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51.
In plants, short chitin oligosaccharides and chitosan fragments (collectively referred to as chitooligosaccharides) are well-known
elicitors that trigger defense gene expression, synthesis of antimicrobial compounds, and cell wall strengthening. Recent
findings have shed new light on chitin-sensing mechanisms and downstream activation of intracellular signaling networks that
mediate plant defense responses. Interestingly, chitin receptors possess several lysin motif domains that are also found in
several legume Nod factor receptors. Nod factors are chitin-related molecules produced by nitrogen-fixing rhizobia to induce
root nodulation. The fact that chitin and Nod factor receptors share structural similarity suggests an evolutionary conserved
relationship between mechanisms enabling recognition of both deleterious and beneficial microorganisms. Here, we will present
an update on molecular events involved in chitooligosaccharide sensing and downstream signaling pathways in plants and will
discuss how structurally related signals may lead to such contrasted outcomes during plant–microbe interactions. 相似文献
52.
Qingxue Li Mir A. Ali Kening Wang Dean Sayre Frederick G. Hamel Elizabeth R. Fischer Robert G. Bennett Jeffrey I. Cohen 《PloS one》2010,5(6)
Varicella-zoster virus (VZV) glycoprotein E (gE) is essential for virus infectivity and binds to a cellular receptor, insulin-degrading enzyme (IDE), through its unique amino terminal extracellular domain. Previous work has shown IDE plays an important role in VZV infection and virus cell-to-cell spread, which is the sole route for VZV spread in vitro. Here we report that a recombinant soluble IDE (rIDE) enhances VZV infectivity at an early step of infection associated with an increase in virus internalization, and increases cell-to-cell spread. VZV mutants lacking the IDE binding domain of gE were impaired for syncytia formation and membrane fusion. Pre-treatment of cell-free VZV with rIDE markedly enhanced the stability of the virus over a range of conditions. rIDE interacted with gE to elicit a conformational change in gE and rendered it more susceptible to proteolysis. Co-incubation of rIDE with gE modified the size of gE. We propose that the conformational change in gE elicited by IDE enhances infectivity and stability of the virus and leads to increased fusogenicity during VZV infection. The ability of rIDE to enhance infectivity of cell-free VZV over a wide range of incubation times and temperatures suggests that rIDE may be useful for increasing the stability of varicella or zoster vaccines. 相似文献
53.
HORACIO ZAGARESE CRAIG WILLIAMSON TIMOTHY VAIL OLAF OLSEN & CLAUDIA QUEIMALIÑOS 《The Plant journal : for cell and molecular biology》2004,37(1):99-106
1. The freshwater calanoid copepod Boeckella gibbosa is typical of high elevation lakes and ponds in Patagonia (Argentina). Previous studies have shown that this species is highly tolerant to short-term exposure to natural and artificial UVB radiation, and that its tolerance is due to photoreactivation by longer wavelength radiation. In this study, we investigate the potential sublethal effects of solar radiation after prolonged exposure.
2. We incubated B. gibbosa at 1 m depth in oligotrophic Lake Toncek for 24 days. The incubation chambers were 1.2 l acrylic cylinders covered with appropriate filters in order to obtain three radiation treatments: visible radiation only, visible radiation + UVA and visible radiation + UVA + UVB.
3. The three treatments did not differ significantly in variables considered as indicators of survival (number of individuals), reproduction (proportion of ovigerous females, clutch size) and development (instar composition). Although resistance to solar UVB radiation is certainly a requisite to live in transparent high elevation habitats, the fact of being effectively exposed to natural levels of UVB radiation does not seem to have measurable consequences on an already adapted species, such as B. gibbosa 相似文献
2. We incubated B. gibbosa at 1 m depth in oligotrophic Lake Toncek for 24 days. The incubation chambers were 1.2 l acrylic cylinders covered with appropriate filters in order to obtain three radiation treatments: visible radiation only, visible radiation + UVA and visible radiation + UVA + UVB.
3. The three treatments did not differ significantly in variables considered as indicators of survival (number of individuals), reproduction (proportion of ovigerous females, clutch size) and development (instar composition). Although resistance to solar UVB radiation is certainly a requisite to live in transparent high elevation habitats, the fact of being effectively exposed to natural levels of UVB radiation does not seem to have measurable consequences on an already adapted species, such as B. gibbosa 相似文献
54.
