Rock phosphate solubilization and colonization of maize rhizosphere by wild and genetically modified strains of Penicillium rugulosum

Maize root colonization and phosphate solubilizing activity of the fungus Penicillium rugulosum were assessed in a greenhouse trial using soil-plant microcosms. The bacterial gene hph conferring resistance to hygromicin B was introduced by electroporation in the wild-type strain IR-94MF1 of P. rugulosum and one transformant, w-T3, was selected. Maize plants were grown for 5 weeks in a P-poor soil and fertilized with a Florida apatite mineral, with Navay, an apatite rock deposit from Venezuela, or with simple superphosphate. Inoculation treatments included strain IR-94MF1, transformant w-T3 and two IR-94MF1 UV-induced mutants with enhanced (Mps++) or reduced (Mps-) in vitro mineral phosphate solubilizing activity. In the absence of P fertilization, inoculation with any P. rugulosum isolate significantly reduced the size of the total and P-solubilizing bacterial community present in maize rhizosphere. The bacterial community significantly increased in maize inoculated with IR-94MF1 and w-T3 when P was added as apatites Navay or Florida. All P. rugulosum strains were able to stimulate the growth of maize plants as indicated by 3.6 to 28.6% increases in dry matter yields. In the presence of rock phosphate, P uptake by maize plants inoculated with the two mutants Mps++ and Mps- was not always in agreement with their P-solubilizing phenotypes. Strain IR-94MF1 and transformant w-T3 increased P assimilation by the plants fertilized with Navay rock phosphate by 26 and 38%, respectively. In this treatment, w-T3 showed its highest significant maize rhizosphere colonization. With the simple superphosphate treatment, w-T3 increased P uptake in plants by 8% over the uninoculated control and also decreased significantly the community size of total bacteria, total fungi, and P-solubilizing fungi in the rhizosphere.

Assessing respiratory status from a distance

Home care professionals are increasingly required to manage patients with chronic respiratory conditions. Under PPS, an even stronger mandate requires that every intervention be timely, necessary, valuable, cost effective, and lead to positive patient outcomes. This article focuses on the cost benefits, tools, and interventions available that enhance the ability to assess respiratory status "from a distance."

Establishment of a gene transfer system for Pseudozyma flocculosa, an antagonistic fungus of powdery mildew fungi

A reliable DNA-mediated transformation system has been developed for Pseudozyma flocculosa, a fungus that is antagonistic to powdery-mildew fungi. Plasmids harboring various selectable markers under the control of different promoters were tested. Molecular analyses demonstrated that successful transformation could be achieved using a plasmid that confers resistance to hygromycin B under the control of the Ustilago maydis hsp70 promoter and terminator sequences. On average, 1-40 (mean = 20) transformants were obtained per 10 microg of linearized DNA per 10(8) protoplasts. Southern analysis of the transformants revealed that, in each case, the vector had integrated in multiple tandem copies into the genome of P. flocculosa, and that integration events were random. Pulsed-field gel electrophoresis was employed to separate the genome of P. flocculosa into at least 11 chromosomes with sizes ranging from 0.55 Mb to 2.9 Mb. Hybridization with the plasmid indicated that integration of vector DNA had occurred in one to several chromosomes depending on the transformant examined.

Identification of a γ-Interferon–Responsive Element in the Promoter of the Human Macrophage Scavenger Receptor A Gene

Abstract —In the present study, we demonstrate γ-interferon (γ-IFN)–inducible scavenger receptor A (SR-A) mRNA expression during the early stages of THP-1 and blood monocyte differentiation. Predominant induction of SR-A type II mRNA parallels the increased accumulation of cholesteryl esters under these conditions. A potential signal transducer and activator of transcription (STAT1) binding site (γ-interferon activation site) in the SR-A promoter demonstrates γ-IFN–inducible DNA binding activity and is most likely responsible for the γ-IFN–dependent expression of an SR-A promoter–luciferase fusion construct. In contrast, γ-IFN inhibits SR-A expression in mature macrophages as well as after prolonged γ-IFN incubation of THP-1 monocytes. Taken together, these results demonstrate opposite effects of γ-IFN on SR-A expression and activity during the early versus late stages of monocyte maturation. γ-IFN–induced STAT1 activation, leading to increased SR-A expression, could therefore play an important role in the initial steps of foam cell formation and xanthomatosis.

