Genetic structure,admixture and invasion success in a Holarctic defoliator,the gypsy moth (Lymantria dispar,Lepidoptera: Erebidae)

Characterizing the current population structure of potentially invasive species provides a critical context for identifying source populations and for understanding why invasions are successful. Non‐native populations inevitably lose genetic diversity during initial colonization events, but subsequent admixture among independently introduced lineages may increase both genetic variation and adaptive potential. Here we characterize the population structure of the gypsy moth (Lymantria dispar Linnaeus), one of the world's most destructive forest pests. Native to Eurasia and recently introduced to North America, the current distribution of gypsy moth includes forests throughout the temperate region of the northern hemisphere. Analyses of microsatellite loci and mitochondrial DNA sequences for 1738 individuals identified four genetic clusters within L. dispar. Three of these clusters correspond to the three named subspecies; North American populations represent a distinct fourth cluster, presumably a consequence of the population bottleneck and allele frequency change that accompanied introduction. We find no evidence that admixture has been an important catalyst of the successful invasion and range expansion in North America. However, we do find evidence of ongoing hybridization between subspecies and increased genetic variation in gypsy moth populations from Eastern Asia, populations that now pose a threat of further human‐mediated introductions. Finally, we show that current patterns of variation can be explained in terms of climate and habitat changes during the Pleistocene, a time when temperate forests expanded and contracted. Deeply diverged matrilines in Europe imply that gypsy moths have been there for a long time and are not recent arrivals from Asia.     

Inter-Annual Variability of Soft Bottom Macrofaunal Communities in Two Ionian Sea Lagoons

Inter-annual variation in the composition of the soft bottom macrobenthic communities of two undisturbed lagoons, in Amvrakikos Gulf, Ionian Sea, Greece, was investigated over three consecutive summers. The environmental parameters that showed the greatest variability were organic carbon of the sediment and salinity. The species found were typical of lagoonal systems, the most common and abundant of which were Abra ovata, Mytilaster minimus and, in the most enclosed areas, larvae of chironomids. Multivariate analysis registered community changes, which were mostly caused by changes in species dominance. Structural community characteristics such as number of species, number of individuals and diversity did not show significant differences among years except in the stations with least water exchange with the sea.     

Omega-3 fatty acids and antioxidants in edible wild plants

Human beings evolved on a diet that was balanced in the omega-6 and omega-3 polyunsaturated fatty acids (PUFA), and was high in antioxidants. Edible wild plants provide alpha-linolenic acid (ALA) and higher amounts of vitamin E and vitamin C than cultivated plants. In addition to the antioxidant vitamins, edible wild plants are rich in phenols and other compounds that increase their antioxidant capacity. It is therefore important to systematically analyze the total antioxidant capacity of wild plants and promote their commercialization in both developed and developing countries. The diets of Western countries have contained increasingly larger amounts of linoleic acid (LA), which has been promoted for its cholesterol-lowering effect. It is now recognized that dietary LA favors oxidative modification of low density lipoprotein (LDL) cholesterol and increases platelet response to aggregation. In contrast, ALA intake is associated with inhibitory effects on the clotting activity of platelets, on their response to thrombin, and on the regulation of arachidonic acid (AA) metabolism. In clinical studies, ALA contributed to lowering of blood pressure, and a prospective epidemiological study showed that ALA is inversely related to the risk of coronary heart disease in men. Dietary amounts of LA as well as the ratio of LA to ALA appear to be important for the metabolism of ALA to longer-chain omega-3 PUFAs. Relatively large reserves of LA in body fat. as are found in vegans or in the diet of omnivores in Western societies, would tend to slow down the formation of long-chain omega-3 fatty acids from ALA. Therefore, the role of ALA in human nutrition becomes important in terms of long-term dietary intake. One advantage of the consumption of ALA over omega-3 fatty acids from fish is that the problem of insufficient vitamin E intake does not exist with high intake of ALA from plant sources.     

Marked mitochondrial alterations upon starvation without cell death, caspases or Bcl-2 family members

Dictyostelium HMX44A cells can withstand starvation under monolayer conditions for a few days without dying. They die only when the differentiation factor DIF-1 is exogenously added. Still, when HMX44A were subjected to starvation without addition of DIF-1 they showed, by electron microscopy and electron tomography, gross mitochondrial lesions including marked cristae alterations with frequent "holes" probably originating from dilated cristae. Since these cells did not die as shown for instance by FACS analysis, these results showed unexpected resilience of cells bearing markedly altered mitochondria, and thus showed that apparently destructive mitochondrial alterations may not lead to cell death. Also, these marked mitochondrial lesions could not be caused by caspases or bcl-2 family members, which these cells do not encode.     

