bluuebunny/crossref_metadata_2025 huggingface dataset:
Impact of Endogenous Intronic Retroviruses on Major Histocompatibility Complex Class II Diversity and Stability
Authors: Doxiadis Gaby G. M. , de Groot Nanine , Bontrop Ronald E.
Published: May 2008

The major histocompatibility complex (MHC) represents a multigene family that is known to display allelic and gene copy number variations. Primate species such as humans, chimpanzees (Pan troglodytes), and rhesus macaques (Macaca mulatta) showDRBregion configuration polymorphism at the population level, meaning that the number and content ofDRBloci may vary per haplotype. Introns of primateDRBalleles differ significantly in length due to insertions of transposable elements as long endogenous retrovirus (ERV) and human ERV (HERV) sequences in theDRB2,DRB6, andDRB7pseudogenes. Although the integration of intronic HERVs resulted sooner or later in the inactivation of the targeted genes, the fixation of these endogenous retroviral segments over long time spans seems to have provided evolutionary advantage. Intronic HERVs may have integrated in a sense or an antisense manner. On the one hand, antisense-oriented retroelements such as HERV-K14I, observed in intron 2 of theDRB7genes in humans and chimpanzees, seem to promote stability, as configurations/alleles containing these hits have experienced strong conservative selection during primate evolution. On the other hand, the HERVK3I present in intron 1 of allDRB2and/orDRB6alleles tested so far integrated in a sense orientation. The data suggest that multigenic regions in particular may benefit from sense introgressions by HERVs, as these elements seem to promote and maintain the generation of diversity, whereas these types of integrations may be lethal in monogenic systems, since they are known to influence transcript regulation negatively.
Cholesterol Effectively Blocks Entry of Flavivirus
Authors: Lee Chyan-Jang , Lin Hui-Ru , Liao Ching-Len , Lin Yi-Ling
Published: May 2008

Japanese encephalitis virus (JEV) and dengue virus serotype 2 (DEN-2) are enveloped flaviviruses that enter cells through receptor-mediated endocytosis and low pH-triggered membrane fusion and then replicate in intracellular membrane structures. Lipid rafts, cholesterol-enriched lipid-ordered membrane domains, are platforms for a variety of cellular functions. In this study, we found that disruption of lipid raft formation by cholesterol depletion with methyl-β-cyclodextrin or cholesterol chelation with filipin III reduces JEV and DEN-2 infection, mainly at the intracellular replication steps and, to a lesser extent, at viral entry. Using a membrane flotation assay, we found that several flaviviral nonstructural proteins are associated with detergent-resistant membrane structures, indicating that the replication complex of JEV and DEN-2 localizes to the membranes that possess the lipid raft property. Interestingly, we also found that addition of cholesterol readily blocks flaviviral infection, a result that contrasts with previous reports of other viruses, such as Sindbis virus, whose infectivity is enhanced by cholesterol. Cholesterol mainly affected the early step of the flavivirus life cycle, because the presence of cholesterol during viral adsorption greatly blocked JEV and DEN-2 infectivity. Flavirial entry, probably at fusion and RNA uncoating steps, was hindered by cholesterol. Our results thus suggest a stringent requirement for membrane components, especially with respect to the amount of cholesterol, in various steps of the flavivirus life cycle.
The Nucleocapsid Protein of Severe Acute Respiratory Syndrome Coronavirus Inhibits Cell Cytokinesis and Proliferation by Interacting with Translation Elongation Factor 1α
Authors: Zhou Bing , Liu Junli , Wang Qiuna , Liu Xuan , Li Xiaorong , Li Ping , Ma Qingjun , Cao Cheng
Published: May 2008

Severe acute respiratory syndrome coronavirus (SARS-CoV) is the etiological agent of SARS, an emerging disease characterized by atypical pneumonia. Using a yeast two-hybrid screen with the nucleocapsid (N) protein of SARS-CoV as a bait, the C terminus (amino acids 251 to 422) of the N protein was found to interact with human elongation factor 1-alpha (EF1α), an essential component of the translational machinery with an important role in cytokinesis, promoting the bundling of filamentous actin (F-actin). In vitro and in vivo interaction was then confirmed by immuno-coprecipitation, far-Western blotting, and surface plasmon resonance. It was demonstrated that the N protein of SARS-CoV induces aggregation of EF1α, inhibiting protein translation and cytokinesis by blocking F-actin bundling. Proliferation of human peripheral blood lymphocytes and other human cell lines was significantly inhibited by the infection of recombinant retrovirus expressing SARS-CoV N protein.
Small Interfering RNAs That Deplete the Cellular Translation Factor eIF4H Impede mRNA Degradation by the Virion Host Shutoff Protein of Herpes Simplex Virus
Authors: Sarma Nandini , Agarwal Deepali , Shiflett Lora A. , Read G. Sullivan
Published: May 2008

