Copper stress proteomics highlights local adaptation of two strains of the model brown alga Ectocarpus siliculosus

Ectocarpus siliculosus is a cosmopolitan brown alga with capacity to thrive in copper enriched environments. Analysis of copper toxicity was conducted in two strains of E. siliculosus isolated from (i) an uncontaminated coast in southern Peru (Es32) and (ii) a copper polluted rocky beach in northern Chile (Es524). Es32 was more sensitive than Es524, with toxicity detected at 50 μg/L Cu, whereas Es524 displayed negative effects only when exposed to 250 μg/L Cu. Differential soluble proteome profiling for each strain exposed to sub‐lethal copper levels allowed to identify the induction of proteins related to processes such as energy production, glutathione metabolism as well as accumulation of HSPs. In addition, the inter‐strain comparison of stress‐related proteomes led to identify features related to copper tolerance in Es524, such as striking expression of a PSII Mn‐stabilizing protein and a Fucoxanthine chlorophyll a–c binding protein. Es524 also expressed specific stress‐related enzymes such as RNA helicases from the DEAD box families and a vanadium‐dependent bromoperoxidase. These observations were supported by RT‐qPCR for some of the identified genes and an enzyme activity assay for vanadium‐dependent bromoperoxidase. Therefore, the occurrence of two different phenotypes within two distinct E. siliculosus strains studied at the physiological and proteomic levels strongly suggest that persistent copper stress may represent a selective force leading to the development of strains genetically adapted to copper contaminated sites.     

JNK Signalling Controls Remodelling of the Segment Boundary through Cell Reprogramming during Drosophila Morphogenesis

Segments are fundamental units in animal development which are made of distinct cell lineages separated by boundaries. Although boundaries show limited plasticity during their formation for sharpening, cell lineages make compartments that become tightly restricted as development goes on. Here, we characterize a unique case of breaking of the segment boundary in late drosophila embryos. During dorsal closure, specific cells from anterior compartments cross the segment boundary and enter the adjacent posterior compartments. This cell mixing behaviour is driven by an anterior-to-posterior reprogramming mechanism involving de novo expression of the homeodomain protein Engrailed. Mixing is accompanied by stereotyped local cell intercalation, converting the segment boundary into a relaxation compartment important for tension-release during morphogenesis. This process of lineage switching and cell remodelling is controlled by JNK signalling. Our results reveal plasticity of segment boundaries during late morphogenesis and a role for JNK-dependent developmental reprogramming in this process.     

Semantic knowledge influences prewired hedonic responses to odors

Background

Odor hedonic perception relies on decoding the physicochemical properties of odorant molecules and can be influenced in humans by semantic knowledge. The effect of semantic knowledge on such prewired hedonic processing over the life span has remained unclear.

Methodology/Principal Findings

The present study measured hedonic response to odors in different age groups (children, teenagers, young adults, and seniors) and found that children and seniors, two age groups characterized by either low level of (children) or weak access to (seniors) odor semantic knowledge, processed odor hedonics more on the basis of their physicochemical properties. In contrast, in teenagers and young adults, who show better levels of semantic odor representation, the role of physicochemical properties was less marked.

Conclusions/Significance

These findings demonstrate for the first time that the biological determinants that make an odor pleasant or unpleasant are more powerful at either end of the life span.     

An immunological method for quantifying antibacterial activity in Salmo salar (Linnaeus, 1758) skin mucus

Antimicrobial peptides (AMPs) are a pivotal component of innate immunity in lower vertebrates. The aim of this study was to develop an immunological method for quantifying AMPs in Salmo salar skin mucus. A known antimicrobial peptide derived from histone H1 previously purified and described from S. salar skin mucus (SAMP H1) was chemically synthesized and used to obtain antibodies for the quantification of the molecule via ELISA. Using skin mucus samples, a correlation of bacterial growth inhibition versus SAMP H1 concentration (ELISA) was established. The results provide the first evidence for quantifying the presence of active AMPs in the skin mucus of S. salar through the use of an immunological method.     

The small heterodimer partner interacts with the pregnane X receptor and represses its transcriptional activity

SHP (small heterodimer partner, NR1I0) is an atypical orphan member of the nuclear receptor subfamily in that it lacks a DNA-binding domain. It is mostly expressed in the liver, where it binds to and inhibits the function of nuclear receptors. SHP is up-regulated by primary bile acids, through the activation of their receptor farnesoid X receptor, leading to the repression of cholesterol 7alpha-hydroxylase (CYP7alpha) expression, the rate-limiting enzyme in bile acid production from cholesterol. PXR (pregnane X receptor, NR1I2) is a broad-specificity sensor that recognizes a wide variety of synthetic drugs as well as endogenous compounds such as bile acid precursors. Upon activation, PXR induces CYP3A and inhibits CYP7alpha, suggesting that PXR can act on both bile acid synthesis and elimination. Indeed, CYP7alpha and CYP3A are involved in biochemical pathways leading to cholesterol conversion into primary bile acids, whereas CYP3A is also involved in the detoxification of toxic secondary bile acid derivatives. Here, we show that PXR is a target for SHP. Using pull-down assays, we show that SHP interacts with both murine and human PXR in a ligand-dependent manner. From transient transfection assays, SHP is shown to be a potent repressor of PXR transactivation. Furthermore, we report that chenodeoxycholic acid and cholic acid, two farnesoid X receptor ligands, induce up-regulation of SHP and provoke a repression of PXR-mediated CYP3A induction in human hepatocytes as well as in vivo in mice. These results reveal an elaborate regulatory cascade, tightly controlled by SHP, for both the maintenance of bile acid production and detoxification in the liver.     