Genetic Variability of Canadian Populations of the Sapstain Fungus Ophiostoma piceae

ABSTRACT Genetic diversity was studied in seven Canadian populations of Ophiostoma piceae, the most prevalent sapstain fungus in Canadian softwoods. A total of 239 single-spore isolates were recovered following a systematic survey of sapstain fungi in logs and lumber at seven selected sawmills in six Canadian provinces (British Columbia, Alberta, Saskatchewan, Ontario, Québec, and New Brunswick). Sampling was carried out on five commercially important softwood species: balsam fir (Abies balsamea), white spruce (Picea glauca), black spruce (Picea mariana), jack pine (Pinus banksiana), and lodgepole pine (Pinus con-torta var. latifolia). The A and B mating types occurred at equal frequency (MAT A/ MAT B = 1.00:1.13) over all populations. Pseudo-allelic frequencies were estimated at each of 24 putative genetic loci by scoring for presence or absence of random amplified polymorphic DNA fragments generated by five primers. A total of 237 haplotypes were found among the 239 isolates, revealing a high level of genotypic diversity among isolates. Total gene diversity (H(T) = 0.414) was mostly attributable to diversity within populations (H(S) = 0.369). Thus, only 11.2% of the total variability was attributable to frequency differences among populations. An analysis of molecular variance revealed that most genetic variability occurred within subpopulations within mills (84.3%; P < 0.001), whereas low but statistically significant levels of genetic differentiation were also observed among subpopulations within populations (5.4%; P < 0.001) and among populations (10.3%; P < 0.001). Estimates of Nei' genetic distances were not correlated with geographic distances among sampling locations (r = -0.092; P = 0.310), although principal component analysis indicated that subpopulations located east of Saskatchewan were grouped on the same side of the second principal component axis. Overall, results suggest moderate genetic differentiation of O. piceae in Canada, which is consistent with the observation that sexual reproduction is frequently observed in this fungus.

Comparative study of a novel nucleoside analogue (Troxatyl, troxacitabine, BCH-4556) and AraC against leukemic human tumor xenografts expressing high or low cytidine deaminase activity

PURPOSE

Troxacitabine (beta-L-dioxolane cytidine, BCH-4556; Troxatyl, BioChem Pharma Inc.) is a novel nucleoside analogue, which in experiments demonstrated potent antitumor activity against both leukemias and solid tumors. Since troxacitabine is a cytidine nucleoside analogue like AraC (1-beta-D-arabinofuranosylcytosine), which is currently used in the treatment of acute myelogenous leukemia, we compared the in vivo antileukemic activity of troxacitabine with that of AraC in human leukemia xenograft models.

METHODS

The antiproliferative activity of troxacitabine and AraC was analyzed on hemapoietic cell lines by use of a thymidine incorporation assay. For in vivo studies, we compared troxacitabine with AraC by using equitotoxic schedules of the two nucleosides optimized for therapeutic activity. The antileukemic activity of both drugs was evaluated by measurement of their effect on the percent increased lifespan.