The herpes simplex virus (HSV) virion host shutoff (Vhs) protein is an endoribonuclease that accelerates decay of many host and viral mRNAs. Purified Vhs does not distinguish mRNAs from nonmessenger RNAs and cuts target RNAs at many sites, yet within infected cells it is targeted to mRNAs and cleaves those mRNAs at preferred sites including, for some, regions of translation initiation. This targeting may result in part from Vhs binding to the translation initiation factor eIF4H; in particular, several mutations in Vhs that abrogate its binding to eIF4H also abolish its mRNA-degradative activity, even though the mutant proteins retain endonuclease activity. To further investigate the role of eIF4H in Vhs activity, HeLa cells were depleted of eIF4H or other proteins by transfection with small interfering RNAs (siRNAs) 48 h prior to infection or mock infection in the presence of actinomycin D. Cellular mRNA levels were then assayed 5 h after infection. In cells transfected with an siRNA for the housekeeping enzyme glyceraldehyde-3-phosphate dehydrogenase, wild-type HSV infection reduced β-actin mRNA levels to between 20 and 30% of those in mock-infected cells, indicative of a normal Vhs activity. In contrast, in cells transfected with any of three eIF4H siRNAs, β-actin mRNA levels were indistinguishable in infected and mock-infected cells, suggesting that eIF4H depletion impeded Vhs-mediated degradation. Depletion of the related factor eIF4B did not affect Vhs activity. The data suggest that eIF4H binding is required for Vhs-induced degradation of many mRNAs, perhaps by targeting Vhs to mRNAs and to preferred sites within mRNAs.
Mutations in the Spacer Peptide and Adjoining Sequences in Rous Sarcoma Virus Gag Lead to Tubular Budding
Authors: Keller Paul W. , Johnson Marc C. , Vogt Volker M.
Published: May 2008

All orthoretroviruses encode a single structural protein, Gag, which is necessary and sufficient for the assembly and budding of enveloped virus-like particles from the cell. The Gag proteins of Rous sarcoma virus (RSV) and human immunodeficiency virus type 1 (HIV-1) contain a short spacer peptide (SP or SP1, respectively) separating the capsid (CA) and nucleocapsid (NC) domains. SP or SP1 and the residues immediately upstream are known to be critical for proper assembly. Using mutagenesis and electron microscopy analysis of insect cells or chicken cells overexpressing RSV Gag, we defined the SP assembly domain to include the last 8 residues of CA, all 12 residues of SP, and the first 4 residues of NC. Five- or two-amino acid glycine-rich insertions or substitutions in this critical region uniformly resulted in the budding of abnormal, long tubular particles. The equivalent SP1-containing HIV-1 Gag sequence was unable to functionally replace the RSV sequence in supporting normal RSV spherical assembly. According to secondary structure predictions, RSV and HIV-1 SP/SP1 and adjoining residues may form an alpha helix, and what is likely the functionally equivalent sequence in murine leukemia virus Gag has been inferred by mutational analysis to form an amphipathic alpha helix. However, our alanine insertion mutagenesis did not provide evidence for an amphipathic helix in RSV Gag. Taken together, these results define a short assembly domain between the folded portions of CA and NC, which is essential for formation of the immature Gag shell.
Annexin II Incorporated into Influenza Virus Particles Supports Virus Replication by Converting Plasminogen into Plasmin
Authors: LeBouder Fanny , Morello Eric , Rimmelzwaan Guus F. , Bosse Françoise , Péchoux Christine , Delmas Bernard , Riteau Béatrice
Published: May 2008

For influenza viruses to become infectious, the proteolytic cleavage of hemagglutinin (HA) is essential. This usually is mediated by trypsin-like proteases in the respiratory tract. The binding of plasminogen to influenza virus A/WSN/33 leads to the cleavage of HA, a feature determining its pathogenicity and neurotropism in mice. Here, we demonstrate that plasminogen also promotes the replication of other influenza virus strains. The inhibition of the conversion of plasminogen into plasmin blocked influenza virus replication. Evidence is provided that the activation of plasminogen is mediated by the host cellular protein annexin II, which is incorporated into the virus particles. Indeed, the inhibition of plasminogen binding to annexin II by using a competitive inhibitor inhibits plasminogen activation into plasmin. Collectively, these results indicate that the annexin II-mediated activation of plasminogen supports the replication of influenza viruses, which may contribute to their pathogenicity.
The UL25 Gene Product of Herpes Simplex Virus Type 1 Is Involved in Uncoating of the Viral Genome
Authors: Preston Valerie G. , Murray Jill , Preston Christopher M. , McDougall Iris M. , Stow Nigel D.
Published: May 2008

Studies on the herpes simplex virus type 1 UL25-null mutant KUL25NS have shown that the capsid-associated UL25 protein is required at a late stage in the encapsidation of viral DNA. Our previous work on UL25 with the UL25 temperature-sensitive (
ts
) mutant
ts
1204 also implicated UL25 in a role at very early times in the virus growth cycle, possibly at the stage of penetration of the host cell. We have reexamined this mutant and discovered that it had an additional
ts
mutation elsewhere in the genome. The
ts
1204 UL25 mutation was transferred into wild-type (wt) virus DNA, and the UL25 mutant
ts
1249 was isolated and characterized to clarify the function of UL25 at the initial stages of virus infection. Indirect immunofluorescence assays and in situ hybridization analysis of virus-infected cells revealed that the mutant
ts
1249 was not impaired in penetration of the host cell but had an uncoating defect at the nonpermissive temperature. When
ts
1249-infected cells were incubated initially at the permissive temperature to allow uncoating of the viral genome and subsequently transferred to the restrictive temperature, a DNA-packaging defect was evident. The results suggested that
ts
1249, like KUL25NS, had a block at a late stage of DNA packaging and that the packaged genome was shorter than the full-length genome. Examination of
ts
1249 capsids produced at the nonpermissive temperature revealed that, in comparison with wt capsids, they contained reduced amounts of UL25 protein, thereby providing a possible explanation for the failure of
ts
1249 to package full-length viral DNA.
Antibodies to Envelope Glycoprotein of Dengue Virus during the Natural Course of Infection Are Predominantly Cross-Reactive and Recognize Epitopes Containing Highly Conserved Residues at the Fusion Loop of Domain II
Authors: Lai Chih-Yun , Tsai Wen-Yang , Lin Su-Ru , Kao Chuan-Liang , Hu Hsien-Ping , King Chwan-Chuen , Wu Han-Chung , Chang Gwong-Jen , Wang Wei-Kung
Published: May 2008

