Phylogeny of Greya (Lepidoptera: Prodoxidae), based on nucleotide sequence variation in mitochondrial cytochrome oxidase I and II: congruence with morphological data

The phylogeny of Greya Busck (Lepidoptera: Prodoxidae) was inferred from nucleotide sequence variation across a 765-bp region in the cytochrome oxidase I and II genes of the mitochondrial genome. Most parsimonious relationships of 25 haplotypes from 16 Greya species and two outgroup genera (Tetragma and Prodoxus) showed substantial congruence with the species relationships indicated by morphological variation. Differences between mitochondrial and morphological trees were found primarily in the positions of two species, G. variabilis and G. pectinifera, and in the branching order of the three major species groups in the genus. Conflicts between the data sets were examined by comparing levels of homoplasy in characters supporting alternative hypotheses. The phylogeny of Greya species suggests that host-plant association at the family level and larval feeding mode are conservative characters. Transition/transversion ratios estimated by reconstruction of nucleotide substitutions on the phylogeny had a range of 2.0-9.3, when different subsets of the phylogeny were used. The decline of this ratio with the increase in maximum sequence divergence among taxa indicates that transitions are masked by transversions along deeper internodes or long branches of the phylogeny. Among transitions, substitutions of A-->G and T-->C outnumbered their reciprocal substitutions by 2-6 times, presumably because of the approximately 4:1 (77%) A+T-bias in nucleotide base composition. Of all transversions, 73%-80% were A<-->T substitutions, 85% of which occurred at third positions of codons; these estimates did not decrease with an increase in maximum sequence divergence of taxa included in the analysis. The high frequency of A<-->T substitutions is either a reflection or an explanation of the 92% A+T bias at third codon positions.      

Regulation of β-catenin stabilization in human platelets

The Wnt/β-catenin pathway controls developmental processes and homeostasis; however, abnormal activation of this pathway has been linked to several human diseases. Recent reports have demonstrated regulation of platelet function by canonical and non-canonical Wnt signalling. Platelet aggregation plays a crucial role in haemostasis and thrombosis. Here we report for the first time that, induction of sustained aggregation of platelets by a strong agonist in the presence of calcium was associated with nearly complete proteolysis of β-catenin, which was abrogated upon depletion of calcium from platelet suspension. β-catenin cleavage was disallowed in absence of aggregation, thus implicating integrin α_IIbβ₃ engagement in β-catenin proteolysis. Degradation of β-catenin was blocked partially by inhibitors of either proteasome or calpain and completely when cells were exposed to both the inhibitors. Protein kinase C inhibition, too, abolished β-catenin degradation. Thus activities of proteasome, calpain and protein kinase C regulate stabilization of β-catenin in aggregated human platelets.     

Analysis of plastid DNA-like sequences within the nuclear genomes of higher plants

A wide-ranging examination of plastid (pt)DNA sequence homologies within higher plant nuclear genomes (promiscuous DNA) was undertaken. Digestion with methylation-sensitive restriction enzymes and Southern analysis was used to distinguish plastid and nuclear DNA in order to assess the extent of variability of promiscuous sequences within and between plant species. Some species, such as Gossypium hirsutum (cotton), Nicotiana tabacum (tobacco), and Chenopodium quinoa, showed homogenity of these sequences, while intraspecific sequence variation was observed among different cultivars of Pisum sativum (pea), Hordeum vulgare (barley), and Triticum aestivum (wheat). Hypervariability of plastid sequence homologies was identified in the nuclear genomes of Spinacea oleracea (spinach) and Beta vulgaris (beet), in which individual plants were shown to possess a unique spectrum of nuclear sequences with ptDNA homology. This hypervariability apparently extended to somatic variation in B. vulgaris. No sequences with ptDNA homology were identified by this method in the nuclear genome of Arabidopsis thaliana.      

On temporal partitioning of a community of ectomycorrhizal fungi

Several mechanisms may contribute to the high species richness often reported in ectomycorrhizal (ECM) fungal communities, including spatial and temporal partitioning. Here, we focus on temporal partitioning. Using molecular methods, we determined the frequencies of occurrence of ECM fungal species detected as hyphae and ECM roots in the forest floor of a Pinus resinosa plantation during a 13-month period. We then used a novel statistical procedure to place the most frequently occurring ECM fungal species into groups distinguished by their patterns of relative frequency over time. Three groups with contrasting temporal patterns were distinguishable for fungal species detected as hyphae. Two groups were distinguishable for species detected as ECM roots. Our results support the hypothesis that temporal partitioning occurs among the species of ECM fungi in this community, but we did not address its causes, which may have involved interactions among species' physiological tolerances, temporal environmental variability, temporal patterns of root production, and variation in fungal genet lifespan. These interactions should be the subjects of future research.     

