1,616 research outputs found
Annotation of Tribolium nuclear receptors reveals an evolutionary overacceleration of a network controlling the ecdysone cascade
The Tribolium genome contains 21 nuclear receptors, representing all of the
six known subfamilies. When compared to other species, this first complete set
for a Coleoptera reveals a strong conservation of the number and identity of
nuclear receptors in holometabolous insects. Two novelties are observed: the
atypical NR0 gene knirps is present only in brachyceran flies, while the NR2E6
gene is found only in Tribolium and in Apis. Using a quantitative analysis of
the evolutionary rate, we discovered that nuclear receptors could be divided
into two groups. In one group of 13 proteins, the rates follow the trend of the
Mecopterida genome-wide acceleration. In a second group of five nuclear
receptors, all acting together at the top of the ecdysone cascade, we observed
an overacceleration of the evolutionary rate during the early divergence of
Mecopterida. We thus extended our analysis to the twelve classic ecdysone
transcriptional regulators and found that six of them (ECR, USP, HR3, E75, HR4
and Kr-h1) underwent an overacceleration at the base of the Mecopterida
lineage. By contrast, E74, E93, BR, HR39, FTZ-F1 and E78 do not show this
divergence. We suggest that coevolution occurred within a network of regulators
that control the ecdysone cascade. The advent of Tribolium as a powerful model
should allow a better understanding of this evolution
Shared and unique patterns of embryo development in extremophile poeciliids
Background: Closely related lineages of livebearing fishes have independently adapted to two extreme environmental factors: toxic hydrogen sulphide (H2S) and perpetual darkness. Previous work has demonstrated in adult specimens that fish from these extreme habitats convergently evolved drastically increased head and offspring size, while cave fish are further characterized by reduced pigmentation and eye size. Here, we traced the development of these (and other) divergent traits in embryos of Poecilia mexicana from benign surface habitats (âsurface molliesâ) and a sulphidic cave (âcave molliesâ), as well as in embryos of the sister taxon, Poecilia sulphuraria from a sulphidic surface spring (âsulphur molliesâ). We asked at which points during development changes in the timing of the involved processes (i.e., heterochrony) would be detectible.
Methods and Results: Data were extracted from digital photographs taken of representative embryos for each stage of development and each type of molly. Embryo mass decreased in convergent fashion, but we found patterns of embryonic fat content and ovum/embryo diameter to be divergent among all three types of mollies. The intensity of yellow colouration of the yolk (a proxy for carotenoid content) was significantly lower in cave mollies throughout development. Moreover, while relative head size decreased through development in surface mollies, it increased in both types of extremophile mollies, and eye growth was arrested in mid-stage embryos of cave mollies but not in surface or sulphur mollies.
Conclusion: Our results clearly demonstrate that even among sister taxa convergence in phenotypic traits is not always achieved by the same processes during embryo development. Furthermore, teleost development is crucially dependent on sufficient carotenoid stores in the yolk, and so we discuss how the apparent ability of cave mollies to overcome this carotenoid-dependency may represent another potential mechanism explaining the lack of gene flow between surface and cave mollies
A tool to promote experimental zoology at the end of the 19th century: the creation of the âArchives de Zoologie ExpĂ©rimentale et GĂ©nĂ©raleâ
1872, France. An eminent zoologist of the time, Henri de Lacaze-Duthiers, realises one of his most important goals: he creates a new journal, focused on zoological discoveries, which he calls âArchives de Zoologie ExpĂ©rimentale et GĂ©nĂ©raleâ. His motivations were threefold. the first was to participate in the intellectual reconstruction of France, humiliated by the defeat against Prussia in 1871. the second was to promote a new way of conceiving and doing zoology: zoology should be approached through experience (and not just observation), and it should be general, including everything related to animal life (embryology, physiology, histology, ecology). the third was to acquire freedom and autonomy by liberating himself from the conservative journal that had a quasi-monopoly on zoology at the time, âles Annales de sciences naturellesâ. the Archives, which had a difficult start, had an impressive success, revealing young talents from all over Europe and reporting on major discoveries, until their last issue in 1981. this article recounts their adventure.journal articl
5. Retro-Review: Michel Verdon, Keynes and the âClassicsâ: a study in language, epistemology and mistaken identities, 1996. Essay review
Les travaux dâAmartya Sen repose sur une conception anthropologique de lâhomme dans laquelle les potentialitĂ©s dâactions lui sont inhĂ©rentes, mais non pas acquises. Câest la formation sociale dans laquelle lâhomme vit qui, selon les circonstances, lui rend un fonctionnement possible, ou impossible. Les travaux de Sen se dĂ©veloppent Ă partir du concept de « capabilité », ce qui ne suppose pas que ce concept soit intĂ©gralement dĂ©terminĂ©.Michel Verdon, aujourdâhui Ă la retraite, est un anthropologue (Ă©tude de lâhomme), Professeur Ă la FacultĂ© des Arts et des Sciences de lâUniversitĂ© de MontrĂ©al. En 1996, il Ă©crivait Keynes and the âClassicsâ: a study in language, epistemology and mistaken identities, dans lequel il cherche Ă mettre Ă jour les consĂ©quences Ă©pistĂ©mologiques, quant au discours Ă©conomique, de ce quâil appelle les fondements cosmologiques et anthropologiques des pensĂ©es nĂ©o-classiques et de John Maynard Keynes. Ă lâheure oĂč les pratiques Ă©conomiques conduisent les sociĂ©tĂ©s Ă rencontrer bien des difficultĂ©s sociales et/ou politiques, une telle discussion demeure dâune brulante actualitĂ©, quand bien mĂȘme cette discussion a plus de 20 ans. Câest la raison de ce « compte rendu » dâun livre paru il y a longtemps, qui est une invitation Ă lire et relire lâouvrage de Michel Verdon
