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The size and conformation of Artemia (brine-shrimp) ribosomal RNA free in solution.

ABSTRACT: The RNA was isolated from the large ribosomal subunits of the brine shrimp Artemia, and its conformation free in solution was studied by determining its sedimentation and diffusion coefficients. A comparison was made of the hydrodynamic radius of the ribosomal subunit and its isolated RNA in various buffers. The conformation of the rRNA free in solution is more extended than when it is incorporated in the ribosome. This is not only the case when the rRNA solution lacks bivalent and polyvalent cations, but even in the presence of Mg2+ and spermidine, which cause a tightening of RNA. Thus the ribosomal proteins should induce a further tightening of the rRNA during the assembly of the ribosome. In the discussion, the reported data on Escherichia coli rRNA species are presented in such a way that large discrepancies between various studied are revealed, and that they can be compared with the data reported here on the larger rRNA of an eukaryote.

SUBMITTER: Donceel K

PROVIDER: S-EPMC1158513 | biostudies-other | 1982 Sep

REPOSITORIES: biostudies-other

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Molecular identification of microorganisms associated with the brine shrimp Artemia franciscana.

Project description:BACKGROUND:Prior research on the microorganisms associated with the brine shrimp, Artemia franciscana, has mainly been limited to culture-based identification techniques or feeding studies for aquaculture. Our objective was to identify bacteria and archaea associated with Artemia adults and encysted embryos to understand the role of microbes in the Artemia life cycle and, therefore, their importance in a hypersaline food chain. RESULTS:We used small subunit (SSU) 16S ribosomal RNA gene sequencing to identify bacteria and archaea associated with adults and encysted Artemia embryos from one of their natural environments - Great Salt Lake (GSL), Utah, USA. We found that bacterial sequences most closely related to the genera Halomonas and Vibrio were commonly extracted from GSL adult Artemia, while bacterial sequences most similar to the genera Halomonas, Psychroflexus and Alkalilimnicola dominate in GSL water. Encysted embryos (cysts) yielded bacterial sequences from the genera Idiomarina and Salinivibrio, which were absent from adults and water. Common archaeal sequences in adults were most closely related to the genera Haloterrigena and Haloarcula, while all of the archaeal sequences from GSL water were most similar to the genus Halogeometricum. Cyst derived archaeal sequences were most closely related to the genera Halorubrum and Haloarcula. CONCLUSIONS:In addition to identifying microbial rRNA sequences that are specific to different stages of the Artemia life cycle, we observed striking differences in the sequences associated with the adult Artemia population in samples collected from GSL at different times and locations. While our study was limited in scope and the sample was small, our findings provide a foundation for future research into how the bacteria and archaea associated with Artemia influence the Artemia life cycle, and GSL food web.

| S-EPMC3599907 | biostudies-literature

Phylogenetic analysis of brine shrimp (Artemia) in China using DNA barcoding.

Project description:DNA barcoding is a powerful approach for characterizing species of organisms, especially those with almost identical morphological features, thereby helping to to establish phylogenetic relationships and reveal evolutionary histories. In this study, we chose a 648-bp segment of the mitochondrial gene, cytochrome c oxidase subunit 1 (COI), as a standard barcode region to establish phylogenetic relationships among brine shrimp (Artemia) species from major habitats around the world and further focused on the biodiversity of Artemia species in China, especially in the Tibetan Plateau. Samples from five major salt lakes of the Tibetan Plateau located at altitudes over 4,000 m showed clear differences from other Artemia populations in China. We also observed two consistent amino acid changes, 153A/V and 183L/F, in the COI gene between the high and low altitude species in China. Moreover, indels in the COI sequence were identified in cyst and adult samples unique to the Co Qen population from the Tibetan Plateau, demonstrating the need for additional investigations of the mitochondrial genome among Tibetan Artemia populations.

| S-EPMC5054130 | biostudies-literature

Mitochondrial differentiation during the early development of the brine shrimp Artemia franciscana.

Project description:During the early development of Artemia there is an increase in mitochondrial enzyme activities of about one order of magnitude, whereas the activities of two cytoplasmic enzymes tested as controls remain unaltered. The mitochondrial enzyme activation correlates with (i) large changes in mitochondrial morphology, (ii) a 5-fold increase in the amount of the H+-ATP synthase beta-subunit and (iii) a dramatic increase in the steady-state level of mitochondrial mRNAs, whereas mitochondrial rRNA concentrations remain mostly unchanged. In contrast, the level of mitochondrial DNA does not change significantly during the first 20 h after resumption of development. After hatching, the mitochondrial DNA content increases twice in parallel with one round of cellular division, thus indicating that mitochondrial and nuclear replication are coupled in Artemia postgastrular development. The data presented strongly suggest that mitochondrial maturation in the absence of significant mitochondrial proliferation is responsible for the dramatic increase in mitochondrial function that takes place after resumption of development in Artemia.

| S-EPMC1217079 | biostudies-other

Sharp phylogeographic breaks and patterns of genealogical concordance in the brine shrimp Artemia franciscana.