The antibody response to the envelope (E) glycoprotein of dengue virus (DENV) is known to play a critical role in both protection from and enhancement of disease, especially after primary infection. However, the relative amounts of homologous and heterologous anti-E antibodies and their epitopes remain unclear. In this study, we examined the antibody responses to E protein as well as to precursor membrane (PrM), capsid, and nonstructural protein 1 (NS1) of four serotypes of DENV by Western blot analysis of DENV serotype 2-infected patients with different disease severity and immune status during an outbreak in southern Taiwan in 2002. Based on the early-convalescent-phase sera tested, the rates of antibody responses to PrM and NS1 proteins were significantly higher in patients with secondary infection than in those with primary infection. A blocking experiment and neutralization assay showed that more than 90% of anti-E antibodies after primary infection were cross-reactive and nonneutralizing against heterologous serotypes and that only a minor proportion were type specific, which may account for the type-specific neutralization activity. Moreover, the E-binding activity in sera of 10 patients with primary infection was greatly reduced by amino acid replacements of three fusion loop residues, tryptophan at position 101, leucine at position 107, and phenylalanine at position 108, but not by replacements of those outside the fusion loop of domain II, suggesting that the predominantly cross-reactive anti-E antibodies recognized epitopes involving the highly conserved residues at the fusion loop of domain II. These findings have implications for our understanding of the pathogenesis of dengue and for the future design of subunit vaccine against DENV as well.
Differential Antigen Requirements for Protection against Systemic and Intranasal Vaccinia Virus Challenges in Mice
Authors: Kaufman David R. , Goudsmit Jaap , Holterman Lennart , Ewald Bonnie A. , Denholtz Matthew , Devoy Colleen , Giri Ayush , Grandpre Lauren E. , Heraud Jean-Michel , Franchini Genoveffa , Seaman Michael S. , Havenga Menzo J. E. , Barouch Dan H.
Published: May 2008

The development of a subunit vaccine for smallpox represents a potential strategy to avoid the safety concerns associated with replication-competent vaccinia virus. Preclinical studies to date with subunit smallpox vaccine candidates, however, have been limited by incomplete information regarding protective antigens and the requirement for multiple boost immunizations to afford protective immunity. Here we explore the protective efficacy of replication-incompetent, recombinant adenovirus serotype 35 (rAd35) vectors expressing the vaccinia virus intracellular mature virion (IMV) antigens A27L and L1R and extracellular enveloped virion (EEV) antigens A33R and B5R in a murine vaccinia virus challenge model. A single immunization with the rAd35-L1R vector effectively protected mice against a lethal systemic vaccinia virus challenge. The rAd35-L1R vector also proved more efficacious than the combination of four rAd35 vectors expressing A27L, L1R, A33R, and B5R. Moreover, serum containing L1R-specific neutralizing antibodies afforded postexposure prophylaxis after systemic vaccinia virus infection. In contrast, the combination of rAd35-L1R and rAd35-B5R vectors was required to protect mice against a lethal intranasal vaccinia virus challenge, suggesting that both IMV- and EEV-specific immune responses are important following intranasal infection. Taken together, these data demonstrate that different protective antigens are required based on the route of vaccinia virus challenge. These studies also suggest that rAd vectors warrant further assessment as candidate subunit smallpox vaccines.
Structural Analysis of Major Species Barriers between Humans and Palm Civets for Severe Acute Respiratory Syndrome Coronavirus Infections
Authors: Li Fang
Published: May 2008

It is believed that a novel coronavirus, severe acute respiratory syndrome coronavirus (SARS-CoV), was passed from palm civets to humans and caused the epidemic of SARS in 2002 to 2003. The major species barriers between humans and civets for SARS-CoV infections are the specific interactions between a defined receptor-binding domain (RBD) on a viral spike protein and its host receptor, angiotensin-converting enzyme 2 (ACE2). In this study a chimeric ACE2 bearing the critical N-terminal helix from civet and the remaining peptidase domain from human was constructed, and it was shown that this construct has the same receptor activity as civet ACE2. In addition, crystal structures of the chimeric ACE2 complexed with RBDs from various human and civet SARS-CoV strains were determined. These structures, combined with a previously determined structure of human ACE2 complexed with the RBD from a human SARS-CoV strain, have revealed a structural basis for understanding the major species barriers between humans and civets for SARS-CoV infections. They show that the major species barriers are determined by interactions between four ACE2 residues (residues 31, 35, 38, and 353) and two RBD residues (residues 479 and 487), that early civet SARS-CoV isolates were prevented from infecting human cells due to imbalanced salt bridges at the hydrophobic virus/receptor interface, and that SARS-CoV has evolved to gain sustained infectivity for human cells by eliminating unfavorable free charges at the interface through stepwise mutations at positions 479 and 487. These results enhance our understanding of host adaptations and cross-species infections of SARS-CoV and other emerging animal viruses.
Comparison of G-to-A Mutation Frequencies Induced by APOBEC3 Proteins in H9 Cells and Peripheral Blood Mononuclear Cells in the Context of Impaired Processivities of Drug-Resistant Human Immunodeficiency Virus Type 1 Reverse Transcriptase Variants
Authors: Knoepfel Stefanie Andrea , Salisch Nadine Christina , Huelsmann Peter Michael , Rauch Pia , Walter Hauke , Metzner Karin Jutta
Published: May 2008

