112 research outputs found
Investigating episodic accretion in a very low-mass young stellar object
Very low-mass Class I protostars have been investigated very little thus far.
Variability of these young stellar objects (YSOs) and whether or not they are
capable of strong episodic accretion is also left relatively unstudied. We
investigate accretion variability in IRS54, a Class I very low-mass protostar
with a mass of M ~ 0.1 - 0.2 M. We obtained spectroscopic
and photometric data with VLT/ISAAC and VLT/SINFONI in the near-infrared (,
, and bands) across four epochs (2005, 2010, 2013, and 2014). We used
accretion-tracing lines (Pa and Br) and outflow-tracing lines
(H and [FeII] to examine physical properties and kinematics of the object.
A large increase in luminosity was found between the 2005 and 2013 epochs of
more than 1 magnitude in the band, followed in 2014 by a steep decrease.
Consistently, the mass accretion rate () rose by an order of
magnitude from ~ 10 M yr to ~ M
yr between the two early epochs. The visual extinction () has also
increased from ~ 15 mag in 2005 to ~ 24 mag in 2013. This rise in in
tandem with the increase in is explained by the lifting up of a
large amount of dust from the disc of IRS54, following the augmented accretion
and ejection activity in the YSO, which intersects our line of sight due to the
almost edge-on geometry of the disc. Because of the strength and timescales
involved in this dramatic increase, this event is believed to have been an
accretion burst possibly similar to bursts of EXor-type objects. IRS54 is the
lowest mass Class I source observed to have an accretion burst of this type,
and therefore potentially one of the lowest mass EXor-type objects known so
far
Comparative genomics of Steinernema reveals deeply conserved gene regulatory networks
Background:
Parasitism is a major ecological niche for a variety of nematodes. Multiple nematode lineages have specialized as pathogens, including deadly parasites of insects that are used in biological control. We have sequenced and analyzed the draft genomes and transcriptomes of the entomopathogenic nematode Steinernema carpocapsae and four congeners (S. scapterisci, S. monticolum, S. feltiae, and S. glaseri).
Results:
We used these genomes to establish phylogenetic relationships, explore gene conservation across species, and identify genes uniquely expanded in insect parasites. Protein domain analysis in Steinernema revealed a striking expansion of numerous putative parasitism genes, including certain protease and protease inhibitor families, as well as fatty acid- and retinol-binding proteins. Stage-specific gene expression of some of these expanded families further supports the notion that they are involved in insect parasitism by Steinernema. We show that sets of novel conserved non-coding regulatory motifs are associated with orthologous genes in Steinernema and Caenorhabditis.
Conclusions:
We have identified a set of expanded gene families that are likely to be involved in parasitism. We have also identified a set of non-coding motifs associated with groups of orthologous genes in Steinernema and Caenorhabditis involved in neurogenesis and embryonic development that are likely part of conserved protein–DNA relationships shared between these two genera
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Social connections predict brain structure in a multidimensional free-ranging primate society
Reproduction and survival in most primate species reflects management of both competitive and cooperative relationships. Here, we investigated the links between neuroanatomy and sociality in free-ranging rhesus macaques. In adults, the number of social partners predicted the volume of the mid–superior temporal sulcus and ventral-dysgranular insula, implicated in social decision-making and empathy, respectively. We found no link between brain structure and other key social variables such as social status or indirect connectedness in adults, nor between maternal social networks or status and dependent infant brain structure. Our findings demonstrate that the size of specific brain structures varies with the number of direct affiliative social connections and suggest that this relationship may arise during development. These results reinforce proposed links between social network size, biological success, and the expansion of specific brain circuits
Molecular Evolution of the Two-Component System BvgAS Involved in Virulence Regulation in Bordetella
The whooping cough agent Bordetella pertussis is closely related to Bordetella bronchiseptica, which is responsible for chronic respiratory infections in various mammals and is occasionally found in humans, and to Bordetella parapertussis, one lineage of which causes mild whooping cough in humans and the other ovine respiratory infections. All three species produce similar sets of virulence factors that are co-regulated by the two-component system BvgAS. We characterized the molecular diversity of BvgAS in Bordetella by sequencing the two genes from a large number of diverse isolates. The response regulator BvgA is virtually invariant, indicating strong functional constraints. In contrast, the multi-domain sensor kinase BvgS has evolved into two different types. The pertussis type is found in B. pertussis and in a lineage of essentially human-associated B. bronchiseptica, while the bronchiseptica type is associated with the majority of B. bronchiseptica and both ovine and human B. parapertussis. BvgS is monomorphic in B. pertussis, suggesting optimal adaptation or a recent population bottleneck. The degree of diversity of the bronchiseptica type BvgS is markedly different between domains, indicating distinct evolutionary pressures. Thus, absolute conservation of the putative solute-binding cavities of the two periplasmic Venus Fly Trap (VFT) domains suggests that common signals are perceived in all three species, while the external surfaces of these domains vary more extensively. Co-evolution of the surfaces of the two VFT domains in each type and domain swapping experiments indicate that signal transduction in the periplasmic region may be type-specific. The two distinct evolutionary solutions for BvgS confirm that B. pertussis has emerged from a specific B. bronchiseptica lineage. The invariant regions of BvgS point to essential parts for its molecular mechanism, while the variable regions may indicate adaptations to different lifestyles. The repertoire of BvgS sequences will pave the way for functional analyses of this prototypic system
Clofarabine-associated acute kidney injury in patients undergoing hematopoietic stem cell transplant
Molecular characterization of the mycobacterial SenX3–RegX3 two-component system: evidence for autoregulation
Additional file 2: of Comparative genomics of Steinernema reveals deeply conserved gene regulatory networks
Supplementary tables and legends. (PDF 1760Â kb
Additional file 13: of Comparative genomics of Steinernema reveals deeply conserved gene regulatory networks
Muscle development network file. Contains motifs that have a conserved association with muscle development-related genes (See âMethodsâ regarding motif conservation) in both S. carpocapsae and C. elegans. The first column contains the motif ID, the second column contains the edge weight, and the third and fourth columns contain C. elegans gene IDs in two different formats. (TXT 5Â kb
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