Avian coronavirus in wild aquatic birds

We detected a high prevalence (12.5%) of novel avian coronaviruses in aquatic wild birds. Phylogenetic analyses of these coronaviruses suggest that there is a diversity of gammacoronaviruses and deltacoronaviruses circulating in birds. Gammacoronaviruses were found predominantly in Anseriformes birds, whereas deltacoronaviruses could be detected in Ciconiiformes, Pelecaniformes, and Anseriformes birds in this study. We observed that there are frequent interspecies transmissions of gammacoronaviruses between duck species. In contrast, deltacoronaviruses may have more stringent host specificities. Our analysis of these avian viral and host mitochondrial DNA sequences also suggests that some, but not all, coronaviruses may have coevolved with birds from the same order.     

Nostophycin biosynthesis is directed by a hybrid polyketide synthase-nonribosomal peptide synthetase in the toxic cyanobacterium Nostoc sp. strain 152

Cyanobacteria are a rich source of natural products with interesting pharmaceutical properties. Here, we report the identification, sequencing, annotation, and biochemical analysis of the nostophycin (npn) biosynthetic gene cluster. The npn gene cluster spans 45.1 kb and consists of three open reading frames encoding a polyketide synthase, a mixed polyketide nonribosomal peptide synthetase, and a nonribosomal peptide synthetase. The genetic architecture and catalytic domain organization of the proteins are colinear in arrangement, with the putative order of the biosynthetic assembly of the cyclic heptapeptide. NpnB contains an embedded monooxygenase domain linking nonribosomal peptide synthetase (NRPS) and polyketide synthase (PKS) catalytic domains and predicted here to hydroxylate the nostophycin during assembly. Expression of the adenylation domains and subsequent substrate specificity assays support the involvement of this cluster in nostophycin biosynthesis. Biochemical analyses suggest that the loading substrate of NpnA is likely to be a phenylpropanoic acid necessitating deletion of a carbon atom to explain the biosynthesis of nostophycin. Biosyntheses of nostophycin and microcystin resemble each other, but the phylogenetic analyses suggest that they are distantly related to one another.     

Estimating the lowest detectable dose of ionizing radiation by FISH whole-chromosome painting

Chromosome translocations are the hallmark of exposure to ionizing radiation, but they also occur spontaneously, and their frequencies increase dramatically with age. This complicates dosimetry unless a pre-exposure sample is available for each putatively exposed individual. Here we use published values for translocations in unexposed subjects from a wide range of ages, together with data from an in vitro (137)Cs dose-response curve, to estimate the minimum dose of whole-body radiation that is detectable by translocation analyses in individuals of a given age. For subjects aged 20 to 69 years, we show that the minimum detectable acute dose increases linearly with age at a rate of 0.179, 0.218 and 0.256 cGy per year for significance levels of P = 0.05, P = 0.01 and P = 0.001, respectively. For chronic exposures, the corresponding minimum detectable doses are 1.591, 2.270 and 3.055 cGy per year. For newborns, the 95th and 99th percentiles of translocation frequencies are 0.20 and 0.31 per 100 cell equivalents, respectively, indicating that values greater than these are consistent with exposures at P = 0.05 and P = 0.01, respectively. These results improve our understanding of the requirements and limitations for performing biological dosimetry when only the age of the exposed individual is known.     

High sensitivity to short wavelengths in a lizard and implications for understanding the evolution of visual systems in lizards

Progress in developing animal communication theory is frequently constrained by a poor understanding of sensory systems. For example, while lizards have been the focus of numerous studies in visual signalling, we only have data on the spectral sensitivities of a few species clustered in two major clades (Iguania and Gekkota). Using electroretinography and microspectrophotometry, we studied the visual system of the cordylid lizard Platysaurus broadleyi because it represents an unstudied clade (Scinciformata) with respect to visual systems and because UV signals feature prominently in its social behaviour. The retina possessed four classes of single and one class of double cones. Sensitivity in the ultraviolet region (UV) was approximately three times higher than previously reported for other lizards. We found more colourless oil droplets (associated with UV-sensitive (UVS) and short wavelength-sensitive (SWS) photoreceptors), suggesting that the increased sensitivity was owing to the presence of more UVS photoreceptors. Using the Vorobyev-Osorio colour discrimination model, we demonstrated that an increase in the number of UVS photoreceptors significantly enhances a lizard's ability to discriminate conspecific male throat colours. Visual systems in diurnal lizards appear to be broadly conserved, but data from additional clades are needed to confirm this.     