RESULTS

AraC had good in vitro antiproliferative activity (IC50 = 14 nM) but was ineffective in vivo against the HL60 promyelocyte leukemia cell line (treated vs control, T/C = 105%). Troxacitabine, which in contrast to AraC is not a substrate for cytidine deaminase, showed potent in vitro and in vivo activity in the same model (IC50 = 53 nM and T/C = 272% to 422%). The poor in vivo activity of AraC against HL60 leukemia cells could be due to the high cytidine deaminase (CDA; EC 3.5.4.5) activity in this cell line. This hypothesis was tested with CCRF-CEM T-lymphoblastoid leukemia cells which have undetectable levels of CDA activity. Short-term exposure of these leukemia cell lines to both drugs indicated that AraC was indeed significantly more effective in the CCRF-CEM cell line than in HL60. In contrast, the antiproliferative activity of troxacitabine was similar for both cell lines. These observations were extended to in vivo studies. Mice bearing CCRF-CEM tumor xenografts were treated with AraC and troxacitabine. In this model, T/C values were comparable for both drugs and ranged from 138% to 157%.

CONCLUSIONS

Our findings indicate that troxacitabine is likely to be effective not only against solid tumors with high CDA activity but also in leukemias which have developed resistance to AraC due to increased CDA levels; this suggests that troxacitabine is a promising agent for the treatment of cancer. Indeed, significant antileukemic activity has been observed with troxacitabine in a phase I clinical trial in patients with primary refractory or relapsed acute myeloid leukemias (AML).

Involvement of oxysterols and lysophosphatidylcholine in the oxidized LDL-induced impairment of serum albumin synthesis by HEPG2 cells

Oxidized low density lipoproteins (Ox-LDLs) are increasingly thought to be a key element in atherogenesis. We have previously reported that serum albumin has important antioxidant properties and that a reduced synthesis of albumin may represent a crucial point in the overall antioxidant defense. In the present work, we aimed at determining whether Ox-LDL could modulate albumin synthesis in cultured human hepatocytes (HepG2 cells). With the use of enzyme immunoassay and radiolabeled leucine incorporation followed by specific immunoprecipitation, Ox-LDL was found to lead to a dose-dependent decrease in albumin secretion. Moreover, the protein synthesis and mRNA levels were decreased in the presence of Ox-LDL, as assessed by Northern blot analysis. Because oxysterols and lysophospholipids are key components of Ox-LDL, we tested the effects of oxysterols (7-ketocholesterol and 25-hydroxycholesterol) and lysophosphatidylcholine on albumin secretion and expression. In our experimental conditions, we found that incubations with oxysterols or lysophosphatidylcholine at pathophysiological concentrations similar to those measured in Ox-LDLs reproduced the above-mentioned inhibitory effects on albumin synthesis. On the basis of our in vitro data, we propose that this newly described biological effect of Ox-LDL might partly explain the findings of epidemiological studies indicating that reduced levels of serum albumin are associated with increased mortality.

The double-stranded RNA-binding protein Staufen is incorporated in human immunodeficiency virus type 1: evidence for a role in genomic RNA encapsidation

Human Staufen (hStau), a double-stranded RNA (dsRNA)-binding protein that is involved in mRNA transport, is incorporated in human immunodeficiency virus type 1 (HIV-1) and in other retroviruses, including HIV-2 and Moloney murine leukemia virus. Sucrose and Optiprep gradient analyses reveal cosedimentation of hStau with purified HIV-1, while subtilisin assays demonstrate that it is internalized. hStau incorporation in HIV-1 is selective, is dependent on an intact functional dsRNA-binding domain, and quantitatively correlates with levels of encapsidated HIV-1 genomic RNA. By coimmunoprecipitation and reverse transcription-PCR analyses, we demonstrate that hStau is associated with HIV-1 genomic RNA in HIV-1-expressing cells and purified virus. Overexpression of hStau enhances virion incorporation levels, and a corresponding, threefold increase in HIV-1 genomic RNA encapsidation levels. This coordinated increase in hStau and genomic RNA packaging had a significant negative effect on viral infectivity. This study is the first to describe hStau within HIV-1 particles and provides evidence that hStau binds HIV-1 genomic RNA, indicating that it may be implicated in retroviral genome selection and packaging into assembling virions.