APOBEC3 proteins can inhibit human immunodeficiency virus type 1 (HIV-1) replication by inducing G-to-A mutations in newly synthesized viral DNA. However, HIV-1 is able to overcome the antiretroviral activity of some of those enzymes by the viral protein Vif. We investigated the impact of different processivities of HIV-1 reverse transcriptases (RT) on the frequencies of G-to-A mutations introduced by APOBEC3 proteins. Wild-type RT or the M184V, M184I, and K65R+M184V RT variants, which are increasingly impaired in their processivities, were used in the context of a
vif
-deficient molecular HIV-1 clone to infect H9 cells and peripheral blood mononuclear cells (PBMCs). After two rounds of infection, a part of the HIV-1
env
gene was amplified, cloned, and sequenced. The M184V mutation led to G-to-A mutation frequencies that were similar to those of the wild-type RT in H9 cells and PBMCs. The frequencies of G-to-A mutations were increased after infection with the M184I virus variant. This effect was augmented when using the K65R+M184V virus variant (
P
< 0.001). Overall, the G-to-A mutation frequencies were lower in PBMCs than in H9 cells. Remarkably, 38% ± 18% (mean ± standard deviation) of the
env
clones derived from PBMCs did not harbor any G-to-A mutation. This was rarely observed in H9 cells (3% ± 3%). Our data imply that the frequency of G-to-A mutations induced by APOBEC3 proteins can be influenced by the processivities of HIV-1 RT variants. The high number of nonmutated clones derived from PBMCs leads to several hypotheses, including that additional antiretroviral mechanisms of APOBEC3 proteins other than their deamination activity might be involved in the inhibition of
vif
-deficient viruses.
Interactions of Murine APOBEC3 and Human APOBEC3G with Murine Leukemia Viruses
Authors: Rulli Samuel J. , Mirro Jane , Hill Shawn A. , Lloyd Patricia , Gorelick Robert J. , Coffin John M. , Derse David , Rein Alan
Published: May 2008

APOBEC3 proteins are cytidine deaminases which help defend cells against retroviral infections. One antiviral mechanism involves deaminating dC residues in minus-strand DNA during reverse transcription, resulting in G-to-A mutations in the coding strand. We investigated the effects of mouse APOBEC3 (mA3) and human APOBEC3G (hA3G) upon Moloney murine leukemia virus (MLV). We find that mA3 inactivates MLV but is significantly less effective against MLV than is hA3G. In contrast, mA3 is as potent against human immunodeficiency virus type 1 (HIV-1, lacking the protective Vif protein) as is hA3G. The two APOBEC3 proteins are packaged to similar extents in MLV particles. Dose-response profiles imply that a single APOBEC3 molecule (or oligomer) is sufficient to inactivate an MLV particle. The inactivation of MLV by mA3 and hA3G is accompanied by relatively small reductions in the amount of viral DNA in infected cells. Although hA3G induces significant levels of G-to-A mutations in both MLV and HIV DNAs, and mA3 induces these mutations in HIV DNA, no such mutations were detected in DNA synthesized by MLV inactivated by mA3. Thus, MLV has apparently evolved to partially resist the antiviral effects of mA3 and to totally resist the ability of mA3 to induce G-to-A mutation in viral DNA. Unlike the resistance of HIV-1 and human T-cell leukemia virus type 1 to hA3G, the resistance of MLV to mA3 is not mediated by the exclusion of APOBEC from the virus particle. The nature of its resistance and the mechanism of inactivation of MLV by mA3 are completely unknown.
Interaction between Polypeptide 3ABC and the 5′-Terminal Structural Elements of the Genome of Aichi Virus: Implication for Negative-Strand RNA Synthesis
Authors: Nagashima Shigeo , Sasaki Jun , Taniguchi Koki
Published: May 2008

Secondary structural elements at the 5′ end of picornavirus genomic RNA function as
cis
-acting replication elements and are known to interact specifically with viral P3 proteins in several picornaviruses. In poliovirus, ribonucleoprotein complex formation at the 5′ end of the genome is required for negative-strand synthesis. We have previously shown that the 5′-end 115 nucleotides of the Aichi virus genome, which are predicted to fold into two stem-loops (SL-A and SL-C) and one pseudoknot (PK-B), act as a
cis
-acting replication element and that correct folding of these structures is required for negative-strand synthesis. In this study, we investigated the interaction between the 5′-terminal 120 nucleotides of the genome and the P3 proteins, 3AB, 3ABC, 3C, and 3CD, by gel shift assay and Northwestern analysis. The results showed that 3ABC and 3CD bound to the 5′-terminal region specifically. The binding of 3ABC was observed on both assays, while that of 3CD was detected only on Northwestern analysis. No binding of 3AB or 3C was observed. Binding assays using mutant RNAs demonstrated that disruption of the base pairings of the stem of SL-A and one of the two stem segments of PK-B (stem-B1) abolished the 3ABC binding. In addition, the specific nucleotide sequence of stem-B1 was responsible for the efficient 3ABC binding. These results suggest that the interaction of 3ABC with the 5′-terminal region of the genome is involved in negative-strand synthesis. On the other hand, the ability of 3CD to interact with the 5′-terminal region did not correlate with the RNA replication ability.
Functional Domains and the Antiviral Effect of the Double-Stranded RNA-Dependent Protein Kinase PKR from
Paralichthys olivaceus
Authors: Zhu Rong , Zhang Yi-Bing , Zhang Qi-Ya , Gui Jian-Fang
Published: May 2008

