bluuebunny/crossref_metadata_2025 huggingface dataset:
The Pseudorabies Virus UL11 Protein Is a Virion Component Involved in Secondary Envelopment in the Cytoplasm
Authors: Kopp Martina , Granzow Harald , Fuchs Walter , Klupp Barbara G. , Mundt Egbert , Karger Axel , Mettenleiter Thomas C.
Published: April 2003

Homologs of the small tegument protein encoded by the UL11 gene of herpes simplex virus type 1 are conserved throughout all herpesvirus subfamilies. However, their function during viral replication has not yet been conclusively shown. Using a monospecific antiserum and an appropriate viral deletion and rescue mutant, we identified and functionally characterized the UL11 protein of the alphaherpesvirus pseudorabies virus (PrV). PrV UL11 encodes a protein with an apparent molecular mass of 10 to 13 kDa that is primarily detected at cytoplasmic membranes during viral replication. In the absence of the UL11 protein, viral titers were decreased approximately 10-fold and plaque sizes were reduced by 60% compared to wild-type virus. Intranuclear capsid maturation and nuclear egress resulting in translocation of DNA-containing capsids into the cytoplasm were not detectably affected. However, in the absence of the UL11 protein, intracytoplasmic membranes were distorted. Moreover, in PrV-ΔUL11-infected cells, capsids accumulated in the cytoplasm and were often found associated with tegument in aggregated structures such as had previously been demonstrated in cells infected with a PrV triple-mutant virus lacking glycoproteins E, I, and M (A. R. Brack, J. M. Dijkstra, H. Granzow, B. G. Klupp, and T. C. Mettenleiter, J. Virol. 73:5364-5372, 1999). Thus, the PrV UL11 protein, like glycoproteins E, I, and M, appears to be involved in secondary envelopment.
Human Rhinovirus Type 2 Is Internalized by Clathrin-Mediated Endocytosis
Authors: Snyers Luc , Zwickl Hannes , Blaas Dieter
Published: April 2003

Using several approaches, we investigated the importance of clathrin-mediated endocytosis in the uptake of human rhinovirus serotype 2 (HRV2). By means of confocal immunofluorescence microscopy, we show that K
+
depletion strongly reduces HRV2 internalization. Viral uptake was also substantially reduced by extraction of cholesterol from the plasma membrane with methyl-β-cyclodextrin, which can inhibit clathrin-mediated endocytosis. In accordance with these data, overexpression of dynamin K44A in HeLa cells prevented HRV2 internalization, as judged by confocal immunofluorescence microscopy, and strongly reduced infection. We also demonstrate that HRV2 bound to the surface of HeLa cells is localized in coated pits but not in caveolae. Finally, transient overexpression of the specific dominant-negative inhibitors of clathrin-mediated endocytosis, the SH3 domain of amphiphysin and the C-terminal domain of AP180, potently inhibited internalization of HRV2. Taken together, these results indicate that HRV2 uses clathrin-mediated endocytosis to infect cells.
Conformational Changes, Plasma Membrane Penetration, and Infection by Human Rhinovirus Type 2: Role of Receptors and Low pH
Authors: Brabec Marianne , Baravalle Günther , Blaas Dieter , Fuchs Renate
Published: April 2003

Human rhinovirus type 2 (HRV2) is internalized by members of the low-density lipoprotein (LDL) receptor (LDLR) family. It then progresses into late endosomes, where it undergoes conversion from D- to C-antigenicity at pH < 5.6. Upon uncoating, the viral RNA is transferred into the cytoplasm across the endsosomal membrane. However, C-antigenic particles fail to attach to LDLR; this raised the question of whether the virus remains attached to the receptors and is carried to late compartments or rather falls off at the higher pH in early endosomes. We therefore determined the pH dependence of virus-receptor dissociation and virus conversion to C-antigen under conditions preventing endocytosis.
35
S-HRV2 was attached to HeLa cells at 4°C and incubated in buffers of pH 7.4 to 5.0; levels of native virus and C-antigenic particles remaining cell associated or having been released into the medium were determined by immunoprecipitation. At pH 6.0, HRV2 was readily released from plasma membrane receptors in its native form, whereas at pH ≤ 5.4, it was entirely converted to C-antigen, which, however, only dissociated from the surface upon prolonged incubation. The antigenic conversion occurred at the same pH regardless of whether HRV2 was free in solution or bound to its receptors. These data suggest that, in vivo, the virus is no longer bound to its receptors when the antigenic conversion and uncoating occur in more acidic late endosomes. When virus was bound to HeLa cells at 4°C, converted into C-antigen by exposure to pH 5.3, and subsequently warmed to 34°C in the presence of bafilomycin (to prevent endosomal uncoating), viral de novo synthesis was detected. This study demonstrates for the first time that a nonenveloped virus such as HRV2 can infect from the plasma membrane when artificially exposed to low pH. This implies that the viral RNA can gain access to the cytoplasm from the plasma membrane.
Disulfide Bonding among μ1 Trimers in Mammalian Reovirus Outer Capsid: a Late and Reversible Step in Virion Morphogenesis
Authors: Odegard Amy L. , Chandran Kartik , Liemann Susanne , Harrison Stephen C. , Nibert Max L.
Published: April 2003

