Convergence and divergence in the evolution of cat skulls: temporal and spatial patterns of morphological diversity

Background

Studies of biological shape evolution are greatly enhanced when framed in a phylogenetic perspective. Inclusion of fossils amplifies the scope of macroevolutionary research, offers a deep-time perspective on tempo and mode of radiations, and elucidates life-trait changes. We explore the evolution of skull shape in felids (cats) through morphometric analyses of linear variables, phylogenetic comparative methods, and a new cladistic study of saber-toothed cats.

Methodology/Principal Findings

A new phylogenetic analysis supports the monophyly of saber-toothed cats (Machairodontinae) exclusive of Felinae and some basal felids, but does not support the monophyly of various saber-toothed tribes and genera. We quantified skull shape variation in 34 extant and 18 extinct species using size-adjusted linear variables. These distinguish taxonomic group membership with high accuracy. Patterns of morphospace occupation are consistent with previous analyses, for example, in showing a size gradient along the primary axis of shape variation and a separation between large and small-medium cats. By combining the new phylogeny with a molecular tree of extant Felinae, we built a chronophylomorphospace (a phylogeny superimposed onto a two-dimensional morphospace through time). The evolutionary history of cats was characterized by two major episodes of morphological divergence, one marking the separation between saber-toothed and modern cats, the other marking the split between large and small-medium cats.

Conclusions/Significance

Ancestors of large cats in the ‘Panthera’ lineage tend to occupy, at a much later stage, morphospace regions previously occupied by saber-toothed cats. The latter radiated out into new morphospace regions peripheral to those of extant large cats. The separation between large and small-medium cats was marked by considerable morphologically divergent trajectories early in feline evolution. A chronophylomorphospace has wider applications in reconstructing temporal transitions across two-dimensional trait spaces, can be used in ecophenotypical and functional diversity studies, and may reveal novel patterns of morphospace occupation.     

A new model for Hendra virus encephalitis in the mouse

Hendra virus (HeV) infection in humans is characterized by an influenza like illness, which may progress to pneumonia or encephalitis and lead to death. The pathogenesis of HeV infection is poorly understood, and the lack of a mouse model has limited the opportunities for pathogenetic research. In this project we reassessed the role of mice as an animal model for HeV infection and found that mice are susceptible to HeV infection after intranasal exposure, with aged mice reliably developing encephalitic disease. We propose an anterograde route of neuroinvasion to the brain, possibly along olfactory nerves. This is supported by evidence for the development of encephalitis in the absence of viremia and the sequential distribution of viral antigen along pathways of olfaction in the brain of intranasally challenged animals. In our studies mice developed transient lower respiratory tract infection without progressing to viremia and systemic vasculitis that is common to other animal models. These studies report a new animal model of HeV encephalitis that will allow more detailed studies of the neuropathogenesis of HeV infection, particularly the mode of viral spread and possible sequestration within the central nervous system; investigation of mechanisms that moderate the development of viremia and systemic disease; and inform the development of improved treatment options for human patients.     

Inverse synaptic tagging of inactive synapses via dynamic interaction of Arc/Arg3.1 with CaMKIIβ

The Arc/Arg3.1 gene product is rapidly upregulated by strong synaptic activity and critically contributes to weakening synapses by promoting AMPA-R endocytosis. However, how activity-induced Arc is redistributed and determines the synapses to be weakened remains unclear. Here, we show targeting of Arc to inactive synapses via a high-affinity interaction with CaMKIIβ that is not bound to calmodulin. Synaptic Arc accumulates in inactive synapses that previously experienced strong activation and correlates with removal of surface GluA1 from individual synapses. A lack of CaMKIIβ either in vitro or in vivo resulted in loss of Arc upregulation in the silenced synapses. The discovery of Arc's role in "inverse" synaptic tagging that is specific for weaker synapses and prevents undesired enhancement of weak synapses in potentiated neurons reconciles essential roles of Arc both for the late phase of long-term plasticity and for reduction of surface AMPA-Rs in stimulated neurons.     

Dissolved Organic Carbon as Major Environmental Factor Affecting Bacterioplankton Communities in Mountain Lakes of Eastern Japan

Relationships between environmental factors and bacterial communities were investigated in 41 freshwater lakes located in mountainous regions of eastern Japan. Bacterioplankton community composition (BCC) was determined by polymerase chain reaction-denaturing gradient gel electrophoresis of the 16S rRNA gene and then evaluated on the basis of physicochemical and biological variables of the lakes. Canonical correspondence analysis revealed that BCC of oligotrophic lakes was significantly influenced by dissolved organic carbon (DOC) content, but its effect was not apparent in the analysis covering all lakes including mesotrophic and eutrophic ones. The generalized linear model showed the negative association of DOC on the taxon richness of bacterioplankton communities. DOC was positively correlated with the catchment area per lake volume, suggesting that a large fraction of DOC supplied to the lake was derived from terrestrial sources. These results suggest that allochthonous DOC has a significant effect on bacterioplankton communities especially in oligotrophic lakes. The genus Polynucleobacter was detected most frequently. The occurrence of Polynucleobacter species was positively associated with DOC and negatively associated with total phosphorus (TP) levels. In addition, TP had a stronger effect than DOC, suggesting that oligotrophy is the most important factor on the occurrence of this genus.     

