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71.
Tropical hardwood hammocks, among the rarest and most threatened vegetative communities in the United States, occur throughout the 225-km Florida Keys archipelago as it extends toward the Caribbean from the southeast tip of peninsular Florida. Compounding their critical conservation status, tropical hardwood hammocks and the dynamics that support their peculiar species diversity in the region are poorly understood. The goal of this study was to explore the dynamics of the species compositional gradient of the hammocks along the Florida Keys, and to identify significant ecological units within the gradient. The primary data for this research were assembled from the Institute for Regional Conservation's floristic database of South Florida. We were able to extract presence/absence data for 295 species from comprehensive surveys of 23 study sites. Nonmetric multidimensional scaling was used to deconstruct the compositional trends into a reduced ordination space. Cluster analysis was subsequently used to identify discrete ecological units. Additionally, we used vector fitting to interpret the significant correlated ancillary variables. Our main results were three well-fitted nonmetric multidimensional scaling axes with three nonoverlapping ecological units. Of the ancillary variables, latitude, longitude, percent composition from biogeographical regions, richness, and area were correlated to the nonmetric multidimensional scaling results. These results increase our understanding of the community structure of the hammocks along the Florida Keys, and can contribute to increasing our ability to adequately protect and restore tropical hardwood hammocks and other similar tropical dry forest communities throughout the Caribbean. 相似文献
72.
Wesley Reardon David A. Fitzpatrick Mario A. Fares Jacqueline M. Nugent 《Plant molecular biology》2009,71(3):241-250
Plantago lanceolata produces small actinomorphic (radially symmetric), wind-pollinated flowers that have evolved from a zygomorphic, biotically
pollinated ancestral state. To understand the developmental mechanisms that might underlie this change in flower shape, and
associated change in pollination syndrome, we analyzed the role of CYC-like genes in P. lanceolata. Related zygomorphic species have two CYC-like genes that are expressed asymmetrically in the dorsal region of young floral meristems and in developing flowers, where
they affect the rate of development of dorsal petals and stamens. Plantago has a single CYC-like gene (PlCYC) that is not expressed in early floral meristems and there is no apparent asymmetry in the pattern of PlCYC expression during later flower development. Thus, the evolution of actinomorphy in Plantago correlates with loss of dorsal-specific CYC-like gene function. PlCYC is expressed in the inflorescence stem, in pedicels, and relatively late in stamen development, suggesting a novel role for
PlCYC in compacting the inflorescence and retarding stamen elongation in this wind pollinated species. 相似文献
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74.
Hyperlipidemia is a major risk factor for developing atherosclerosis in humans, and epidemiological studies have correlated specific lipoprotein levels with cardiovascular disease risk. Murine models of atherosclerosis rely on the induction of hyperlipidemia for vascular lesions to form, but the pathogenic contributions attributed to different lipoprotein populations are not well defined. To address this issue, we analyzed over 300 LDL receptor (LDLR) deficient mice that have been fed a high-fat diet and for which a full lipoprotein profile and aortic root atherosclerosis values were assessed. Overall, aortic root atherosclerosis is best predicted by plasma VLDL cholesterol levels with less predictive value derived from either LDL or HDL cholesterol. Triglyceride levels are more atherogenic in female mice, especially immune competent females, and depletion of the adaptive immune system leads to a global reduction in plasma lipid levels and aortic root lesion size yet does not appear to alter the atherogenic potential of individual lipoprotein subspecies. In contrast, HDL-cholesterol is a better predictor of aortic root atherosclerosis in apoE-deficient mice. In summary, this large scale analysis of high-fat diet fed LDLR deficient mice highlight the relationship between different plasma lipid components, especially VLDL-cholesterol, and aortic root atherosclerosis. 相似文献
75.
