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31.
Xuemei Han Shauna P. Dendy Karen A. Garrett Liang Fang Melinda D. Smith 《Plant Ecology》2008,198(2):197-210
We surveyed the prevalence and amount of leaf damage related to herbivory and pathogens on 12 pairs of exotic (invasive and
noninvasive) and ecologically similar native plant species in tallgrass prairie to examine whether patterns of damage match
predictions from the enemy release hypothesis. We also assessed whether natural enemy impacts differed in response to key
environmental factors in tallgrass prairie by surveying the prevalence of rust on the dominant C4 grass, Andropogon gerardii, and its congeneric invasive exotic C4 grass, A. bladhii, in response to fire and nitrogen fertilization treatments. Overall, we found that the native species sustain 56.4% more
overall leaf damage and 83.6% more herbivore-related leaf damage when compared to the exotic species. Moreover, we found that
the invasive exotic species sustained less damage from enemies relative to their corresponding native species than the noninvasive
exotic species. Finally, we found that burning and nitrogen fertilization both significantly increased the prevalence of rust
fungi in the native grass, while rust fungi rarely occurred on the exotic grass. These results indicate that reduced damage
from enemies may in part explain the successful naturalization of exotic species and the spread of invasive exotic species
in tallgrass prairie. 相似文献
32.
Measles virus (MeV), a member of the paramyxovirus family of enveloped RNA viruses and one of the most infectious viral pathogens identified, accounts for major pediatric morbidity and mortality worldwide although coordinated efforts to achieve global measles control are in place. Target cell entry is mediated by two viral envelope glycoproteins, the attachment (H) and fusion (F) proteins, which form a complex that achieves merger of the envelope with target cell membranes. Despite continually expanding knowledge of the entry strategies employed by enveloped viruses, our molecular insight into the organization of functional paramyxovirus fusion complexes and the mechanisms by which the receptor binding by the attachment protein triggers the required conformational rearrangements of the fusion protein remain incomplete. Recently reported crystal structures of the MeV attachment protein in complex with its cellular receptors CD46 or SLAM and newly developed functional assays have now illuminated some of the fundamental principles that govern cell entry by this archetype member of the paramyxovirus family. Here, we review these advances in our molecular understanding of MeV entry in the context of diverse entry strategies employed by other members of the paramyxovirus family. 相似文献
33.
Summary Three closely affiliated species of Heterospathe Scheff. (H. elegans (Becc.) Becc., H. humilis Becc. and H. versteegiana Becc.) from New Guinea are revised. They are reduced to a single species which is divided into two subspecies, and the new
combination H. elegans subsp. humilis (Becc.) M. S. Trudgen & W. J. Baker is made. The subspecies can be readily distinguished by their growth habit. Epitypes
are designated for the three previously published names, as informative material on the habit is not included in the existing
type specimens. A new, potentially related species is described as H. pullenii M. S. Trudgen & W. J. Baker. 相似文献
34.
Molecular cloning and expression of major structural protein VP1 of the human polyomavirus JC virus: formation of virus-like particles useful for immunological and therapeutic studies 总被引:3,自引:0,他引:3
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Goldmann C Petry H Frye S Ast O Ebitsch S Jentsch KD Kaup FJ Weber F Trebst C Nisslein T Hunsmann G Weber T Lüke W 《Journal of virology》1999,73(5):4465-4469
The major structural viral protein, VP1, of the human polyomavirus JC virus (JCV), the causative agent of progressive multifocal leukoencephalopathy (PML), was expressed by using recombinant baculoviruses. Recombinant VP1 formed virus-like particles (VLP) with the typical morphology of empty JCV capsids. Purified VP1 VLP bind to SVG, B, and T cells, as well as to monkey kidney cells. After binding, VP1 VLP were also internalized with high efficiency and transported to the nucleus. Immunization studies revealed these particles as highly immunogenic when administered with adjuvant, while immunization without adjuvant induced no immune response. VP1 VLP hyperimmune serum inhibits binding to SVG cells and neutralizes natural JCV. Furthermore, the potential of VP1 VLP as an efficient transporter system for gene therapy was demonstrated. Exogenous DNA could be efficiently packaged into VP1 VLP, and the packaged DNA was transferred into COS-7 cells as shown by the expression of a marker gene. Thus, VP1 VLP are useful for PML vaccine development and represent a potential new transporter system for human gene therapy. 相似文献
35.
