Metal influence on metallothionein synthesis in the hydrothermal vent mussel Bathymodiolus thermophilus

International audienceThe present study reports on the metallothionein expression in the hydrothermal vent mussel Bathymodiolus thermophilus. Metallothioneins (MT) are proteins involved in intracellular metal regulation and conserved throughout the animal kingdom. The hydrothermal vent environment presents peculiarities (high levels of sulfides and metals, low pH, anoxia) that may have driven associated species to develop original evolutionary ways to face these extreme living conditions. Mussels were exposed to different metal solutions at the atmospheric pressure. The MT mRNA levels and MT contents were measured in gills and mantles of each exposed mussel. The intracellular metal distribution was estimated in fractions obtained after the centrifugation of tissue homogenates. A few of the tested metals (Ag, Cu, Cd, Hg and Zn) were able to significantly induce MT mRNA levels. Silver was the only one that produced a significant increase of the MT protein level in both mantle and gills. The gills always presented higher MT protein levels than the mantle did, while their MT mRNA levels were similar. Our data show that MT mRNA and MT protein levels do not follow a clear relationship in the gills and mantle of B. thermophilus and we assume that a post-transcriptional control occurs in these mussels

Caractérisation et expression des gènes de métallothionéines chez deux modioles hydrothermales (Bathymodiolus thermophilus et Bathymodiolus azoricus)

Il existe au niveau des sources hydrothermales océaniques une grande biodiversité où lespopulations peuvent être caractérisées par de fortes densités. Les modioles du genre Bathymodiolus(Mytilidae) sont présentes au niveau de ces écosystèmes particuliers caractérisés par de fortesconcentrations en métaux qui sont en général toxiques pour les animaux. Lors de ces travaux, deuxespèces de modioles ont été étudiées : Bathymodiolus azoricus, qui est une espèce dominante de plusieurssources hydrothermales identifiées sur la dorsale médio Atlantique et Bathymodiolus thermophilus qui estune espèce commune de la dorsale du Pacifique Oriental. On peut se demander si ces modioles ont mis enoeuvre des stratégies adaptatives particulières qui leur ont permis de résister aux fortes concentrationsmétalliques pour coloniser cet environnement. Pour comprendre ces phénomènes adaptatifs, nous avonschoisi d'étudier les métallothionéines qui sont de petites protéines ubiquistes impliquées dans lemétabolisme des métaux et dont l'induction par les métaux est établie chez de nombreuses espèces.La caractérisation des séquences des gènes de métallothionéines a permis de montrer l'existenced'au moins deux gènes de métallothionéines (MT-10 et MT-20) chez les deux espèces étudiées. Desanalyses phylétiques indiquent que les séquences de ces gènes sont proches de celles caractérisées chezdes mollusques littoraux. L'analyse de l'activité des gènes de métallothionéines a permis d'identifier le particularisme desmodioles hydrothermales face aux expositions métalliques. La quantification des métallothionéines et desARNm MT extraits de modioles exposées à différents métaux en conditions hyperbares ou à pressionatmosphérique montre que l'hypothèse de l'induction des gènes de métallothionéines par les ionsmétalliques émise chez un grand nombre d'espèces n'est pas clairement identifiée chez les modioleshydrothermales étudiées. Il n'existe pas de lien explicite entre la stabilité observée des niveaux d'ARNmMT et les variations identifiées des teneurs en métallothionéines. Des mécanismes différents de ceux misen oeuvre par les mollusques littoraux pourraient permettre aux modioles de vivre au sein de l'écosystèmehydrothermal.A high biodiversity occurs at hydrothermal vents. Populations of this environment are oftencharacterised by high densities. Modioles of the Bathymodiolus gender (Mytilidae) are present in thesepeculiar ecosystems where high metal concentrations are found that are generally toxic for animals. Inthis work, two modiole species were studied: Bathymodiolus azoricus which is dominant in severalhydrothermal vents identified on the Mid Atlantic Ridge and Bathymodiolus thermophilus which iscommon on the Eastern Pacific Ridge. We wondered if these animals may have settled up some peculiaradaptive strategies to colonise such an environment. To understand these adaptive phenomena, wedecided to study metallothioneins which are small ubiquist proteins involved in metal metabolism. Theirinduction by metals has been established in numerous species. The characterization of the metallothionein gene sequences permitted to identify at least two genes (MT-10 and MT-20) in both studied species. Phyletic analyses based on the sequences of thesegenes emphasized the homology between the two studied modioles and with littoral molluscs.The analysis of the metallothionein gene activity permitted to show the particularism of thehydrothermal modioles. The quantification of the metallothionein levels and the levels of MT mRNAextracted from modioles exposed to different metals in hyperbaric conditions or at atmospheric pressureshow that the hypothesis of the induction of metallothionein genes by metal ions emitted in variousspecies is not clearly identified in the hydrothermal modioles. There is no explicit link between theobserved stability of the MT mRNA levels and the variations identified in the metallothionein levels.Other mechanisms than those implemented by littoral molluscs may occur to permit the hydrothermalmussels to live in the hydrothermal environment.LE MANS-BU Sciences (721812109) / SudocSudocFranceF