The double-stranded RNA (dsRNA)-dependent protein kinase PKR is thought to mediate a conserved antiviral pathway by inhibiting viral protein synthesis via the phosphorylation of the alpha subunit of eukaryotic initiation factor 2 (eIF2α). However, little is known about the data related to the lower vertebrates, including fish. Recently, the identification of PKR-like, or PKZ, has addressed the question of whether there is an orthologous PKR in fish. Here, we identify the first fish
PKR
gene from the Japanese flounder
Paralichthys olivaceus
(
PoPKR
).
PoPKR
encodes a protein that shows a conserved structure that is characteristic of mammalian PKRs, having both the N-terminal region for dsRNA binding and the C-terminal region for the inhibition of protein translation. The catalytic activity of
PoPKR
is further evidence that it is required for protein translation inhibition in vitro.
PoPKR
is constitutively transcribed at low levels and is highly induced after virus infection. Strikingly,
PoPKR
overexpression increases eIF2α phosphorylation and inhibits the replication of
Scophthalmus maximus
rhabdovirus (SMRV) in flounder embryonic cells, whereas phosphorylation and antiviral effects are impaired in transfected cells expressing the catalytically inactive PKR-K421R variant, indicating that
PoPKR
inhibits virus replication by phosphorylating substrate eIF2α. The interaction between
PoPKR
and eIF2α is demonstrated by coimmunoprecipitation assays, and the transfection of
PoPKR
-specific short interfering RNA further reveals that the enhanced eIF2α phosphorylation is catalyzed by
PoPKR
during SMRV infection. The current data provide significant evidence for the existence of a PKR-mediated antiviral pathway in fish and reveal considerable conservation in the functional domains and the antiviral effect of PKR proteins between fish and mammals.
Hypovirus Papain-Like Protease p48 Is Required for Initiation but Not for Maintenance of Virus RNA Propagation in the Chestnut Blight Fungus
Cryphonectria parasitica
Authors: Deng Fuyou , Nuss Donald L.
Published: May 2008

The prototypic hypovirus CHV1-EP713, responsible for virulence attenuation (hypovirulence) of the chestnut blight fungus
Cryphonectria parasitica
, encodes two papain-like proteases, p29 and p48. Protein p29 has been shown to be dispensable for hypovirus RNA replication and to act as a suppressor of RNA silencing. Here we describe a role for p48 in hypovirus RNA propagation. CHV1-EP713 infectious cDNA clones in which the p48 coding region was deleted, Δp48, were unable to establish infection in
C. parasitica
when introduced as a DNA form by transformation or as a coding strand transcript by electroporation. However, the Δp48 mutant virus RNA was rescued when p48 was provided in
trans
. Surprisingly, the Δp48 mutant viruses retained replication competence in the apparent absence of p48 following transmission to wild-type
C. parasitica
and successive subculturing. The replicating Δp48 mutant virus was reduced in RNA accumulation by 60% both in the absence and presence of p48 provided in
trans
and was transmitted through asexual spores (conidia) at a rate 3 to 8% of that for full-length CHV1-EP713. Complementary analysis of strains expressing p48 or containing the replicating Δp48 mutant virus showed that like p29, p48 contributes to virus-mediated suppression of host pigmentation and conidiation, although to a lesser extent, and is dispensable for hypovirus-mediated hypovirulence. The combined results suggest that papain-like protease p48 plays an essential role in the initiation but not the maintenance of virus RNA propagation and also contributes to the regulation of viral RNA accumulation and vertical transmission.
High soil fertility decreases sucrose content and susceptibility of loblolly pine roots to ectomycorrhizal infection by Pisolithus tinctorius
Authors: Marx Donald H. , Hatch A. B. , Mendicino J. F.
Published: May 2008

Pinus taeda seedlings were grown for 10 weeks without ectomycorrhizae under low and high rates of complete soil fertility, as well as these rates minus N, P, K, or Ca. Seedling growth, inorganic chemical content of needles, and soluble-carbohydrate content of short roots were significantly affected by soil fertility, especially the high rates of N and P. Number and length of lateral and short roots were not affected by soil fertility. Sucrose and fructose contents of short roots were lowest at high levels of N and P; glucose was not detected. Seedlings from each of the 10 fertility combinations were inoculated with vegetative inoculum of Pisolithus tinctorius and incubated for 19 to 21 days at a moderate level of complete soil fertility. Significantly more ectomycorrhizae were formed on seedlings from the complete low fertility rate than on those from the high rates of N and P. Ectomycorrhizal development on seedlings from the other fertility combinations were intermediate from these extremes. Sucrose content of short roots determined before inoculation was significantly correlated with ectomycorrhizal development and accounted for 85% of the variation in susceptibility of short roots to infection by P. tinctorius. Fructose content of short roots was not correlated with ectomycorrhizal development. These results indicate that high levels of N and Pin soil decrease sucrose content of short roots of loblolly pine and decrease their susceptibility to ectomycorrhizal development by P. tinctorius.
A glycerine–water–DMSO–carmine stain used to determine the effect of IPC, EDTA, and aeration on the accumulation of metaphase figures in root tips of Pinus resinosa
Authors: Bonga J. M.
Published: May 2008

A squash technique based on the use of glycerine, water, dimethyl sulfoxide, and carmine (GWDC) at high temperature (150–160 °C) was developed for root tips of Pinus resinosa Ait. The chromosomes stained intensely and most of the cells spread into a single layer. This allowed determination of the number of metaphase figures in the root tips and thus analysis of the effect of various chemical–physical factors on metaphase figure accumulation. Isopropyl-N-phenylcarbamate (IPC) stimulated accumulation of metaphase figures more under well aerated conditions than under poorly aerated ones. Without IPC, aeration had an inhibitory effect. Ethylenediamine tetraacetate (EDTA) had a slightly stimulatory effect and acted synergistically with IPC.
RAPD markers reveal diversity within and among clonal and seedling stands of aspen in Yellowstone National Park, U.S.A.
Authors: Tuskan G.A. , Francis K.E. , Russ S.L. , Romme W.H. , Turner M.G.
Published: May 2008

