Suchergebnisse

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. ; This project was mainly funded by the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie Grant Agreement 657732 to I.A., Grant BFU2015-66040-P to F.Ca., institutional Grant MDM-2016-0687 (MINECO, Spain). Additional funding was provided by the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program (ERC-StG-LS2-637591 to M.I.), the Spanish Ministerio de Ciencia (BFU2017-89201-P to M.I., RYC-2016-20089 and PGC2018-099392-A-I00 to I.M.)

The mechanisms by which entire programmes of gene regulation emerged during evolution are poorly understood. Neuronal microexons represent the most conserved class of alternative splicing in vertebrates, and are critical for proper brain development and function. Here, we discover neural microexon programmes in non-vertebrate species and trace their origin to bilaterian ancestors through the emergence of a previously uncharacterized 'enhancer of microexons' (eMIC) protein domain. The eMIC domain originated as an alternative, neural-enriched splice isoform of the pan-eukaryotic Srrm2/SRm300 splicing factor gene, and subsequently became fixed in the vertebrate and neuronal-specific splicing regulator Srrm4/nSR100 and its paralogue Srrm3. Remarkably, the eMIC domain is necessary and sufficient for microexon splicing, and functions by interacting with the earliest components required for exon recognition. The emergence of a novel domain with restricted expression in the nervous system thus resulted in the evolution of splicing programmes that qualitatively expanded the neuronal molecular complexity in bilaterians. ; This work has been funded by the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (ERC-StG-LS2-637591 to M.Ir. and ERC-AdvG-670146 to J.V.), the Spanish Ministry of Economy and Competitiveness (BFU2014-55076-P and BFU2017-89201-P to M.Ir., BFU2014-005153 to J.V., and the 'Centro de Excelencia Severo Ochoa 2013–2017' (SEV-2012-0208)), AGAUR, Fundación Botín (to J.V.) and the Canadian Institutes of Health Research (to B.J.B. and A.-C.G.). RNP mass spectrometric analyses were performed at the CRG/UPF Proteomics Unit (part of ProteoRed-PRB3, supported by PE I+D+i 2013–2016 (PT17/0019) of the ISCIII and ERDF) by 'Programa CERCA Generalitat de Catalunya' and 'Secretaria d'Universitats i Recerca del Departament d'Economia i Coneixement' (2017SGR595). A.T.-M. held an FPI-SO fellowship, and Y.M. a Marie Skłodowska-Curie individual fellowship.