The cost of ant attendance and melezitose secretion in the black bean aphid Aphis fabae

1. The aphid Aphis fabae (Scopoli) is facultatively tended by Lasius niger (Linnaeus) ants. Previously, we found that A. fabae colonies can be made up of several clones, and that clones display significant differences in the composition of their honeydew sugars, especially in the amount of the ant attractant sugar melezitose that they produce. 2. These clonal differences could greatly impact the strength of the mutualistic interaction with ants as well as the aphids' fitness. 3. Hence, the aim of this study was to compare the fitness of different A. fabae clones that differed in their melezitose secretion, and whether or not they were tended by ants. 4. Individual fitness indices, colony growth, and alate production of single‐clone aphid colonies were analysed. 5. The results demonstrate that the fitness consequences of ant attendance critically depend on an interaction between levels of melezitose production. In particular, we show that high‐melezitose secreting clones produce fewer alates and hence might have a lower dispersal ability in the presence of ants. 6. Furthermore, these data confirm previous evidence that ant attendance is costly and results in the production of fewer apterae.     

A non-covalent method of attaching antibodies to liposomes

A novel non-covalent method of attaching antibodies to liposomes which exploits the high affinity of streptavidin for biotin, is described. The two-step coupling protocol involves the initial attachment of streptavidin to liposomes containing biotin PE, followed by the coupling of biotinated antibodies to streptavidin-liposomes. The association of streptavidin with liposomes containing biotinated PE is rapid (less than 5 min), resulting in a maximum association of 40 molecules of streptavidin per 100 nm vesicle. In the presence of equimolar cholesterol, the amount of streptavidin bound is twice that observed when biotin PE/egg PC liposomes are used. Irrespective of the mole ratio of biotin to antibody (e.g. for 1-6 biotins per antibody), or the molar ratio of antibody to streptavidin in the second incubation step, equimolar amounts of antibody bind to streptavidin. It is shown that anti-rat-erythrocyte IgG or F(ab')2 complexed to liposomes via the streptavidin linker bind specifically to rat erythrocytes but not to human erythrocytes. This coupling protocol can be readily extended to other biotinated antibodies.     

Analysis of bronchoalveolar lavage fluid proteome from systemic sclerosis patients with or without functional, clinical and radiological signs of lung fibrosis

Lung fibrosis is a major cause of mortality and morbidity in systemic sclerosis (SSc). However, its pathogenesis still needs to be elucidated. We examined whether the alteration of certain proteins in bronchoalveolar lavage fluid (BALF) might have a protective or a causative role in the lung fibrogenesis process. For this purpose we compared the BALF protein profile obtained from nine SSc patients with lung fibrosis (SSc_Fib+) with that obtained from six SSc patients without pulmonary fibrosis (SSc_Fib-) by two-dimensional gel electrophoresis (2-DE). Only spots and spot-trains that were consistently expressed in a different way in the two study groups were taken into consideration. In total, 47 spots and spot-trains, corresponding to 30 previously identified proteins in human BALF, showed no significant variation between SSc_Fib+ patients and SSc_Fib- patients, whereas 24 spots showed a reproducible significant variation in the two study groups. These latter spots corresponded to 11 proteins or protein fragments, including serum albumin fragments (13 spots), 5 previously recognized proteins (7 spots), and 4 proteins (3 spots) that had not been previously described in human BALF maps, namely calumenin, cytohesin-2, cystatin SN, and mitochondrial DNA topoisomerase 1 (mtDNA TOP1). Mass analysis did not determine one protein-spot. The two study groups revealed a significant difference in BALF protein composition. Whereas levels of glutathione S-transferase P (GSTP), Cu–Zn superoxide dismutase (SOD) and cystatin SN were downregulated in SSc_Fib+ patients compared with SSc_Fib- patients, we observed a significant upregulation of α1-acid glycoprotein, haptoglobin-α chain, calgranulin (Cal) B, cytohesin-2, calumenin, and mtDNA TOP1 in SSc_Fib+ patients. Some of these proteins (GSTP, Cu–Zn SOD, and cystatin SN) seem to be involved in mechanisms that protect lungs against injury or inflammation, whereas others (Cal B, cytohesin-2, and calumenin) seem to be involved in mechanisms that drive lung fibrogenesis. Even if the 2-DE analysis of BALF did not provide an exhaustive identification of all BALF proteins, especially those of low molecular mass, it allows the identification of proteins that might have a role in lung fibrogenesis. Further longitudinal studies on larger cohorts of patients will be necessary to assess their usefulness as predictive markers of disease.     