Selective cytotoxicity of Pancratistatin-related natural <Emphasis Type="Italic">Amaryllidaceae</Emphasis> alkaloids: evaluation of the activity of two new compounds

Background  

Pancratistatin (PST), a compound extracted from an Amaryllidaceae (AMD) family plant, has been shown to specifically induce apoptosis in cancer cells with no/minimal toxic effect on normal cells. A systematic synthetic approach has indicated that the minimum cytotoxic pharmacophore comprises the trans-fused b/c-ring system containing the 2, 3, 4-triol unit in the C-ring. To further explore the structure-activity relationship of this group of compounds we have investigated the anti-cancer efficacy and specificity of two PST-related natural compounds, AMD4 and AMD5. Both of these compounds lack the polyhydroxylated lycorane element of PST instead having a methoxy-substuituted crinane skeleton.     

Contrasting below-ground views of an ectomycorrhizal fungal community

Ectomycorrhizal fungal communities have been characterized in a number of ways. Here we compare colonized root-tip and mycelia views of an ectomycorrhizal fungal community. Ectomycorrhizal fungi, both as mycelia and colonized root tips, were identified in soil samples taken from a pine plantation. We determined that for some ectomycorrhizal fungal species multiple root tips from a single soil sample were not independent. Therefore in the comparison of root-tip and mycelia views, we considered species to be present or absent from each soil sample irrespective of the number of root tips colonized by the species. We observed 39 ectomycorrhizal fungal species in total, but 12 were observed exclusively as mycelia and 11 exclusively colonizing root tips. The relative frequencies of 10 species occurring as both mycelia and root tips were not independent of the method of observation. Our results suggest that ectomycorrhizal fungal species differ in their spatial distributions on root tips, and that root-tip and mycelia views of the community are different.     

Lifespan and stress resistance of Caenorhabditis elegans are increased by expression of glutathione transferases capable of metabolizing the lipid peroxidation product 4-hydroxynonenal

Caenorhabditis elegans expresses a glutathione transferase (GST) belonging to the Pi class, for which we propose the name CeGSTP2-2. CeGSTP2-2 (the product of the gst-10 gene) has the ability to conjugate the lipid peroxidation product 4-hydroxynonenal (4-HNE). Transgenic C. elegans strains were generated in which the 5'-flanking region and promoter of gst-10 were placed upstream of gst-10 and mGsta4 cDNAs, respectively. mGsta4 encodes the murine mGSTA4-4, an enzyme with particularly high catalytic efficiency for 4-HNE. The localization of both transgenes was similar to that of native CeGSTP2-2. The 4-HNE-conjugating activity in worm lysates increased in the order: control相似文献   

Symbiotic interactions between arbuscular mycorrhizal (AM) fungi and male papaya plants: Its status,role and implications

Experiments were conducted to study the arbuscular mycorrhizal (AM) status and its role in P-uptake through assay of root phosphatases activities in four varieties of male Carica papaya L. viz. CO-1, CO-2, Honey Dew and Washington during flowering stages. In the present study, mean total root colonization of AM fungi recorded peak increase in flowering stage-II while mean root phosphatase (acid and alkaline) activities recorded peak increase in flowering stage-I. Unlike root colonization and root phosphatase activities, spore density did not exhibit any definite patterns and recorded a narrow range of fluctuation during different flowering stages of male C. papaya. The study brought out the fact that root colonization and spore density of AM fungi along with root phosphatase activities varied significantly within the four varieties of male C. papaya plants during each flowering stage. The study also recorded consistently higher acid root phosphatase activity than alkaline root phosphatase activity under P-deficient, acidic soil conditions during all flowering stages of male C. papaya plants. Studies revealed that the root colonization of AM fungi influenced root phosphatase activities (acid and alkaline) positively and significantly during all flowering stages of male C. papaya plants. A total of twelve species of AM fungi belonging to five genera viz. Acaulospora, Dentiscutata, Gigaspora, Glomus, and Racocetra were recovered from the rhizosphere of male C. papaya plants.     

Activation of the N-Terminally Truncated Form of the Stk Receptor Tyrosine Kinase Sf-Stk by Friend Virus-Encoded gp55 Is Mediated by Cysteine Residues in the Ecotropic Domain of gp55 and the Extracellular Domain of Sf-Stk

