Feeding mice with diets containing mercury-contaminated fish flesh from French Guiana: a model for the mercurial intoxication of the Wayana Amerindians

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Detection and Functional Characterization of a 215 Amino Acid N-Terminal Extension in the Xanthomonas Type III Effector XopD

During evolution, pathogens have developed a variety of strategies to suppress plant-triggered immunity and promote successful infection. In Gram-negative phytopathogenic bacteria, the so-called type III protein secretion system works as a molecular syringe to inject type III effectors (T3Es) into plant cells. The XopD T3E from the strain 85-10 of Xanthomonas campestris pathovar vesicatoria (Xcv) delays the onset of symptom development and alters basal defence responses to promote pathogen growth in infected tomato leaves. XopD was previously described as a modular protein that contains (i) an N-terminal DNA-binding domain (DBD), (ii) two tandemly repeated EAR (ERF-associated amphiphillic repression) motifs involved in transcriptional repression, and (iii) a C-terminal cysteine protease domain, involved in release of SUMO (small ubiquitin-like modifier) from SUMO-modified proteins. Here, we show that the XopD protein that is produced and secreted by Xcv presents an additional N-terminal extension of 215 amino acids. Closer analysis of this newly identified N-terminal domain shows a low complexity region rich in lysine, alanine and glutamic acid residues (KAE-rich) with high propensity to form coiled-coil structures that confers to XopD the ability to form dimers when expressed in E. coli. The full length XopD protein identified in this study (XopD1-760) displays stronger repression of the XopD plant target promoter PR1, as compared to the XopD version annotated in the public databases (XopD216-760). Furthermore, the N-terminal extension of XopD, which is absent in XopD216-760, is essential for XopD type III-dependent secretion and, therefore, for complementation of an Xcv mutant strain deleted from XopD in its ability to delay symptom development in tomato susceptible cultivars. The identification of the complete sequence of XopD opens new perspectives for future studies on the XopD protein and its virulence-associated functions in planta

Modulation of uranium bioaccumulation by hypoxia in the freshwater clam Corbicula fluminea: Induction of multixenobiotic resistance protein and heat shock protein 60 in gill tissues

The influence of hypoxia on the bioaccumulation of uranium in the clam Corbicula fluminea was investigated in ecologically relevant conditions. The cellular impact at the gill-tissue level was assessed by analyzing the induction of multixenobiotic resistance protein (MXR) and heat shock protein 60. Analyses were performed at three biological levels. First, at the organism level, uranium induced a significant decrease in the valve open duration under normoxia, but not under hypoxia, in which oxygen drive imposed an increase of the valve open duration. Second, at the tissue level, the uranium bioaccumulation rate in the gills was higher under hypoxia than under normoxia. Third, at the cellular level, MXR was induced by uranium but not by hypoxia. The threshold of tissular uranium concentration triggering MXR induction was between 3 and 5 nmol/g. On the contrary, Hsp60 was induced by hypoxia but not by uranium. © 2005 SETAC

In Vivo Properties of Colicin A: Channel Activity and Translocation

International audienceColicin A belongs to the group of colicins which form voltage dependent ionic channels in planar lipid bilayers. (Schein et al., 1978; Pattus et al., 1983). In vivo, the primary effects of these colicins are a leakage of cytoplasmic K+ (Wendt, 1970) and small ions (Lusk and Nelson, 1972), a decrease of internal ATP, a collapse of the electrochemical gradient of protons (Δ μH +), and consequently an inhibition of the ΔμH+-driven active transport systems (for reviews see Luria, 1975; Konisky, 1978, 1982). On the basis of these in vitro and in vivo properties, it is generally admitted that the killing activity of these colicins results from the formation of channels in the cytoplasmic membrane

In Vivo Properties of Colicin A: Channel Activity and Translocation

International audienceColicin A belongs to the group of colicins which form voltage dependent ionic channels in planar lipid bilayers. (Schein et al., 1978; Pattus et al., 1983). In vivo, the primary effects of these colicins are a leakage of cytoplasmic K+ (Wendt, 1970) and small ions (Lusk and Nelson, 1972), a decrease of internal ATP, a collapse of the electrochemical gradient of protons (Δ μH +), and consequently an inhibition of the ΔμH+-driven active transport systems (for reviews see Luria, 1975; Konisky, 1978, 1982). On the basis of these in vitro and in vivo properties, it is generally admitted that the killing activity of these colicins results from the formation of channels in the cytoplasmic membrane