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51.
International workshop on opportunities for ecosystem approaches to fisheries management in the Pacific Ocean tuna fisheries 总被引:1,自引:0,他引:1
52.
Desmond A. Mackell Michael L. Casazza Cory T. Overton J. Patrick Donnelly David Olson Fiona McDuie Joshua T. Ackerman John M. Eadie 《Ecology and evolution》2021,11(20):14056
Identifying migration routes and fall stopover sites of Cinnamon Teal (Spatula cyanoptera septentrionalium) can provide a spatial guide to management and conservation efforts, and address vulnerabilities in wetland networks that support migratory waterbirds. Using high spatiotemporal resolution GPS‐GSM transmitters, we analyzed 61 fall migration tracks across western North America during our three‐year study (2017–2019). We marked Cinnamon Teal primarily during spring/summer in important breeding and molting regions across seven states (California, Oregon, Washington, Idaho, Utah, Colorado, and Nevada). We assessed fall migration routes and timing, detected 186 fall stopover sites, and identified specific North American ecoregions where sites were located. We classified underlying land cover for each stopover site and measured habitat selection for 12 land cover types within each ecoregion. Cinnamon Teal selected a variety of flooded habitats including natural, riparian, tidal, and managed wetlands; wet agriculture (including irrigation ditches, flooded fields, and stock ponds); wastewater sites; and golf and urban ponds. Wet agriculture was the most used habitat type (29.8% of stopover locations), and over 72% of stopover locations were on private land. Relatively scarce habitats such as wastewater ponds, tidal marsh, and golf and urban ponds were highly selected in specific ecoregions. In contrast, dry non‐habitat across all ecoregions, and dry agriculture in the Cold Deserts and Mediterranean California ecoregions, was consistently avoided. Resources used by Cinnamon Teal often reflected wetland availability across the west and emphasize their adaptability to dynamic resource conditions in arid landscapes. Our results provide much needed information on spatial and temporal resource use by Cinnamon Teal during migration and indicate important wetland habitats for migrating waterfowl in the western United States. 相似文献
53.
Richard N. Bohnsack Xuezheng Song Linda J. Olson Mariko Kudo Russell R. Gotschall William M. Canfield Richard D. Cummings David F. Smith Nancy M. Dahms 《The Journal of biological chemistry》2009,284(50):35215-35226
The 300-kDa cation-independent mannose 6-phosphate receptor (CI-MPR), which contains multiple mannose 6-phosphate (Man-6-P) binding sites that map to domains 3, 5, and 9 within its 15-domain extracytoplasmic region, functions as an efficient carrier of Man-6-P-containing lysosomal enzymes. To determine the types of phosphorylated N-glycans recognized by each of the three carbohydrate binding sites of the CI-MPR, a phosphorylated glycan microarray was probed with truncated forms of the CI-MPR. Surface plasmon resonance analyses using lysosomal enzymes with defined N-glycans were performed to evaluate whether multiple domains are needed to form a stable, high affinity carbohydrate binding pocket. Like domain 3, adjacent domains increase the affinity of domain 5 for phosphomannosyl residues, with domain 5 exhibiting ∼60-fold higher affinity for lysosomal enzymes containing the phosphodiester Man-P-GlcNAc when in the context of a construct encoding domains 5–9. In contrast, domain 9 does not require additional domains for high affinity binding. The three sites differ in their glycan specificity, with only domain 5 being capable of recognizing Man-P-GlcNAc. In addition, domain 9, unlike domains 1–3, interacts with Man8GlcNAc2 and Man9GlcNAc2 oligosaccharides containing a single phosphomonoester. Together, these data indicate that the assembly of three unique carbohydrate binding sites allows the CI-MPR to interact with the structurally diverse phosphorylated N-glycans it encounters on newly synthesized lysosomal enzymes. 相似文献
54.