Augustus AM Reardon PN Heller WT Spicer LD 《The Journal of biological chemistry》2006,281(45):34269-34276
The Met regulon in Escherichia coli encodes several proteins responsible for the biosynthesis of methionine. Regulation of the expression of most of these proteins is governed by the methionine repressor protein MetJ and its co-repressor, the methionine derivative S-adenosylmethionine. Genes controlled by MetJ contain from two to five sequential copies of a homologous 8-bp sequence called the metbox. A crystal structure for one of the complexes, the repressor tetramer bound to two metboxes, has been reported (Somers, W. S., and S. E. Phillips (1992) Nature 359, 387-393), but little structural work on the larger assemblies has been done presumably because of the difficulties in crystallization and the variability in the number and sequences of metboxes for the various genes. Small angle neutron scattering was used to study complexes of MetJ and S-adenosylmethionine with double-stranded DNA containing two, three, and five metboxes. Our results demonstrate that the crystal structure of the two-metbox complex is not the native solution conformation of the complex. Instead, the system adopts a less compact conformation in which there is decreased interaction between the adjacent MetJ dimers. Models built of the higher order complexes from the scattering data show that the three-metbox complex is organized much like the two-metbox complex. However, the five-metbox complex differs significantly from the smaller complexes, providing much closer packing of the adjacent MetJ dimers and allowing additional contacts not available in the crystal structure. The results suggest that there is a structural basis for the differences observed in the regulatory effectiveness of MetJ for the various genes of the Met regulon. 相似文献
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77.
Duff RM Tay V Hackman P Ravenscroft G McLean C Kennedy P Steinbach A Schöffler W van der Ven PF Fürst DO Song J Djinović-Carugo K Penttilä S Raheem O Reardon K Malandrini A Gambelli S Villanova M Nowak KJ Williams DR Landers JE Brown RH Udd B Laing NG 《American journal of human genetics》2011,(6):79-740
Linkage analysis of the dominant distal myopathy we previously identified in a large Australian family demonstrated one significant linkage region located on chromosome 7 and encompassing 18.6 Mbp and 151 genes. The strongest candidate gene was FLNC because filamin C, the encoded protein, is muscle-specific and associated with myofibrillar myopathy. Sequencing of FLNC cDNA identified a c.752T>C (p.Met251Thr) mutation in the N-terminal actin-binding domain (ABD); this mutation segregated with the disease and was absent in 200 controls. We identified an Italian family with the same phenotype and found a c.577G>A (p.Ala193Thr) filamin C ABD mutation that segregated with the disease. Filamin C ABD mutations have not been described, although filamin A and filamin B ABD mutations cause multiple musculoskeletal disorders. The distal myopathy phenotype and muscle pathology in the two families differ from myofibrillar myopathies caused by filamin C rod and dimerization domain mutations because of the distinct involvement of hand muscles and lack of pathological protein aggregation. Thus, like the position of FLNA and B mutations, the position of the FLNC mutation determines disease phenotype. The two filamin C ABD mutations increase actin-binding affinity in a manner similar to filamin A and filamin B ABD mutations. Cell-culture expression of the c.752T>C (p.Met251)Thr mutant filamin C ABD demonstrated reduced nuclear localization as did mutant filamin A and filamin B ABDs. Expression of both filamin C ABD mutants as full-length proteins induced increased aggregation of filamin. We conclude filamin C ABD mutations cause a recognizable distal myopathy, most likely through increased actin affinity, similar to the pathological mechanism of filamin A and filamin B ABD mutations. 相似文献
78.
This study tested the prediction that hypoxia may reduce the frequency of energetically expensive behaviours by quantifying male mating and aggressive displays in the cichlid Pseudocrenilabrus multicolor victoriae after long-term acclimation (5 months) to either high dissolved oxygen (DO) or low DO. Regardless of DO treatment, males engaged in more aggressive displays than mating displays; however, males acclimated to low DO reduced their total number of displays compared to high DO-acclimated males. 相似文献
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80.
Rachel Knevel Diederik PC de Rooy Tore Saxne Elisabet Lindqvist Martha K Leijsma Nina A Daha Bobby PC Koeleman Roula Tsonaka Jeanine J Houwing-Duistermaat Joris JM Schonkeren Rene EM Toes Tom WJ Huizinga Elisabeth Brouwer Anthony G Wilson Annette HM van der Helm-van Mil 《Arthritis research & therapy》2014,16(3):R108