O'Neill SK Cao Y Hamel KM Doodes PD Hutas G Finnegan A 《Journal of immunology (Baltimore, Md. : 1950)》2007,179(8):5109-5116
Depletion of B cells in rheumatoid arthritis is therapeutically efficacious. Yet, the mechanism by which B cells participate in the inflammatory process is unclear. We previously demonstrated that Ag-specific B cells have two important functions in the development of arthritis in a murine model of rheumatoid arthritis, proteoglycan (PG)-induced arthritis (PGIA). PG-specific B cells function as autoantibody-producing cells and as APCs that activate PG-specific T cells. Moreover, the costimulatory molecule CD86 is up-regulated on PG-specific B cells in response to stimulation with PG. To address the requirement for CD80/CD86 expression on B cells in the development of PGIA, we generated mixed bone marrow chimeras in which CD80/CD86 is specifically deleted on B cells and not on other APC populations. Chimeras with a specific deficiency in CD80/CD86 expression on B cells are resistant to the induction of PGIA. The concentration of PG-specific autoantibody is similar in mice sufficient or deficient for CD80/86-expressing B cells, which indicates that resistance to PGIA is not due to the suppression of PG-specific autoantibody production. CD80/86-deficient B cells failed to effectively activate PG-specific autoreactive T cells as indicated by the failure of T cells from PG-immunized CD80/86-deficient B cell chimeras to transfer arthritis into SCID mice. In vitro secondary recall responses to PG are also dependent on CD80/86-expressing B cells. These results demonstrate that a CD80/86:CD28 costimulatory interaction between B cells and T cells is required for autoreactive T cell activation and the induction of arthritis but not for B cell autoantibody production. 相似文献
55.
Hansen K Wagner B Hamel W Schweizer M Haag F Westphal M Lamszus K 《Journal of neurochemistry》2007,103(1):259-275
The neurotrophin receptor tropomyosin-related kinase A (TrkA) and its ligand nerve growth factor (NGF) are expressed in astrocytomas, and an inverse association of TrkA expression with malignancy grade was described. We hypothesized that TrkA expression might confer a growth disadvantage to glioblastoma cells. To analyze TrkA function and signaling, we transfected human TrkA cDNA into the human glioblastoma cell line G55. We obtained three stable clones, all of which responded with striking cytoplasmic vacuolation and subsequent cell death to NGF. Analyzing the mechanism of cell death, we could exclude apoptosis and cellular senescence. Instead, we identified several indications of autophagy: electron microscopy showed typical autophagic vacuoles; acridine orange staining revealed acidic vesicular organelles; acidification of acidic vesicular organelles was prevented using bafilomycin A1; cells displayed arrest in G2/M; increased processing of LC3 occurred; vacuolation was prevented by the autophagy inhibitor 3-methyladenine; no caspase activation was detected. We further found that both activation of ERK and c-Jun N-terminal kinase but not p38 were involved in autophagic vacuolation. To conclude, we identified autophagy as a novel mechanism of NGF-induced cell death. Our findings suggest that TrkA activation in human glioblastomas might be beneficial therapeutically, especially as several of the currently used chemotherapeutics also induce autophagic cell death. 相似文献
56.
James S. Wakeley Michael P. Guilfoyle Terry J. Antrobus Richard A. Fischer Wylie C. BarrowJr. Paul B. Hamel 《Wetlands Ecology and Management》2007,15(5):417-439
We used an ordination approach to identify factors important to the organization of breeding bird communities in three floodplains:
Cache River, Arkansas (AR), Iatt Creek, Louisiana (LA), and the Coosawhatchie River, South Carolina (SC), USA. We used 5-min
point counts to sample birds in each study area each spring from 1995 to 1998, and measured ground-surface elevations and
a suite of other habitat variables to investigate bird distributions and community characteristics in relation to important
environmental gradients. In both AR and SC, the average number of Neotropical migrant species detected was lowest in semipermanently
flooded Nyssa aquatica Linnaeus habitats and greatest in the highest elevation floodplain zone. Melanerpes carolinus Linnaeus, Protonotaria citrea Boddaert, Quiscalus quiscula Linnaeus, and other species were more abundant in N. aquatica habitats, whereas Wilsonia citrina Boddaert, Oporornis formosus Wilson, Vireo griseus Boddaert, and others were more abundant in drier floodplain zones. In LA, there were no significant differences in community
metrics or bird species abundances among forest types. Canonical correspondence analyses revealed that structural development
of understory vegetation was the most important factor affecting bird distributions in all three study areas; however, potential
causes of these structural gradients differed. In AR and SC, differences in habitat structure were related to the hydrologic
gradient, as indexed by ground-surface elevation. In LA, structural variations were related mainly to the frequency of canopy
gaps. Thus, bird communities in all three areas appeared to be organized primarily in response to repeated localized disturbance.
