Linkage studies in the Pacific Spider Mite Tetranychus pacificus II. Genes for white eyeii, lemon and flamingo

The linkage relationships between eight different loci in Tetranychus pacificus are presented. It appears that from the 20 two-factor crosses studied, only two combinations show linkage. In 18 cases no linkage effects could be demonstrated, notwithstanding the considerable resolving power of recombinational analysis. Since T. pacificus has few chromosomes (n=3), the high recombination index is surprising and has to be explained by a high chiasmata-frequency.

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Zusammenfassung Die Koppelungs-Verhältnisse zwischen 8 verschiedenen Genloci von Tetranychus pacificus McGregor werden dargestellt. Es scheint, daß von den 20 geprüften Zweifaktor-Kreuzungen nur 2 Kombinationen Koppelung aufweisen. In 18 Fällen konnten keine Koppelungs-Effekte nachgewiesen werden, ungeachtet der beträchtlichen Aussagekraft der Rekombinationsanalyse. Da T. pacificus nur wenige Chromosomen (n=3) besitzt, ist der hohe Rekombinationsgrad überraschend. Er kann nur durch eine hohe Chiasmata-Häufigkeit erklärt werden.

     

Global non-covalent SUMO interaction networks reveal SUMO-dependent stabilization of the non-homologous end joining complex

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GTSF‐1 is required for formation of a functional RNA‐dependent RNA Polymerase complex in Caenorhabditis elegans

Argonaute proteins and their associated small RNAs (sRNAs) are evolutionarily conserved regulators of gene expression. Gametocyte‐specific factor 1 (Gtsf1) proteins, characterized by two tandem CHHC zinc fingers and an unstructured C‐terminal tail, are conserved in animals and have been shown to interact with Piwi clade Argonautes, thereby assisting their activity. We identified the Caenorhabditis elegans Gtsf1 homolog, named it gtsf‐1 and characterized it in the context of the sRNA pathways of C. elegans. We report that GTSF‐1 is not required for Piwi‐mediated gene silencing. Instead, gtsf‐1 mutants show a striking depletion of 26G‐RNAs, a class of endogenous sRNAs, fully phenocopying rrf‐3 mutants. We show, both in vivo and in vitro, that GTSF‐1 interacts with RRF‐3 via its CHHC zinc fingers. Furthermore, we demonstrate that GTSF‐1 is required for the assembly of a larger RRF‐3 and DCR‐1‐containing complex (ERIC), thereby allowing for 26G‐RNA generation. We propose that GTSF‐1 homologs may act to drive the assembly of larger complexes that act in sRNA production and/or in imposing sRNA‐mediated silencing activities.     

Variola virus genome sequenced from an eighteenth-century museum specimen supports the recent origin of smallpox

Smallpox, caused by the variola virus (VARV), was a highly virulent disease with high mortality rates causing a major threat for global human health until its successful eradication in 1980. Despite previously published historic and modern VARV genomes, its past dissemination and diversity remain debated. To understand the evolutionary history of VARV with respect to historic and modern VARV genetic variation in Europe, we sequenced a VARV genome from a well-described eighteenth-century case from England (specimen P328). In our phylogenetic analysis, the new genome falls between the modern strains and another historic strain from Lithuania, supporting previous claims of larger diversity in early modern Europe compared to the twentieth century. Our analyses also resolve a previous controversy regarding the common ancestor between modern and historic strains by confirming a later date around the seventeenth century. Overall, our results point to the benefit of historic genomes for better resolution of past VARV diversity and highlight the value of such historic genomes from around the world to further understand the evolutionary history of smallpox as well as related diseases.This article is part of the theme issue ‘Insights into health and disease from ancient biomolecules’.     

Deletion of glutamate dehydrogenase 1 (Glud1) in the central nervous system affects glutamate handling without altering synaptic transmission

Glutamate dehydrogenase (GDH), encoded by GLUD1, participates in the breakdown and synthesis of glutamate, the main excitatory neurotransmitter. In the CNS, besides its primary signaling function, glutamate is also at the crossroad of metabolic and neurotransmitter pathways. Importance of brain GDH was questioned here by generation of CNS‐specific GDH‐null mice (CnsGlud1^?/?); which were viable, fertile and without apparent behavioral problems. GDH immunoreactivity as well as enzymatic activity were absent in Cns‐Glud1^?/? brains. Immunohistochemical analyses on brain sections revealed that the pyramidal cells of control animals were positive for GDH, whereas the labeling was absent in hippocampal sections of Cns‐Glud1^?/? mice. Electrophysiological recordings showed that deletion of GDH within the CNS did not alter synaptic transmission in standard conditions. Cns‐Glud1^?/? mice exhibited deficient oxidative catabolism of glutamate in astrocytes, showing that GDH is required for Krebs cycle pathway. As revealed by NMR studies, brain glutamate levels remained unchanged, whereas glutamine levels were increased. This pattern was favored by up‐regulation of astrocyte‐type glutamate and glutamine transporters and of glutamine synthetase. Present data show that the lack of GDH in the CNS modifies the metabolic handling of glutamate without altering synaptic transmission.     

Genetic variability of photoperiodic response in an arrhenotokous mite (Tetranychus urticae)

Starting with a population of Tetranychus urticae, a number of lines were inbred by sibmating for seven generations. When these inbred lines were exposed to different photoperiodic regimens, a diversity of response curves was obtained. This indicated that great genetic variability of photoperiodic response existed in the original colony.From reciprocal mass-crosses between one line, characterized by a low level response (LR), and several lines which showed a nearly saturated photoperiodic response (HR), it was concluded that HR was dominant over LR. From a study of the backcrosses to LR-males, it appeared that the transmission of the character was different in the two types of F₁-hybrids. The difference could be explained by assuming a cytoplasmic determinant. The possibility that the difference in inheritance resulted from a peculiar haplo-diploid sex-determination was also considered.

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Zusammenfassung Von einer Wildpopulation der Spinnmilbe Tetranychus urticae von Sambucus ausgehend, wurden durch Geschwisterpaarung über 7 Generationen eine Anzahl Inzucht-Linien gezüchtet. Wenn diese Inzucht-Linien verschiedenen Tageslängen ausgesetzt wurden, ergaben sich unterschiedliche photoperiodische Wirkungskurven bezüglich der Diapause-Reaktion. Diese weisen auf das Vorhandensein einer großen genetischen Variabilität in der photoperiodischen Reaktion der Ausgangspopulation hin.Aus reziproken Massenkreuzungen zwischen einer durch einen niedrigen Reaktionsspiegel (LR) gekennzeichneten Linie mit verschiedenen Linien mit hahezu vollständiger, photoperiodisch bedingter Diapause-Reaktion (HR) wird geschlossen, daß HR (hohe Diapause-Auslösung) über LR (schwache Diapause-Auslösung) dominant ist. Aus einer Untersuchung von Rückkreuzungen der weiblichen Hybriden mit LR-Männchen ergibt sich, daß die Weitergabe der Reaktionseigenschaft bei den beiden Typen der F₁-Bastarde (HR x LR bzw. LR x HR) anscheinend verschieden ist. Der Unterschied könnte mit der Annahme eines cytoplasmatischen Vererbungsfaktors erklärt werden. Doch wird auch die Möglichkeit erwogen, daß der Unterschied im Erbgang durch die Besonderheit einer geschlechtsgebundenen haplo-diploiden Vererbung bedingt sei.

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The study is a part of an International Biological Programme Project in the Netherlands.