We examined how a particular type of intermolecular disulfide (ds) bond is formed in the capsid of a cytoplasmically replicating nonenveloped animal virus despite the normally reducing environment inside cells. The μ1 protein, a major component of the mammalian reovirus outer capsid, has been implicated in penetration of the cellular membrane barrier during cell entry. A recent crystal structure determination supports past evidence that the basal oligomer of μ1 is a trimer and that 200 of these trimers surround the core in the fenestrated T=13 outer capsid of virions. We found in this study that the predominant forms of μ1 seen in gels after the nonreducing disruption of virions are ds-linked dimers. Cys679, near the carboxyl terminus of μ1, was shown to form this ds bond with the Cys679 residue from another μ1 subunit. The crystal structure in combination with a cryomicroscopy-derived electron density map of virions indicates that the two subunits that contribute a Cys679 residue to each ds bond must be from adjacent μ1 trimers in the outer capsid, explaining the trimer-dimer paradox. Successful in vitro assembly of the outer capsid by a nonbonding mutant of μ1 (Cys679 substituted by serine) confirmed the role of Cys679 and suggested that the ds bonds are not required for assembly. A correlation between μ1-associated ds bond formation and cell death in experiments in which virions were purified from cells at different times postinfection indicated that the ds bonds form late in infection, after virions are exposed to more oxidizing conditions than those in healthy cells. The infectivity measurements of the virions with differing levels of ds-bonded μ1 showed that these bonds are not required for infection in culture. The ds bonds in purified virions were susceptible to reduction and reformation in situ, consistent with their initial formation late in morphogenesis and suggesting that they may undergo reduction during the entry of reovirus particles into new cells.
Recruitment of Tat to Heterochromatin Protein HP1 via Interaction with CTIP2 Inhibits Human Immunodeficiency Virus Type 1 Replication in Microglial Cells
Authors: Rohr Olivier , Lecestre Dominique , Chasserot-Golaz Sylvette , Marban Céline , Avram Dorina , Aunis Dominique , Leid Mark , Schaeffer Evelyne
Published: April 2003

The Tat protein of human immunodeficiency virus type 1 (HIV-1) plays a key role as inducer of viral gene expression. We report that Tat function can be potently inhibited in human microglial cells by the recently described nuclear receptor cofactor chicken ovalbumin upstream promoter transcription factor-interacting protein 2 (CTIP2). Overexpression of CTIP2 leads to repression of HIV-1 replication, as a result of inhibition of Tat-mediated transactivation. In contrast, the related CTIP1 was unable to affect Tat function and viral replication. Using confocal microscopy to visualize Tat subcellular distribution in the presence of the CTIPs, we found that overexpression of CTIP2, and not of CTIP1, leads to disruption of Tat nuclear localization and recruitment of Tat within CTIP2-induced nuclear ball-like structures. In addition, our studies demonstrate that CTIP2 colocalizes and associates with the heterochromatin-associated protein HP1α. The CTIP2 protein harbors two Tat and HP1 interaction interfaces, the 145-434 and the 717-813 domains. CTIP2 and HP1α associate with Tat to form a three-protein complex in which the 145-434 CTIP2 domain interacts with the N-terminal region of Tat, while the 717-813 domain binds to HP1. The importance of this Tat binding interface and of Tat subnuclear relocation was confirmed by analysis of CTIP2 deletion mutants. Our findings suggest that inhibition of HIV-1 expression by CTIP2 correlates with recruitment of Tat within CTIP2-induced structures and relocalization within inactive regions of the chromatin via formation of the Tat-CTIP2-HP1α complex. These data highlight a new mechanism of Tat inactivation through subnuclear relocalization that may ultimately lead to inhibition of viral pathogenesis.
Functional Surfaces of the Human Immunodeficiency Virus Type 1 Capsid Protein
Authors: von Schwedler Uta K. , Stray Kirsten M. , Garrus Jennifer E. , Sundquist Wesley I.
Published: April 2003

The human immunodeficiency virus type 1 initially assembles and buds as an immature particle that is organized by the viral Gag polyprotein. Gag is then proteolyzed to produce the smaller capsid protein CA, which forms the central conical capsid that surrounds the RNA genome in the mature, infectious virus. To define CA surfaces that function at different stages of the viral life cycle, a total of 48 different alanine-scanning surface mutations in CA were tested for their effects on Gag protein expression, processing, particle production and morphology, capsid assembly, and infectivity. The 27 detrimental mutations fall into three classes: 13 mutations significantly diminished or altered particle production, 9 mutations failed to assemble normal capsids, and 5 mutations supported normal viral assembly but were nevertheless reduced more than 20-fold in infectivity. The locations of the assembly-defective mutations implicate three different CA surfaces in immature particle assembly: one surface encompasses helices 4 to 6 in the CA N-terminal domain (NTD), a second surrounds the crystallographically defined CA dimer interface in the C-terminal domain (CTD), and a third surrounds the loop preceding helix 8 at the base of the CTD. Mature capsid formation required a distinct surface encompassing helices 1 to 3 in the NTD, in good agreement with a recent structural model for the viral capsid. Finally, the identification of replication-defective mutants with normal viral assembly phenotypes indicates that CA also performs important nonstructural functions at early stages of the viral life cycle.
A Long Terminal Repeat-Containing Retrotransposon of
Schizosaccharomyces pombe
Expresses a Gag-Like Protein That Assembles into Virus-Like Particles Which Mediate Reverse Transcription
Authors: Teysset Laure , Dang Van-Dinh , Kim Min Kyung , Levin Henry L.
Published: April 2003

