Species diversity in Gymnogeophagus (Teleostei: Cichlidae) and comparative biogeography of cichlids in the Middle Paraná basin,an emerging hotspot of fish endemism

Hydrobiologia - We address the diversity of two species groups of the cichlid genus Gymnogeophagus in the Middle Paraná basin using molecular phylogeography and traditional morphological...     

DNA methylation as a possible mechanism affecting ability of natural populations to adapt to changing climate

Environmentally induced epigenetic variation has been recently recognized as a possible mechanism allowing plants to rapidly adapt to novel conditions. Despite increasing evidence on the topic, little is known on how epigenetic variation affects responses of natural populations to changing climate. We studied the effects of experimental demethylation (DNA methylation is an important mediator of heritable control of gene expression) on performance of a clonal grass, Festuca rubra, coming from localities with contrasting temperature and moisture regimes. We compared performance of demethylated and control plants from different populations under two contrasting climatic scenarios and explored whether the response to demethylation depended on genetic relatedness of the plants. Demethylation significantly affected plant performance. Its effects interacted with population of origin and partly with conditions of cultivation. The effects of demethylation also varied between distinct genotypes with more closely related genotypes showing more similar response to demethylation. For belowground biomass, demethylated plants showed signs of adaptation to drought that were not apparent in plants that were naturally methylated. The results suggest that DNA methylation may modify the response of this species to moisture. DNA methylation may thus affect the ability of clonal plants to adapt to novel climatic conditions. Whether this variation in DNA methylation may also occur under natural conditions, however, remains to be explored. Despite the significant interactions between population of origin and demethylation, our data do not provide clear evidence that DNA methylation enabled adaptation to different environments. In fact, we obtained stronger evidence of local adaptation in demethylated than in naturally‐methylated plants. As changes in DNA methylation may be quite dynamic, it is thus possible that epigenetic variation can mask plant adaptations to conditions of their origin due to pre‐cultivation of the plants under standardized conditions. This possibility should be considered in future experiments exploring plant adaptations.     

The first specimen of Archaeopteryx from the Upper Jurassic Mörnsheim Formation of Germany

From an initial isolated position as the oldest evolutionary prototype of a bird, Archaeopteryx has, as a result of recent fossil discoveries, become embedded in a rich phylogenetic context of both more and less crownward stem-group birds. This has prompted debate over whether Archaeopteryx is simply a convergently bird-like non-avialan theropod. Here we show, using the first synchrotron microtomographic examination of the genus, that the eighth or Daiting specimen of Archaeopteryx possesses a character suite that robustly constrains it as a basal avialan (primitive bird). The specimen, which comes from the Mörnsheim Formation and is thus younger than the other specimens from the underlying Solnhofen Formation, is distinctive enough to merit designation as a new species, Archaeopteryx albersdoerferi sp. nov., but is recovered in close phylogenetic proximity to Archaeopteryx lithographica. Skeletal innovations of the Daiting specimen, such as fusion and pneumatization of the cranial bones, well vascularized pectoral girdle and wing elements, and a reinforced configuration of carpals and metacarpals, suggest that it may have had more characters seen in flying birds than the older Archaeopteryx lithographica. These innovations appear to be convergent on those of more crownward avialans, suggesting that Bavarian archaeopterygids independently acquired increasingly bird-like traits over time. Such mosaic evolution and iterative exploration of adaptive space may be typical for major functional transitions like the origin of flight.     

Double drugging of prolyl-tRNA synthetase provides a new paradigm for anti-infective drug development

Toxoplasmosis is caused by Toxoplasma gondii and in immunocompromised patients it may lead to seizures, encephalitis or death. The conserved enzyme prolyl-tRNA synthetase (PRS) is a validated druggable target in Toxoplasma gondii but the traditional ‘single target–single drug’ approach has its caveats. Here, we describe two potent inhibitors namely halofuginone (HFG) and a novel ATP mimetic (L95) that bind to Toxoplasma gondii PRS simultaneously at different neighbouring sites to cover all three of the enzyme substrate subsites. HFG and L95 act as one triple-site inhibitor in tandem and form an unusual ternary complex wherein HFG occupies the 3’-end of tRNA and the L-proline (L-pro) binding sites while L95 occupies the ATP pocket. These inhibitors exhibit nanomolar IC₅₀ and EC₅₀ values independently, and when given together reveal an additive mode of action in parasite inhibition assays. This work validates a novel approach and lays a structural framework for further drug development based on simultaneous targeting of multiple pockets to inhibit druggable proteins.     

