BackgroundSexual reproduction involving the fusion of egg and sperm is prevailing among eukaryotes. In contrast, the nematode Diploscapter coronatus, a close relative of the model Caenorhabditis elegans, reproduces parthenogenetically. Neither males nor sperm have been observed and some steps of meiosis are apparently skipped in this species. To uncover the genomic changes associated with the evolution of parthenogenesis in this nematode, we carried out a genome analysis.ResultsWe obtained a 170 Mbp draft genome in only 511 scaffolds with a N50 length of 1 Mbp. Nearly 90% of these scaffolds constitute homologous pairs with a 5.7% heterozygosity on average and inversions and translocations, meaning that the 170 Mbp sequences correspond to the diploid genome. Fluorescent staining shows that the D. coronatus genome consists of two chromosomes (2n = 2). In our genome annotation, we found orthologs of 59% of the C. elegans genes. However, a number of genes were missing or very divergent. These include genes involved in sex determination (e.g. xol-1, tra-2) and meiosis (e.g. the kleisins rec-8 and coh-3/4) giving a possible explanation for the absence of males and the second meiotic division. The high degree of heterozygosity allowed us to analyze the expression level of individual alleles. Most of the homologous pairs show very similar expression levels but others exhibit a 2–5-fold difference.ConclusionsOur high-quality draft genome of D. coronatus reveals the peculiarities of the genome of parthenogenesis and provides some clues to the genetic basis for parthenogenetic reproduction. This draft genome should be the basis to elucidate fundamental questions related to parthenogenesis such as its origin and mechanisms through comparative analyses with other nematodes. Furthermore, being the closest outgroup to the genus Caenorhabditis, the draft genome will help to disclose many idiosyncrasies of the model C. elegans and its congeners in future studies.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-017-3860-x) contains supplementary material, which is available to authorized users.

Eine umfangreiche Fehleranalyse von Aufsätzen, die Studenten mit Englisch bzw. Japanisch als Zweitsprache geschrieben haben, hat ergeben, daß fortgeschrittene Lernende in diesen beiden Sprachen in bezug auf das Passiv noch viele Fehler machen. Diese Fehler sind teilweise formaler, vor allem aber funktionaler Art. Die Analyse zeigt, daß die Lernenden irrtümlicher-weise annehmen, daß die Formen in der Fremdsprache, die denen in der Muttersprache vergleichbar sind, auch dieselben Funktionen wie in der Muttersprache haben. Insofern handelt es sich um einen speziellen Fall von muttersprachlicher Interferenz beim Fremdsprachenerwerb.Une analyse extensive de fautes commises dans des compositions dues a des etudiants ayant anglais et japonais respectivement comme deuxieme langue a montro que meme des otudiants avances de ces deux langues commettent encore de nombreuses fautes, notamment dans leur emploi du passif. Ces fautes sont en partie formelles mais surtout de caractere fonctionnel. II ressort de l'analyse que les etudiants commettent l'erreur d'identifier la forme dans la langue etrangere avec celle de la langue maternelle en attribuant aux deux la meme fonction. Dans ce cas, il s'agit d'un cas special d'interference entre la langue maternelle et la langue etrangere.

Thymidylate synthase (TS; N 5 ,N 10 -methylenetetrahydrofolate: dUMP C-methyltransferase; EC 2.1.1.45) catalyzes the conversion of deoxyuridylate to thymidylate, and is a key enzyme that controls a balanced supply of four DNA precursors. The gene for TS is a typical housekeeping gene and its expression is regulated depending on both the cell cycle [1][2][3] and the state of cell proliferation.4-7) The human TS gene and its cDNA were isolated [8][9][10][11] and their primary and functional structures have been extensively elucidated.