The multiple sex chromosomes of platypus and echidna are not completely identical and several share homology with the avian Z

Background

Sex-determining systems have evolved independently in vertebrates. Placental mammals and marsupials have an XY system, birds have a ZW system. Reptiles and amphibians have different systems, including temperature-dependent sex determination, and XY and ZW systems that differ in origin from birds and placental mammals. Monotremes diverged early in mammalian evolution, just after the mammalian clade diverged from the sauropsid clade. Our previous studies showed that male platypus has five X and five Y chromosomes, no SRY, and DMRT1 on an X chromosome. In order to investigate monotreme sex chromosome evolution, we performed a comparative study of platypus and echidna by chromosome painting and comparative gene mapping.

Results

Chromosome painting reveals a meiotic chain of nine sex chromosomes in the male echidna and establishes their order in the chain. Two of those differ from those in the platypus, three of the platypus sex chromosomes differ from those of the echidna and the order of several chromosomes is rearranged. Comparative gene mapping shows that, in addition to bird autosome regions, regions of bird Z chromosomes are homologous to regions in four platypus X chromosomes, that is, X₁, X₂, X₃, X₅, and in chromosome Y₁.

Conclusion

Monotreme sex chromosomes are easiest to explain on the hypothesis that autosomes were added sequentially to the translocation chain, with the final additions after platypus and echidna divergence. Genome sequencing and contig anchoring show no homology yet between platypus and therian Xs; thus, monotremes have a unique XY sex chromosome system that shares some homology with the avian Z.     

Identifying dynamical modules from genetic regulatory systems: applications to the segment polarity network

Background  

It is widely accepted that genetic regulatory systems are 'modular', in that the whole system is made up of smaller 'subsystems' corresponding to specific biological functions. Most attempts to identify modules in genetic regulatory systems have relied on the topology of the underlying network. However, it is the temporal activity (dynamics) of genes and proteins that corresponds to biological functions, and hence it is dynamics that we focus on here for identifying subsystems.     

Tissue distribution of DNA-Hsp65/TDM-loaded PLGA microspheres and uptake by phagocytic cells

Background

Mucopolysaccharidosis type IIIA (MPS IIIA) is the most common of the mucopolysaccharidoses. The disease is caused by a deficiency of the lysosomal enzyme sulphamidase and results in the storage of the glycosaminoglycan (GAG), heparan sulphate. MPS IIIA is characterised by widespread storage and urinary excretion of heparan sulphate, and a progressive and eventually profound neurological course. Gene therapy is one of the few avenues of treatment that hold promise of a sustainable treatment for this disorder.

Methods

The murine sulphamidase gene cDNA was cloned into a lentiviral vector and high-titre virus produced. Human MPS IIIA fibroblast cultures were transduced with the sulphamidase vector and analysed using molecular, enzymatic and metabolic assays. High-titre virus was intravenously injected into six 5-week old MPS IIIA mice. Three of these mice were pre-treated with hyperosmotic mannitol. The weight of animals was monitored and GAG content in urine samples was analysed by polyacrylamide gel electrophoresis.

Results

Transduction of cultured MPS IIIA fibroblasts with the sulphamidase gene corrected both the enzymatic and metabolic defects. Sulphamidase secreted by gene-corrected cells was able to cross correct untransduced MPS IIIA cells. Urinary GAG was found to be greatly reduced in samples from mice receiving the vector compared to untreated MPS IIIA controls. In addition, the weight of treated mice became progressively normalised over the 6-months post-treatment.

Conclusion

Lentiviral vectors appear promising vehicles for the development of gene therapy for MPS IIIA.