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131.
Torsten Wronski Timothy Wacher Robert L. Hammond Bruce Winney Kris J. Hundertmark Mark J. Blacket 《分类学与生物多样性》2013,11(1):119-129
Mountain gazelles (Gazella gazella) rank among the most critically endangered mammals on the Arabian Peninsula. Past conservation efforts have been plagued by confusion about the phylogenetic relationship among various ‘phenotypically discernable’ populations, and even the question of species boundaries was far from being certain. This lack of knowledge has had a direct impact on conservation measures, especially ex situ breeding programmes, hampering the assignment of captive stocks to potential conservation units. Here, we provide a phylogenetic framework, based on the analysis of mtDNA sequences (360 bp cytochrome b and 213 bp Control Region) of 126 individuals collected from the wild throughout the Arabian Peninsula and from captive stocks. Our analyses revealed two reciprocally monophyletic genetic lineages within the presumed species Gazella gazella: one ‘northern clade’ on the Golan Heights (Israel/Syrian border) and one genetically diverse larger clade from the rest of the Arabian Peninsula including the Arava Valley (Negev, Israel). Applying the Strict Phylogenetic Species Concept (sensu Mishler & Theriot, 2000) allows assigning species status to these two major clades. 相似文献
132.
Eckstein TM Chandrasekaran S Mahapatra S McNeil MR Chatterjee D Rithner CD Ryan PW Belisle JT Inamine JM 《The Journal of biological chemistry》2006,281(8):5209-5215
Mycobacterium avium subspecies paratuberculosis (MAP), the causative agent of Johne disease in cattle and other ruminants, is proposed to be at least one of the causes of Crohn disease in humans. MAP and Mycobacterium avium subspecies avium, a closely related opportunistic environmental bacterium, share 95% of their genes and exhibit homologies of more than 99% between these genes. The identification of molecules specific for MAP is essential for understanding its pathogenicity and for development of useful diagnostic tools. The application of gas chromatography, mass spectrometry, and nuclear magnetic resonance led to the structural identification of a major cell wall lipopeptide of MAP, termed Para-LP-01, defined as C20 fatty acyl-D-Phe-N-Me-L-Val-L-Ile-L-Phe-L-Ala methyl ester. Variations of this lipopeptide with different fatty acyl moieties (C16 fatty acyl through C17, C18, C19, C21 to C22) were also identified. Besides the specificity of this lipopeptide for MAP, the presence of an N-Me-L-valine represents the first reported N-methylated amino acid within an immunogenic lipopeptide of mycobacteria. Sera from animals with Johne disease, but not sera from uninfected cattle, reacted with this lipopeptide, indicating potential biological importance. 相似文献
133.
Christoph Korte Torsten Jasper Ján Veizer 《Palaeogeography, Palaeoclimatology, Palaeoecology》2005,224(4):333-351
Two hundred sixty-four δ18O and δ13C values of Permian articulate brachiopod shells were analyzed and 81 of these values were characterized as well preserved and biostratigraphically well defined. These were then utilized for construction of baseline oxygen and carbon isotope curves for the Permian interval. In addition, 21 δ13C whole rock values are reported for the Wordian and Capitanian.The early Permian, Asselian to Artinskian, times are characterized by ∼ 2.5‰ decrease in oxygen isotope values, from ∼ − 0.7‰ to − 3.3‰ (V-PDB). This is attributed to a ∼ 4-7 °C increase in temperature in the Southern Urals, concomitant with the retreat of the Permo-Carboniferous ice sheets and return of the 18O-depleted melt water into the oceans. The Late Permian samples from Iran (Jolfa at Kuh-e-Ali-Bashi) and China (Meishan) yield δ18O values, and presumably temperatures, similar to those that followed the termination of the large-scale glaciation in the Lower Permian. In between, the upper Kungurian to Capitanian samples from the Delaware Basin (Guadalupe Mountains) are enriched in 18O, at − 1.5‰ to − 3‰. We have no definitive explanation for these data, but tentatively suggest that the “anomaly” can potentially be a result of evaporative enrichment of seawater in 18O, due to intracratonic arid setting of the basin. The 18O-enriched nature of the Zechstein samples (− 1.2‰ to + 2.5‰), on the other hand, is in all probability a reflection of the high evaporation rates in the Zechstein sea.The Permian interval is characterized by a relatively constant δ13C, at about 4‰. The exceptions are again the brachiopods from the Delaware Basin (Guadalupe Mountains), which show ∼ 1.6‰ increase in the Guadalupian, to values of up to 5.9‰ in the Wordian. A tentative explanation, as in the case of oxygen, is based on the proposition that the semi-enclosed Delaware Basin was likely stratified, with sequestration of the 13C-depleted carbon to the deeper water layers and a complementary 13C enrichment in the upper oxygenated layer. The coeval open ocean water DIC may have been similar to that of the remainder of the Permian interval, at ∼ 4‰, as indicated by whole rock carbonate samples from Oman, Sicily, and Iran. In the latest Permian, the trend mimics the well-known δ13C drop at the Permian/Triassic boundary. 相似文献
134.
