The EMBO | EMBL Symposium ‘Wild frontiers of model organisms‘ took place earlier this month at EMBL Heidelberg and virtually.

This brand-new symposium showcased how exploring the wild frontiers of model systems is increasing our understanding of the biology, ecology, and evolution of organisms, ranging from microbes to plants and animals. We brought together lab- and field-focused researchers from ecology, genomics, quantitative cell and molecular biology in order to debate the possibilities and limitations inherent to these disciplines and to develop unified approaches to gain comprehensive, mechanistic insights into the natural world.

For the inaugural edition of the conference, we had 83 people attending on-site and 23 participants attending remotely. There were 20 fellowships provided by the EMBL Corporate Partnership Programme, EMBO, and other sponsors. With the total of 28 posters to view, we held two poster sessions during which the presenters could discuss their research — their work was then voted for by all participants. There were five poster prizes awarded during the meeting. We are pleased to share with you all five of the winners’ abstracts!

Motility matters: Scoping the impact of a non-model diatom-ciliate symbiosis

Presenter: Thomas Beavis

Authors: Flora Vincent, Thomas Beavis

Abstract:

Diatoms are photosynthetic unicellular eukaryotes responsible for over 20% of global primary production. Microbial interactions with viruses, bacteria and ciliated protists can alter how diatoms function in aquatic environments. Diatoms, mostly planktonic, can gain motility when in epibiosis with loricated ciliates. But, our understanding of how this impacts the fate of both partners is limited by our inability to maintain them long-term in culture. To address this, we studied these organisms in their most natural state during the Traversing European Coastlines (TREC) expedition by bringing cutting-edge technology to the field. We used image-enabled cell sorting to acquire near mono-populations of diatoms in epibiosis with ciliates for multiple downstream applications including temporal analysis. Single cell 18S rDNA data revealed both genera in this novel interaction – the sessile ciliate Cothurnia and centric diatom Chaetoceros. Other possible planktonic substrata were cosampled but 100% of Cothurnia were attached to Chaetoceros across three days of sampling. We established that division of both partners is not inhibited by epibiosis and uncovered the step-wise process of initiation through live microscopy. We acquired ultrastructure information through 3D FIB-SEM and identified microfilaments within the Cothurnia attachment stalk which suggest a microtubule-associated matrix secretion mechanism. Ongoing quantification of live tracking data and mathematical modeling show a dynamic range of movement potentially reducing predator encounter rate in the natural environment. As a consequence – both partners would gain a survival advantage. Overall, this work illustrates the benefit of applying advanced technologies in natura to infer a mutualistic function of a non-model symbiosis.

Due to the confidentiality of the unpublished data, we cannot share the poster

Cell-type-specific control of developmental rate across species

Presenter: Jess Bourn

Authors: Jess Bourn

Abstract:

Temperature exerts a universal influence on the developmental rates of diverse organisms, and challenges the robustness of development at species-specific thermal limits. However, comparably-sized organisms living in similar thermal environments can vary significantly in their developmental rates. This insight suggests a complex interplay between genetic and environmental mechanisms that control development. Here, we aim to explore the molecular and cellular mechanisms that drive dynamic differences in developmental pace of two ectothermic vertebrates, zebrafish and medaka. Leveraging the power of individual embryo sci-RNA-seq (single-cell combinatorial indexing), we have assembled a time-resolved developmental atlas of medaka from blastula to hatch, comprising over 1M cells from 1029 embryos at 19 developmental time points. Despite an evolutionary divergence time of more than 100 million years, medaka and zebrafish share a significant number of orthologous genes that direct the genetic program of development. These shared features enable integration of transcriptomic data across species to assess temporal differences in gene expression. This technique has allowed us to represent the developmental progression of both species – which takes ~3x longer in clock time for medaka – on the same latent developmental timescale. We find non-linear relationships in embryo-level developmental stages between species, and examine developmental trajectories of specific cell types that mirror this trend, using the notochord to identify species-specific variation in developmental dynamics within a cell lineage. This method will facilitate the systematic comparison of developmental progression in all cell types between the two species, and will enable analysis of developmental timing control mechanisms across diverse strains and species

Due to the confidentiality of the unpublished data, we cannot share the poster

Proteome stability in tardigrade anhydrobiosis: insights into mechanisms from Ramazzottius varieornatus