Fire in 1988 created a situation that allowed a rare aspen seedling recruitment event to occur within Yellowstone National Park. Through the use of (i) 194 randomly amplified polymorphic DNA (RAPD) markers from 14 select primers, (ii) measures of population diversity, and (iii) neighbor-joining analysis it was determined that the postfire aspen seedling population contains greater diversity within each of the four sampled stands than that found within all of the 10 sampled mature aspen stands that pre-existed the fire. Unlike previous studies, a large portion of the molecular variation in both the seedling and mature populations was partitioned among stands. Furthermore, variation was unexpectedly detected among ramets within each mature stand. The mature stands appear to be clonally derived, yet individual ramets within stands varied slightly and incrementally in their RAPD profile. These data suggest that somatic mutations may be occurring and accumulating in clonal aspen stands. A proposed scenario of stand establishment and development involving the accumulation of somatic mutations and elimination of genetically related seedlings arising from a rare founder event provides the theoretical basis for the observed differences among and within seedling and mature stands of aspen in Yellowstone National Park.
Bark stripping of young Pinussylvestris by Alcesalces on the individual, stand, and landscape level in Sweden
Authors: Faber William E. , Thorson Erik M.
Published: May 2008

Physical characteristics of Scots pine (Pinussylvestris L.) trees bark stripped by moose (Alcesalces L.) and frequencies of bark stripping were quantified at the Grimsö Wildlife Research Area in south-central Sweden during July 1995. Twenty-one young Scots pine stands evenly distributed over two areas of differing forest productivity were included in the study. Each stand was systematically plot-surveyed to determine the frequency of affected Scots pine trees. Additionally, we quantified data (i.e., 13 variables) on 420 recently (i.e., spring 1995) bark-stripped pine trees located through visual walking surveys of each stand. Less than 3% of the trees within the susceptible height range (1.5–4.0 m) were bark stripped annually, and 99% of these trees were between 1.5 and 4 m in height and wounds were concentrated within the 3- and 4-year-old internodes. There was a weak positive relationship between frequency of bark stripping and forest productivity at the stand and landscape levels, whereas weak negative relationships were found between bark-stripping frequency and stand size and bark-stripping frequency and pine stem density. Overall, the results suggest bark stripping has a minor impact on the trees. Forestry practices to reduce bark-stripping damage are discussed.
Fungal associates of five bark beetle species colonizing Norway spruce
Authors: Krokene Paal , Solheim Halvor
Published: May 2008

Fungi associated with five bark beetle species colonizing Norway spruce (Piceaabies (L.) Karst.) were isolated from beetle-inoculated logs. Ipstypographus L., an aggressive tree-killing bark beetle, was associated with a different range of blue-stain fungi than the nonaggressive Pityogeneschalcographus L., Polygraphuspoligraphus L., and Hylurgopspalliatus Gyll. The flora of the nonaggressive Ipsduplicatus Sahib. was similar to that of I. typographus. The pathogenic fungus Ceratocystispolonica (Siem.) C. Moreau, and other blue-stain fungi, were isolated in high frequency from inoculations with both Ips species. Pathogenic blue-stain fungi were absent, or isolated in low frequencies, from inoculations with the other nonaggressive beetle species. With the exception of I. duplicatus, these results support the hypothesis that aggressive bark beetles carry more pathogenic blue-stain fungi than other bark beetles and indicate that pathogenic fungi are important for aggressive bark beetles to kill trees.
Factors regulating throughfall flux in a New Hampshire forested landscape
Authors: Lovett Gary M. , Nolan Scott S. , Driscoll Charles T. , Fahey Timothy J.
Published: May 2008

This study examined the regulation of throughfall flux by six factors: precipitation amount, dry deposition, precipitation acidity, precipitation ion concentrations, forest type, and leaf area index. The influences of these factors were determined by analyzing the spatial and temporal variance in net throughfall flux (throughfall minus precipitation) in the forested landscape of the Hubbard Brook Experimental Forest (White Mountains, New Hampshire, U.S.A.). Throughfall was collected during the growing seasons of 1989–1992 in eight sites encompassing differences in elevation, forest type (including mature northern hardwood, young northern hardwood, and spruce–fir–birch types), and canopy surface area. Regression analysis of single-event data showed that within a forest type, the most important factor regulating the event-to-event variation in net throughfall flux was the amount of precipitation, suggesting that canopy exchange (leaching and uptake) regulated the net throughfall flux for most solutes. The leaching of Ca2+ and Mg2+ were significantly higher in more acid rain events. Hydrogen ion, NH4+, and NO3− were all retained by at least some of the canopies. However, the data indicate that the retention mechanism for NO3− was saturated under ambient concentrations in precipitation, whereas the retention of NH4+ and H+ was not saturated and increased with increasing concentrations of those ions in precipitation. Duration of the interevent dry periods was not a significant factor in most of the regressions, contrasting with results from studies at other sites. Regressions using precipitation amount, length of the dry period, and precipitation acidity as independent variables explained 50–90% of the variance for most sites and solutes. For SO42−, which had a small net throughfall flux relative to the precipitation flux, the regressions were not significant or explained <50% of the between-event variation in net throughfall flux. For most solutes, forest type was the major factor controlling spatial variation in net throughfall flux among stands. Particularly strong differences between forest types were noted for NO3−, SO42−, NH4+, and Cl−. The contrast in net throughfall flux between two young hardwood stands of different leaf area index indicated that leaf area was a major controlling factor for K+, H +, and total organic carbon.
Branch Growth of Pinusresinosa Ait. with Particular Reference to Potassium Nutrition
Authors: Madgwick H. A. I.
Published: May 2008