The Tf1 element of
Schizosaccharomyces pombe
is a long terminal repeat-containing retrotransposon that encodes functional protease, reverse transcriptase, and integrase proteins. Although these proteins are known to be necessary for protein processing, reverse transcription, and integration, respectively, the function of the protein thought to be Gag has not been determined. We present here the first electron microscopy of Tf1 particles. We tested whether the putative Gag of Tf1 was required for particle formation, packaging of RNA, and reverse transcription. We generated deletions of 10 amino acids in each of the four hydrophilic domains of the protein and found that all four mutations reduced transposition activity. The N-terminal deletion removed a nuclear localization signal and inhibited nuclear import of the transposon. The two mutations in the center of Gag destabilized the protein and resulted in no virus-like particles. The C-terminal deletion caused a defect in RNA packaging and, as a result, low levels of cDNA. The electron microscopy of cells expressing a truncated Tf1 showed that Gag alone was sufficient for the formation of virus-like particles. Taken together, these results indicate that Tf1 encodes a Gag protein that is a functional equivalent of the Gag proteins of retroviruses.
Human Papillomavirus Type 16 E7 Peptide-Directed CD8+T Cells from Patients with Cervical Cancer Are Cross-Reactive with the Coronavirus NS2 Protein
Authors: Nilges Katja , Höhn Hanni , Pilch Henryk , Neukirch Claudia , Freitag Kirsten , Talbot P. J. , Maeurer Markus J.
Published: April 2003

Human papillomavirus type 16 (HPV16) E6 and E7 oncoproteins are required for cellular transformation and represent candidate targets for HPV-specific and major histocompatibility complex class I-restricted CD8+-T-cell responses in patients with cervical cancer. Recent evidence suggests that cross-reactivity represents the inherent nature of the T-cell repertoire. We identified HLA-A2 binding HPV16 E7 variant peptides from human, bacterial, or viral origin which are able to drive CD8+-T-cell responses directed against wild-type HPV16 E7 amino acid 11 to 19/20 (E711-19/20) epitope YMLDLQPET(T) in vitro. CD8+T cells reacting to the HLA-A2-presented peptide from HPV16 E711-19(20)recognized also the HLA-A2 binding peptide TMLDIQPED (amino acids 52 to 60) from the human coronavirus OC43 NS2 gene product. Establishment of coronavirus NS2-specific, HLA-A2-restricted CD8+-T-cell clones and ex vivo analysis of HPV16 E7 specific T cells obtained by HLA-A2 tetramer-guided sorting from PBL or tumor-infiltrating lymphocytes obtained from patients with cervical cancer showed that cross-reactivity with HPV16 E711-19(20)and coronavirus NS252-60represents a common feature of this antiviral immune response defined by cytokine production. Zero of 10 patients with carcinoma in situ neoplasia and 3 of 18 patients with cervical cancer showed ≥0.1% HPV16 E7-reactive T cells in CD8+peripheral blood lymphocytes. In vivo priming with HPV16 was confirmed in patients with cervical cancer or preinvasive HPV16-positive lesions using HLA-A2 tetramer complexes loaded with the E6-derived epitope KLPQLCTEL. In contrast, we could not detect E6-reactive T cells in healthy individuals. These data imply that the measurement of the HPV16 E711-19(20)CD8+-T-cell response may reflect cross-reactivity with a common pathogen and that variant peptides may be employed to drive an effective cellular immune response against HPV.
Crystal Structure of Swine Vesicular Disease Virus and Implications for Host Adaptation
Authors: Fry Elizabeth E. , Knowles Nick J. , Newman John W. I. , Wilsden Ginette , Rao Zihe , King Andrew M. Q. , Stuart David I.
Published: April 2003

Swine vesicular disease virus
(SVDV) is an
Enterovirus
of the family
Picornaviridae
that causes symptoms indistinguishable from those of foot-and-mouth disease virus. Phylogenetic studies suggest that it is a recently evolved genetic sublineage of the important human pathogen coxsackievirus B5 (CBV5), and in agreement with this, it has been shown to utilize the coxsackie and adenovirus receptor (CAR) for cell entry. The 3.0-Å crystal structure of strain UK/27/72 SVDV (highly virulent) reveals the expected similarity in core structure to those of other picornaviruses, showing most similarity to the closest available structure to CBV5, that of coxsackievirus B3 (CBV3). Features that help to cement together and rigidify the protein subunits are extended in this virus, perhaps explaining its extreme tolerance of environmental factors. Using the large number of capsid sequences available for both SVDV and CBV5, we have mapped the amino acid substitutions that may have occurred during the supposed adaptation of SVDV to a new host onto the structure of SVDV and a model of the SVDV/CAR complex generated by reference to the cryo-electron microscopy-visualized complex of CBV3 and CAR. The changes fall into three clusters as follows: one lines the fivefold pore, a second maps to the CAR-binding site and partially overlaps the site for decay accelerating factor (DAF) to bind to echovirus 7 (ECHO7), and the third lies close to the fivefold axis, where the low-density lipoprotein receptor binds to the minor group of rhinoviruses. Later changes in SVDV (post-1971) map to the first two clusters and may, by optimizing recognition of a pig CAR and/or DAF homologue, have improved the adaptation of the virus to pigs.
Interleukin-1 Inhibits Hepatitis C Virus Subgenomic RNA Replication by Activation of Extracellular Regulated Kinase Pathway
Authors: Zhu Haizhen , Liu Chen
Published: April 2003