A pilot study of genetic differentiation between two phenotypes of a Mediterranean population of the bivalve Cerastoderma glaucum and genetic discrimination with other Cerastoderma glaucum and Cerastoderma edule populations outside the Mediterranean

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DNA Binding Specificity and Cleavage Activity of Pacmmar Transposase

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DNA Binding Specificity and Cleavage Activity of Pacmmar TransposaseRID C-6465-2009

International audienceMariner-like elements (MLEs) are members of the Tc1/mariner superfamily of transposable elements which transpose by a "cut and paste" mechanism. Most of the MLEs characterized to date are transpositionally inactive due to the accumulation of mutations in their transposase gene. Here, we report the biochemical study of two copies of the Pacmmar element (Pacmmar1.1 and Pacmmar1.2), isolated from the coastal crab Pachygrapsus marmoratus. These two copies present an open reading frame encoding a putative active transposase. Using an in vitro transposition assay, we show that Pacmmar transposases are unable to perform by themselves the transposition reaction. However, we demonstrate by an electrophoretic mobility shift assay that both transposases bind specifically to the inverted terminal repeat of the Pacmmar element. Moreover, an in vitro cleavage assay showed that both transposases have the capacity to cleave the transposon. The in vitro cleavage activity of Pacmmar transposases appears imprecise, suggesting the requirement of specific host factors or the presence of mutations which have modified the cleavage specificity of the enzyme

Identification of agents causing vibriosis in Litopenaeus vannamei shrimp culture in Kendal, Central Java, Indonesia and application of microalgae Dunaliella salina and Tetraselmis chui as bio-control agents against vibriosis

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Identification of agents causing vibriosis in litopenaeusvannamei shrimp culture in Kendal, Central Java, Indonesia and application of microalgae dunaliellasalina and tetraselmischui as bio-control agents against vibriosis

Aquaculture of Vannamei shrimp at Kendal, Central Java, Indonesia has been using an intensive system, which could provoke the degradation of water quality in the pond. One of the emerging effects due to such degradation becoming threat for shrimp aquaculture is the loss caused by vibriosis disease. This study aimed to identify the presence of vibriosis-causing bacteria in shrimp pond at Kaliwungu, Kendal, Central Java and use the microalgae Dunaliella salina and Tetraselmis chui as bio control agents against Vibriosis. The Vibriosis-causing bacteria were isolated from the hepatopancreas and tails of ten shrimps showing clinical signs of vibriosis infection, cultured on the Thiosulfate Citrate Bile Salt Sucrose media. Out of 20 isolates, three isolates were selected for further gene sequence identification of 16rRNA using the Repetitive Sequence-based Polymerase Chain Reaction (rep-PCR) and were analyzed with BLAST. Universal primer 27F (5’AGAGTTTGATCMTGGCTCAG-3’) and 1492R (5’TACGGTTAACCTTGTTACGACTT-3’) were selected as the primers to identify the isolated bacteria. Results demonstrated that the three isolated bacteria were positive as vibriosis-causing agent in shrimp, which were U1H1 AND U4H1, identified as Vibrio alginolyticus, and U1E1 as V. harveyi. The use of microalgae as biocontrols was performed. Forty-five shrimps infected by vibrio reared during 21 days and feed with D. salina and T. chui showed a decreased of bacteria amount, which were counted by Total Plate Count method. The result indicated that the microalgae was capable to produce an antibacterial compounds against vibrio

Antioxidant activity of three microalgae Dunaliella salina, Tetraselmis chuii and Isochrysis galbana clone Tahiti

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