The FRP1 F-box gene has different functions in sexuality, pathogenicity and metabolism in three fungal pathogens

Plant‐pathogenic fungi employ a variety of infection strategies; as a result, fungi probably rely on different sets of proteins for successful infection. The F‐box protein Frp1, only present in filamentous fungi belonging to the Sordariomycetes, Leotiomycetes and Dothideomycetes, is required for nonsugar carbon catabolism and pathogenicity in the root‐infecting fungus Fusarium oxysporum. To assess the role of Frp1 in other plant‐pathogenic fungi, FRP1 deletion mutants were generated in Fusarium graminearum and Botrytis cinerea, and their phenotypes were analysed. Deletion of FgFRP1 in F. graminearum led to impaired infection of barley roots, but not of aerial plant parts. Deletion of BcFRP1 in B. cinerea did not show any effect on pathogenicity. Sexual reproduction, however, was impaired in both F. graminearum and B. cinerea FRP1 deletion mutants. The mutants of all three fungi displayed different phenotypes when grown on an array of carbon sources. The F. oxysporum and B. cinerea deletion mutants showed opposite growth phenotypes on sugar and nonsugar carbon sources. Replacement of FoFRP1 in F. oxysporum with the B. cinerea BcFRP1 resulted in the restoration of pathogenicity, but also in a switch from impaired growth on nonsugar carbon sources to impaired growth on sugar carbon sources. This effect could be ascribed in part to the B. cinerea BcFRP1 promoter sequence. In conclusion, the function of the F‐box protein Frp1, despite its high sequence conservation, is not conserved between different fungi, leading to differential requirements for pathogenicity and carbon source utilization.     

Changes in proteomics profile during maturation of marrow-derived dendritic cells treated with oxidized low-density lipoprotein

Increasing evidence suggests that dendritic cells (DCs) and oxidized low-density lipoprotein (ox-LDL) participate in atherosclerosis. However, few data on the molecular mechanisms of this process are available. To address this question, we used iTRAQ labeling followed by LC-MS/MS analysis to identify many proteins that changed markedly during the maturation of dendritic cells stimulated with ox-LDL. Among a total of 781 identified proteins, 93 were upregulated and 100 were downregulated. The major and significant changes in upregulated proteins were that ox-LDL not only affected the levels of intracellular cathepsins G, Z, D and S, but also significantly enhanced cathepsin S secretion by the treated cells. Our results may provide clues for a more comprehensive understanding the pathogenesis of atherosclerosis.     

Whole genome PCR scanning reveals the syntenic genome structure of toxigenic Vibrio cholerae strains in the O1/O139 population

Vibrio cholerae is commonly found in estuarine water systems. Toxigenic O1 and O139 V. cholerae strains have caused cholera epidemics and pandemics, whereas the nontoxigenic strains within these serogroups only occasionally lead to disease. To understand the differences in the genome and clonality between the toxigenic and nontoxigenic strains of V. cholerae serogroups O1 and O139, we employed a whole genome PCR scanning (WGPScanning) method, an rrn operon-mediated fragment rearrangement analysis and comparative genomic hybridization (CGH) to analyze the genome structure of different strains. WGPScanning in conjunction with CGH revealed that the genomic contents of the toxigenic strains were conservative, except for a few indels located mainly in mobile elements. Minor nucleotide variation in orthologous genes appeared to be the major difference between the toxigenic strains. rrn operon-mediated rearrangements were infrequent in El Tor toxigenic strains tested using I-CeuI digested pulsed-field gel electrophoresis (PFGE) analysis and PCR analysis based on flanking sequence of rrn operons. Using these methods, we found that the genomic structures of toxigenic El Tor and O139 strains were syntenic. The nontoxigenic strains exhibited more extensive sequence variations, but toxin coregulated pilus positive (TCP+) strains had a similar structure. TCP+ nontoxigenic strains could be subdivided into multiple lineages according to the TCP type, suggesting the existence of complex intermediates in the evolution of toxigenic strains. The data indicate that toxigenic O1 El Tor and O139 strains were derived from a single lineage of intermediates from complex clones in the environment. The nontoxigenic strains with non-El Tor type TCP may yet evolve into new epidemic clones after attaining toxigenic attributes.     

Evolution of scaling emergence in large-scale spatial epidemic spreading

Background

Zipf''s law and Heaps'' law are two representatives of the scaling concepts, which play a significant role in the study of complexity science. The coexistence of the Zipf''s law and the Heaps'' law motivates different understandings on the dependence between these two scalings, which has still hardly been clarified.

Methodology/Principal Findings

In this article, we observe an evolution process of the scalings: the Zipf''s law and the Heaps'' law are naturally shaped to coexist at the initial time, while the crossover comes with the emergence of their inconsistency at the larger time before reaching a stable state, where the Heaps'' law still exists with the disappearance of strict Zipf''s law. Such findings are illustrated with a scenario of large-scale spatial epidemic spreading, and the empirical results of pandemic disease support a universal analysis of the relation between the two laws regardless of the biological details of disease. Employing the United States domestic air transportation and demographic data to construct a metapopulation model for simulating the pandemic spread at the U.S. country level, we uncover that the broad heterogeneity of the infrastructure plays a key role in the evolution of scaling emergence.

Conclusions/Significance

The analyses of large-scale spatial epidemic spreading help understand the temporal evolution of scalings, indicating the coexistence of the Zipf''s law and the Heaps'' law depends on the collective dynamics of epidemic processes, and the heterogeneity of epidemic spread indicates the significance of performing targeted containment strategies at the early time of a pandemic disease.     