Interleukin-1 (IL-1) plays an important role in the inflammatory process. Some studies have demonstrated that IL-1 production was impaired in patients with chronic infections of hepatitis C virus (HCV), implying that IL-1 may play a role in viral clearance. Using an HCV subgenomic replicon cell line, we demonstrate that IL-1 can effectively inhibit HCV subgenomic RNA replication and viral protein expression, suggesting that IL-1 has direct antiviral activity. The inhibitory effect is associated with the extracellular regulatory kinase (ERK) activation. In addition, we also show that IL-1 can induce one of the interferon-stimulated genes (ISGs), 1-8U, which exhibits antiviral activity. However, it has no effect on the other ISG, 6-16, suggesting that IL-1 induces novel antiviral pathways within a cell.
Hepatitis B Virus-Mediated Changes of Apolipoprotein mRNA Abundance in Cultured Hepatoma Cells
Authors: Norton Pamela A. , Gong Qiaoke , Mehta Anand S. , Lu Xuanyong , Block Timothy M.
Published: April 2003

An inverse correlation between hepatitis B virus (HBV) and steady-state levels of apolipoprotein AI and CIII mRNAs was observed in two hepatoma cell lines. Analysis of a third line containing an inducible viral genome implicated viral pregenomic RNA in apolipoprotein mRNA reduction. We conclude that HBV alters infected cells despite the absence of overt cytopathogenicity.
Activation of PKR by Bunyamwera Virus Is Independent of the Viral Interferon Antagonist NSs
Authors: Streitenfeld Hein , Boyd Amanda , Fazakerley John K. , Bridgen Anne , Elliott Richard M. , Weber Friedemann
Published: April 2003

Double-stranded RNA (dsRNA) is a by-product of viral RNA polymerase activity, and its recognition is one mechanism by which the innate immune system is activated. Cellular responses to dsRNA include induction of alpha/beta interferon (IFN) synthesis and activation of the enzyme PKR, which exerts its antiviral effect by phosphorylating the eukaryotic initiation factor eIF-2 alpha, thereby inhibiting translation. We have recently identified the nonstructural protein NSs of
Bunyamwera virus
(BUNV), the prototype of the family
Bunyaviridae
, as a virulence factor that blocks the induction of IFN by dsRNA. Here, we investigated the potential of NSs to inhibit PKR. We show that wild-type (wt) BUNV that expresses NSs triggered PKR-dependent phosphorylation of eIF-2 alpha to levels similar to those of a recombinant virus that does not express NSs (BUNdelNSs virus). Furthermore, the sensitivity of viruses in cell culture to IFN was independent of PKR and was not determined by NSs. PKR knockout mice, however, succumbed to infection approximately 1 day earlier than wt mice or mice deficient in expression of RNase L, another dsRNA-activated antiviral enzyme. Our data indicate that (i) bunyaviruses activate PKR, but are only marginally sensitive to its antiviral effect, and (ii) NSs is different from other IFN antagonists, since it inhibits dsRNA-dependent IFN induction but has no effect on the dsRNA-activated PKR and RNase L systems.
Characterization of the DNA-Binding Properties of the Origin-Binding Domain of Simian Virus 40 Large T Antigen by Fluorescence Anisotropy
Authors: Titolo S. , Welchner E. , White P. W. , Archambault J.
Published: April 2003

The affinity of the origin-binding domain (OBD) of simian virus 40 large T antigen for its cognate origin was measured at equilibrium using a DNA binding assay based on fluorescence anisotropy. At a near-physiological concentration of salt, the affinities of the OBD for site II and the core origin were 31 and 50 nM, respectively. Binding to any of the four 5′-GAGGC-3′ binding sites in site II was only slightly weaker, between 57 and 150 nM. Although the OBD was shown previously to assemble as a dimer on two binding sites spaced by 7 bp, we found that increasing the distance between both binding sites by 1 to 3 bp had little effect on affinity. Similar results were obtained for full-length T antigen in absence of nucleotide. Addition of ADP-Mg, which promotes hexamerization of T antigen, greatly increased the affinity of full-length T antigen for the core origin and for nonspecific DNA. The implications of these findings for the assembly of T antigen at the origin and its transition to a non-specific DNA helicase are discussed.
The Cell-Rounding Activity of the Vesicular Stomatitis Virus Matrix Protein Is due to the Induction of Cell Death
Authors: Kopecky Sarah A. , Lyles Douglas S.
Published: April 2003

The matrix (M) protein of vesicular stomatitis virus (VSV) expressed in the absence of other viral components causes many of the cytopathic effects of VSV, including an inhibition of host gene expression and the induction of cell rounding. It was recently shown that M protein also induces apoptosis in the absence of other viral components. This raises the possibility that the activation of apoptotic pathways causes the inhibition of host gene expression and cell rounding by M protein. To test this hypothesis, host gene expression and cell rounding were analyzed after the transfection of M mRNA into HeLa cells stably overexpressing Bcl-2 (HeLa-Bcl-2 cells). We have shown previously that Bcl-2 inhibits M-protein-induced apoptosis. Here, we show that activation of the apoptotic pathways downstream of Bcl-2 is not required for the inhibition of host gene expression by M protein. In contrast, overexpression of Bcl-2 inhibited cell rounding induced by M protein, indicating that apoptotic pathways downstream of Bcl-2 are required for the cell-rounding activities of M protein.
Itchy, a Nedd4 Ubiquitin Ligase, Downregulates Latent Membrane Protein 2A Activity in B-Cell Signaling
Authors: Ikeda Akiko , Caldwell Robert G. , Longnecker Richard , Ikeda Masato
Published: April 2003