Jank T Reinert DJ Giesemann T Schulz GE Aktories K 《The Journal of biological chemistry》2005,280(45):37833-37838
The large cytotoxins of Clostridia species glycosylate and thereby inactivate small GTPases of the Rho family. Clostridium difficile toxins A and B and Clostridium sordellii lethal toxin use UDP-glucose as the donor for glucosylation of Rho/Ras GTPases. In contrast, alpha-toxin from Clostridium novyi N-acetylglucosaminylates Rho GTPases by using UDP-N-acetylglucosamine as a donor substrate. Based on the crystal structure of C. difficile toxin B, we studied the sugar donor specificity of the toxins by site-directed mutagenesis. The changing of Ile-383 and Gln-385 in toxin B to serine and alanine, respectively, largely increased the acceptance of UDP-N-acetylglucosamine as a sugar donor for modification of RhoA. The K(m) value was reduced from 960 to 26 mum for the double mutant. Accordingly, the potential of the double mutant of toxin B to hydrolyze UDP-N-acetylglucosamine was higher than that for UDP-glucose. The changing of Ile-383 and Gln-385 in the lethal toxin of C. sordellii allowed modification of Ras in the presence of UDP-N-acetyl-glucosamine and reduced the acceptance of UDP-glucose as a donor for glycosylation. Vice versa, the changing of the equivalent residues in C. novyi alpha-toxin from Ser-385 and Ala-387 to isoleucine and glutamine, respectively, reversed the donor specificity of the toxin from UDP-N-acetylglucosamine to UDP-glucose. These data demonstrate that two amino acid residues are crucial for the co-substrate specificity of clostridial glycosylating toxins. 相似文献
135.
The frequency and intensity of extreme weather events and global temperature are rising, which poses a potential threat to
life, specifically crops, and therefore food and bioenergy supply. Reduced water availability has the most severe impact on
potential grain yield. Negative effects of transient drought stress (dry spells) can be countered by drought tolerance-inducing
chemicals. In search for useful compounds, biochemical assays are fast but limited in scope, whereas whole-plant assays are
slow, require large amounts of compounds, and are usually not concentration-related. Here we report the development of a fast,
concentration-dependent whole-plant assay using the fast growing duckweed Lemna minor L. 4-Amino-1,8-naphthalimide (1) and the imidacloprid metabolite 6-chloronicotinic acid (2) were affirmed as drought stress tolerance enhancers. Both also reduce oxidative stress-induced cell death in Arabidopsis thaliana (L.) Heynh. cell suspension culture but show differences in their mode of action. 相似文献
136.
Nucleobase ascorbate transporters (NATs), also known as Nucleobase:Cation-Symporter 2 (NCS2) proteins, belong to an evolutionary widespread family of transport proteins with members in nearly all domains of life. We present the biochemical characterization of two NAT proteins, NAT3 and NAT12 from Arabidopsis thaliana after their heterologous expression in Escherichia coli UraA knockout mutants. Both proteins were shown to transport adenine, guanine and uracil with high affinities. The apparent KM values were determined with 10.12 μM, 4.85 μM and 19.95 μM, respectively for NAT3 and 1.74 μM, 2.44 μM and 29.83 μM, respectively for NAT12. Competition studies with the three substrates suggest hypoxanthine as a further substrate of both transporters. Furthermore, the transport of nucleobases was markedly inhibited by low concentrations of a proton uncoupler indicating that NAT3 and NAT12 act as proton–nucleobase symporters. Transient expression studies of NAT-GFP fusion constructs revealed a localization of both proteins in the plasma membrane. Based on the structural information of the uracil permease UraA from E. coli, a three-dimensional experimentally validated homology model of NAT12 was created. The NAT12 structural model is composed of 14 TM segments and divided into two inverted repeats of TM1–7 and TM8–14. Docking studies and mutational analyses identified residues involved in NAT12 nucleobase binding including Ser-247, Phe-248, Asp-461, Thr-507 and Thr-508. This is the first study to provide insight into the structure–function of plant NAT proteins, which reveals differences from the other members of the NCS2 protein family. 相似文献
137.
