Leaf-cutting ant fungi produce cell wall degrading pectinase complexes reminiscent of phytopathogenic fungi

<p>Abstract</p> <p>Background</p> <p>Leaf-cutting (attine) ants use their own fecal material to manure fungus gardens, which consist of leaf material overgrown by hyphal threads of the basidiomycete fungus <it>Leucocoprinus gongylophorus </it>that lives in symbiosis with the ants. Previous studies have suggested that the fecal droplets contain proteins that are produced by the fungal symbiont to pass unharmed through the digestive system of the ants, so they can enhance new fungus garden growth.</p> <p>Results</p> <p>We tested this hypothesis by using proteomics methods to determine the gene sequences of fecal proteins in <it>Acromyrmex echinatior </it>leaf-cutting ants. Seven (21%) of the 33 identified proteins were pectinolytic enzymes that originated from the fungal symbiont and which were still active in the fecal droplets produced by the ants. We show that these enzymes are found in the fecal material only when the ants had access to fungus garden food, and we used quantitative polymerase chain reaction analysis to show that the expression of six of these enzyme genes was substantially upregulated in the fungal gongylidia. These unique structures serve as food for the ants and are produced only by the evolutionarily advanced garden symbionts of higher attine ants, but not by the fungi reared by the basal lineages of this ant clade.</p> <p>Conclusions</p> <p>Pectinolytic enzymes produced in the gongylidia of the fungal symbiont are ingested but not digested by <it>Acromyrmex </it>leaf-cutting ants so that they end up in the fecal fluid and become mixed with new garden substrate. Substantial quantities of pectinolytic enzymes are typically found in pathogenic fungi that attack live plant tissue, where they are known to breach the cell walls to allow the fungal mycelium access to the cell contents. As the leaf-cutting ant symbionts are derived from fungal clades that decompose dead plant material, our results suggest that their pectinolytic enzymes represent secondarily evolved adaptations that are convergent to those normally found in phytopathogens.</p

Human Rights Shaming Through INGOs and Foreign Aid Delivery

Does the ``shaming" of human rights violations influence foreign aid delivery decisions across OECD donor countries? We examine the effect of shaming, defined as targeted negative attention by human rights international nongovernmental organizations (INGOs), on donor decisions about how to deliver bilateral aid. We argue that INGO shaming of recipient countries leads donor governments, on average, to ``bypass" the recipient government in favor of non-state aid delivery channels, including international and local NGOs and international organizations (IOs). However, we expect this relationship to be conditional on a donor country's position in the international system. Minor power countries have limited influence in global affairs and are therefore more able to centrally promote human rights in their foreign policy. Major power countries, on the other hand, shape world politics and often confront ``realpolitik" concerns that may require government-to-government aid relations in the presence of INGO shaming. We expect aid officials of minor donor countries to be more likely to condition aid delivery decisions on human rights shaming than their counterparts of major donor countries. Using compositional data analysis, we test our argument using originally collected data on human rights shaming events in a time-series cross-sectional framework from 2004 to 2010. We find support for our hypotheses: On average, OECD donor governments increase the proportion of bypass when INGOs shame the recipient government. When differentiating between donor types we find that this finding holds for minor but not for major powers. These results add to both our understanding of the influences of aid allocation decision-making and our understanding of the role of INGOs on foreign-policy

Anti-dsDNA Antibodies Promote Initiation, and Acquired Loss of Renal Dnase1 Promotes Progression of Lupus Nephritis in Autoimmune (NZBxNZW)F1 Mice

BACKGROUND:Lupus nephritis is characterized by deposition of chromatin fragment-IgG complexes in the mesangial matrix and glomerular basement membranes (GBM). The latter defines end-stage disease. METHODOLOGY/PRINCIPALS: In the present study we determined the impact of antibodies to dsDNA, renal Dnase1 and matrix metalloprotease (MMP) mRNA levels and enzyme activities on early and late events in murine lupus nephritis. The major focus was to analyse if these factors were interrelated, and if changes in their expression explain basic processes accounting for lupus nephritis. FINDINGS:Early phases of nephritis were associated with chromatin-IgG complex deposition in the mesangial matrix. A striking observation was that this event correlated with appearance of anti-dsDNA antibodies and mild or clinically silent nephritis. These events preceded down-regulation of renal Dnase1. Later, renal Dnase1 mRNA level and enzyme activity were reduced, while MMP2 mRNA level and enzyme activity increased. Reduced levels of renal Dnase1 were associated in time with deficient fragmentation of chromatin from dead cells. Large fragments were retained and accumulated in GBM. Also, since chromatin fragments are prone to stimulate Toll-like receptors in e.g. dendritic cells, this may in fact explain increased expression of MMPs. SIGNIFICANCE:These scenarios may explain the basis for deposition of chromatin-IgG complexes in glomeruli in early and late stages of nephritis, loss of glomerular integrity and finally renal failure

Mathematical Model of Plasmid-Mediated Resistance to Ceftiofur in Commensal Enteric Escherichia coli of Cattle