Nedd4 family ubiquitin protein ligases (E3s) specifically associate with latent membrane protein 2A (LMP2A) of Epstein-Barr virus. Our previous studies analyzing LMP2A function in vitro have suggested that Nedd4 family E3s regulate LMP2A function. To determine the role of Nedd4 family E3s in LMP2A B-cell signaling, LMP2A transgenic (LMP2A
+
) mice were crossed with mice with the Itch-deficient (Itch
−/−
) background. Itchy, a mouse homologue of human AIP4, is a Nedd4 family E3 and is also the most abundant Nedd4 family E3 found in LMP2A affinity precipitates from B cells. There were significantly fewer B-cell receptor-positive B cells in spleen and bone marrow B cells in LMP2A
+
Itch
−/−
mice than in LMP2A
+
mice. In addition, LMP2A
+
Itch
−/−
bone marrow B cells formed larger colonies in cultures treated with interleukin-7 (IL-7) than control bone marrow B cells did. Finally, there was a dramatic increase in tyrosine phosphorylation of LMP2A and Syk in IL-7-cultured LMP2A
+
Itch
−/−
B cells. These results indicate that Nedd4 family E3s, in particular Itchy, downmodulate LMP2A activity in B-cell signaling.
Sphingosine Kinase-Dependent Migration of Immature Dendritic Cells in Response to Neurotoxic Prion Protein Fragment
Authors: Kaneider Nicole C. , Kaser Arthur , Dunzendorfer Stefan , Tilg Herbert , Wiedermann Christian J.
Published: April 2003

The concept that circulating dendritic cells mediate neuroinvasion in transmissible spongiform encephalopathies received strong support from recent observations that prion protein is expressed in myeloid dendritic cells. We observed that prion protein fragment 106-126 is a chemoattractant for monocyte-derived immature but not mature dendritic cells. Signaling events in chemotaxis involved enzymes downstream of Gqprotein and were inhibited by blockade of sphingosine kinase, suggesting transactivation of sphingosine-1-phosphate-dependent cell motility by prion protein.
Evolutionary Indicators of Human Immunodeficiency Virus Type 1 Reservoirs and Compartments
Authors: Nickle David C. , Jensen Mark A. , Shriner Daniel , Brodie Scott J. , Frenkel Lisa M. , Mittler John E. , Mullins James I.
Published: April 2003

In vivo virologic compartments are cell types or tissues between which there is a restriction of virus flow, while virologic reservoirs are cell types or tissues in which there is a relative restriction of replication. The distinction between reservoirs and compartments is important because therapies that would be effective against a reservoir may not be effective against viruses produced by a given compartment, and vice versa. For example, the use of cytokines to “flush out” long-lived infected cells in patients on highly active antiretroviral therapy (T. W. Chun, D. Engel, M. M. Berrey, T. Shea, L. Corey, and A. S. Fauci, Proc. Natl. Acad. Sci. USA 95:8869-8873, 1998) may be successful for a latent reservoir but may not impact a compartment in which virus continues to replicate because of poor drug penetration. Here, we suggest phylogenetic criteria to illustrate, define, and differentiate between reservoirs and compartments. We then apply these criteria to the analysis of simulated and actual human immunodeficiency virus type 1 sequence data sets. We report that existing statistical methods work quite well at detecting viral compartments, and we learn from simulations that viral divergence from a calculated most recent common ancestor is a strong predictor of viral reservoirs.
Exploitation of composting management for either reclamation of organic wastes or solid-phase treatment of contaminated environmental matrices
Authors: Vallini G , Gregorio S Di , Pera A , Cunha Queda A CF
Published: April 2003

This paper is an overview of the potential use of composting technology in programmes aimed at organic waste recycling (product-oriented perspective) or decomposition of hazardous materials (process-oriented perspective). This latter approach includes composting as a tool for bioremediation of environmental matrices, such as contaminated soils and sediments. In all above-mentioned cases, biological reactions that characterize composting must be managed carefully to allow putrescible residues to become a humified agricultural fertilizer with no phytotoxic effects, or the degradation of organic pollutants (e.g., aliphatic and aromatic hydrocarbons or halogenated solvents) to proceed to the highest extent with formation of innocuous end products. Thus, the fundamental aspects of controlling the microbial environment in composting matrices are singled out as a means for better evaluating the range of adverse conditions possibly responsible for hindering the correct evolution of the process within different applications. Key words: biopiles, bioremediation, composting, ex situ soil biotreatments, in-vessel systems, open systems, organo-nitro explosives, organic waste reclamation, polycyclic aromatic hydrocarbons, soil composting windrows.
Clonal growth and reproductive strategies of the understory tropical palmGeonoma brevispatha: an ontogenetic approach
Authors: Souza Alexandre F , Martins Fernando R , Bernacci Luis Carlos
Published: April 2003

We investigated the patterns of growth and reproduction of the understory clonal palm Geonoma brevispatha based on the identification of post-germinative ontogenetic stages, over a 3-year period. Genets were monitored in 100 5 × 5 m plots and 100 2 × 2 m subplots, in a 1-ha area of swamp forest in São Paulo state, southeastern Brazil. Ramets pass through four ontogenetic stages (bifid-leafed juveniles, pinnatifid-leafed stemless immatures, stemmed nonreproductive virgins, and reproducers). Leaf size, leaf number, and leaf production rate increased during ontogeny, but diameter growth rate was higher among immatures. Stem length, number of nodes, and leaf rachis length were positively correlated across ontogenetic stages, but crown height was smaller than stem length in adult palms because of frequent leaning. Leaf number and sexual fecundity increased with ramet size, but declined in larger, senescent ramets. Clonal fecundity preceded sexual fecundity, and sexual and clonal fecundity increased continuously with genet size. No relationship was found between sexual and clonal fecundity. Growth and survival strategies of G. brevispatha were consistent with the patterns found in other tropical clonal palm species. Sexual fecundity and cloning seem to be two integrated processes favored by environmental conditions that also support the growth of existing ramets.Key words: stage-structured populations, ontogenetic stages, swamp forest, Brazil, Atlantic forest, senescence.
The beneficial effect of ants on the reproductive success of Dyckia floribunda (Bromeliaceae), an extrafloral nectary plant
Authors: Vesprini José L , Galetto Leonardo , Bernardello Gabriel
Published: April 2003