Host Adaptation in Legionellales Is 1.9 Ga,Coincident with Eukaryogenesis

Bacteria adapting to living in a host cell caused the most salient events in the evolution of eukaryotes, namely the seminal fusion with an archaeon, and the emergence of both mitochondrion and chloroplast. A bacterial clade that may hold the key to understanding these events is the deep-branching gammaproteobacterial order Legionellales—containing among others Coxiella and Legionella—of which all known members grow inside eukaryotic cells. Here, by analyzing 35 novel Legionellales genomes mainly acquired through metagenomics, we show that this group is much more diverse than previously thought, and that key host-adaptation events took place very early in its evolution. Crucial virulence factors like the Type IVB secretion (Dot/Icm) system and two shared effector proteins were gained in the last Legionellales common ancestor (LLCA). Many metabolic gene families were lost in LLCA and its immediate descendants, including functions directly and indirectly related to molybdenum metabolism. On the other hand, genome sizes increased in the ancestors of the Legionella genus. We estimate that LLCA lived approximately 1.89 Ga, probably predating the last eukaryotic common ancestor by approximately 0.4–1.0 Gy. These elements strongly indicate that host adaptation arose only once in Legionellales, and that these bacteria were using advanced molecular machinery to exploit and manipulate host cells early in eukaryogenesis.     

Implication of synaptotagmins 4 and 7 in activity-dependent somatodendritic dopamine release in the ventral midbrain

Dopamine (DA) neurons can release DA not just from axon terminals, but also from their somatodendritic (STD) compartment through a mechanism that is still incompletely understood. Using voltammetry in mouse mesencephalic brain slices, we find that STD DA release has low capacity and shows a calcium sensitivity that is comparable to that of axonal release. We find that the molecular mechanism of STD DA release differs from axonal release with regard to the implication of synaptotagmin (Syt) calcium sensors. While individual constitutive knockout of Syt4 or Syt7 is not sufficient to reduce STD DA release, the removal of both isoforms reduces this release by approximately 50%, leaving axonal release unimpaired. Our work unveils clear differences in the mechanisms of STD and axonal DA release.     

Sequence and structure of the mouse gene coding for the largest neurofilament subunit

We have determined the complete nucleotide sequence of the mouse gene encoding the neurofilament NF-H protein. The C-terminal domain of NF-H is very rich in charged amino acids (aa) and contains a 3-aa sequence, Lys-Ser-Pro, that is repeated 51 times within a stretch of 368 aa. The location of this serine-rich repeat in the phosphorylated domain of NF-H indicates that it represents the major protein kinase recognition site. The nfh gene shares two common intron positions with the nfl and nfm genes, but has an additional intron that occurs at a location equivalent to one of the introns in non-neuronal intermediate filament-coding genes. This additional nfh intron may have been acquired via duplication of a primordial intermediate filament gene.     

The iron mineralization of Spongia officinalis L. (Porifera,Dictyoceratida) and its relationships with the collagen skeleton

Lepidocrocite (γ FeOOH) granules are frequently found in the spongin fibers of some horny sponges. The granules also contain calcite and a small amount of goethite (α FeOOH). In the genus Spongia, the amount of iron is highly variable according to the habitat and to the age of the fiber. Some indications about the skeletal growth and structure can be inferred from the distribution of the biominerals and the arrangement of the crystallites: i.e. (1) Mineralization is a slow process in comparison with fiber formation; (2) Secondary connective fibers may have a discontinuous growth; (3) The collagen microfibrils display a definite arrangement in the successive spongin layers; (4) Although spongin is a collagen highly resistant in vitro to enzymatic digestion, the sponge is able to perform remodeling of its skeleton through autodigestion of the fibers.