Project description:Genealogical concordance is a critical overlay of all phylogenetic analyses, irrespective of taxonomic level. To assess such patterns of congruence we have compiled and derived sequence data for two mitochondrial (16S rRNA, COI) and two nuclear (ITS1, p26) markers in 14 American populations of the hypersaline branchiopod Artemia franciscana. Cladistic analysis revealed three reciprocally monophyletic mitochondrial clades. For nuclear DNA, incomplete lineage sorting was evident presumably as a result of slower coalescence or male-mediated dispersal. Our findings capture the genealogical interval between gene splitting and population divergence. In this sense, strong indications are provided in favour of a superspecies status and ongoing speciation in A. franciscana.

| S-EPMC2802004 | biostudies-literature

Toxicity of benthic dinoflagellates on grazing, behavior and survival of the brine shrimp Artemia salina.

Project description:Harmful algae may differently affect their primary grazers, causing sub-lethal effects and/or leading to their death. The present study aim to compare the effects of three toxic benthic dinoflagellates on clearance and grazing rates, behavioral changes, and survival of Artemia salina. Feeding assays consisted in 1-h incubations of brine shrimps with the toxic Prorocentrum lima, Gambierdiscus excentricus and Ostreopsis cf. ovata and the non-toxic Tetraselmis sp. Brine shrimps fed unselectively on all toxic and non-toxic algal preys, without significant differences in clearance and ingestion rates. Acute toxicity assays were performed with dinoflagellate cells in two growth phases during 7-h to assess differences in cell toxicity to A. salina. Additionally, exposure to cell-free medium was performed to evaluate its effects on A. salina survival. The behavior of brine shrimps significantly changed during exposure to the toxic dinoflagellates, becoming immobile at the bottom by the end of the trials. Dinoflagellates significantly affected A. salina survival with 100% mortality after 7-h exposure to cells in exponential phase (all treatments) and to P. lima in stationary phase. Mortality rates of brine shrimps exposed to O. cf. ovata and G. excentricus in stationary phase were 91% and 75%, respectively. However, incubations of the brine shrimps with cell-free medium did not affect A. salina survivorship. Significant differences in toxic effects between cell growth phases were only found in the survival rates of A. salina exposed to G. excentricus. Acute exposure to benthic toxic dinoflagellates induced harmful effects on behavior and survival of A. salina. Negative effects related to the toxicity of benthic dinoflagellates are thus expected on their primary grazers making them more vulnerable to predation and vectors of toxins through the marine food webs.

| S-EPMC5384755 | biostudies-literature

Early dolichyl sugar synthesis during differentiation of non-growing brine-shrimp (Artemia salina) embryos.

Project description:Incubation of cell-free extracts of Artemia salina with sugar nucleotides resulted in the formation of dolichyl derivatives. These enzymic activities were detected early in the development of the encysted Artemia embryos. Dolichyl sugars seemed to act as intermediates in the glycosylation of proteins, which may be involved in the initiation of cellular differentiation.

| S-EPMC1163269 | biostudies-other

The structure of Artemia sp. (brine shrimp) haemoglobins. Purification of a structural unit to homogeneity.

Project description:The extracellular haemoglobins (Mr 260 000) of the brine shrimp Artemia sp. were cleaved by limited digestion with subtilisin. Structural units of Mr 16 000, which can bind dioxygen reversibly, were isolated. Analysis of the 16 000-Mr fraction (E) reveals the presence of a limited number of structural units. A single type of structural unit, E1 (Mr 15 800; pI4.8), was purified to homogeneity and characterized.

| S-EPMC1144922 | biostudies-other

Formation of diapause cyst shell in brine shrimp, Artemia parthenogenetica, and its resistance role in environmental stresses.