Dyckia floribunda is a perennial herb from the Argentinian Chaco with extrafloral nectaries. Ants visited these nectaries while patrolling inflorescences and infructescences. We anticipated that ants attracted to extrafloral nectaries might protect the reproductive organs, increasing plant reproductive output. To evaluate the possibility of mutualism between D. floribunda and ant visitors, we determined whether ant-accessible plants showed a higher seed production than ant-excluded plants. Experimental fieldwork suggested a decrease in fruit set of ant-excluded plants compared with ant-accessible plants but the seed number per fruit was not affected by ant exclusion. Thus, total seed number per plant was highly reduced in treated spikes. Analyses of covariance confirmed these trends, indicating that total seed production per plant was strongly affected by ant exclusion. This study marks the first experimental report of this mutualistic association in Bromeliaceae.Key words: antplant interaction, Bromeliaceae, Chaco, Dyckia floribunda, fruit set, seed set, mutualism.
Aspects of inflorescence and floral development in the putative basal angiospermAmborella trichopoda(Amborellaceae)
Authors: Posluszny Usher , Tomlinson P Barry
Published: April 2003

Amborella has woody axes whose development is intrinsically plagiotropic and determinate. The tree habit is achieved through overtopping of older axes by basally produced younger axes, as in Mangenot's model. Inflorescence units, which are produced in the axils of distal leaves, may be described as extended cymes, each branch ending in a flower. Basal bracteoles have a decussate arrangement, which is modified to an alternate phyllotaxis distally. Flowers produce one or more additional bracteoles with a rapid transition to the spiral phyllotaxis of the broad overlapping tepals. In this transition the initially conical floral apex becomes invaginated to form a floral cup, with subsequent appendages appearing on its inner margin. The floral apex then forms the flat base of the cup but retains a discrete single tunica layer. The receptacular bowl is deepened and narrowed by the basal meristem of each appendage, the last formed floral organs usually consuming the floral meristem. Sexual parts are more numerous in male than female flowers, accounting for their size difference, but primordia of stamens and carpels are initially very similar. Floral symmetry is largely a consequence of close packing of appendages within the floral cup. In its initial stages of development the flower does not conform to any conventional floral model in angiosperms and is better regarded as highly specialized rather than ancestral in its synorganization. This is not unexpected in a lineage of such long independent evolution.Key words: Amborella, basal angiosperm, development, inflorescence, primitive flower.
Quantitative importance of staminodes for female reproductive success inParnassia palustrisunder contrasting environmental conditions
Authors: Sandvik Sylvi M , Totland Ørjan
Published: April 2003

The five sterile stamens, or staminodes, in Parnassia palustris act both as false and as true nectaries. They attract pollinators with their conspicuous, but non-rewarding tips, and also produce nectar at the base. We removed staminodes experimentally and compared pollinator visitation rate and duration and seed set in flowers with and without staminodes in two different populations. We also examined the relative importance of the staminode size to other plant traits. Finally, we bagged, emasculated, and supplementary cross-pollinated flowers to determine the pollination strategy and whether reproduction was limited by pollen availability. Flowers in both populations were highly dependent on pollinator visitation for maximum seed set. In one population pollinators primarily cross-pollinated flowers, whereas in the other the pollinators facilitated self-pollination. The staminodes caused increased pollinator visitation rate and duration to flowers in both populations. The staminodes increased female reproductive success, but only when pollen availability constrained female reproduction. Simple linear regression indicated a strong selection on staminode size, multiple regression suggested that selection on staminode size was mainly caused by correlation with other traits that affected female fitness.Key words: staminodes, insect activity, seed set, spatial variation, Parnassia palustris.
Early TertiaryChamaecyparisSpach from Axel Heiberg Island, Canadian High Arctic
Authors: Kotyk M EA , Basinger James F , McIver Elisabeth E
Published: April 2003

Exquisitely preserved fossil remains of Chamaecyparis Spach (Cupressaceae) have been recovered from Middle Eocene sediments of the Buchanan Lake Formation, Eureka Sound Group, of Axel Heiberg Island, Canadian Arctic Archipelago. Foliage consists of flattened, frondlike sprays considered typical for the genus. Leaves are decussate, scalelike, imbricate, appressed, and persistent. Seed cones are globose to subellipsoid, are borne on leafy peduncles, and bear 812 woody, peltate cone scales in a decussate arrangement. Seeds are two or more per scale, and winged. Within the genus, this fossil is most similar to extant Chamaecyparis pisifera (Siebold & Zucc.) Endl. of Japan, although the suite of features found in the fossil does not occur in any single living species of the genus. These fossil remains are assigned to a new species, Chamaecyparis eureka Kotyk sp. nov. A review of the fossil record indicates that Chamaecyparis eureka is the oldest known member of the genus, as the Late Cretaceous taxon Chamaecyparis corpulenta (Bell) McIver appears most closely related to Cupressus nootkatensis D. Don [= Chamaecyparis nootkatensis (D. Don) Spach], and should therefore be excluded from the genus Chamaecyparis. As revealed by the fossil assemblages of the Buchanan Lake deposits, Chamaecyparis was an uncommon constituent of lowland, swampforest communities growing at high paleolatitudes (about 78°N) during a period of global warmth prior to the onset of global climatic deterioration that led to Late Cenozoic glaciation. It was one of the few evergreen taxa in a largely deciduous broad-leaved and coniferous vegetation of early Tertiary regions in the far north.Key words: fossil, Tertiary, Chamaecyparis, Cupressaceae, Arctic, Canada.
Black fungal colonies as units of survival: hyphal mycosporines synthesized by rock-dwelling microcolonial fungi
Authors: Gorbushina Anna A , Whitehead Kenia , Dornieden Thomas , Niesse Astrid , Schulte Anette , Hedges John I
Published: April 2003