Orme CD Davies RG Olson VA Thomas GH Ding TS Rasmussen PC Ridgely RS Stattersfield AJ Bennett PM Owens IP Blackburn TM Gaston KJ 《PLoS biology》2006,4(7):e208
Large-scale patterns of spatial variation in species geographic range size are central to many fundamental questions in macroecology and conservation biology. However, the global nature of these patterns has remained contentious, since previous studies have been geographically restricted and/or based on small taxonomic groups. Here, using a database on the breeding distributions of birds, we report the first (to our knowledge) global maps of variation in species range sizes for an entire taxonomic class. We show that range area does not follow a simple latitudinal pattern. Instead, the smallest range areas are attained on islands, in mountainous areas, and largely in the southern hemisphere. In contrast, bird species richness peaks around the equator, and towards higher latitudes. Despite these profoundly different latitudinal patterns, spatially explicit models reveal a weak tendency for areas with high species richness to house species with significantly smaller median range area. Taken together, these results show that for birds many spatial patterns in range size described in geographically restricted analyses do not reflect global rules. It remains to be discovered whether global patterns in geographic range size are best interpreted in terms of geographical variation in species assemblage packing, or in the rates of speciation, extinction, and dispersal that ultimately underlie biodiversity. 相似文献
55.
Valyl-tRNA synthetase modification-dependent restriction of bacteriophage T4 总被引:1,自引:1,他引:1 下载免费PDF全文
A strain of Escherichia coli, CP 790302, severely restricts the growth of wild-type bacteriophage T4. In broth culture, most infections of single cells are abortive, although a few infected cells exhibit reduced burst sizes. In contrast, bacteriophage T4 mutants impaired in the ability to modify valyl-tRNA synthetase develop normally on this strain. Biochemical evidence indicates that the phage-modified valyl-tRNA synthetase in CP 790302 is different from that previously described. Although the enzyme is able to support normal protein synthesis, a disproportionate amount of phage structural protein (serum blocking power) fails to mature into particles of the appropriate density. The results with host strain CP 790302 are consistent with either a gratuitous inhibition of phage assembly by faulty modification or abrogation of an unknown role that valyl-tRNA synthetase might normally play in viral assembly. 相似文献
56.
Type A botulinum neurotoxin is one of the most lethal of the seven serotypes and is increasingly used as a therapeutic agent
in neuromuscular dysfunctions. Its toxic function is related to zinc-endopeptidase activity of the N-terminal light chain
(LC) on synaptosome-associated protein-25 kDa (SNAP-25) of the SNARE complex. To understand the determinants of substrate
specificity and assist the development of strategies for effective inhibitors, we used site-directed mutagenesis to investigate
the effects of 13 polar residues of the LC on substrate binding and catalysis. Selection of the residues for mutation was
based on a computational analysis of the three-dimensional structure of the LC modeled with a 17-residue substrate fragment
of SNAP-25. Steady-state kinetic parameters for proteolysis of the substrate fragment were determined for a set of 16 single
mutants. Of the mutated residues non-conserved among the serotypes, replacement of Arg-230 and Asp-369 by polar or apolar
residues resulted in drastic lowering of the catalytic rate constant (k
cat), but had less effect on substrate affinity (K
m). Substitution of Arg-230 with Lys decreased the catalytic efficiency (k
cat/K
m) by 50-fold, whereas replacement by Leu yielded an inactive protein. Removal of the electrostatic charge at Asp-369 by mutation
to Asn resulted in 140-fold decrease in k
cat/K
m. Replacement of other variable residues surrounding the catalytic cleft (Glu-54, Glu-63, Asn-66, Asp-130, Asn-161, Glu-163,
Glu-170, Glu-256), had only marginal effect on decreasing the catalytic efficiency, but unexpectedly the substitution of Lys-165
with Leu resulted in fourfold increase in k
cat/K
m. For comparison purposes, two conserved residues Arg-362 and Tyr-365 were investigated with substitutions of Leu and Phe,
respectively, and their catalytic efficiency decreased 140- and 10-fold, respectively, whereas substitution of the tyrosine
ring with Asn abolished activity. The altered catalytic efficiencies of the mutants were not due to any significant changes
in secondary or tertiary structures, or in zinc content and thermal stability. We suggest that, despite the large minimal
substrate size for catalysis, only a few non-conserved residues surrounding the active site are important to render the LC
competent for catalysis or provide conformational selection of the substrate. 相似文献
57.
