretory machinery toward preactivated B cells. Furthermore, both naive and preactivated B cells reoriented their microtubule-organizing center toward the synaptic T cell during cognate interactions. This phenomenon was rapid and not dependent on T cell secretory activity. Interestingly, not only the microtubule-organizing center but also the Golgi apparatus and Lamp-3(+) and MHC class II(+) vesicles all repositioned beneath the IS, suggesting that the entire endocytic/exocytic B cell compartment was reoriented toward the T cell. Taken together, our results show that the B cell activation status fine-tunes T cell polarization responses and reveal the capacity of naive and activated B cells to polarize toward T cells during cognate interactions. 相似文献
999.
Bordiec S Paquis S Lacroix H Dhondt S Ait Barka E Kauffmann S Jeandet P Mazeyrat-Gourbeyre F Clément C Baillieul F Dorey S 《Journal of experimental botany》2011,62(2):595-603
Plant growth-promoting rhizobacteria (PGPR) are beneficial microorganisms that colonize the rhizosphere of many plant species and confer beneficial effects, such as an increase in plant growth. PGPR are also well known as inducers of systemic resistance to pathogens in plants. However, the molecular mechanisms involved locally after direct perception of these bacteria by plant cells still remain largely unknown. Burkholderia phytofirmans strain PsJN is an endophytic PGPR that colonizes grapevine and protects the plant against the grey mould disease caused by Botrytis cinerea. This report focuses on local defence events induced by B. phytofirmans PsJN after perception by the grapevine cells. It is demonstrated that, after addition to cell suspension cultures, the bacteria were tightly attaching to plant cells in a way similar to the grapevine non-host bacteria Pseudomonas syringae pv. pisi. B. phytofirmans PsJN perception led to a transient and monophasic extracellular alkalinization but no accumulation of reactive oxygen species or cell death were detected. By contrast, challenge with P. syringae pv. pisi induced a sustained and biphasic extracellular alkalinization, a two phases oxidative burst, and a HR-like response. Perception of the PGPR also led to the production of salicylic acid (SA) and the expression of a battery of defence genes that was, however, weaker in intensity compared with defence gene expression triggered by the non-host bacteria. Some defence genes up-regulated after B. phytofirmans PsJN challenge are specifically induced by exogenous treatment with SA or jasmonic acid, suggesting that both signalling pathways are activated by the PGPR in grapevine. 相似文献
1000.
The folding and interactions of amyloid proteins are at the heart of the debate as to how these proteins may or may not become toxic to their host. Although little is known about this issue, the structure seems to be clearly involved with effects on molecular events. To understand how an amyloid may be toxic, we previously generated a yeast toxic amyloid (mutant 8) from the nontoxic HET-s(218-289) prion domain of Podospora anserina. Here, we performed a comprehensive structure-toxicity study by mutating individually each of the 10 mutations found in mutant 8. The study of the library of new mutants generated allowed us to establish a clear link between Fourier transform infrared antiparallel signature and amyloid toxicity. All of the mutants that form parallel β-sheets are not toxic. Double mutations may be sufficient to shift a parallel structure to antiparallel amyloids, which are toxic to yeast. Our findings also suggest that the toxicity of antiparallel structured mutants may be linked to interaction with membranes. 相似文献