Microcolonial fungi, long-living modified mycelia frequently occurring on desert and pseudodesert rock surfaces, are exposed to strong ultraviolet (UV) radiation, desiccation, and nutrient scarcity. They lack ascospores; all their cells grow by mitotic cell divisions and possess a thick melanized cell wall. Colonies of several randomly selected microcolonial strains were cultured and their structure was examined by cryo-scanning and transmission electron microscopy. Extracts of nine strains were analyzed by high performance liquid chromatography interfaced with mass spectrometry for the presence of mycosporines. These UV-absorbing compounds, common in spores and other survival structures, were thought to be limited to reproductive morphogenesis and unknown in growing hyphae. Mycosporines were present in eight of the strains, and mycosporineglutaminolglucoside (λmax = 310 nm; MH+ = 465) was the major mycosporine detected. Mycosporines present in the vegetative fungal microcolonies may be associated with the high survival potential, nonexpansive intracolonial growth, and longevity of these fungi. Intrahyphal growth and recolonization of old cells by new ones were observed in all strains investigated.Key words: mycosporines, microcolonial fungi, intrahyphal growth, survival, resting structures, rock surface.
Short- and long-term effects of irradiance and CO2 availability on carbon fixation by two marine diatoms
Authors: Bartual Ana , Gálvez J Angel
Published: April 2003

Unbuffered and nutrient-replete dilute batch cultures of Skeletonema costatum Cleve and Phaeodactylum tricornutum Bohlin were grown at high and low CO2 availability conditions and two incident irradiances, 150 and 30 µmol photons·m2·s1. Long-term combined effects of such light and CO2 availability conditions on carbon fixation rates of both diatoms were compared. At saturating light, P. tricornutum showed higher photosynthetic rates than S. costatum at both CO2 conditions. However, under subsaturating light, carbon fixation rates of P. tricornutum were higher than observed for S. costatum only at low CO2. Skeletonema costatum showed a strong reduction in photosynthetic rates only when both resources, irradiance and CO2, were low. Short-term alterations of light and CO2 availability on carbon fixation showed that the response of S. costatum differed considerably from long-term trends: the short-term reduction in CO2 availability at both light levels resulted in a considerable decrease in the maximum photosynthetic rates. This effect was much less noticeable in P. tricornutum. The results show that, at saturating light, both diatoms maintain maximum photosynthetic rates under low CO2 levels, but only P. tricornutum is well adapted to rapid changes in this resource. This capacity of adaptation seems to be light dependent, since light limitation altered the responses of both diatoms to low CO2 availability conditions.Key words: CO2, 14C fixation, irradiance, Phaeodactylum tricornutum, Skeletonema costatum.
The relationship between nectar spur curvature in jewelweed (Impatiens capensis) and pollen removal by hummingbird pollinators
Authors: Travers Steven E , Temeles Ethan J , Pan Irvin
Published: April 2003

Floral nectar spurs are hypothesized to have had a major role in the evolution of floral diversity and plant-pollinator coadaptation. We examined variation in the degree of nectar spur curvature in two species of jewelweed (Impatiens capensis and Impatiens pallida) pollinated by different sets of pollinators. To distinguish between adaptive and nonadaptive explanations for between-species differences in curvature, we determined the relationship between spur curvature and pollen removal, which is one estimate of male reproductive success. Spur curvature exhibited considerable variation both within and among three populations, with spur angles ranging from 0° to 297°. A greenhouse experiment determined that spur curvature of I. capensis flowers has a broad-sense heritability of 0.636. Laboratory experiments indicated that flowers having recurved spurs deposit significantly more pollen grains on hummingbird visitors than flowers having perpendicular spurs, apparently as a result of greater contact between the androecium of curve-spurred flowers and the upper bill of hummingbirds. We also found a significant relationship between spur curvature and flower length, suggesting a developmental link between the two traits. We discuss the degree of spur curvature in bird-pollinated I. capensis as a function of both adaptive evolution and developmental constraint.Key words: pollination, nectar spurs, hummingbirds, Impatiens capensis, Impatiens pallida, pollen export, floral morphology, floral polymorphisms.
Understanding Holocene peat accumulation pattern of continental fens in western Canada
Authors: Yu Zicheng , Vitt Dale H , Campbell Ian D , Apps Michael J
Published: April 2003