Kinetic studies of human tyrosyl-DNA phosphodiesterase, an enzyme in the topoisomerase I DNA repair pathway.

Tyrosyl-DNA phosphodiesterase (TDP) cleaves the phosphodiester bond linking the active site tyrosine residue of topoisomerase I with the 3' terminus of DNA in topoisomerase I-DNA complexes which accumulate during treatment of cancer with camptothecin. In yeast, TDP mutation confers a 1000-fold hypersensitivity to camptothecin in the presence of an additional mutation of RAD9 gene [Pouliot, J.J., Yao, K.C., Robertson, C.A. & Nash, H.A. (1999) Science 286, 552-555]. Based on the recently solved crystal structure, human TDP belongs to a distinct class within the phospholipase D superfamily in spite of very low sequence homology [Interthal, H., Pouliot, J.J. & Champoux, J.J. (2001) Proc. Natl Acad. Sci. USA 98, 12009-12014, and Davies, D.R., Interthal, H., Champoux, J.J. & Hol, W.G.J. (2002) Structure 10, 237-248]. To understand the enzymatic mechanism of this novel enzyme, and to facilitate inhibitor screening of human TDP, we have expressed and purified recombinant human TDP variants carrying deletions of 1-39 or 1-174 amino acids. Furthermore, a continuous colorimetric assay in a 96-well format was also developed using p-nitrophenyl-thymidine-3'-phosphate as substrate. This assay system is able to detect enzymatic activity at enzyme concentrations as low as 15 nm. Purified recombinant human TDPNDelta39 cleaved p-nitrophenyl-thymidine-3'-phosphate with Km and kcat values of 211.14 +/- 23.83 micro m and 8.82 +/- 0.57 per min in the presence of Mn2+.     

Iron chelation and a free radical scavenger suppress angiotensin II-induced upregulation of TGF-beta1 in the heart

Long-term administration of angiotensin II causes myocardial loss and cardiac fibrosis. We previously found iron deposition in the heart of the angiotensin II-infused rat, which may promote angiotensin II-induced cardiac damage. In the present study, we have investigated whether an iron chelator (deferoxamine) and a free radical scavenger (T-0970) affect the angiotensin II-induced upregulation of transforming growth factor-beta1 (TGF-beta1). Angiotensin II infusion for 7 days caused a robust increase in TGF-beta1 mRNA expression in vascular smooth muscle cells, myofibroblast-like cells, and migrated monocytes/macrophages. T-0970 and deferoxamine suppressed the upregulation of TGF-beta1 mRNA and reduced the extent of cardiac fibrosis in the heart of rats treated with angiotensin II. These agents blocked the angiotensin II-induced upregulation of heme oxygenase-1, a potent oxidative and cellular stress-responsive gene, but they did not significantly affect systolic blood pressure or plasma levels of aldosterone. In addition, T-0970 and deferoxamine suppressed the angiotensin II-induced upregulation of monocyte chemoattractant protein-1 in the heart. These results collectively suggest that iron and the iron-mediated generation of reactive oxygen species may contribute to angiotensin II-induced upregulation of profibrotic and proinflammatory genes, such as TGF-beta1 and monocyte chemoattractant protein-1.     

New tool for an old problem: can RNAi efficiently resolve the issue of genetic redundancy?

RNA interference (RNAi) has become a generally accepted tool for inhibiting gene expression in many laboratory organisms. Nagel et al.,(1) in a recent paper, give an example of how this tool can also be used to address the question of genetic redundancy. Their focus was on the redundancy in Drosophila melanogaster of the Enhancer of split gene complex [E(spl)-C] which comprises seven highly related genes. Their somewhat conflicting findings are probably the typical scenario for most RNAi experiments: some expected results and some surprises.     

Replicating rather than nonreplicating adenovirus-human immunodeficiency virus recombinant vaccines are better at eliciting potent cellular immunity and priming high-titer antibodies

A major challenge in combating the human immunodeficiency virus (HIV) epidemic is the development of vaccines capable of inducing potent, persistent cellular immunity and broadly reactive neutralizing antibody responses to HIV type 1 (HIV-1). We report here the results of a preclinical trial using the chimpanzee model to investigate a combination vaccine strategy involving sequential priming immunizations with different serotypes of adenovirus (Ad)/HIV-1(MN)env/rev recombinants and boosting with an HIV envelope subunit protein, oligomeric HIV(SF162) gp140deltaV2. The immunogenicities of replicating and nonreplicating Ad/HIV-1(MN)env/rev recombinants were compared. Replicating Ad/HIV recombinants were better at eliciting HIV-specific cellular immune responses and better at priming humoral immunity against HIV than nonreplicating Ad-HIV recombinants carrying the same gene insert. Enhanced cellular immunity was manifested by a greater frequency of HIV envelope-specific gamma interferon-secreting peripheral blood lymphocytes and better priming of T-cell proliferative responses. Enhanced humoral immunity was seen in higher anti-envelope binding and neutralizing antibody titers and better induction of antibody-dependent cellular cytotoxicity. More animals primed with replicating Ad recombinants mounted neutralizing antibodies against heterologous R5 viruses after one or two booster immunizations with the mismatched oligomeric HIV-1(SF162) gp140deltaV2 protein. These results support continued development of the replicating Ad-HIV recombinant vaccine approach and suggest that the use of replicating vectors for other vaccines may prove fruitful.