Presenter: Adrian Nogales Moral

Authors: Adrian Nogales Moral, Christian Zimmerli, John Reinhard, David Hollenstein, Iskander Khusainov, Maren Schneider, Takekazu Kunieda, Markus Hartl, Khanh Huy Bui, Martin Beck, Alwin Koehler

Abstract:

Tardigrades are renowned for their remarkable ability to withstand physicochemical extremes, such as desiccation. Upon water loss, tardigrades enter a reversible ametabolic state termed anhydrobiosis, which is sustained until water reintroduction. Desiccation induces aberrant molecular interactions and crowding, ultimately leading to protein denaturing and aggregation. How tardigrades maintain proteostasis upon desiccation remains poorly understood. Here, we explore the effects of anhydrobiosis on proteostasis in the extremotolerant tardigrade Ramazzottius varieornatus by quantitative proteomics, electron microscopy, and functional assays. We report the exceptional stability of the R. varieornatus proteome throughout anhydrobiosis, also observed at a single-cell level. Additionally, structural analyses unravel features that may contribute to preserving the proteostasis machinery upon desiccation. These findings shed light on the unique molecular and structural adaptations tardigrades employ to protect their cellular integrity during anhydrobiosis, providing new mechanistic insights on the molecular basis of extremotolerance.

Due to the confidentiality of the unpublished data, we cannot share the poster.

Convergent evolution of H4K16ac-mediated dosage compensation shapes sex-dependent lifespan in a ZW species

Presenter: Frederic Zimmer

Authors: Frederic Zimmer, Annika Maria Fox, Qiaowei Pan, Felicia Basilicata, Frank Ruehle, Claudia Keller Valsecchi

Abstract:

Sex chromosome dosage compensation (SCDC) mechanisms evolved to re-equilibrate sex chromosomal gene expression in species with heteromorphic sex chromosomes (XY/ZW). This requires the precise regulation of hundreds of genes across an entire sex chromosome. The diversity of SCDC mechanisms across species offers exceptional opportunities for research in non-model organisms to uncover entirely new gene regulatory principles. Our work focuses on the brine shrimp Artemia franciscana, a female-heterogametic species (ZZ/ZW) that provides a unique system for studying SCDC. Firstly, female-heterogametic systems are heavily understudied with regards to SCDC mechanisms. Secondly, A. franciscana’s ability to follow alternative developmental pathways in response to environmental changes presents a rare and exciting opportunity to investigate sex chromosomal gene regulation across two distinct developmental programs. We aim to understand the molecular basis of SCDC in this species, with a particular focus on its unique lifecycle and sex-specific differences in ageing and lifespan. Using epigenome profiling and microscopy, we found that the single female Z chromosome is upregulated via H4K16 acetylation. H4K16ac-mediated dosage compensation is established during embryogenesis and maintained through adulthood. However, acetylation levels on the female Z chromosome become increasingly variable with age. This is associated with a lower lifespan of females compared to males, which can be alleviated upon chemical perturbation of acetylation. Current work is focused on the generation of stable transgenic lines and knock-outs to test SCDC candidate genes in vivo. Our findings reveal an H4K16ac-mediated sex chromosome dosage compensation mechanism in A. franciscana that appears to have convergently evolved in Drosophila and the Anole lizard. This suggests that histone acetylation has a conserved function in SCDC across species. Furthermore, our work sheds light on how these histone acetylation dynamics influence sex-specific ageing and lifespan differences

View poster

Probing the universality of the nucleocytoplasmic density ratio

Presenter: Mirko Pleitner

Authors:  Mirko Pleitner, PI: Simone Reber

Abstract:

The cell is a densely packed environment. How intracellular density distributions vary and affect cellular physiology remains largely unknown. In a variety of model organisms ranging from yeast to humans, our lab has recently shown that the nucleus is less dense than the cytoplasm and that living systems establish and maintain a constant density ratio between these compartments. While we understand that the lower nuclear density is established and maintained by a pressure balance across the nuclear envelope, its functional relevance remains unknown. Tetrahymena thermophila is an excellent model to study how two very different nuclei located within the same cytoplasm can have two different nuclear mass density as we recently discovered. My poster presents how cellular processes determine nuclear mass densities within these different nuclei.

Poster prize kindly sponsored by FEBS Letters

Due to the confidentiality of the unpublished data, we cannot share the poster

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The EMBO | EMBL Symposium ‘Wild frontiers of model organisms‘ took place from 8 – 11 April 2025 at EMBL Heidelberg and virtually.