Branch production on 10 Pinusresinosa stands of varying potassium status and stocking was closely related to total foliage on the stand. The production of branch material per unit of needle weight was little affected by either potassium status or stocking. Since needle longevity is closely related to potassium status, the ratio of branch production to needle production increased with potassium status.
The Growth Response of Young Jack Pine to Nitrogen and Phosphorus
Authors: Calvert R. F. , Armson K. A.
Published: May 2008

N as urea at rates of 0 and 100 kg/ha and P as triple superphosphate at 0, 200, and 400 kg/ha were applied to 5-year-old jack pine growing in a well-drained, sandy, orthic humo-ferric podzol. The urea was broadcast, but two types of application were made for the P: it was either broadcast or placed in the soil about each tree. One half of each plot received herbicide treatment. Tree measurements and foliage sampling were made later in the year of treatment and also during the next year. Fertilizer treatments increased the needle weight of foliage produced in the treatment year but did not affect height. Simazine–paraquat herbicide reduced height growth the year after treatment. From the changes in nutrient concentrations it is argued that K is a most likely limiting nutrient.
A Data Structure Analogue for Modelling Tree Crowns
Authors: Smith Stephen , Scoullar K.
Published: May 2008

A rooted-tree computer data structure is used as an analogue of coniferous tree crowns in building a simulation model of a single tree. Submodels of branch death and the allocation of stored reserves are used to illustrate the model. The programming language used is PL/1.
Survey for Gnathotrichussulcatus (Coleoptera: Scolytidae) in a Commercial Sawmill with the Pheromone, Sulcatol
Authors: Mclean J. A. , Borden J. H.
Published: May 2008

Ethanol and sulcatol (6-methyl-5-hepten-2-ol), primary attractant and population aggregation pheromone, respectively, for Gnathotrichussulcatus, were deployed alone or in combination in traps at 10 locations in a commercial sawmill at Chemainus, B.C. The traps were in operation for the last week of the months, April through October 1974, and caught 3098 beetles. Sulcatol was the only significant treatment. Traps baited with it alone or in combination with ethanol caught over 98% of the beetles. There was no significant interaction between ethanol and sulcatol. There was a distinct bimodal seasonal trend in numbers of beetles caught. Locations with the greatest catches of beetles were those where unseasoned lumber was stored, which suggests that beetles either emerged from and (or) oriented to such lumber.
Relations entre la densité de peuplement et la qualité du bouleau jaune
Authors: Fortin A. , Roberge M. R. , Vézina P. E.
Published: May 2008

A sugar maple (Acersaccharum Marsh.) – yellow birch (Betulaalleghaniensis Britton)–beech (Fagusgrandifolia Ehrh.) stand has been treated in 1963 by two thinning intensities. Yellow birch stems of the sample plots established before cutting have been studied in 1972. The various characteristics determining stem quality were considered in factorial analysis. Branch number did not affect stem quality to any degree; curve and diseases of the stem contributed equally to its qualitative depreciation. Thinning intensity did not substantially affect branch number and curve of the stem. Competition removal in a radius up to 6 m around yellow birch did not cause stem diseases. On the contrary, the growth increase inherent in the thinning has helped wound closure and has checked disease entry.
Concrete Frost along an Elevational Gradient in New Hampshire
Authors: Fahey Timothy J. , Lang Gerald E.
Published: May 2008

The occurrence and duration of concrete frost were observed at 28 forested sites along an elevational gradient on a New Hampshire mountain. The presence of concrete frost was determined with an aluminum probe on 17 dates between November 1973 and June 1974. Concrete frost was found at all sample points in soils of coniferous forest ecosystems above 950-m elevation from mid-November to mid-May; some concrete frost remained into early June. Concrete frost occurred at most sample points in soils of transition zone forests that were composed of mixed hardwoods and conifers for 4 months, in soils of northern hardwoods forests for 2 months, and in soils of successional fir stands at low elevations for 4 months. Winter weather conditions and differences in leaf litter insulation probably accounted for the variation of soil frost beneath these forest types.
Effects of Photoperiod on Growth and Peroxidase in Three Hybrid Poplars
Authors: Wray Paul H. , Gordon John C.
Published: May 2008

Three Populus hybrids (Tristis No. 1, Crandon, and Wisconsin No. 5) were grown for 5 weeks under 12- or 18- photoperiods in growth chambers. At four times during growth, dry weight and total peroxidase activity and isoenzyme expression were determined. The 12-h photoperiod resulted in less dry weight accumulation and height growth in all clones. Total peroxidase activity in the first mature internode was related to growth in the Crandon clone, whereas changes in the activity of specific anodic peroxidase isoenzymes were related to growth in the Tristis No. 1 and Wisconsin No. 5 clones.
Frost-Hardiness Development in Pinussilvestris L. Seedlings at Different Levels of Potassium and Calcium Fertilization
Authors: Christersson Lars
Published: May 2008