Tesch LD Raghavendra MP Bedsted-Faarvang T Gettins PG Olson ST 《Protein science : a publication of the Protein Society》2005,14(2):533-542
The viral serpin, crmA, is distinguished by its small size and ability to inhibit both serine and cysteine proteases utilizing a reactive loop shorter than most other serpins. Here, we characterize the mechanism of crmA inhibition of serine proteases and probe the reactive loop length requirements for inhibition with two crmA reactive loop variants. P1 Arg crmA inhibited the trypsin-like proteases, thrombin, and factor Xa, with moderate efficiencies (approximately 10(2)-10(4) M(-1)sec(-1)), near equimolar inhibition stoichiometries, and formation of SDS-stable complexes which were resistant to dissociation (k(diss) approximately 10(-7) sec(-1)), consistent with a serpin-type inhibition mechanism. Trypsin was not inhibited, but efficiently cleaved the variant crmA as a substrate (k(cat)/K(M) of approximately 10(6) M(-1) sec(-1)). N-terminal sequencing confirmed that the P1 Arg-P1'Cys bond was the site of cleavage. Altering the placement of the Arg in a double mutant P1 Gly-P1'Arg crmA resulted in minimal ability to inhibit any of the trypsin family proteases. This variant was cleaved by the proteases approximately 10-fold less efficiently than P1 Arg crmA. Surprisingly, pancreatic elastase was rapidly inhibited by wild-type and P1 Arg crmAs (10(5)-10(6) M(-1)sec(-1)), although with elevated inhibition stoichiometries and higher rates of complex dissociation. N-terminal sequencing showed that elastase attacked the P1'Cys-P2'Ala bond, indicating that crmA can inhibit proteases using a reactive loop length similar to that used by other serpins, but with variations in this inhibition arising from different effective P2 residues. These results indicate that crmA inhibits serine proteases by the established serpin conformational trapping mechanism, but is unusual in inhibiting through either of two adjacent reactive sites. 相似文献
58.
A. Randall Olson 《American journal of botany》1994,81(6):718-725
Monotropsis odorata Elliott. is one of the most cryptic and relatively rare North American endemic species of the Monotropaceae; therefore, information concerning the biology of this achlorophyllous, mycotrophic angiosperm is limited. Bright field and fluorescence microscopic investigations of postpollination gynoecia reveal that pollen tubes follow a continuous pathway from the receptive surface of the stigma to micropyles of the ovules. The pollen tube pathway is characterized by discrete strands of transmitting tissue connecting an exudate-coated stigma to an exudate-filled, stylar canal that leads directly to exudate-coated placentae. Pollen tube growth appears restricted to those areas associated with an exudate. The gynoecial pathway for pollen tube growth in this taxon conforms to those described from other monotropàceous species. 相似文献
59.
Development of a RIVPACS-type predictive model for bioassessment of wadeable streams in Wyoming 总被引:3,自引:0,他引:3
Eric G. Hargett Jeremy R. ZumBerge Charles P. Hawkins John R. Olson 《Ecological Indicators》2007,7(4):807-826
RIVPACS models produce a community-level measure of biological condition known as O/E, which is derived from a comparison of the observed (O) biota with those expected (E) to occur in the absence of anthropogenic stress. We used benthic macroinvertebrate and environmental data collected at 925 stream monitoring stations, from 1993 to 2001, to develop, validate, and apply a RIVPACS model to assess the biological condition of wadeable streams in Wyoming. From this dataset, 296 samples were identified as reference, 157 of which were used to calibrate the model, 46 to validate it, and 93 to examine temporal variability in reference site O/E-values. We used cluster analyses to group the model development reference sites into biologically similar classes of streams and multiple discriminant function analysis to determine which environmental variables best discriminated among reference groups. A suite of 14 categorical and continuous environmental variables best discriminated among 15 reference groups and explained a large proportion of the natural variability in biota within the reference dataset. Eleven of the predictor variables were derived from GIS. As expected, mean O/E-values for reference sites used in model development and validation were near unity and statistically similar. Temporal variability in O/E-values for reference sites was low. Test site values ranged from 0 to 1.45 (mean = 0.73). The model was accurate in both space and time and precise enough (S.D. of O/E-values for calibration data = 0.17) to detect modest alteration in biota associated with anthropogenic stressors. Our model was comparable in performance to other RIVPACS models developed in the United States and can produce effective assessments of biological condition over a broad, ecologically diverse region. We also provide convincing evidence that RIVPACS models can be developed primarily with GIS-based predictor variables. This framework not only simplifies the extraction of predictor variable information while potentially reducing expenditures of time and money in the collection of predictor variable information, but opens the door for development and/or application of RIVPACS models in regions where there is a paucity of local-scale, abiotic information. 相似文献
60.