Streptomyces yatensis sp. nov., a novel bioactive streptomycete isolated from a New-Caledonian ultramafic soil

The taxonomic position of an actinomycete isolated from an ultramafic soil in New Caledonia was examined using a polyphasic approach. The organism, which was designated SFOCin 76, was found to have chemical and morphological properties typical of streptomycetes and formed a distinct phyletic line in the Streptomyces violaceusniger clade of the 16S rDNA tree. It also showed a unique pattern of phenotypic properties that distinguished it from representatives of all of the validly described species classified in this clade. It is, therefore, proposed that strain SFOCin 76 be classified in the genus Streptomyces as Streptomyces yatensis sp. nov. This revised version was published online in June 2006 with corrections to the Cover Date.     

Karyotypic and molecular identification of laboratory stocks of the South American fruit fly Anastrepha fraterculus (Wied) (Diptera: Tephritidae)

The taxonomic status of the tephritid pest Anastrepha fraterculus (Wied.) is a controversial subject, mainly because of misinterpretation of the observed genetic variation. In this work, the different karyotypes and DNA polymorphism of a geographically defined population from Northeastern Argentina were studied, using derived stocks maintained in the laboratory during 25 generations. The karyotypes were analyzed using C-banding and N-banding techniques, while DNA analysis was performed through the DNA polymerase chain reaction (PCR). The variants isolated from both the wild Montecarlo population and the derived laboratory stocks were fully compatible and are present in other wild populations from South Brazil (lat 31 degrees 30' S) to Mid-Argentina (lat 34 degrees 30' S). Single-pair crosses among stocks carrying different chromosomal variants demonstrated the absence of isolation barriers. The polymorphic fragments isolated by RAPDs/PCR showed polymorphisms among stocks whereas the analysis of rDNA ITS1 exhibit a unique ITS1 length. Our results seem to indicate that all the examined variants belong to a single species with extended polymorphism and therefore do not support the hypothesis that the extended chromosomal polymorphism in A. fraterculus implies the existence of a complex of cryptic species.     

Immobilization of pectin fragments on solid supports: novel coupling by thiazolidine formation

As a prerequisite to solid-phase and sequence analyses and for the study of the fine structure of pectin, we have developed oriented and chemoselective methodologies to couple model pectin fragments onto a solid support. Polyethylene glycol polyacrylamide (PEGA) resins were selected due to their excellent swelling properties in a wide range of solvents, including water, and their easy accessibility to enzymes. Following appropriate derivatization of amino-terminated PEGA resins, oligomers of alpha-D-galacturonic acid (GalA), up to the trimer, were anchored to the support through their reducing end. In addition to reductive amination, the strategies included the formation of an oxime bond, a glycosyl hydrazide, and a pyroglutamyl ring. Further, we developed a new immobilization approach based on the formation of a thiazolidine ring. All methods proved efficient and did not require modification of the GalA oligomers prior to coupling. In addition, very mild conditions and few steps for derivatization of the support were required. Immobilization by thiazolidine ring and oxime bond formation were the preferred methods, given the stability of the linkages formed, their compatibility with aqueous solvents, the few number of steps required, and their potential for application to larger pectin fragments. Thiazolidine and pyroglutamyl anchoring were developed further by the insertion of a disulfide bond which allowed release of the saccharides under mild, selective conditions.     

Abnormal production of interleukin (IL)-11 and IL-8 in polycythaemia vera

We studied the production of interleukin (IL)-11 and IL-8, two cytokines known to affect erythropoiesis, in polycythemia vera (PV). In vivo, IL-11 was detected more frequently in serum and bone marrow (BM) plasma of PV patients than in controls (healthy donors and patients with idiopathic erythrocytosis (IE)). In addition, serum IL-11 levels of PV patients were higher than those of controls. IL-8 was elevated in serum of both PV and IE patients (respective median levels: 38.6 and 242pg/ml, vs 4.4pg/ml for healthy donors). BM plasma IL-8 levels of PV patients (508pg/ml) were significantly higher than those of IE patients (120pg/ml). In vitro, bone marrow (BM) stromal cells (BMSC) of PV patients produced significantly more IL-11 (x6.4) and IL-8 (x8.3) than BMSC of healthy donors or IE patients. In conclusion, both IL-11 and IL-8 are overproduced in PV, apparently by BMSC; IL-8 is also overproduced in IE, by cells other than BMSC.