Rupture of totally implantable central venous access devices (Intraports) in patients with cancer: report of four cases

Background  

Totally implantable central venous access devices (intraports) are commonly used in cancer patients to administer chemotherapy or parenteral nutrition. Rupture of intraport is a rare complication.     

Plasma Membrane Localization of Solanum tuberosum Remorin from Group 1, Homolog 3 Is Mediated by Conformational Changes in a Novel C-Terminal Anchor and Required for the Restriction of Potato Virus X Movement]

The formation of plasma membrane (PM) microdomains plays a crucial role in the regulation of membrane signaling and trafficking. Remorins are a plant-specific family of proteins organized in six phylogenetic groups, and Remorins of group 1 are among the few plant proteins known to specifically associate with membrane rafts. As such, they are valuable to understand the molecular bases for PM lateral organization in plants. However, little is known about the structural determinants underlying the specific association of group 1 Remorins with membrane rafts. We used a structure-function approach to identify a short C-terminal anchor (RemCA) indispensable and sufficient for tight direct binding of potato (Solanum tuberosum) REMORIN 1.3 (StREM1.3) to the PM. RemCA switches from unordered to α-helical structure in a nonpolar environment. Protein structure modeling indicates that RemCA folds into a tight hairpin of amphipathic helices. Consistently, mutations reducing RemCA amphipathy abolished StREM1.3 PM localization. Furthermore, RemCA directly binds to biological membranes in vitro, shows higher affinity for Detergent-Insoluble Membranes lipids, and targets yellow fluorescent protein to Detergent-Insoluble Membranes in vivo. Mutations in RemCA resulting in cytoplasmic StREM1.3 localization abolish StREM1.3 function in restricting potato virus X movement. The mechanisms described here provide new insights on the control and function of lateral segregation of plant PM.Protein-lipid interactions are increasingly recognized as key regulatory processes for signal perception and cellular signaling cascades (Cho and Stahelin, 2005). During signal transduction and trafficking, a number of soluble proteins dynamically associate with plasma membranes (PMs) to deliver their cargo and to recruit pathway components to the sites of action (Seong et al., 2011). For such proteins, membrane association can be critical for function (Porter and Koelle, 2010).PM targeting of peripheral proteins is achieved through (1) binding to integral membrane proteins, (2) posttranslational modifications, or (3) directly by intrinsic membrane anchor domains. Posttranslational modifications function as auxiliary modifications for transient or weak association of soluble proteins to the intracellular face of the PM. In plants, these include N-myristoylation, S-palmitoylation, prenylation by farnesyl or geranylgeranyl moieties, or attachment of glycosylphosphatidylinositol (GPI) anchors (Thompson and Okuyama, 2000). GPI anchors, for example, tightly associate proteins to the extracellular face of PMs by interaction of the inositol head group of the membrane lipid phosphatidylinositol with a glucosamine residue linked to the C-terminal amino acid of the protein (Paulick and Bertozzi, 2008). As an alternative mechanism, globular structures either recognize phospholipids in a stereospecific manner or associate with membranes by their biophysical properties (for review, see Lemmon, 2008). Other proteins expose unstructured clusters of basic and hydrophobic residues to mediate PM binding (McLaughlin et al., 2002; McLaughlin and Murray, 2005).Selective recognition of membrane compartments or domains by protein anchors can be critical in triggering the appropriate downstream trafficking and signaling events (for review, see Gruenberg, 2003; De Matteis and Godi, 2004). Membrane domain selectivity can be specified by the anchoring posttranslational modification or by a protein anchor domain. For instance, proteins carrying GPI anchors are overrepresented in membrane rafts, indicating that addition of this lipid anchor directs proteins to these microdomains (Cordy et al., 2003; Kierszniowska et al., 2009). Membrane rafts are enriched in highly saturated long-chain sphingolipids, sterols, and saturated phospholipids, creating tightly packed domains, designated as “liquid ordered.” These lipids display a stronger affinity to saturated acyl chains as found in GPI-anchored and acylated proteins (Brown, 2006). The composition of membrane rafts also prevents solubilization by detergent at low temperature with nonionic detergent and allows the partial purification of rafts in so-called Detergent-Insoluble Membrane (DIM) fractions, which are supposedly biochemical counterparts of membrane rafts. Many signaling proteins are found in membrane rafts, supporting the hypothesis that they serve as key platforms for cellular signal transduction and cell-to-cell communication (Lingwood and Simons, 2010; Simon-Plas et al., 2011). For example, in human (Homo sapiens) cells, key soluble signaling components such as the Ser/Thr kinase Akt (protein kinase B) are recruited to membrane rafts where they activate signal transduction cascades (Lasserre et al., 2008). Nevertheless, few protein motifs were described to contribute to raft targeting (Rossin et al., 2010), although the 6-amino-acid-long raft target signal from human Tyr phosphatase Src homology 2-containing phosphatase1 is the only known motif sufficient to anchor soluble proteins specifically to domains of the intracellular face of the PM (Sankarshanan et al., 2007). However, the anchoring mechanism itself remains to be unraveled in plants even though DIMs also exist (Mongrand et al., 2010) and functional PM domains have been reported (Bhat et al., 2005). The molecular basis for specific targeting and binding of proteins to membrane rafts has never been described.Remorins form a diverse family of plant-specific proteins organized in six distinct phylogenetic groups (Raffaele et al., 2007). Remorins from group 1 have been reported to localize to the PM despite their overall hydrophilic nature (Reymond et al., 1996; Raffaele et al., 2007). Moreover, group 1 Remorins almost exclusively associate to DIMs and localize to membrane microdomains in a sterol-dependent manner (Lefebvre et al., 2007; Kierszniowska et al., 2009; Raffaele et al., 2009). The function of Remorins is mostly unknown, but we showed in a previous study that StREM1.3 (for potato (Solanum tuberosum) Remorin from group 1, homolog 3; initially described in Reymond et al., 1996) regulates cell-to-cell propagation of the potato virus X (PVX), likely by directly interacting with the viral movement protein Triple Gene Block protein1 (TGBp1; Raffaele et al., 2009). StREM1.3 localizes to the inner leaflet of PMs and along plasmodesmata, bridges connecting neighbor cells essential for cell-to-cell communication in plants (Maule, 2008). Other members of the Remorin family group 1 are likely involved in innate immune responses (Liu et al., 2009; Widjaja et al., 2009; Keinath et al., 2010). Remorins from group 2 are involved in the control of infection by symbiotic bacteria at nodular infection threads and the peribacteroid membrane (Lefebvre et al., 2010) These data suggest general roles for Remorins in regulating signaling in plant-microbe interactions (Jarsch and Ott, 2011).Elucidating the mechanisms driving StREM1.3 association with PM microdomains therefore provides a unique opportunity for understanding the regulation and function of membrane lateral segregation in plants. StREM1.3 does not contain predictable transmembrane or membrane-associated domains. The bases for its association to PMs and selective targeting to DIMs are unknown. Here we identified a novel membrane anchor domain required for StREM1.3 tight and direct association with the detergent-insoluble fraction of the PM. We combined biophysics, in silico analysis, and directed mutagenesis to unravel the molecular bases of StREM1.3 membrane binding and its biological significance in the control of PVX propagation.     

