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7Th International Choanoflagellates & Friends Meeting 24Th-27Th May 2019

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7Th International Choanoflagellates & Friends Meeting 24Th-27Th May 2019 7th International Choanoflagellates & Friends Meeting 24th-27th May 2019 ~ Barcelona Organizing Committee Omaya Dudin Andrej Ondacka Postdoctoral Researcher Postdoctoral Researcher [email protected] [email protected] Daniel J. Richter Núria Ros i Rocher Postdoctoral Researcher Postdoctoral Researcher [email protected] [email protected] Acknowledgements for organizational support Administration & Communication Services - Institute of Evolutionary Biology (CSIC-UPF) The King Lab – UC Berkeley Sponsors Book of Abstracts 7th International Choanoflagellates & Friends Meeting 24th-27th May 2019 ~ Barcelona Book of Abstracts Friday, 24th May 2019 The evolutionary origin of animal cell differentiation and synaptic signalling machinery Pawel Burkhardt Sars International Centre for Marine Molecular Biology, University of Bergen, Norway Choanoflagellates, the closest unicellular relatives of animals, express many genes previously thought to be animal specific. Strikingly, these tiny protists can alternate between unicellular and multicellular states, making choanoflagellates powerful models to investigate the origin of animal multicellularity, the mechanisms underlying cell differentiation and the ancestry of synaptic protein machinery. We used electron microscopy to reconstruct in three dimensions the total subcellular composition of unicellular and multicellular choanoflagellates as well as the collar cells from a marine sponge. We found differences between single and multicellular choanoflagellates in structures associated with cellular energetics, membrane trafficking and cell morphology and identified a putative novel cell type within rosette colonies. These findings are an important step forward in reconstructing the biology of last common ancestor of the animals and suggests that both, temporal and spatial cell type differentiation was present in the stem lineage leading to animals. In the second part of my talk, I will present our recent discoveries on synaptic protein homologs found in choanoflagellates. We have biochemically and structurally characterized several synaptic protein complexes from choanoflagellates and gained insights into their molecular mechanism. For example, we identified a primordial neurosecretory apparatus and found that the mechanism, by which presynaptic proteins required for secretion of neurotransmitters interact, is conserved in choanoflagellates and animals. 2019 International Choanoflagellates & Friends Meeting Page 2 of 38 Book of Abstracts Saturday, 25th May 2019 Abundance and diversity of loricate choanoflagellates in subtropical oligotrophic South Pacific Ocean Nina Kamennaya Tel Aviv University Nutrient-depleted regions dominate the World Ocean because they cover ~40% of the Earth surface. Since nutrient availability generally controls growth of bacterioplankton, concentration of bacteria in surface waters of these oligotrophic regions is particularly low. This makes bacteria a scarcer prey for unicellular eukaryotic predators. To identify the unicellular bacterivores of the oligotrophic regions we flow sorted small, non-pigmented eukaryotes directly from the Atlantic and Pacific Oceans and imaged them using electron microscopy. The sorted eukaryotes routinely comprised loricate Acanthoecida and occasionally non-loricate Craspedida choanoflagellate species. In addition to evident bacterivory, several micrographs suggest that some choanoflagellate species could also feed on armored eukaryotes. 2019 International Choanoflagellates & Friends Meeting Page 3 of 38 Book of Abstracts Choanoflagellate gene expression in the open ocean Daniel Richter Institute of Evolutionary Biology (CSIC-UPF) The Tara Oceans expedition sailed the globe over a three-year period, collecting samples from over 150 individual stations. For eukaryotic plankton ranging from 0.8 μm-2 mm, we apply phylogenetic methods to Tara metatranscriptomic data to catalog transcriptional activity in the world’s surface oceans. First, we map Tara Oceans metatranscriptomic sequences to a database of phylogenetic trees for 300 conserved genes to produce a eukaryotic tree of life with each branch weighted by its transcriptional activity. We find that, globally, metatranscriptomes show a similar representation of eukaryotic lineages to Tara metabarcodes (from the V9 region of the 18S locus), indicating that both sources likely reflect the biomass of active cells in the surface ocean. Within the catalog of conserved genes, choanoflagellates represent roughly 1% of global transcript abundance. We next present an analysis of the biogeography of choanoflagellate transcription in the ocean, with the following questions: which species are the most active in different parts of the global ocean? Next, how is the expression of specific functional genes in choanoflagellates (for example, the gene for silicon transport, a requirement for lorica construction) related to local environmental conditions? 