Friend virus induces an erythroleukemia in susceptible mice that is initiated by the interaction of the Friend virus-encoded glycoprotein gp55 with the erythropoietin (Epo) receptor and the product of the host Fv2 gene, a naturally occurring truncated form of the Stk receptor tyrosine kinase (Sf-Stk). We have previously demonstrated that the activation of Sf-Stk, recruitment of a Grb2/Gab2/Stat3 signaling complex, and induction of Pu.1 expression by Stat3 are required for the development of the early stage of Friend disease both in vitro and in vivo. Here we demonstrate that the interaction of gp55 with Sf-Stk is dependent on cysteine residues in the ecotropic domain of gp55 and the extracellular domain of Sf-Stk. Point mutation of these cysteine residues or deletion of these domains inhibits the ability of gp55 to interact with Sf-Stk, resulting in the inability of these proteins to promote the Epo-independent growth of erythroid progenitor cells. We also demonstrate that the interaction of gp55 with Sf-Stk does not promote dimerization of Sf-Stk but results in enhanced phosphorylation of Sf-Stk and the relocalization of Sf-Stk from the cytosol to the plasma membrane. Finally, we demonstrate that a constitutively active form of Sf-Stk (Sf-StkM330T), as well as its human counterpart, Sf-Ron, promotes Epo-independent colony formation in the absence of gp55 and that this response is also dependent on the cysteines in the extracellular domains of Sf-StkM330T and Sf-Ron. These data suggest that the cysteines in the extracellular domains of Sf-Stk and Sf-Ron may also mediate the interaction of these truncated receptors with other cellular factors that regulate their ability to promote cytokine-independent growth.Since Friend disease was first reported in 1957 (19), the acute erythroleukemia induced by the various strains of Friend virus have provided an excellent model to study multistage carcinogenesis (5). In the first stage, the virus infects erythroid progenitor cells and a viral glycoprotein, gp55, interacts with both the erythropoietin receptor (EpoR) and a naturally occurring truncated form of the stem cell-derived tyrosine kinase (Stk), Sf-Stk, resulting in the Epo-independent (Epo^ind) expansion of erythroid progenitor cells. The late stage of erythroleukemia in Friend disease is marked by inactivation of the p53 locus (6, 28, 38, 39, 51) and proviral integration into the Spi-1 locus (36, 43, 44), resulting in enhanced expression of Pu.1, which causes a block in erythroid differentiation and promoting the onset of acute erythroleukemia.Friend virus is a complex of two viruses, the spleen focus-forming virus (SFFV), which is a replication-defective C-type retrovirus, and the ecotropic Friend murine leukemia virus (F-MuLV). SFFV is responsible for the rapid splenomegaly and acute erythroleukemia induced by Friend virus infection (7, 64, 65, 67), while F-MuLV provides helper function and can be substituted for by other murine leukemia viruses (35). Specifically, the glycoprotein gp55, encoded by the SFFV env gene, acts as the transforming viral oncoprotein (2, 65).Several loci in the mouse genome that control Friend virus susceptibility have been identified. Fv1, Fv3, and Fv4 affect the ability of Friend virus to infect early erythroid progenitor cells. The Fv1 gene product inhibits Friend virus infection by interacting with the viral capsid protein (60). The Fv3 gene encodes cytidine deaminase Apobec3, which broadly inhibits retrovirus infection (42, 53, 57). The Fv4 gene product affects viral binding by competing for receptors on the cell membrane (59). Another set of genes, W, Sl, f, and Fv2, are required for the development or expansion of infected progenitor cells. Our previous work demonstrated that W, Sl, and f, which encode the kit receptor, its ligand SCF, and Smad5, respectively, also play key roles in the BMP4-dependent stress erythropoiesis pathway(46, 47, 55). Analysis of those mutants showed that Friend virus activates this pathway, leading to acute amplification of stress progenitors, which are targets of Friend virus in the spleen, and resulting in rapid onset of disease.The Friend virus susceptibility gene Fv2 encodes the stem cell-derived tyrosine kinase (Stk) receptor (48). A naturally occurring N-terminally truncated form of Stk, short-form Stk (Sf-Stk), is required for Friend virus susceptibility. Fv2^r/r mice, including C57BL/6, lack expression of Sf-Stk and are resistant to Friend virus infection, while full-length Stk expression is unaffected in these mice. An internal promoter within the Stk locus drives Sf-Stk expression, and Fv2^r/r mice harbor mutations in the internal promoter. Sf-Stk lacks the N-terminal ligand binding domain of full-length Stk but retains the transmembrane and tyrosine kinase domains. In vitro and in vivo expression of Sf-Stk in C57BL/6 bone marrow cells has been shown to confer Friend virus susceptibility to Fv2^r/r mice (18).Sf-Stk covalently interacts with gp55, resulting in constitutive activation of Sf-Stk (41). However, the mechanism by which this occurs is currently unknown. Here, we identify cysteines in the extracellular domains of Sf-Stk and gp55 that mediate this interaction. Furthermore, we demonstrate that while the association with gp55 is not required for the dimerization of Sf-Stk, the interaction of gp55 with Sf-Stk promotes tyrosine phosphorylation of Sf-Stk. In addition, while the extracellular cysteines in Sf-Stk promote retention of Sf-Stk in the cytoplasm in the absence of gp55, the interaction of Sf-Stk with gp55 through these cysteines results in enhanced cell surface localization of Sf-Stk. These changes in receptor activation and subcellular localization mediate the ability of Sf-Stk to induce gene expression and promote the Epo^ind growth of primary erythroblasts.