Assortative mating in sympatric ascomycete fungi revealed by experimental fertilizations

Mate recognition mechanisms resulting in assortative mating constitute an effective reproductive barrier that may promote sexual isolation and speciation. While such mechanisms are widely documented for animals and plants, they remain poorly studied in fungi. We used two interfertile species of Epichloë (Clavicipitaceae, Ascomycota), E. typhina and E. clarkii, which are host-specific endophytes of two sympatrically occurring grasses. The life cycle of these obligatory outcrossing fungi entails dispersal of gametes by a fly vector among external fungal structures (stromata). To test for assortative mating, we mimicked the natural fertilization process by applying mixtures of spermatia from both species and examined their reproductive success. Our trials revealed that fertilization is non-random and preferentially takes place between conspecific mating partners, which is indicative of assortative mating. Additionally, the viability of hybrid and non-hybrid ascospore offspring was assessed. Germination rates were lower in E. clarkii than in E. typhina and were reduced in ascospore progeny from treatments with high proportions of heterospecific spermatia. The preferential mating between conspecific genotypes and reduced hybrid viability represent important reproductive barriers that have not been documented before in Epichloë. Insights from fungal systems will deepen our understanding of the evolutionary mechanisms leading to reproductive isolation and speciation.     

Functional characterization of the histidine kinase of the E. coli two-component signal transduction system AtoS–AtoC

The Escherichia coli AtoS–AtoC two-component signal transduction system regulates the expression of the atoDAEB operon genes, whose products are required for short-chain fatty acid catabolism. In this study purified his-tagged wild-type and mutant AtoS proteins were used to prove that these proteins are true sensor kinases. The phosphorylated residue was identified as the histidine-398, which was located in a conserved Η-box since AtoS carrying a mutation at this site failed to phosphorylate. This inability to phosphorylate was not due to gross structural alterations of AtoS since the H398L mutant retained its capability to bind ATP. Furthermore, the H398L mutant AtoS was competent to catalyze the trans-phosphorylation of an AtoS G-box (G565A) mutant protein which otherwise failed to autophosphorylate due to its inability to bind ATP. The formation of homodimers between the various AtoS proteins was also shown by cross-linking experiments both in vitro and in vivo.