Search results for "arthropods"

Arthropod 7SK RNA

2008

The 7SK small nuclear RNA (snRNA) is a key player in the regulation of polymerase (pol) II transcription. The 7SK RNA was long believed to be specific to vertebrates where it is highly conserved. Homologs in basal deuterostomes and a few lophotrochozoan species were only recently reported. On longer timescales, 7SK evolves rapidly with only few conserved sequence and structure motifs. Previous attempts to identify the Drosophila homolog thus have remained unsuccessful despite considerable efforts. Here we report on the discovery of arthropod 7SK RNAs using a novel search strategy based on pol III promoters, as well as the subsequent verification of its expression. Our results demonstrate th…

The impact of arthropods on fungal community structure in Lascaux Cave

2009

Aims: To determine the major components of the fungal population present in Lascaux Cave, France. The ceiling, walls, sediments and soil were colonized by Fusarium solani in 2001 and later, in 2006, black stains appeared. However, the origin of the successive fungal invasions is unknown as well as the ecology of the cave. Methods and Results: The primers nu-SSU-0817F and nu-SSU-1536R were used for the direct amplification of fungal 18S-rDNA sequences from 11 samples. A total of 607 clones were retrieved. Eight out of the ten most abundant phylotypes corresponded to fungi associated with arthropods and represented about 50% of the clones. Conclusions: Entomophilous fungi play an important ro…

Effects of Terbuthylazine on Soil Fauna and Decomposition Processes

1996

Abstract Acute lethal and sublethal effects of terbuthylazine and the commercial herbicide preparation Gardoprim [terbuthylazine is the active ingredient (a.i.)] on soil organisms (microbes, oppioid mites, two gamasid mite species, enchytraeids, and nematodes) were studied. In the humus soil terbuthylazine had no toxic effects on soil animals tested. However, the herbicide preparation had acute toxic effects on enchytraeids [no-observed-effect level (NOEL) 1.0 g a.i./m 2 ] and both gamasid mites (NOEL 2.4 and 5.0 g a.i./m 2 ). According to filter paper test, the LC 50 value for oppioid mites was 14.5 g a.i./m 2 . In the humus soil the commercial preparation caused no dose-related mortality …

Molecular evolution of the arthropod hemocyanin superfamily.

2001

Arthropod hemocyanins are members of a protein superfamily that also comprises the arthropod phenoloxidases (tyrosinases), crustacean pseudohemocyanins (cryptocyanins), and insect storage hexamerins. The evolution of these proteins was inferred by neighbor-joining, maximum-parsimony, and maximum-likelihood methods. Monte Carlo shuffling approaches provided evidence against a discernible relationship of the arthropod hemocyanin superfamily and molluscan hemocyanins or nonarthropodan tyrosinases. Within the arthropod hemocyanin superfamily, the phenoloxidase probably emerged early in the (eu-)arthropod stemline and thus form the most likely outgroup. The respiratory hemocyanins evolved from t…

Temperature–Time Relationship in Collembolan Response to Chemical Exposure

1999

Abstract Effects of temperature on chemical toxicity to a collembolan, Folsomia candida , in relation to time were studied in this experiment. Field soil was used as a test substrate. Collembolans were incubated at three different temperatures (+13, +16, and +19°C) and in two different dimethoate concentrations (1 and 3 mg/kg), clean soil serving as the control. Four destructive samplings were done at 2-week intervals. Dimethoate degradation was also analyzed. Dimethoate 1 mg/kg had a slight effect on both adult growth and reproduction, whereas 3 mg/kg was fatal to F. candida in the soil used. Toxic effects tended to last longer at low temperature than at high temperature, but the differenc…

Identification, structure, and properties of hemocyanins from Diplopod myriapoda.

1999

Hemocyanins are copper-containing, respiratory proteins that occur in the hemolymph of many arthropod species. Here we report for the first time the presence of hemocyanins in the diplopod Myriapoda, demonstrating that these proteins are more widespread among the Arthropoda than previously thought. The hemocyanin of Spirostreptus sp. (Diplopoda: Spirostreptidae) is composed of two immunologically distinct subunits in the 75-kDa range that are most likely arranged in a 36-mer (6 x 6) native molecule. It has a high oxygen affinity (P(50) = 4.7 torr) but low cooperativity (h = 1.3 +/- 0.2). Spirostreptus hemocyanin is structurally similar to the single known hemocyanin from the myriapod taxon,…

Tryptophan quenching as linear sensor for oxygen binding of arthropod hemocyanins.

2008

Oxygen binding of hemocyanins results in an absorption band around 340nm and a strong quenching of the intrinsic tryptophan fluorescence. Our study analyses in detail the fluorescence quenching within two hemocyanins, a hexamer (Panulirus interruptus) and a 4 x 6-mer (Eurypelma californicum). Based on the comparison of calculated and measured transfer efficiencies we could show that: (1) For both hemocyanins FRET (fluorescence resonance energy transfer) is exclusively responsible for quenching of the tryptophan fluorescence upon oxygen binding. (2) Tryptophan quenching by FRET is independent of the oxy- or deoxy conformation of the protein. (3) The quenching takes place at the subunit level…

Recent findings on phenoloxidase activity and antimicrobial activity of hemocyanins

2003

Complete subunit sequences, structure and evolution of the 6 x 6-mer hemocyanin from the common house centipede, Scutigera coleoptrata.

2003

Hemocyanins are large oligomeric copper-containing proteins that serve for the transport of oxygen in many arthropod species. While studied in detail in the Chelicerata and Crustacea, hemocyanins had long been considered unnecessary in the Myriapoda. Here we report the complete molecular structure of the hemocyanin from the common house centipede Scutigera coleoptrata (Myriapoda: Chilopoda), as deduced from 2D-gel electrophoresis, MALDI-TOF mass spectrometry, protein and cDNA sequencing, and homology modeling. This is the first myriapod hemocyanin to be fully sequenced, and allows the investigation of hemocyanin structure-function relationship and evolution. S. coleoptrata hemocyanin is a 6…

Structure, diversity and evolution of myriapod hemocyanins

2014

Oxygen transport in the hemolymph of many arthropods is mediated by hemocyanins, large copper-containing proteins that are well-studied in Chelicerata and Crustacea, but had long been considered unnecessary in the subphylum of Myriapoda. Only recently has it become evident that hemocyanins are present in Scutigeromorpha (Chilopoda) and Spirostreptida (Diplopoda). Here we present evidence for a more widespread occurrence of hemocyanin in the myriapods. By means of RT-PCR, western blotting and database searches, hemocyanins were identified in the symphylans Hanseniella audax and Symphylella vulgaris, the chilopod Scolopendra subspinipes dehaani and the diplopod Polydesmus angustus. No hemocya…