The DYW-E-PPR protein MEF14 is required for RNA editing at site matR-1895 in mitochondria of Arabidopsis thaliana

We here identify the PPR protein MEF14 of the DYW subclass as a specific trans-factor required for C to U editing of site matR-1895 by genetic mapping of an EMS induced editing mutant in Arabidopsis thaliana. The wild type Col MEF14 gene complements mutant protoplasts. A T-DNA insertion in the MEF14 gene abolishes detectable editing at the matR-1895 site. Lack of RNA editing at the matR-1895 site does not alter the level of mature and precursor nad1 mRNA molecules. Such RNA editing mutants can be used to analyse the function of genes like this maturase related reading frame in plant mitochondria.     

Male reproductive cycle of the Siberian salamander Salamandrella keyserlingii (Caudata: Hynobiidae) in coastal tundra of the Sea of Okhotsk

The adaptations which allowed the Siberian salamander (Salamandrella keyserlingii Dybowski, 1870) to form its exceptionally large, polyzonal range (forest-steppe, forests, and southern tundras of Siberia and part of European Russia) remain insufficiently studied. We checked the hypothesis that S. keyserlingii was able to colonize the northern territories, characterized by a short and cold summer and therefore unsuitable for other amphibians, due to multiyear maturation of its spermatozoa and eggs which was described in the southern part of Western Siberia. For this purpose, the male reproductive cycle of S. keyserlingii was studied during the entire 4-month active season in the Sea of Okhotsk coastal tundras. The complete development of gametes there took only 3 months: proliferation of spermatogonia started already in the spawning pond soon after spermiation in May and ended by the time the males left the water; spermatocytes were formed at the end of June, and spermatozoa, by the second half of August. Spermatogenesis occurred synchronously in all the maturing lobules along the entire length of the testis. Mature spermatozoa were stored in the testes until spring when external fertilization took place in the pond. Morphological and histological changes in the testes and vasa deferentia, the mode of fertilization, and annual reproduction of S. keyserlingii were similar to those of other studied species of the family. Our data disprove the previous conclusion about multiyear spermatogenesis of S. keyserlingii, which, therefore, cannot be considered among the possible adaptations which facilitated colonization of the northern territories by this species.     

Insects from the Buntsandstein of Lower Franconia and Thuringia

Upper Buntsandstein deposits (mainly Myophoria beds, R?t Formation, Early Anisian) in Lower Franconia and Thuringia have yielded a rather rich insect fauna comprising ca. 300 insect specimens assigned to ten orders: Archaeognatha (Dasyleptidae), Ephemeroptera, Blattodea, Grylloblattida, Orthoptera, Hemiptera, Glosselytrodea, Coleoptera, Mecoptera and Diptera. The systematic list of recorded insects is provided. Two species are identified as Triassodotes vogesiacus Sinitshenkova, Marchal-Papier, Grauvogel-Stamm et Gall, 2005 (Ephemeroptera: Misthodotidae) and Pseudopolycentropus triasicus Papier, Nel et Grauvogel-Stamm, 1996 (Mecoptera), which were previously described from the ??Grès à Voltzia?? Formation of the Vosges, the stratigraphically closest insect fauna. All grylloblattid specimens are identified as Chauliodites picteti Heer, 1864 (Chaulioditidae), known previously from the Middle Buntsandstein of G?dewitz, Saxony-Anhalt. The new genus and species Hammephemera pulchra Sinitshenkova, gen. et sp. n. (Ephemeroptera: Sharephemeridae) is described.     

Structural Basis for Group B Streptococcus Pilus 1 Sortases C Regulation and Specificity

Gram-positive bacteria assemble pili through class C sortase enzymes specialized in polymerizing pilin subunits into covalently linked, high-molecular-weight, elongated structures. Here we report the crystal structures of two class C sortases (SrtC1 and SrtC2) from Group B Streptococcus (GBS) Pilus Island 1. The structures show that both sortases are comprised of two domains: an 8-stranded β-barrel catalytic core conserved among all sortase family members and a flexible N-terminal region made of two α-helices followed by a loop, known as the lid, which acts as a pseudo-substrate. In vitro experiments performed with recombinant SrtC enzymes lacking the N-terminal portion demonstrate that this region of the enzyme is dispensable for catalysis but may have key roles in substrate specificity and regulation. Moreover, in vitro FRET-based assays show that the LPXTG motif common to many sortase substrates is not the sole determinant of sortase C specificity during pilin protein recognition.     