The influence of potassium and calcium contents on frost-hardiness development of 6-month-old seedlings of Pinussilvestris L. was investigated. The frost hardiness was determined by cooling the shoots of the seedlings at a rate of 1 °C per minute. There was no correlation between frost-hardiness development and potassium content, calcium content, or the ratio of potassium to calcium content.
Photosynthetic responses of black walnut (Juglansnigra) to shading
Authors: Dean T. J. , Pallardy S. G. , Cox G. S.
Published: May 2008

Photosynthetic characteristics and morphology of leaves of black walnut (Juglansnigra L.) seedlings grown under different types and degrees of shade were investigated by measuring insitu gross photosynthesis (Ps) and by microscopic study of leaf material. During the growing season of 1979, seedlings were subjected to artificial shading of two types: the first type simulated two overstory densities (leaf-area indices of 1 and 2) with corresponding proportions of sunflecks and total transmission of 50 and 21%, respectively, of incident photosynthetically active radiation (PAR, 400–700 nm); the second consisted of two densities of greenhouse shading screen which transmitted approximately 16 and 3% of incident PAR. From quantum efficiency values derived from Ps – quantum flux density response curves it was determined that the walnut seedlings adjusted photosynthetically to shade. Quantum efficiency increased as much as 44% with the densest shading. Light-saturated Ps did not appear to decline with increased shading if sunflecks were present, and it declined only 18% under complete shade that transmitted about 16% of incident PAR. Estimated daily photosynthesis per unit leaf area for black walnut growing under heavy and complete shade (3% of incident PAR) was nearly one-half that of the unshaded control. Shading resulted in plants that possessed leaves that were thinner, had less palisade mesophyll, had lower stomatal density, and had more chlorophyll per unit of leaf area. These data indicate that black walnut seedlings have the capacity for substantial photosynthesis under shade and may be more shade tolerant than silvicultural classifications suggest.
Characteristics of trees damaged by sugar maple borer, Glycobiusspeciosus (Say)
Authors: Newton William G. , Allen Douglas C.
Published: May 2008

The distribution, abundance, and characteristics of sugar maples (Acersaccharum Marsh.) at time of attack by sugar maple borer, Glycobiusspeciosus (Say), were determined on 1.9 ha in Wanakena, New York. Twenty-six percent (n = 78) of the maple stems in the study area were damaged. Average dbh of trees attacked remained the same throughout the 40-year history of the infestation. Mean dbh of trees at time of attack by sugar maple borer was 18.7 cm. Percent cross-sectional area growth at breast height in control trees (3.7%) was significantly greater (P < 0.01) than growth of attacked trees (1.9%) the year preceeding year of attack. Annual mean percentage growth of successfully attacked trees declined 5–10 years prior to year of attack. The cryptic nature of much borer damage indicates that previous estimates of impact are conservative.
Loss of mass and nutrient changes of decaying woody roots in lodgepole pine forests, southeastern Wyoming
Authors: Yavitt Joseph B. , Fahey Timothy J.
Published: May 2008

Woody root decomposition was studied in two lodgepole pine (Pinuscontorta Dougl. ex Loud. ssp. latifolia (Engelm.) Critchfield) stands in the Medicine Bow Mountains, Wyoming, from samples obtained beneath stumps that remained following: (i) partial cuttings 1–2, 5–7, 12–15, and 45 years ago, and (ii) fires that originated in the present stands 80 and 110 years ago. The specific gravity of root wood declined exponentially (mean k = 0.0415 year−1) during the first 15 years of decay. Mass-loss rates were faster for smaller (0.5–1.0 cm) than larger (2.6–5.0 cm) size classes of material, and rates were slightly faster on the site with fine textured soil than on the site with gravelly soil. Bark decay rates were not calculated due to a number of errors associated with estimating bark specific gravity. Nitrogen and calcium concentrations increased in both root wood and bark after 80 years of decay. Rapid decreases in potassium and phosphorous concentration occurred in the first 15 years of decay; however, contents increased slightly in wood in the advanced decay classes. Magnesium concentration initially increased with decay but thereafter decreased after moderate decay. Woody roots of lodgepole pine appear to persist for many years (>110 years) following death of the aboveground portion of the tree, but nitrogen immobilization in decaying root wood (10 mg N•m−2•year−1) is much less than the amount immobilized in aboveground detritus (500 mg N•m−2•year−1).
The stomatal response of red alder and black cottonwood to changing water status
Authors: Pezeshki S. R. , Hinckley T. M.
Published: May 2008

Response of stomata of newly planted red alder (Alnusrubra Bong.) and black cottonwood (Populustrichocarpa Torr. & Gray) to periods of water stress and changes in light intensity, vapor pressure gradient, and xylem pressure potential were studied in the field and in controlled environments. The results indicated that soil drought had a pronounced effect, reducing stomatal conductance in both species. Lower predawn xylem pressure potential values at the beginning of the day resulted in lower stomatal conductance irrespective of vapor pressure gradient in both species. Under field conditions of high soil water potential, stomatal conductance decreased as xylem pressure potential decreased below −1.0 MPa in black cottonwood and −1.1 MPa in red alder. As soil water potential decreased to −0.13 MPa, the threshold value of xylem pressure potential resulting in stomatal closure shifted from −1.0 to −0.5 MPa in cottonwood; it did not change in alder. Laboratory experiments indicated that cottonwood had greater rates of net photosynthesis on a per-unit leaf-area basis as compared with red alder. The mean maximum photosynthetic rates were 0.46 mg CO2•m−2•s−1 in black cottonwood and 0.25 mg CO2•m−2•s−1 in red alder. Net CO2 uptake also had a temperature optimum around 20 °C when the corresponding relative humidity was about 50%. Both species, when compared with other deciduous hardwoods, could be ranked as relatively drought sensitive.