Franziska S. Kemter Nadine Schallopp Theodor Sperlea Javier Serrania Patrick Sobetzko Georg Fritz Torsten Waldminghaus 《Molecular microbiology》2019,111(6):1617-1637
Vibrio cholerae is an aquatic bacterium with the potential to infect humans and cause the cholera disease. While most bacteria have single chromosomes, the V. cholerae genome is encoded on two replicons of different size. This study focuses on the DNA replication and cell division of this bi‐chromosomal bacterium during the stringent response induced by starvation stress. V. cholerae cells were found to initially shut DNA replication initiation down upon stringent response induction by the serine analog serine hydroxamate. Surprisingly, cells temporarily restart their DNA replication before finally reaching a state with fully replicated single chromosome sets. This division‐replication pattern is very different to that of the related single chromosome model bacterium Escherichia coli. Within the replication restart phase, both chromosomes of V. cholerae maintained their known order of replication timing to achieve termination synchrony. Using flow cytometry combined with mathematical modeling, we established that a phase of cellular regrowth be the reason for the observed restart of DNA replication after the initial shutdown. Our study shows that although the stringent response induction itself is widely conserved, bacteria developed different ways of how to react to the sensed nutrient limitation, potentially reflecting their individual lifestyle requirements. 相似文献
138.
Christine Herbst Nicole Wäschke E. Kathryn Barto Sabrina Arnold Daniel Geuß Ivonne Halboth Sabina Reschke Jakob Sänger Torsten Meiners Elisabeth Obermaier 《Entomologia Experimentalis et Applicata》2013,147(3):269-281
Increasing land use intensity and human influence are leading to a reduction in plant and animal species diversity. However, little is known about how these changes may affect higher trophic levels, apart from simply reducing species numbers. Here we investigated, over 3 years, the influence of different land practices on a tritrophic system in grassland habitats. The system consisted of the host plant Plantago lanceolata L. (Plantaginaceae), two monophagous weevils, Mecinus labilis Herbst and Mecinus pascuorum Gyllenhal (Coleoptera: Curculionidae), and their parasitoid Mesopolobus incultus Walker (Hymenoptera: Pteromalidae). At over 70 sites across three geographic regions in Germany, we measured plant species diversity and vegetation structure, as well as abundance of P. lanceolata, the two weevils, and the parasitoid. Land use intensity (fertilization) and type (mowing vs. grazing) negatively affected not only plant species richness but also the occurrence of the two specialized herbivores and their parasitoid. In contrast, land use had a mostly positive effect on host plant size, vegetation structure, and parasitization rate. This study reveals that intensification of land use influences higher trophic organisms even without affecting the availability of the host plant. The observed relationships between land use, vegetation complexity, and the tritrophic system are not restricted locally; rather they are measureable along a broad range of environmental conditions and years throughout Germany. Our findings may have important implications for the conservation of insect species of nutrient‐poor grasslands. 相似文献
139.
Ratjadone and leptomycin B block CRM1-dependent nuclear export by identical mechanisms 总被引:3,自引:0,他引:3
Research on the export of proteins and nucleic acids from the nucleus to the cytoplasm has greatly gained from the discovery that the actinobacterial toxin leptomycin B (LMB) specifically inactivates the export receptor chromosomal region maintenance 1 (CRM1). Recently, it was shown that myxobacterial cytotoxins, named ratjadones (RATs), also bind to CRM1 and inhibit nuclear export. However, the reaction mechanism of RATs was not resolved. Here, we show that LMB and RAT A employ the same molecular mechanism to inactivate CRM1. Alkylation of residue Cys528 of CRM1 determines both LMB and RAT sensitivity and prevents nuclear export of CRM1 cargo proteins. 相似文献
140.
Sandholt CH Vestmar MA Bille DS Borglykke A Almind K Hansen L Sandbæk A Lauritzen T Witte D Jørgensen T Pedersen O Hansen T 《PloS one》2011,6(9):e23531