Microevolution of cis-Regulatory Elements: An Example from the Pair-Rule Segmentation Gene fushi tarazu in the Drosophila melanogaster Subgroup
The importance of non-coding DNAs that control transcription is ever noticeable, but the characterization and analysis of the evolution of such DNAs presents challenges not found in the analysis of coding sequences. In this study of the cis-regulatory elements of the pair rule segmentation gene fushi tarazu (ftz) I report the DNA sequences of ftz's zebra element (promoter) and a region containing the proximal enhancer from a total of 45 fly lines belonging to several populations of the species Drosophila melanogaster, D. simulans, D. sechellia, D. mauritiana, D. yakuba, D. teissieri, D. orena and D. erecta. Both elements evolve at slower rate than ftz synonymous sites, thus reflecting their functional importance. The promoter evolves more slowly than the average for ftz's coding sequence while, on average, the enhancer evolves more rapidly, suggesting more functional constraint and effective purifying selection on the former. Comparative analysis of the number and nature of base substitutions failed to detect significant evidence for positive/adaptive selection in transcription-factor-binding sites. These seem to evolve at similar rates to regions not known to bind transcription factors. Although this result reflects the evolutionary flexibility of the transcription factor binding sites, it also suggests a complex and still not completely understood nature of even the characterized cis-regulatory sequences. The latter seem to contain more functional parts than those currently identified, some of which probably transcription factor binding. This study illustrates ways in which functional assignments of sequences within cis-acting sequences can be used in the search for adaptive evolution, but also highlights difficulties in how such functional assignment and analysis can be carried out
Annotation of Tribolium nuclear receptors reveals an increase in evolutionary rate of a network controlling the ecdysone cascade
Special Issue on the Tribolium GenomeThe Tribolium genome contains 21 nuclear receptors, representing all of the six known subfamilies. This first complete set for a coleopteran species reveals a strong conservation of the number and identity of nuclear receptors in holometabolous insects. Two novelties are observed: the atypical NR0 gene knirps is present only in brachyceran flies, while the NR2E6 gene is found only in Tribolium and in Apis. Using a quantitative analysis of the evolutionary rate, we discovered that nuclear receptors could be divided into two groups. In one group of 13 proteins, the rates follow the trend of the Mecopterida genome-wide acceleration. In a second group of five nuclear receptors, all acting early during the ecdysone cascade, we observed an even higher increase of the evolutionary rate during the early divergence of Mecopterida. We thus extended our analysis to the twelve classic ecdysone transcriptional regulators and found that six of them (ECR, USP, HR3, E75, HR4 and Kr-h1) underwent an increase in evolutionary rate at the base of the Mecopterida lineage. By contrast, E74, E93, BR, HR39, FTZ-F1 and E78 do not show this divergence. We suggest that coevolution occurred within a network of regulators that control the ecdysone cascade. The advent of Tribolium as a powerful model should allow a better understanding of this evolutionary event
Anemonefishes: A model system for evolutionary genomics
Anemonefishes are an iconic group of coral reef fish particularly known for their mutualistic relationship with sea anemones. This mutualism is especially intriguing as it likely prompted the rapid diversification of anemonefish. Understanding the genomic architecture underlying this process has indeed become one of the holy grails of evolutionary research in these fishes. Recently, anemonefishes have also been used as a model system to study the molecular basis of highly complex traits such as color patterning, social sex change, larval dispersal and life span. Extensive genomic resources including several high-quality reference genomes, a linkage map, and various genetic tools have indeed enabled the identification of genomic features controlling some of these fascinating attributes, but also provided insights into the molecular mechanisms underlying adaptive responses to changing environments. Here, we review the latest findings and new avenues of research that have led to this group of fish being regarded as a model for evolutionary genomics.journal articl
Studying non-mammalian models? Not a fool's ERRand!
Through studies in mammalian model systems, the estrogen-receptor-related receptor (ERR) alpha, an orphan nuclear receptor, has been shown to interfere with estrogen signaling and might therefore be an interesting pharmaceutical target in estrogen-related diseases. ERRalpha is also involved in energy storage and consumption, and its modulation might be of relevance in the treatment of obesity and diabetes. Recent data have also been published on the effects of this receptor, as well as other members of the ERR family, in non-mammalian animal model systems. Besides indications concerning their mechanisms of action, this analysis demonstrated a role for ERRalpha in controlling cellular movements, and suggested that ERRs might be implicated in a more subtle range of processes than originally envisioned
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