Sucrose phosphate phosphatase in the green alga <Emphasis Type="Italic">Klebsormidium flaccidum</Emphasis> (Streptophyta) lacks an extensive C-terminal domain and differs from that of land plants

Previously, it was reported that like land plants, the green alga Klebsormidium flaccidum (Streptophyta) accumulates sucrose during cold acclimation (Nagao et al. Plant Cell Environ 31:872–885, 2008), suggesting that synthesis of sucrose could enhance the freezing tolerance of this alga. Because sucrose phosphate phosphatase (SPP; EC 3.1.3.24) is a key enzyme in the sucrose synthesis pathway in plants, we analyzed the SPP gene in K. flaccidum (KfSPP, GenBank accession number AB669024) to clarify its role in sucrose accumulation. As determined from its deduced amino acid sequence, KfSPP contains the N-terminal domain that is characteristic of the L-2-haloacid-dehalogenase family of phosphatases/hydrolases (the HAD phosphatase domain). However, it lacks the extensive C-terminal domain found in SPPs of land plants. Database searches revealed that the SPPs in cyanobacteria also lack the C-terminal domain. In addition, the green alga Coccomyxa (Chlorophyta) and K. flaccidum, which are closely related to land plants, have cyanobacterial-type SPPs, while Chlorella (Chlorophyta) has a land plant-type SPP. These results demonstrate that even K. flaccidum (Streptophyta), as a recent ancestor of land plants, has the cyanobacterial-type SPP lacking the C-terminal domain. Because SPP and sucrose phosphate synthase (SPS) catalyze sequential reactions in sucrose synthesis in green plant cells and the lack of the C-terminal domain in KfSPP is predicted to decrease its activity, the interaction between decreased KfSPP activity and SPS activity may alter sucrose synthesis during cold acclimation in K. flaccidum.     

Antibacterial activity of the lactoperoxidase system combined with edible Laminaria hot-water extract as a source of halide ions

Hot-water extracts prepared from nine out of 12 samples of dried edible Laminaria reduced the viable numbers of Aggregatibacter actinomycetemcomitans, Staphylococcus aureus, and Esherichia coli below the detection limit after incubation for 5 min when combined with lactoperoxidase, glucose oxidase, and glucose. Some extracts showed higher bactericidal activity and a higher OI(-) concentration in the assay mixture after ultrafiltration.     

Orally administered heat-killed Lactobacillus gasseri TMC0356 can upregulate cell-mediated immunity in senescence-accelerated mice

The present study was conducted to test the ability of probiotic lactobacilli to alter age-related immunosenescence in host animals. Senescence-accelerated mouse prone 1 mice were orally fed heat-killed Lactobacillus gasseri TMC0356 (TMC0356) for 4 and 8?weeks at dosages of 10?mg?day(-1) after a 16-week period of prefeeding with a standard diet. After 4 and 8?weeks of TMC0356 intervention, splenic activation of natural killer (NK) cells and mRNA expression of cytokines and other immune molecules in the lungs were analysed. After 4 and 8?weeks, splenic NK cell activities were significantly higher in the TMC0356-fed mice compared with control mice (P?相似文献   

Molecular cloning and expression analysis of ultraspiracle (USP) from the rice stem borer Chilo suppressalis

cDNA for ultraspiracle (USP) from the lepidopteran rice stem borer Chilo suppressalis was cloned using PCR techniques. The deduced amino acid sequence of C. suppressalis USP (CsUSP) was very similar to those of other lepidopteran USPs, especially to the Manduca sexta USP-2 isoform. Northern hybridization analysis detected a 6.5-kb message in the epidermis, fat body, and midgut of wandering larvae. CsUSP mRNA expression in the epidermis varied little during the last larval instar. Gel mobility shift assays showed that in vitro translated C. suppressalis ecdysone receptor (CsEcR) and CsUSP proteins bound to the Pal1 or Drosophila melanogaster hsp27 ecdysone response element as a heterodimer. In a ligand-receptor binding assay, [(3)H]ponasterone A ([(3)H]PoA) did not bind to individual CsEcR or CsUSP protein, but bound strongly to the CsEcR/CsUSP complex. [(3)H]PoA binding to CsEcR/CsUSP complex was competed by 20-hydroxyecdysone and a non-steroidal ecdysteroid agonist, RH-5992, but not by cholesterol, indicating that compounds with molting hormone activity against C. suppressalis can bind specifically to the CsEcR/CsUSP complex.