The structure of E. coli IgG-binding protein D suggests a general model for bending and binding in trimeric autotransporter adhesins

The Escherichia coli Ig-binding (Eib) proteins are trimeric autotransporter adhesins (TAAs) and receptors for IgG Fc. We present the structure of a large fragment of the passenger domain of EibD, the first TAA structure to have both a YadA-like head domain and the entire coiled-coil stalk. The stalk begins as a right-handed superhelix, but switches handedness halfway down. An unexpected β-minidomain joins the two and inserts a ～120° rotation such that there is no net twist between the beginning and end of the stalk. This may be important in folding and autotransport. The surprisingly large cavities we found in EibD and other TAAs may explain how TAAs bend to bind their ligands. We identified how IgA and IgG bind and modeled the EibD-IgG Fc complex. We further show that EibD promotes autoagglutination and biofilm formation and forms a fibrillar layer covering the cell surface making zipper-like contacts between cells.     

Innate immune activation of CD4 T cells in salmonella-infected mice is dependent on IL-18

Production of IFN-gamma by CD4 T cells is generally thought to be mediated by TCR triggering, however, Ag-nonspecific activation of effector CD8 T cells has been reported in infection models. In this study, we demonstrate that Ag-experienced CD4 T cells in the spleen of Salmonella-infected mice acquire the capacity to rapidly secrete IFN-gamma in response to stimulation with bacterial lysate or LPS. This innate responsiveness of T cells was transient and most apparent during, and immediately following, active Salmonella infection. Furthermore, innate T cell production of IFN-gamma in response to bacterial lysate or LPS was Ag independent and could be induced in Listeria-infected mice and in the absence of MHC class II expression. IL-18 was required for maximal innate responsiveness of CD4 T cells in Salmonella-infected mice and for optimal bacterial clearance in vivo. These data demonstrate that CD4 T cells acquire the capacity to respond to innate stimuli during active bacterial infection, a process that may contribute significantly to amplifying effector responses in vivo.     

Steady state dendritic cells present parenchymal self-antigen and contribute to, but are not essential for, tolerization of naive and Th1 effector CD4 cells

Bone marrow-derived APC are critical for both priming effector/memory T cell responses to pathogens and inducing peripheral tolerance in self-reactive T cells. In particular, dendritic cells (DC) can acquire peripheral self-Ags under steady state conditions and are thought to present them to cognate T cells in a default tolerogenic manner, whereas exposure to pathogen-associated inflammatory mediators during the acquisition of pathogen-derived Ags appears to reprogram DCs to prime effector and memory T cell function. Recent studies have confirmed the critical role of DCs in priming CD8 cell effector responses to certain pathogens, although the necessity of steady state DCs in programming T cell tolerance to peripheral self-Ags has not been directly tested. In the current study, the role of steady state DCs in programming self-reactive CD4 cell peripheral tolerance was assessed by combining the CD11c-diphtheria toxin receptor transgenic system, in which DC can be depleted via treatment with diphtheria toxin, with a TCR-transgenic adoptive transfer system in which either naive or Th1 effector CD4 cells are induced to undergo tolerization after exposure to cognate parenchymally derived self-Ag. Although steady state DCs present parenchymal self-Ag and contribute to the tolerization of cognate naive and Th1 effector CD4 cells, they are not essential, indicating the involvement of a non-DC tolerogenic APC population(s). Tolerogenic APCs, however, do not require the cooperation of CD4(+)CD25(+) regulatory T cells. Similarly, DC were required for maximal priming of naive CD4 cells to vaccinia viral-Ag, but priming could still occur in the absence of DC.     

A novel PIP2 binding of epsilonPKC and its contribution to the neurite induction ability

Protein kinase C-epsilon (epsilonPKC) induces neurite outgrowth in neuroblastoma cells but molecular mechanism of the epsilonPKC-induced neurite outgrowth is not fully understood. Therefore, we investigated the ability of phosphatidylinositol 4,5-bisphosphate (PIP(2)) binding of epsilonPKC and its correlation with the neurite extension. We found that full length epsilonPKC bound to PIP(2) in a 12-omicron-tetradecanoylphorbol-13-acetate dependent manner, while the regulatory domain of epsilonPKC (epsilonRD) bound to PIP(2) without any stimulation. To identify the PIP(2) binding region, we made mutants lacking several regions from epsilonRD, and examined their PIP(2) binding activity. The mutants lacking variable region 1 (V1) bound to PIP(2) stronger than intact epsilonRD, while the mutants lacking pseudo-substrate or common region 1 (C1) lost the binding. The PIP(2) binding ability of the V3-deleted mutant was weakened. Those PIP(2) bindings of epsilonPKC, epsilonRD and the mutants well correlated to their neurite induction ability. In addition, a chimera of pleckstrin homology domain of phospholipase Cdelta and the V3 region of epsilonPKC revealed that PIP(2) binding domain and the V3 region are sufficient for the neurite induction, and a first 16 amino acids in the V3 region was important for neurite extension. In conclusion, epsilonPKC directly binds to PIP(2) mainly through pseudo-substrate and common region 1, contributing to the neurite induction activity.