Fungi that cause sapstain in Canadian softwoods

The Canadian forest products industry suffers considerable losses due to discoloration caused by sapstain fungi. Although studied for a number of years, the identity, biology, and ecology of these fungi are still only partly understood. To determine which fungi caused stain problems, a detailed survey was conducted at seven selected sawmills across Canada. In summer 1997, fresh logs and lumber were set aside in the mills 1 month prior to sampling for fungi. We excluded bark-beetle-attacked wood and our logs remained free from their attack during storage. Five commercially important softwood species, Abies balsamea (L.) Mill., Picea mariana (Mill.) B.S.P., Picea glauca (Moench) Voss, Pinus contorta Dougl., and Pinus banksiana Lamb., were included in the studies. A total of 1863 isolates were isolated from stained and adjacent areas on test wood, and were identified based on their morphological and physiological characteristics and mating compatibility to 13 different species representing five genera. The most commonly encountered genus, Ophiostoma (97%), was represented by nine species. A more diverse range of fungi was found in logs than in lumber; some species were more frequently isolated from one type of substrate and rarely (or not at all) from the other. No fungal species occurred exclusively in a particular region or wood substrate.Key words: bluestain, lumber, logs, Ophiostoma, Ceratocystis.

Genetic Structure of Cronartium ribicola Populations in Eastern Canada

ABSTRACT The genetic structure of populations of Cronartium ribicola was studied by sampling nine populations from five provinces in eastern Canada and generating DNA profiles using nine random amplified polymorphic DNA markers. Most of the total gene diversity (H(t) = 0.386) was present within populations (H(w) = 0.370), resulting in a low level of genetic differentiation among populations in northeastern North America (F(st) = 0.062). A hierarchical analysis of genetic structure using an analysis of molecular variance (AMOVA) revealed no statistically significant genetic differentiation among provinces or among regions. Yet, genetic differentiation among populations within regions or provinces was small (AMOVA phi(st) = 0.078) but statistically significant (P < 0.001) and was several orders of magnitude larger than differentiation among provinces. This is consistent with a scenario of subpopulations within a metapopulation, in which random drift following migration and new colonization are major evolutionary forces. A phenetic analysis using genetic distances revealed no apparent correlation between genetic distance and the province of origin of the populations. The hypothesis of isolation-by-distance in the eastern populations of C. ribicola was rejected by computing Mantel correlation coefficients between genetic and geographic distance matrices (P > 0.05). These results show that eastern Canadian provinces are part of the same white pine blister rust epidemiological unit. Nursery distribution systems are controlled provincially, with virtually no seedling movement among provinces; therefore, infected nursery material may not play an important role in the dissemination of this disease. Long-distance spore dispersal across provincial boundaries appears to be an epidemiologically important factor for this pathogen.

Apolipoprotein E and atherosclerosis: insight from animal and human studies

Major advances have been made in our understanding of the role of apolipoprotein E (apoE) in the onset and development of atherosclerosis. Increasing evidence from both animal and human studies suggests that apoE is able to protect against atherosclerosis by: a) promoting efficient uptake of triglyceride-rich lipoproteins from the circulation; b) maintaining normal macrophage lipid homeostasis; c) playing a role in cellular cholesterol efflux and reverse cholesterol transport; d) acting as an antioxidant; e) inhibiting platelet aggregation; and f) modulating immune function. In humans, apoE is polymorphic, and this genetic variation has a strong effect on its antiatherogenic characteristics. Thus, compared to the epsilon3 allele, the epsilon4 allele promotes atherosclerosis, whereas the epsilon2 allele is either pro- or anti-atherogenic, depending on the influence of both environmental and genetic factors. ApoE and its gene are prime targets for therapeutic intervention aimed at preventing or treating atherosclerotic vascular disease.

