ABC Proteins of Leishmania

ABC proteins were first characterized in the protozoan parasite Leishmania while studying mechanisms of drug resistance. PGPA is involved in resistance to arsenite and antimonite and it most likely confers resistance by sequestering metal–thiol conjugates into an intracellular vesicle. PGPA is part of gene family with at least four more members which are in search of a function. Leishmania also contains a P-glycoprotein, homologous to the mammalian MDR1, that is involved in multidrug resistance. The ongoing genome project of Leishmania has pinpointed several novel ABC transporters and experiments are carried out to study the function of the ABC proteins in drug resistance and in host–pathogen interactions.     

Genomic data reveal deep genetic structure but no support for current taxonomic designation in a grasshopper species complex

Taxonomy has traditionally relied on morphological and ecological traits to interpret and classify biological diversity. Over the last decade, technological advances and conceptual developments in the field of molecular ecology and systematics have eased the generation of genomic data and changed the paradigm of biodiversity analysis. Here we illustrate how traditional taxonomy has led to species designations that are supported neither by high throughput sequencing data nor by the quantitative integration of genomic information with other sources of evidence. Specifically, we focus on Omocestus antigai and Omocestus navasi, two montane grasshoppers from the Pyrenean region that were originally described based on quantitative phenotypic differences and distinct habitat associations (alpine vs. Mediterranean‐montane habitats). To validate current taxonomic designations, test species boundaries, and understand the factors that have contributed to genetic divergence, we obtained phenotypic (geometric morphometrics) and genome‐wide SNP data (ddRADSeq) from populations covering the entire known distribution of the two taxa. Coalescent‐based phylogenetic reconstructions, integrative Bayesian model‐based species delimitation, and landscape genetic analyses revealed that populations assigned to the two taxa show a spatial distribution of genetic variation that do not match with current taxonomic designations and is incompatible with ecological/environmental speciation. Our results support little phenotypic variation among populations and a marked genetic structure that is mostly explained by geographic distances and limited population connectivity across the abrupt landscapes characterizing the study region. Overall, this study highlights the importance of integrative approaches to identify taxonomic units and elucidate the evolutionary history of species.     

The role of the chemokines MCP-1, GRO-alpha, IL-8 and their receptors in the adhesion of monocytic cells to human atherosclerotic plaques

Monocyte adhesion to the arterial endothelium and subsequent migration into the intima are central events in the pathogenesis of atherosclerosis. Previous experimental models have shown that chemokines can enhance monocyte–endothelial adhesion by activating monocyte integrins. Our study assesses the role of chemokines IL-8, MCP-1 and GRO-α, together with their monocyte receptors CCR2 and CXCR2 in monocyte adhesion to human atherosclerotic plaques. In an adhesion assay, a suspension of monocytic U937 cells was incubated with human atherosclerotic artery sections and the levels of endothelial adhesion were quantified. Adhesion performed in the presence of a monoclonal antibody to a chemokine, chemokine receptor or of an isotype matched control immunoglobulin, shows that antibodies to all chemokines tested, as well as their receptors, inhibit adhesion compared to the control immunoglobulins. Immunohistochemistry demonstrated the expression of MCP-1, GRO-α and their receptors in the endothelial cells and intima of all atherosclerotic lesions. These results suggest that all these chemokines and their receptors can play a role in the adhesion of monocytes to human atherosclerotic plaques. Furthermore, they suggest that these chemokine interactions provide potential targets for the therapy of atherosclerosis.     

Molecular cloning and characterization of triterpene synthases from Medicago truncatula and Lotus japonicus

Cloning of OSCs required for triterpene synthesis from legume species that are amenable to molecular genetics will provide tools to address the importance of triterpenes and their derivatives during normal plant growth and development and also in interactions with symbionts and pathogens. Here we report the cloning and characterization of a total of three triterpene synthases from the legume species Medicago truncatula and Lotus japonicus. These include a -amyrin synthase from M. truncatula (MtAMYI) and a mixed function triterpene synthase from Lotus japonicus (LjAMY2). A partial cDNA predicted to encode a -amyrin synthase (LjAMY1) was also isolated from L. japonicus. The expression patterns of MtAMY1, LjAMY1 and LjAMY2 and of additional triterpene synthases previously characterised from M. truncatula and pea differ in different plant tissues and during nodulation, suggesting that these enzymes may have distinct roles in plant physiology and development.     