Assessing carbon sinksource relationships in peatlands must be based on the understanding of processes responsible for long-term carbon accumulation patterns. In contrast with ombrogeneous bogs, however, the processes in geogeneous fens are poorly understood. Here, we present high-resolution Holocene peat accumulation and macrofossil data from a rich fen (Upper Pinto Fen (UPF)) in west-central Alberta, Canada. The ~8000-year chronology of a 397 cm peat core was controlled by 20 accelerator mass spectrometry14C dates. The paludified peatland initially consisted of diverse brown moss species and some Larix trees but was dominated by Scorpidium scorpioides from 6500 to 1300 calibrated years BP. The last 1300 years are characterized by the reappearance of Larix together with abundant woody materials and Cyperaceae, culminating in a sharp increase in Tomenthypnum nitens in the last several decades. During the Scorpidium-dominated period, the peat accumulation pattern derived from 1514C dates and 260 bulk density measurements indicates declining mass accumulation rates over time (i.e., convex agedepth curve), in contrast with the standard bog growth model (i.e., concave curve). The analysis of the UPF data using an extended model incorporating variable peat addition rates (PAR) to the catotelm suggests a unidirectional sevenfold decrease in PAR from 191.8 to 26.0 g dry mass·m2·year1during the ~5000-year "convex period". Decreasing vegetation production and (or) increasing acrotelm decomposition could have produced the convex pattern. Decreasing PAR might be owing to autogenically induced changes in local hydrology and nutrient availability, which are pronounced in the moisture-limited climate of the region and in peatlands that have a strong groundwater influence. The convex-pattern model, explicit to the height-induced long-term drying hypothesis, has important implications for building simulation models and for projecting future carbon dynamics of peatlands. Prior to recent human disturbance, the UPF site has a time-weighted mean carbon accumulation rate of 31.1 g C·m2·year1, ranging from 7.2 to 182.5 g C·m2·year1during the last 8000 years. This large variation results from the gradual decline of long-term accumulation and short-term climate-induced accumulation "pulses". The results imply that in the absence of climatic change, peatlands with a convex accumulation pattern will reach their growth limit sooner and that their carbon sequestration capacity will decline faster than would be expected given the concave-pattern model.Key words: carbon dynamics, moisture and nutrient availability, macrofossils, peatland model, brown moss Scorpidium scorpioides.
Seed bank size and composition ofBetula nana,Vaccinium uliginosum, andCampanula rotundifoliahabitats in Svalbard and northern Norway
Authors: Alsos Inger Greve , Spjelkavik Sigmund , Engelskjøn Torstein
Published: April 2003

The rare thermophilous species in the arctic archipelago of Svalbard are probably relicts from previous warmer periods and may be unable to reproduce sexually under the present climatic conditions. Germination of seeds, seed banks, and vegetative sprouts were studied in one Betula nana L., one Vaccinium uliginosum L., and two Campanula rotundifolia L. habitats in Svalbard. For comparison, one islet and three alpine habitats in northern Norway were studied. In each habitat, 50 soil cores (9.6 cm2) were collected and placed in a phytotron for germination tests. In Svalbard, no germinable seeds or seed bank of the three species were observed, whereas vegetative sprout densities were 83, 1060, and 211060/m2for B. nana, V. uliginosum, and C. rotundifolia, respectively. In northern Norway, germination percentages of the collected seeds were 59, 1027, and 1540%, seed bank densities of seedlings 212765, 21187, and 21374/m2, and vegetative sprouts densities 94206, 56674, and 94711/m2for B. nana, V. uliginosum, and C. rotundifolia, respectively. Less thermophilous plant species produced germinable seeds in Svalbard, as 12475405 seedlings/m2of 26 species germinated from the soil cores. In comparison, 53229626 seedlings/m2of 43 species germinated in soil cores from the alpine habitats and 3534 seedlings/m2of 26 species from the islet habitat. The results suggest that the most thermophilous species in Svalbard rarely produce germinable seeds under the present climatic conditions.Key words: arcticalpine, Betula nana, Campanula rotundifolia, seed bank, sexual reproduction, thermophily, Vaccinium uliginosum.
The peanut gynophore: a developmental and physiological perspective
Authors: Moctezuma Edgar
Published: April 2003

The peanut plant (Arachis hypogaea L.) produces flowers aerially, but it is able to "sow" its own seeds as a result of the growth of a specialized organ called the gynophore. The peanut gynophore is sensitive to light, touch, and gravity, and it is capable of transporting the recently fertilized ovules into the soil. For gynophore growth to occur, many physiological changes in plant hormone accumulation and distribution take place throughout its development. The unique characteristics and physiological events occurring during the gynophore's growth and development, such as its growth rates and indole-3-acetic acid redistribution during gravistimulation, will be reviewed. The peanut gynophore illustrates that the study of the odd or unusual can often provide valuable answers about the typical.Key words: Arachis hypogaea, geocarpy, gravitropism, gynophore, indole-3-acetic acid (IAA), peanut.
DISTRIBUTIONS OF MONEY IN MODEL MARKETS OF ECONOMY
Authors: CHAKRABORTI ANIRBAN
Published: April 2003

We study the distributions of money in a simple closed economic system for different types of monetary transactions. We know that for arbitrary and random sharing with locally conserving money transactions, the money distribution goes to the Gibb's distribution of statistical mechanics. We then consider the effects of savings, etc. and see how the distribution changes. We also propose a new model where the agents invest equal amounts of money in each transaction. We find that for short time-period, the money distribution obeys a power-law with an exponent very close to unity, and has an exponential tail; after a very long time, this distribution collapses and the entire amount of money goes to a tiny fraction of the population.
CONT–BOUCHAUD PERCOLATION MODEL INCLUDING TOBIN TAX
Authors: EHRENSTEIN GUDRUN
Published: April 2003

The Tobin tax is an often discussed method to tame speculation and get a source of income. The discussion is especially heated when the financial markets are in crisis. In this article we refer to the foreign exchange markets. The Tobin tax should be a small international tax affecting all currency transactions and thus consequently reducing destabilizing speculations. In this way this tax should take over a control function. By including the Tobin tax in the microscopic model of Cont and Bouchaud one finds that this tax could be the right method to control foreign exchange operations and to get a good source of income.