Mitochondrial iron sequestration in dopamine-challenged astroglia: role of heme oxygenase-1 and the permeability transition pore

Little is currently known concerning the mechanisms responsible for the excessive deposition of redox-active iron in the substantia nigra of subjects with Parkinson's disease (PD). In the present study, we demonstrate that dopamine promotes the selective sequestration of non-transferrin-derived iron by the mitochondrial compartment of cultured rat astroglia and that the mechanism underlying this novel dopamine effect is oxidative in nature. We also provide evidence that up-regulation of the stress protein heme oxygenase-1 (HO-1) is both necessary and sufficient for mitochondrial iron trapping in dopamine-challenged astroglia. Finally, we show that opening of the mitochondrial transition pore (MTP) mediates the influx of non-transferrin-derived iron into mitochondria of dopamine-stimulated and HO-1-transfected astroglia. Our findings provide an explanation for the pathological iron sequestration, mitochondrial insufficiency, and amplification of oxidative injury reported in the brains of PD subjects. Pharmacological blockade of transition metal trapping by "stressed" astroglial mitochondria (e.g., using HO-1 inhibitors or modulators of the MTP) may afford effective neuroprotection in patients with PD and other neurological afflictions.

Rubidium marking of Anopheles stephensi (Diptera: Culicidae)

Immature Anopheles stephensi Liston were reared in untreated water and water containing eight 2-fold dilutions of rubidium (Rb) from 1,000 to 7.8 ppm to determine the concentration that allowed reliable detection and produced the least toxic effects as measured by adult emergence, weight, and survival. The amount of Rb detected in mosquitoes increased positively with increasing concentrations in the rearing water. Concentrations > or = 31.2 ppm Rb in the rearing water provided high and consistent detection levels of > or = 3,500 ppm Rb/mg of adult mosquito. There were no adverse effects of Rb on the weights of mosquitoes. However, increased Rb concentrations in the rearing water were associated with decreased emergence and survival. After 8 d, percentage emergence from Rb concentrations of 0-31.2 ppm was > or = 50%. At day 21, Rb concentrations of 0-31.2 ppm showed < or = 29% reduction of female survival compared with controls. The recommended concentration for reliable Rb detection with minimal toxic effects in An. stephensi was 32 ppm.

A glycosyl hydrolase activity of mammalian reovirus sigma1 protein can contribute to viral infection through a mucus layer

The mammalian reovirus sigma1 protein is responsible for viral attachment to host cells and hemagglutination properties of the virus. In the present study, sequence similarity between sigma1 and chicken-type lysozymes prompted us to investigate additional functions of the sigma1 protein. Expression in Pichia pastoris yeast cells showed that sigma1 can actually cleave lysozyme substrates, including complex sugars found in bacterial cell walls. Replacement by site-directed mutagenesis of acidic amino acid residues in sigma1 by their respective isosteric, uncharged, amino acid residues has allowed us to identify Glu36 and Asp54 as the catalytic pair involved in sigma1-mediated glycosidase activity. The enzyme appears inactive in virions but its activity is unmasked upon generation of infectious subviral particles (ISVPs) by partial proteolytic removal of the outer capsid proteins. Purified sigma1 protein and ISVPs can also hydrolyze mucins, heavily glycosylated glycoproteins that are a major component of the mucus layer overlaying the intestinal epithelium. Furthermore, reovirus infection of epithelial Madin Darby canine kidney cells was inhibited tenfold in cells expressing mucin at their apical surface, while this inhibition was overcome by ISVPs. Unmasking of sigma1 mucinolytic activity in the intestine, consecutive to proteolytic cleavage of virions to ISVPs, thus likely contributes to the known increase in infectivity of reovirus ISVPs compared to complete virions. This work presents the first evidence that some mammalian viruses have evolved mechanisms to facilitate their penetration through the protective barrier of the mucus layer in the intestinal tract.