Sandra Blanco Sabine Dietmann Joana V Flores Shobbir Hussain Claudia Kutter Peter Humphreys Margus Lukk Patrick Lombard Lucas Treps Martyna Popis Stefanie Kellner Sabine M Hölter Lillian Garrett Wolfgang Wurst Lore Becker Thomas Klopstock Helmut Fuchs Valerie Gailus‐Durner Martin Hrabĕ de Angelis Ragnhildur T Káradóttir Mark Helm Jernej Ule Joseph G Gleeson Duncan T Odom Michaela Frye 《The EMBO journal》2014,33(18):2020-2039
36.
Stephanie Eby Deron E. Burkepile Richard W. S. Fynn Catherine E. Burns Navashni Govender Nicole Hagenah Sally E. Koerner Katherine J. Matchett Dave I. Thompson Kevin R. Wilcox Scott L. Collins Kevin P. Kirkman Alan K. Knapp Melinda D. Smith 《Oecologia》2014,175(1):293-303
Large herbivore grazing is a widespread disturbance in mesic savanna grasslands which increases herbaceous plant community richness and diversity. However, humans are modifying the impacts of grazing on these ecosystems by removing grazers. A more general understanding of how grazer loss will impact these ecosystems is hampered by differences in the diversity of large herbivore assemblages among savanna grasslands, which can affect the way that grazing influences plant communities. To avoid this we used two unique enclosures each containing a single, functionally similar large herbivore species. Specifically, we studied a bison (Bos bison) enclosure at Konza Prairie Biological Station, USA and an African buffalo (Syncerus caffer) enclosure in Kruger National Park, South Africa. Within these enclosures we erected exclosures in annually burned and unburned sites to determine how grazer loss would impact herbaceous plant communities, while controlling for potential fire-grazing interactions. At both sites, removal of the only grazer decreased grass and forb richness, evenness and diversity, over time. However, in Kruger these changes only occurred with burning. At both sites, changes in plant communities were driven by increased dominance with herbivore exclusion. At Konza, this was caused by increased abundance of one grass species, Andropogon gerardii, while at Kruger, three grasses, Themeda triandra, Panicum coloratum, and Digitaria eriantha increased in abundance. 相似文献
37.
38.
The proto-oncogene c-Src is involved in a variety of signaling processes. Therefore, c-Src spatiotemporal localization is critical for interaction with downstream targets. However, the mechanisms regulating this localization have remained elusive. Previous studies have shown that c-Src trafficking is a microtubule-dependent process that facilitates c-Src turnover in neuronal growth cones. As such, microtubule depolymerization lead to the inhibition of c-Src recycling. Alternatively, c-Src trafficking was also shown to be regulated by RhoB-dependent actin polymerization. Our results show that c-Src vesicles primarily exhibit microtubule-dependent trafficking; however, microtubule depolymerization does not inhibit vesicle movement. Instead, vesicular movement becomes both faster and less directional. This movement was associated with actin polymerization directly at c-Src vesicle membranes. Interestingly, it has been shown previously that c-Src delivery is an actin polymerization-dependent process that relies on small GTPase RhoB at c-Src vesicles. In agreement with this finding, microtubule depolymerization induced significant activation of RhoB, together with actin comet tail formation. These effects occurred downstream of GTP-exchange factor, GEF-H1, which was released from depolymerizing MTs. Accordingly, GEF-H1 activity was necessary for actin comet tail formation at the Src vesicles. Our results indicate that regulation of c-Src trafficking requires both microtubules and actin polymerization, and that GEF-H1 coordinates c-Src trafficking, acting as a molecular switch between these two mechanisms. 相似文献
39.
Summary Seed distribution (clump size) selection has been proposed as a possible mechanism of resource subdivision for competing heteromyid rodent species. To test this hypothesis, field experiments were conducted over two years during both richer and sparser seasons of the year. None of the predictions derived from the hypothesis were supported by our results. Though some selectivity was displayed by both Dipodomys spectabilis and D. merriami, the patterns of selectivity did not match the expected patterns. Our results further indicate that clump selection may be influenced by variables other than the density of seeds within a clump. These results have led us to conclude that clump size selection is unlikely to play a role in the coexistence of different species of the genus Dipodomys. 相似文献
40.
Adriana Vergs Alexandra H. Campbell Georgina Wood Lana Kajlich Aaron M. Eger Derrick Cruz Madelaine Langley Damon Bolton Melinda A. Coleman Jennifer Turpin Michaelie Crawford Nigel Coombes Adam Camilleri Peter D. Steinberg Ezequiel M. Marzinelli 《Ecological Management & Restoration》2020,21(2):74-85
Operation Crayweed focuses on the restoration of underwater forests that disappeared from the coastline of Sydney, Australia’s largest city, 40 years previously. We show how a combination of science, hands‐on restoration, community engagement and art has helped the project to reach its goals as well as raise awareness about the importance of underwater kelp forests that are experiencing global decline. 相似文献