Project description:Artemia has attracted much attention for its ability to produce encysted embryos wrapped in a protective shell when subject to extremely harsh environmental conditions. However, what the cyst shell is synthesized from and how the formative process is performed remains, as yet, largely unknown. Over 20 oviparous specifically expressed genes were identified through screening the subtracted cDNA library enriched between oviparous and ovoviviparous Artemia ovisacs. Among them, a shell gland-specifically expressed gene (SGEG) has been found to be involved in the cyst shell formation. Lacking SGEG protein (by RNA interference) caused the cyst shell to become translucent and the chorion layer of the shell to become less compact and pultaceous and to show a marked decrease of iron composition within the shell. The RNA interference induced defective diapause cysts with a totally compromised resistibility to UV irradiation, extremely large temperature differences, osmotic pressure, dryness, and organic solvent stresses. In contrast, the natural cyst would provide adequate protection from all such factors. SGEG contains a 345-bp open reading frame, and its consequentially translated peptide consists of a 33-amino acid residue putative signal peptide and an 81-amino acid residue mature peptide. The results of Northern blotting and in situ hybridization indicate that the gene is specifically expressed in the cells of shell glands during the period of diapause cyst formation of oviparous Artemia. This investigation adds strong insight into the mechanism of cyst shell formation of Artemia and may be applicable to other areas of research in extremophile biology.

| S-EPMC2719330 | biostudies-literature

Sex-Biased Gene Expression and Isoform Profile of Brine Shrimp <i>Artemia franciscana</i> by Transcriptome Analysis.

Project description:The brine shrimp Artemia has a ZW sex determination system with ZW chromosomes in females and ZZ chromosomes in males. Artemia has been considered a promising model organism for ZW sex-determining systems, but the genes involved in sex determination and differentiation of Artemia have not yet been identified. Here, we conducted transcriptome sequencing of female and male A. franciscana using PacBio Iso-Seq and Illumina RNA-Seq techniques to identify candidate sex determination genes. Among the 42,566 transcripts obtained from Iso-Seq, 23,514 were analyzed. Of these, 2065 (8.8%) were female specific, 2513 (10.7%) were male specific, and 18,936 (80.5%) were co-expressed in females and males. Based on GO enrichment analysis and expression values, we found 10 female-biased and 29 male-biased expressed genes, including DMRT1 and Sad genes showing male-biased expression. Our results showed that DMRT1 has three isoforms with five exons, while Sad has seven isoforms with 2-11 exons. The Sad gene is involved in ecdysteroid signaling related to molting and metamorphosis in arthropods. Further studies on ecdysteroid biosynthetic genes are needed to improve our understanding of Artemia sex determination. This study will provide a valuable resource for sex determination and differentiation studies on Artemia and other crustaceans with ZW systems.

| S-EPMC8465105 | biostudies-literature

Characterization of the bis(5'-nucleosidyl) tetraphosphate pyrophosphohydrolase from encysted embryos of the brine shrimp Artemia.

Project description:The P1P4-bis(5'-nucleosidyl) tetraphosphate asymmetrical-pyrophosphohydrolase from encysted embryos of the brine shrimp Artemia has been purified over 11,000-fold to homogeneity. Anion-exchange chromatography resolves two major species with very similar properties. The enzyme is a single polypeptide of Mr 17,600 and is maximally active at pH 8.4 and 2 mM-Mg2+. It is inhibited by Ca2+ (IC50 = 0.9 mM with 2 mM-Mg2+) but not by Zn2+ ions. It preferentially hydrolyses P1P4-bis(5'-nucleosidyl) tetraphosphates, e.g. P1P4-bis(5'-adenosyl) tetraphosphate (Ap4A) (kcat. = 12.7 s-1; Km = 33 microM) and P1P4-bis(5'-guanosyl) tetraphosphate (Gp4G) (kcat. = 6.2 s-1; Km = 5 microM). With adenosine 5'-P1-tetraphospho-P4-5"'-guanosine (Ap4G) as substrate, there is a 4.5-fold preference for AMP and GTP as products and biphasic reaction kinetics are observed giving Km values of 4.7 microM and 34 microM, and corresponding rate constants of 6.5 s-1 and 11.9 s-1. The net rate constant for Ap4G hydrolysis is 7.6 s-1. The enzyme will also hydrolyse nucleotides with more than four phosphate groups, e.g. Ap5G, Ap6A and Gp5G are hydrolysed at 25%, 18% and 10% of the rate of Ap4A respectively. An NTP is always one of the products. Ap2A and Gp2G are not hydrolysed, while Ap3A and Gp3G are very poor substrates. When the enzyme is partially purified from embryos and larvae at different stages of development by sedimentation through a sucrose density gradient, its activity increases 3-fold during the first 12 h of pre-emergence development. This is followed by a slow decline during subsequent larval development. The similarity of this enzyme to other asymmetrical-pyrophosphohydrolases suggests that it did not evolve specifically to degrade the large yolk platelet store of Gp4G which is found in Artemia embryos, but that it probably serves the same general function in bis(5'-nucleosidyl) oligophosphate metabolism as in other cells.

| S-EPMC1138592 | biostudies-other

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