Unravelling spiral cleavage

Snails, earthworms and flatworms are remarkably different animals, but they all exhibit a very similar mode of early embryogenesis: spiral cleavage. This is one of the most widespread developmental programs in animals, probably ancestral to almost half of the animal phyla, and therefore its study is essential for understanding animal development and evolution. However, our knowledge of spiral cleavage is still in its infancy. Recent technical and conceptual advances, such as the establishment of genome editing and improved phylogenetic resolution, are paving the way for a fresher and deeper look into this fascinating early cleavage mode

Ancient expansion of the Hox cluster in Lepidoptera generated four homeobox genes implicated in extra-embryonic tissue formation

Gene duplications within the conserved Hox cluster are rare in animal evolution, but in Lepidoptera an array of divergent Hox-related genes (Shx genes) has been reported between pb and zen. Here, we use genome sequencing of five lepidopteran species (Polygonia c-album, Pararge aegeria, Callimorpha dominula, Cameraria ohridella, Hepialus sylvina) plus a caddisfly outgroup (Glyphotaelius pellucidus) to trace the evolution of the lepidopteran Shx genes. We demonstrate that Shx genes originated by tandem duplication of zen early in the evolution of large clade Ditrysia; Shx are not found in a caddisfly and a member of the basally diverging Hepialidae (swift moths). Four distinct Shx genes were generated early in ditrysian evolution, and were stably retained in all descendent Lepidoptera except the silkmoth which has additional duplications. Despite extensive sequence divergence, molecular modelling indicates that all four Shx genes have the potential to encode stable homeodomains. The four Shx genes have distinct spatiotemporal expression patterns in early development of the Speckled Wood butterfly (Pararge aegeria), with ShxC demarcating the future sites of extraembryonic tissue formation via strikingly localised maternal RNA in the oocyte. All four genes are also expressed in presumptive serosal cells, prior to the onset of zen expression. Lepidopteran Shx genes represent an unusual example of Hox cluster expansion and integration of novel genes into ancient developmental regulatory networks

Time-calibrated molecular phylogeny of pteropods

© 2017 Burridge et al. This is an open access article distributed under the terms of the [4.0] Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. The attached file is the published version of the article

Parallel evolution of amphioxus and vertebrate small-scale gene duplications

Background: Amphioxus are non-vertebrate chordates characterized by a slow morphological and molecular evolution. They share the basic chordate body-plan and genome organization with vertebrates but lack their 2R whole-genome duplications and their developmental complexity. For these reasons, amphioxus are frequently used as an outgroup to study vertebrate genome evolution and Evo-Devo. Aside from whole-genome duplications, genes continuously duplicate on a smaller scale. Smallscale duplicated genes can be found in both amphioxus and vertebrate genomes, while only the vertebrate genomes have duplicated genes product of their 2R wholegenome duplications. Here, we explore the history of small-scale gene duplications in the amphioxus lineage and compare it to small- and large-scale gene duplication history in vertebrates. Results: We present a study of the European amphioxus (Branchiostoma lanceolatum) gene duplications thanks to a new, high-quality genome reference. We fnd that, despite its overall slow molecular evolution, the amphioxus lineage has had a history of small-scale duplications similar to the one observed in vertebrates. We fnd parallel gene duplication profles between amphioxus and vertebrates and conserved func‑tional constraints in gene duplication. Moreover, amphioxus gene duplicates show lev‑ els of expression and patterns of functional specialization similar to the ones observed in vertebrate duplicated genes. We also fnd strong conservation of gene synteny between two distant amphioxus species, B. lanceolatum and B. foridae, with two major chromosomal rearrangements. Conclusions: In contrast to their slower molecular and morphological evolution, amphioxus' small-scale gene duplication history resembles that of the vertebrate line‑age both in quantitative and in functional terms

High-efficiency, long-pulse operation of MW-level dual-frequency gyrotron, 84/126GHz, for the TCV Tokamak

The first unit of the dual-frequency gyrotron, 84126GHz/1MW/2s, for the upgrade of the TCV ECH system has been delivered and is presently being commissioned. During a first phase, long-pulse operation (TRF gt 0.5 mathrm{s}) has been achieved and powers in excess of 0.93MW/1.1s and 1MW/1.2s have been measured in the evacuated RF-load at the two frequencies, 84GHz (TE {17,5} mode) and 126GHz (TE {26,7} mode), respectively. Considering the different rf losses in the experimental setup, the power level generated in the gyrotron cavity is in excess of 1.1MW and 1.2MW, with a corresponding electronic efficiency of 35% and 36%. These values are in excellent agreement with the design parameters and would likely lead to a gyrotron total efficiency higher than 50% in case of implementation of a depressed collector. The gyrotron behavior is remarkably reliable and robust with the pulse length extension to 2s presently only limited by external auxiliary systems

Genomic adaptations to aquatic and aerial life in mayflies and the origin of insect wings

The evolution of winged insects revolutionized terrestrial ecosystems and led to the largest animal radiation on Earth. However, we still have an incomplete picture of the genomic changes that underlay this diversification. Mayflies, as one of the sister groups of all other winged insects, are key to understanding this radiation. Here, we describe the genome of the mayfly Cloeon dipterum and its gene expression throughout its aquatic and aerial life cycle and specific organs. We discover an expansion of odorant-binding-protein genes, some expressed specifically in breathing gills of aquatic nymphs, suggesting a novel sensory role for this organ. In contrast, flying adults use an enlarged opsin set in a sexually dimorphic manner, with some expressed only in males. Finally, we identify a set of wing-associated genes deeply conserved in the pterygote insects and find transcriptomic similarities between gills and wings, suggesting a common genetic program. Globally, this comprehensive genomic and transcriptomic study uncovers the genetic basis of key evolutionary adaptations in mayflies and winged insects