Our results suggest that regular disturbance due to flooding plays an important role in structuring breeding bird communities
in floodplains subject to prolonged inundation, whereas other agents of disturbance (e.g., canopy gaps) may be more important
in headwater systems subject to only short-duration flooding. Management for avian community integrity in these systems should
strive to maintain forest zonation and natural disturbance regimes. 相似文献
57.
Navid Bazghaleh Chantal Hamel Yantai Gan Bunyamin Tar'an Joan Diane Knight 《Applied and environmental microbiology》2015,81(7):2368-2377
Increasing evidence supports the existence of variations in the association of plant roots with symbiotic fungi that can improve plant growth and inhibit pathogens. However, it is unclear whether intraspecific variations in the symbiosis exist among plant cultivars and if they can be used to improve crop productivity. In this study, we determined genotype-specific variations in the association of chickpea roots with soil fungal communities and evaluated the effect of root mycota on crop productivity. A 2-year field experiment was conducted in southwestern Saskatchewan, the central zone of the chickpea growing region of the Canadian prairie. The effects of 13 cultivars of chickpea, comprising a wide range of phenotypes and genotypes, were tested on the structure of root-associated fungal communities based on internal transcribed spacer (ITS) and 18S rRNA gene markers using 454 amplicon pyrosequencing. Chickpea cultivar significantly influenced the structure of the root fungal community. The magnitude of the effect varied with the genotypes evaluated, and effects were consistent across years. For example, the roots of CDC Corrine, CDC Cory, and CDC Anna hosted the highest fungal diversity and CDC Alma and CDC Xena the lowest. Fusarium sp. was dominant in chickpea roots but was less abundant in CDC Corrine than the other cultivars. A bioassay showed that certain of these fungal taxa, including Fusarium species, can reduce the productivity of chickpea, whereas Trichoderma harzianum can increase chickpea productivity. The large variation in the profile of chickpea root mycota, which included growth-promoting and -inhibiting species, supports the possibility of improving the productivity of chickpea by improving its root mycota in chickpea genetic improvement programs using traditional breeding techniques. 相似文献
58.
Romagnoli R Baraldi PG Cruz-Lopez O Tolomeo M Di Cristina A Pipitone RM Grimaudo S Balzarini J Brancale A Hamel E 《Bioorganic & medicinal chemistry letters》2011,21(9):2746-2751
Microtubules are dynamic structures that play a crucial role in cellular division and are recognized as an important target for cancer therapy. In search of new compounds with strong antiproliferative activity and simple molecular structure, a new series of 2-amino-3-(3′,4′,5′-trimethoxybenzoyl)-5-(hetero)aryl ethynyl thiophene derivatives was prepared by the Sonogashira coupling reaction of the corresponding 5-bromothiophenes with several (hetero)aryl acetylenes. When these compounds were analyzed in vitro for their inhibition of cell proliferation, the 2- and 3-thiophenyl acetylene derivatives were the most powerful compounds, both of which exerted cytostatic effects at submicromolar concentrations. In contrast, the presence of a more flexible ethyl chain between the (hetero)aryl and the 5-position of the thiophene ring resulted in significant reduction in activity relative to the 5-(hetero)aryl acetylene substituted derivatives. The effects of a selected series of compounds on cell cycle progression correlated well with their strong antiproliferative activity and inhibition of tubulin polymerization. We found that the antiproliferative effects of the most active compounds were associated with increase of the proportion of cells in the G2/M and sub-G1 phases of the cell cycle. 相似文献
59.
Simard D Leblanc Y Berthelette C Zaghdane MH Molinaro C Wang Z Gallant M Lau S Thao T Hamel M Stocco R Sawyer N Sillaots S Gervais F Houle R Lévesque JF 《Bioorganic & medicinal chemistry letters》2011,21(2):841-845
A new class of 7-azaindole analogs of MK-7246 as potent and selective CRTH2 antagonists is reported. The SAR leading to the identification of the optimal azaindole regioisomer as well as the pharmacokinetics and off-target activities of the most potent antagonists are disclosed. 相似文献
60.
Zaghdane H Boyd M Colucci J Simard D Berthelette C Leblanc Y Wang Z Houle R Lévesque JF Molinaro C Hamel M Stocco R Sawyer N Sillaots S Gervais F Gallant M 《Bioorganic & medicinal chemistry letters》2011,21(11):3471-3474
A new series of indole amide acting as hCRTH2 receptor ligands had been explored and are described herein. Several amide derivatives displaying low nanomolar activity in hCRTH2 binding and whole blood assays were identified. They were found to behave as a full antagonists, exhibiting good selectivity over related prostaglandin receptors. Also, prototypical compounds in this novel series which displayed acceptable CYP profiles and were orally bioavailable in rats were identified. 相似文献