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51.
Coral calcification responds to seawater acidification: a working hypothesis towards a physiological mechanism 总被引:3,自引:1,他引:2
The decrease in the saturation state of seawater, Ω, following seawater acidification, is believed to be the main factor leading
to a decrease in the calcification of marine organisms. To provide a physiological explanation for this phenomenon, the effect
of seawater acidification was studied on the calcification and photosynthesis of the scleractinian tropical coral Stylophora pistillata. Coral nubbins were incubated for 8 days at three different pH (7.6, 8.0, and 8.2). To differentiate between the effects
of the various components of the carbonate chemistry (pH, CO32−, HCO3−, CO2, Ω), tanks were also maintained under similar pH, but with 2-mM HCO3− added to the seawater. The addition of 2-mM bicarbonate significantly increased the photosynthesis in S. pistillata, suggesting carbon-limited conditions. Conversely, photosynthesis was insensitive to changes in pH and pCO2. Seawater acidification decreased coral calcification by ca. 0.1-mg CaCO3 g−1 d−1 for a decrease of 0.1 pH units. This correlation suggested that seawater acidification affected coral calcification by decreasing
the availability of the CO32− substrate for calcification. However, the decrease in coral calcification could also be attributed either to a decrease in
extra- or intracellular pH or to a change in the buffering capacity of the medium, impairing supply of CO32− from HCO3−. 相似文献
52.
Moya A Tambutté S Béranger G Gaume B Scimeca JC Allemand D Zoccola D 《Marine biotechnology (New York, N.Y.)》2008,10(6):653-663
This paper aims to validate reference genes for gene expression studies between light and dark conditions in the scleractinian
coral Stylophora pistillata for future gene expression studies of the “light-enhanced calcification” phenomenon. For this purpose, we cloned, sequenced,
and characterized a candidate reference gene, the 36B4 gene from the coral S. pistillata, and validated 36B4 and β-actin as reference genes. To illustrate the future applications of these reference genes, we tested
the dark and light expression of two photosynthetic genes (Rubisco and D1 protein of the photosystem II) and two genes encoding
proteins involved in calcium transport for coral calcification (a calcium ATPase and a calcium channel). Results show that
both photosynthetic genes are enhanced during the light when standardized against 36B4 and β-actin, whereas the two genes
encoding proteins involved in calcium transport are not differentially expressed between light and dark conditions. The characterization
of a coral 36B4 and the establishment of such valid reference genes will be useful for future gene expression studies between
diverse conditions (aposymbiotic/symbiotic, stress/control, light/dark conditions) in scleractinian corals.
Nucleotide sequence of the coral 36B4 gene cloned in this study is available in the Genbank database under the accession number
EU069460. 相似文献
53.
Recognition of exonic splicing enhancer sequences by the Drosophila splicing repressor RSF1. 下载免费PDF全文
E Labourier E Allemand S Brand M Fostier J Tazi H M Bourbon 《Nucleic acids research》1999,27(11):2377-2386
The Drosophila repressor splicing factor 1 (RSF1) comprises an N-terminal RNA-binding region and a C-terminal domain rich in glycine, arginine and serine residues, termed the GRS domain. Recently, RSF1 has been shown to antagonize splicing factors of the serine/arginine-rich (SR) family and it is, therefore, expected to play a role in processing of a subset of Drosophila pre-mRNAs through specific interactions with RNA. To investigate the RNA-binding specificity of RSF1, we isolated RSF1-binding RNAs using an in vitro selection approach. We have identified two RNA target motifs recognized by RSF1, designated A (CAACGACGA)- and B (AAACGCGCG)-type sequences. We show here that the A-type cognate sequence behaves as an SR protein-dependent exonic splicing enhancer. Namely, three copies of the A-type ligand bind SR proteins, stimulate the efficiency of splicing of reporter pre-mRNAs several fold and lead to inclusion of a short internal exon both in vitro and in vivo. However, three copies of a B-type ligand were much less active. The finding that RSF1 acts as a potent repressor of pre-mRNA splicing in vitro led us to propose that the equilibrium between a limited number of structurally-related general splicing activators or repressors, competing for common or promiscuous binding sites, may be a major determinant of the underlying mechanisms controlling many alternative pre-mRNA process-ing events. 相似文献
54.
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56.