Cerato-ulmin, a hydrophobin secreted by the causal agents of Dutch elm disease, is a parasitic fitness factor

Dutch elm disease is caused by the aggressive Ophiostoma novo-ulmi and the nonaggressive O. ulmi. Both secrete the protein cerato-ulmin (CU). To determine what role CU plays in the pathology of Dutch elm disease, we constructed a CU overexpression mutant of the nonaggressive O. ulmi H5. Stable integration of a single copy of the cu gene from the aggressive O. novo-ulmi into the genome of the nonaggressive isolate resulted in increased secretion of CU protein. Trials with American elm, Ulmus americana, suggested no alteration of virulence of this overexpressing transformant. Using aggressive and nonaggressive wild types, the cu overexpressing mutant, and our cu- mutant (Bowden et al., 1996), we have demonstrated that CU production is correlated with an altered phenotype and more hydrophobic and adherent yeast-like cells. Our results also demonstrate that CU has a role in protecting infectious propagules from desiccation. These biological roles for CU would affect transmission of Dutch elm disease, and we therefore propose that this hydrophobin acts as a parasitic fitness factor.

A meiotically reproducible chromosome length polymorphism in the ascomycete fungus Ophiostoma ulmi (sensu lato)

We have followed the transmission of Ophiostoma ulmi s.l. chromosome length polymorphisms (CLPs) into the F2 generation to determine the reproducibility of a genome rearrangement culminating in the conversion of a 1.0 Mb chromosome into a 800 kb chromosome. The 1.0 Mb chromosome in strain CESS16K is thus far unique among O ulmi s.l. wild-type strains, as no other wild-type strains have been observed with chromosomes smaller than 2.3 Mb. It has been previously shown that the 1.0 Mb chromosome is mitotically stable, carries at least one normally expressed gene, and is transmitted through meiosis. In this study, a series of crosses were performed to further elucidate the pattern of inheritance of the 1.0 Mb chromosome and the process of conversion of the 1.0 Mb species to 800 kb. In crosses where the 1.0 Mb chromosome was allowed to pair with itself or with the 800 kb chromosome, all progeny inherited a copy of the 1.0 Mb or 800 kb form, further demonstrating the A-type nature of these small chromosomes. When a cross was repeated between the strains CESS16K (1.0 Mb chromosome) and FG245Br-O (no 1.0 Mb or 800 kb chromosome), the occurrence of a 800 kb chromosome was observed in 9% of the progeny. A reciprocal cross between an 800 kb strain and a strain with no 800 kb or 1.0 Mb chromosome was conducted, and a progeny strain containing a 1.0 Mb chromosome was recovered. The reproducibility and reciprocality of the 1.0 Mb to 800 kb chromosome conversion demonstrates that meiotic processes are responsible for this CLP, and that O. ulmi s.l. strains with various divergent genome architectures can remain sexually compatible.

Identification of numerous hepatitis C virus genotypes in Montreal, Canada

Hepatitis C virus genotypes were determined for 358 viremic individuals in Montreal, Canada, by restriction endonuclease analysis of PCR products and phylogenetic analysis of core gene sequences. Types 1, 2, and 3 occurred in 62.8, 14.2, and 13.7%, respectively; types 4 and 5 were found in 3.9 and 4.5%, respectively; and genotypes 6a and 7c and a novel genotype each occurred in 0.3%. Types 4, 6, and 7 and the novel genotype were mostly from persons who had immigrated to Canada.

A prospective view on phosphatases and replicative senescence

Addition of phosphate to proteins by kinases, or its removal by phosphatases, is probably the control mechanism most often used by cells to maintain homeostasis. This mechanism presents the advantage of being fast, versatile, and easily reversible. It is used by all organisms from bacteria to man. Although more is known about the kinases, recent studies are beginning to shed light on the role of phosphatases, the enzymes that are responsible for terminating the effects of phosphorylation. These enzymes are perfect candidates for controlling all the crucial check points during cell cycle traverse, and as such, will be found to be responsible for many important decision in the life of a cell, including entry into replicative senescence.