The origin and evolution of variable-region helices in V4 and V7 of the small-subunit ribosomal RNA of branchiopod crustaceans.
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We sequenced the V4 and V7 regions of the small-subunit ribosomal RNA (SSU rRNA) from 38 species of branchiopod crustaceans (e.g., Artemia, Daphnia, Triops) representing all eight extant orders. Ancestral large-bodied taxa in the orders Anostraca, Notostraca, Laevicaudata, and Spinicaudata (limnadiids and cyzicids) possess the typical secondary structure in these regions, whereas the spinicaudatan Cyclestheria and all of the cladocerans (Anomopoda, Ctenopoda, Onychopoda, and Haplopoda) possess three unique helices. Although the lengths and primary sequences of the distal ends of these helices are extremely variable, their locations, secondary structures, and primary sequences at the proximal end are conserved, indicating that they are homologous. This evidence supports the classical view that Cladocera is a monophyletic group and that the cyclestheriids are transitional between spinicaudatans and cladocerans. The single origin and persistence since the Permian of the unique cladoceran helices suggests that births and deaths of variable region helices have been rare. The broad range of sequence divergences observed among the cladoceran helices permitted us to make inferences about their evolution. Although their proximal ends are very GC-biased, there is a significant negative correlation between length and GC content due to an increasing proportion of U at their distal ends. Slippage-like processes occurring at unpaired nucleotides or bulges, which are very U-biased, are associated with both helix origin and runaway length expansion. The overall GC contents and lengths of V4 and V7 are highly correlated. More surprisingly, the lengths of these SSU rRNA variable regions are also highly correlated with the length of the large-subunit rRNA expansion segment, D2, indicating that mechanisms affecting length variation do so both across single genes and across genes in the rRNA gene family. (+info)
Identification and characterization of a prawn white spot syndrome virus gene that encodes an envelope protein VP31.
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Based on a combination of SDS-PAGE and mass spectrometry, a protein with an apparent molecular mass of 31 kDa (termed as VP31) was identified from purified shrimp white spot syndrome virus (WSSV) envelope fraction. The resulting amino acid (aa) sequence matched an open reading frame (WSV340) of the WSSV genome. This ORF contained 783 nucleotides (nt), encoding 261 aa. A fragment of WSV340 was expressed in Escherichia coli as a glutathione S-transferase (GST) fusion protein with a 6His-tag, and then specific antibody was raised. Western blot analysis and the immunoelectron microscope method (IEM) confirmed that VP31 was present exclusively in the viral envelope fraction. The neutralization experiment suggested that VP31 might play an important role in WSSV infectivity. (+info)
Acute toxicity of pharmaceutical and personal care products on freshwater crustacean (Thamnocephalus platyurus) and fish (Oryzias latipes).
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Pharmaceutical and personal care products (PPCPs) enter aquatic environments via sewage treatment facilities and their potentially toxic effects on biota, particularly aquatic organisms, are of considerable concern. In this study, we investigated the acute toxicity of selected PPCPs on a freshwater crustacean (Thamnocephalus platyurus) and a fish species (Oryzias latipes). The 24-hr median lethal concentration (LC(50)) values of ibuprofen, mefenamic acid, indometacin, carbamazepine, propranolol, ifenprodil, clarithromycin and triclosan for T. platyurus were estimated to be 19.59, 3.95, 16.14, > 100, 10.31, 4.43, 94.23 and 0.47 mg/l respectively. Conversely, the 96-hr LC(50) values for these PPCPs were estimated at > 100, 8.04, 81.92, 45.87, 11.40, 8.71, > 100 and 0.60 mg/l for O. latipes, respectively. The toxic sensitivity of T. platyurus to these PPCPs, except for carbamazepine, was therefore higher than for O. latipes. No acute toxicity effects were associated with PPCPs, such as atenolol, disopyramide, famotidine, fluconazole, erythromycin and levofloxacin, in the two aquatic organisms at the concentrations tested in this study (> 100 mg/l). These findings may help us to understand the potential biological effects and risks associated with PPCP exposure in aquatic organisms. Further long-term studies are required to fully assess the growth and reproduction of these compounds on aquatic biota. (+info)
Stress hormones and the fitness consequences associated with the transition to a novel diet in larval amphibians.
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Long distance dispersal of zooplankton endemic to isolated mountaintops--an example of an ecological process operating on an evolutionary time scale.
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The effect of composition of different ecotoxicological test media on free and bioavailable copper from CuSO4 and CuO nanoparticles: comparative evidence from a Cu-selective electrode and a Cu-biosensor.
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