Denis Allemand Guy De Renzis Corrinne Maistre Jean-Pierre Girard Patrick Payan 《The Journal of membrane biology》1985,87(3):217-224
Summary The characteristics of valine and alanine uptake (respectively, preferential substrates of the L and A or ASC systems in mammalian cells) were studied in sea urchin eggs before and 40 min after fertilization. Substrate concentration dependence showed that in unfertilized eggs alanine is absorbed linearly up to an external concentration of 20mm, whereas valine uptake presented a saturable kinetic with aK
m of 6 m. Competition experiments showed that valine is absorbed by a carriermediated transport resembling the L system. Fertilization develops a new Na-dependent system, resembling the ASC system which is specific for neutral amino acids but does not discriminate between them. This system is superimposed on that of the unfertilized egg. In fertilized eggs, amino-acid transport displayed cyclic variations which have been previously associated with cell cleavage. We have found that eggs prevented from cleavage by treatment with antimitotic undergo a sequence of periodic amino-acid uptake timed with the mitotic cycle of untreated eggs. In addition, artificially activated eggs (A23187) which failed to divide showed a time course of amino-acid uptake similar to that observed in fertilized eggs. Furthermore, these variations are independent of protein synthesis. These results suggest to us that a biological clock exists in the cytoplasm or cortex of sea urchin eggs, which may be involved in timing the cell cycle. 相似文献
57.
The effect of TPA (12-O-tetradecanoylphorbol-13-acetate) upon ionic exchanges was investigated in eggs of the sea urchin Arbacia lixula. Ouabain-sensitive 86Rb uptake and amiloride-sensitive 24Na influx were dramatically stimulated after TPA addition, indicating an enhancement of total ionic permeabilities. Stimulation by TPA of both Na+/H+ and Na+/K+ exchanges was canceled by amiloride, suggesting that activation of protein kinase C elicits, via Na+/H+ activity, stimulation of the sodium pump. However, TPA did not stimulate sodium pump activity and Na+/H+ exchange at the same rate as fertilization, probably because of an absence of calcium-dependent events. Further fertilization of TPA-pretreated eggs triggered an enhancement of sodium pump activity when the TPA treatment duration did not exceed 10 min. It is suggested that TPA activates preexisting transporting mechanisms in plasma membranes of unfertilized eggs (Na+ pump, Na+/H+ exchange) without eliciting corresponding regulatory mechanisms (Na+ stat, pH stat). 相似文献
58.
Anthony Bertucci Aurélie Moya Sylvie Tambutté Denis Allemand Claudiu T. Supuran Didier Zoccola 《Bioorganic & medicinal chemistry》2013,21(6):1437-1450
Coral reefs are among the most biologically diverse and economically important ecosystems on the planet. The deposition of massive calcium carbonate skeletons (biomineralization or calcification) by scleractinian corals forms the coral reef framework/architecture that serves as habitat for a large diversity of organisms. This process would not be possible without the intimate symbiosis between corals and photosynthetic dinoflagellates, commonly called zooxanthellae. Carbonic anhydrases play major roles in those two essential processes of coral’s physiology: they are involved in the carbon supply for calcium carbonate precipitation as well as in carbon-concentrating mechanisms for symbiont photosynthesis. Here, we review the current understanding of diversity and function of carbonic anhydrases in corals and discuss the perspective of theses enzymes as a key to understanding impacts of environmental changes on coral reefs. 相似文献
59.
Phenotypic plasticity and genotype-by-environment interactions are usually studied by testing environmental factors separately. However, several environmental factors may vary simultaneously across the geographic range of a species, and thus interact to drive phenotypic and genotypic evolution. Here, we address the question of the interaction between two environmental factors in the case of a koinobiont parasitoid of Drosophila , Leptopilina heterotoma (Hymenoptera: Figitidae). Using two allopatric parasitoid lines, we analysed the joint effect of developmental temperature and host species on two major fitness components (pre-imaginal survival and fecundity) of emerged parasitoids. Our results indicate that both environmental factors strongly interact to shape the parasitoid phenotype. Moreover, complex genotype-by-environment interactions appeared that can even invert the relative fitness of the two parasitoid lines. 相似文献
60.
Stretching DNA and RNA to probe their interactions with proteins 总被引:7,自引:0,他引:7
When interacting with a single stretched DNA, many proteins modify its end-to-end distance. This distance can be monitored in real time using various micromanipulation techniques that were initially used to determine the elastic properties of bare nucleic acids and their mechanically induced structural transitions. These methods are currently being applied to the study of DNA enzymes such as DNA and RNA polymerases, topoisomerases and structural proteins such as RecA. They permit the measurement of the probability distributions of the rate, processivity, on-time, affinity and efficiency for a large variety of DNA-based molecular motors. 相似文献