Antimicrobial use in food animals may contribute to antimicrobial resistance in bacteria of animals and humans. Commensal bacteria of animal intestine may serve as a reservoir of resistance-genes. To understand the dynamics of plasmid-mediated resistance to cephalosporin ceftiofur in enteric commensals of cattle, we developed a deterministic mathematical model of the dynamics of ceftiofur-sensitive and resistant commensal enteric Escherichia coli (E. coli) in the absence of and during parenteral therapy with ceftiofur. The most common treatment scenarios including those using a sustained-release drug formulation were simulated; the model outputs were in agreement with the available experimental data. The model indicated that a low but stable fraction of resistant enteric E. coli could persist in the absence of immediate ceftiofur pressure, being sustained by horizontal and vertical transfers of plasmids carrying resistance-genes, and ingestion of resistant E. coli. During parenteral therapy with ceftiofur, resistant enteric E. coli expanded in absolute number and relative frequency. This expansion was most influenced by parameters of antimicrobial action of ceftiofur against E. coli. After treatment (>5 weeks from start of therapy) the fraction of ceftiofur-resistant cells among enteric E. coli, similar to that in the absence of treatment, was most influenced by the parameters of ecology of enteric E. coli, such as the frequency of transfer of plasmids carrying resistance-genes, the rate of replacement of enteric E. coli by ingested E. coli, and the frequency of ceftiofur resistance in the latter

Silencing of Renal DNaseI in Murine Lupus Nephritis Imposes Exposure of Large Chromatin Fragments and Activation of Toll Like Receptors and the Clec4e

Recent studies demonstrate that transformation of mild lupus nephritis into end-stage disease is imposed by silencing of renal DNaseI gene expression in (NZBxNZW)F1 mice. Down-regulation of DNaseI results in reduced chromatin fragmentation, and in deposition of extracellular chromatin-IgG complexes in glomerular basement membranes in individuals that produce IgG anti-chromatin antibodies. The main focus of the present study is to describe the biological consequences of renal DNaseI shut-down and reduced chromatin fragmentation with a particular focus on whether exposed large chromatin fragments activate Toll like receptors and the necrosis-related Clec4e receptor in murine and human lupus nephritis. Furthermore, analyses where performed to determine if matrix metalloproteases are up-regulated as a consequence of chromatin-mediated Toll like receptors/Clec4e stimulation. Mouse and human mRNA expression levels of DNaseI, Toll like receptors 7–9, Clec4e, pro-inflammatory cytokines and MMP2/MMP9 were determined and compared with in situ protein expression profiles and clinical data. We demonstrate that exposure of chromatin significantly up-regulate Toll like receptors and Clec4e in mice, and also but less pronounced in patients with lupus nephritis treated with immunosuppresants. In conclusion, silencing of renal DNaseI gene expression initiates a cascade of inflammatory signals leading to progression of both murine and human lupus nephritis. Principal component analyses biplot of data from murine and human lupus nephrits demonstrate the importance of DNaseI gene shut down for progression of the organ disease

Characterisation and internalisation of recombinant humanised HMFG-1 antibodies against MUC1

The humanised HMFG-1 immunoglobulin has been extensively developed as a clinical immunotherapeutic agent for MUC1 expressing tumours. We have constructed a single-chain Fv (scFv) and Fab fragment from this antibody and shown that both these species retain their specificity for MUC1. The scFv was less stable and less soluble than the Fab. Detailed analyses of the binding kinetics of the whole IgG and Fab fragment show that the affinity for MUC1 synthetic peptides is low (approximately 100 n for the IgG and 10 μ for the Fab), with particularly low but similar dissociation rate constants (0.031–0.095 s−1). Binding to native antigen on the cell surface is over two orders of magnitude better. Confocal immunofluorescence microscopy shows that both the IgG and Fab are internalised rapidly (the IgG is internalised within 15 min) and colocalise to early endosomes. This work provides an appreciation of the binding, internalising and trafficking kinetics, important for the development of future therapeutics based on this antibody

Monoculture of Leafcutter Ant Gardens

Background -- Leafcutter ants depend on the cultivation of symbiotic Attamyces fungi for food, which are thought to be grown by the ants in single-strain, clonal monoculture throughout the hundreds to thousands of gardens within a leafcutter nest. Monoculture eliminates cultivar-cultivar competition that would select for competitive fungal traits that are detrimental to the ants, whereas polyculture of several fungi could increase nutritional diversity and disease resistance of genetically variable gardens. Methodology/Principal Findings -- Using three experimental approaches, we assessed cultivar diversity within nests of Atta leafcutter ants, which are most likely among all fungus-growing ants to cultivate distinct cultivar genotypes per nest because of the nests' enormous sizes (up to 5000 gardens) and extended lifespans (10–20 years). In Atta texana and in A. cephalotes, we resampled nests over a 5-year period to test for persistence of resident cultivar genotypes within each nest, and we tested for genetic differences between fungi from different nest sectors accessed through excavation. In A. texana, we also determined the number of Attamyces cells carried as a starter inoculum by a dispersing queens (minimally several thousand Attamyces cells), and we tested for genetic differences between Attamyces carried by sister queens dispersing from the same nest. Except for mutational variation arising during clonal Attamyces propagation, DNA fingerprinting revealed no evidence for fungal polyculture and no genotype turnover during the 5-year surveys. Conclusions/Significance -- Atta leafcutter ants can achieve stable, fungal monoculture over many years. Mutational variation emerging within an Attamyces monoculture could provide genetic diversity for symbiont choice (gardening biases of the ants favoring specific mutational variants), an analog of artificial selection.The research was supported by National Science Foundation awards DEB-0920138, DEB-0639879, and DEB-0110073 to UGM; DEB-0949689 to T.R. Schultz, N. Mehdiabadi, and UGM; and a Fellowship (02/05) from the Conselho Nacional de Desenvolvimento Científico e Tecnológico to AR. The funding agencies had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.Biological Sciences, School o