Retrieving sequences of enzymes experimentally characterized but erroneously annotated : the case of the putrescine carbamoyltransferase

Background  

Annotating genomes remains an hazardous task. Mistakes or gaps in such a complex process may occur when relevant knowledge is ignored, whether lost, forgotten or overlooked. This paper exemplifies an approach which could help to ressucitate such meaningful data.     

Fluorination of Lithium‐Excess Transition Metal Oxide Cathode Materials

Fluorination of Li‐ion cathode materials is of significant interest as it is claimed to lead to significant improvements in long‐term reversible capacity. However, the mechanism by which LiF incorporates and improves performance remains uncertain. Indeed, recent evidence suggests that fluorine is often present as a coating layer rather than incorporated into the bulk of the material. In this work, first‐principles calculations are used to investigate the thermodynamics of fluorination in transition metal oxide cathodes to determine the conditions under which bulk fluorination is possible. It is found that unlike classic well‐ordered cathodes, which cannot incorporate fluorine, disordered rock salt‐structured materials achieve significant fluorination levels due to the presence of locally metal‐poor, lithium‐rich environments that are highly preferred for fluorine. As well as explaining the fluorination process in known materials, this finding is encouraging for the development of new disordered rock salt lithium‐excess transition metal oxides, a promising new class of Li‐ion battery cathode materials that offer superior practical capacity to traditional layered oxides. In particular, it is found that bulk fluorination may serve as an alternative source of Li‐excess in these compounds that can replace the conventional substitution of a heavy redox‐inactive element on the transition metal sublattice.     

Seven large variations in the extent of RNA editing in plant mitochondria between three ecotypes of Arabidopsis thaliana

Most RNA editing sites in flowering plant mitochondria are located in coding regions of mRNAs and are usually essential for correct gene expression. Although accordingly little variation should be tolerated, editing sites appear and disappear even between closely related flowering plant species. To investigate whether such editing site variations also occur within species, we analyzed 379 RNA editing sites in the three ecotypes Columbia, Landsberg erecta and C24 of Arabidopsis thaliana. While all editing sites as such are conserved, we identify seven RNA editing sites with 40-60% differences in effective editing between individual ecotypes. These quantitative variations show that the extent of RNA editing in plant mitochondria is very flexible and can change even more rapidly than the evolution of species. The ecotype-specific variations of the RNA editing extent are Mendelian-inherited and can now be used to follow and identify the nuclear loci responsible for these RNA editing phenotypes.     

Effect of Fluorination on Lithium Transport and Short‐Range Order in Disordered‐Rocksalt‐Type Lithium‐Ion Battery Cathodes

Fluorine substitution is a critical enabler for improving the cycle life and energy density of disordered rocksalt (DRX) Li‐ion battery cathode materials which offer prospects for high energy density cathodes, without the reliance on limited mineral resources. Due to the strong Li–F interaction, fluorine also is expected to modify the short‐range cation order in these materials which is critical for Li‐ion transport. In this work, density functional theory and Monte Carlo simulations are combined to investigate the impact of Li–F short‐range ordering on the formation of Li percolation and diffusion in DRX materials. The modeling reveals that F substitution is always beneficial at sufficiently high concentrations and can, surprisingly, even facilitate percolation in compounds without Li excess, giving them the ability to incorporate more transition metal redox capacity and thereby higher energy density. It is found that for F levels below 15%, its effect can be beneficial or disadvantageous depending on the intrinsic short‐range order in the unfluorinated oxide, while for high fluorination levels the effects are always beneficial. Using extensive simulations, a map is also presented showing the trade‐off between transition‐metal capacity, Li‐transport, and synthetic accessibility, and two of the more extreme predictions are experimentally confirmed.