2019 International Choanoflagellates & Friends Meeting Page 4 of 38 Book of Abstracts Spotlight on Nudiform Choanoflagellates – an Evolutionary Paradox Sabine Schiwitza, Frank Nitsche University of Cologne Lorica-bearing choanoflagellates (Acanthoecida) are separated into two families based on their way of lorica production. In the tectiform condition, the mother cell provides a bundle of costal strips prior to cell division to the juvenile cell, whereas nudiform reproducing species have to develop the lorica after division independently. This observation could be confirmed by molecular analysis, but the ecological and evolutionary significance is still under debate. Nudiform choanoflagellates are discussed as an evolutionary paradox as the species are indeed consistent in their way of cell division and lorica production but in terms of morphological characterization they lack coherency. Considering species richness, tectiform choanoflagellates contain a multitude of species compared to nudiforms, where until now only six species were present. With our study we draw attention to the prior neglected and as minor described family of nudiform choanoflagellates. Only recently, we could discover a new sister clade within the nudiforms and described the genus Enibas, comprising until now the species E. tolerabilis and E. thessalia, but with high potential of a greater extent as eDNA data suggest. Interestingly, these species resemble morphologically the tectiform genus Stephanoeca, but show clearly the nudiform cell division and lorica production, supporting the phylogenetic classification within the nudiforms. This particular stephanoecid morphology is now present in both families. It becomes even more obvious that the genus Stephanoeca is in need of revision as we could additionally assign a previous only morphologically described Stephanoeca species to the nudiform family based on molecular data. With our study we could show that the family of nudiform choanoflagellates is broadly underestimated. The combination of molecular and morphological tools together with distinct observations regarding the condition of reproduction will lead to a revision within the Acanthoecida and will help to understand the evolutionary relationship between both conditions. 2019 International Choanoflagellates & Friends Meeting Page 5 of 38 Book of Abstracts Further evidence for phylogenetic and morphological discrepancies within the genus Acanthocorbis Frank Nitsche, Mona Rosse and Sabine Schiwitza Biological Department, Institute of Zoology, Biocenter Cologne, University of Cologne, Zuelpicher Straße 47b, 50674 Cologne, Germany The genus Acanthocorbis Hara & Takahashi has one of the most troubled histories within the choanoflagellates. Prior described as Acanthoecopsis Norris it was renamed due to discrepancies based on misleading morphological descriptions. Within the genus Acanthocorbis, nine species are morphologically described but only one, Acanthocorbis unguiculata has been sequenced so far. In 2008, Leadbeater et al. had indication that Acanthocorbis nana might be incorrectly positioned to the tectiform genus as a four-gene analysis placed this species within the nudiforms. A following morphological and molecular analysis gave evidence that this species shows a nudiform lorica reproduction allowing the erection of a new genus, Helgoeca within the nudiform clade. According to latest phylogenetic analyses, Acanthocorbis unguiculata is placed in a clade with Cosmoeca ventricosa, Parvicobicula pedunculata and Stephanoeca apheles with low bootstrap support. In our study we could describe one new Acanthocorbis camarensis-like species with molecular data of the SSU and LSU rDNA which is clustering apart from the other Acanthocorbis species. This polyphyly within loricated choanoflagellates is already known from another genus, the morphological “meltingpot” Stephanoeca. As molecular data of type species are crucial to resolve phylogenetic analyses, our results indicates that only morphological characteristics without observation of “life- cycle”, e.g. reproduction, might be misleading for taxonomic classification. We hypothesize that the morphology of Acanthocorbis as well as of Stephanoeca could be an ancestral state as both are present in the nudiform as well as tectiform condition. 2019 International Choanoflagellates & Friends Meeting Page 6 of 38 Book of Abstracts Evolution of metazoan genome regulation, from molecular components to epigenomic landscapes Arnau Sebé-Pedrós Centre for Genomic Regulation (CRG) A fundamental question in biology
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