Genetic relatedness among dioecious Ficus carica L. cultivars by random amplified polymorphic DNA analysis,and evaluation of agronomic and morphological characters

A collection of 64 fig (Ficus carica L.) accessions was characterized through the use of RAPD markers, and results were evaluated in conjunction with morphological and agronomical characters, in order to determine the genetic relatedness of genotypes with diverse geographic origin. The results indicate that fig cultivars have a rather narrow genetic base. Nevertheless, RAPD markers could detect enough polymorphism to differentiate even closely related genotypes (i.e., clones of the same cultivar) and a unique fingerprint for each of the genotypes studied was obtained. No wasteful duplications were found in the collection. Cluster analysis allowed the identification of groups in accordance with geographic origin, phenotypic data and pedigree. Taking into account the limited information concerning fig cultivar development, the results of this study, which provide information on the genetic relationships of genetically distinct material, dramatically increase the fundamental and practical value of the collection and represent an invaluable tool for fig germplasm management.     

Functional studies of shaggy/glycogen synthase kinase 3 phosphorylation sites in Drosophila melanogaster

Early studies of glycogen synthase kinase 3 (GSK-3) in mammalian systems focused on its pivotal role in glycogen metabolism and insulin-mediated signaling. It is now recognized that GSK-3 is central to a number of diverse signaling systems. Here, we show that the major form of the kinase Shaggy (Sgg), the GSK-3 fly ortholog, is negatively regulated during insulin-like/phosphatidylinositol 3-kinase (PI3K) signaling in vivo. Since genetic studies of Drosophila melanogaster had previously shown that Wingless (Wg) signaling also acts to antagonize Sgg, we investigate how the kinase might integrate, or else discriminate, signaling inputs by Wg and insulin. Using Drosophila cell line assays, we found, in contrast to previous reports, that Wg induces accumulation of its transducer Armadillo (Arm)/beta-catenin without significant alteration of global Sgg-specific activity. In agreement with a previous study using human GSK-3beta, Wg did not cause phosphorylation changes of the Ser9 or Tyr214 regulatory phosphorylated sites of Sgg. Conversely, as shown in mammalian systems, insulin-induced inhibition of Sgg-specific activity by phosphorylation at the N-terminal pseudosubstrate site (Ser9) did not induce Arm/beta-catenin accumulation, showing selectivity in response to the different signaling pathways. Interestingly, a minigene bearing a Ser9-to-Ala change rescued mutant sgg without causing abnormal development, suggesting that the regulation of Sgg via the inhibitory pseudosubstrate domain is dispensable for many aspects of its function. Our studies of Drosophila show that Wg and insulin or PI3K pathways do not converge on Sgg but that they exhibit cross-regulatory interactions.     

Synthesis of novel 2-nitroimidazole-tethered tricyclic quinolines, bearing a second heteroatom, and their in vitro evaluation as hypoxia-selective cytotoxins and radiosensitizers

Two novel nitroimidazole-based bioreductive compounds, 10-[3-(2-nitroimidazolyl)-propylamino]-3,4-dihydro-1H-thiopyrano[4,3-b]quinoline hydrochloride (8a) and 10-[3-(2-nitroimidazolyl)propylamino]-2-methyl-1,2,3,4-tetrahydro-benzo[b]-1,6-naphthyridine hydrochloride (8b) have been synthesized and evaluated in V79 cells as hypoxia-selective cytotoxins and radiosensitizers that target DNA through weak intercalation. Both compounds were relatively good radiosensitizers (C(1.6) values of 40.0+/-0.8 and 59.0+/-0.4 microM for 8a and 8b, respectively) but neither of the compounds was superior to 2 which does not carry a second heteroatom in the DNA-intercalating chromophore.