Richardson, E. H. | bioRxiv Science

bioRxiv2025

Comparative genomics of the lipid droplet-associated protein Seipin across eukaryotic diversity illuminates an ancient origin and conserved structural diversity.

Lipid droplets (LDs) are ubiquitous across living organisms. Characterised in eukaryotes by their lipid monolayer and essential for lipid storage and metabolism in animals, plants, and yeast, little is known about the evolutionary diversity of extant LDs across the eukaryotic tree of life. LDs facilitate an impressive variety of cellular functions outside of just lipid storage; in Metazoa, these include stress responses, cellular signaling, and membrane remodeling. Likewise, the distribution of these functions across eukaryotic diversity is unknown. We have examined the evolutionary trajectory of seipin, a protein associated with LD biogenesis, across eukaryotic diversity. We have identified a pan-eukaryotic distribution of seipin, with an evolutionary pattern that indicates presence in the Last Eukaryotic Common Ancestor. Ancient conservation of multiple variants of seipin suggests that seipin may multiple conserved functional roles within the cell. Finally, we identify a lack of sequence homology between BSCL2/seipin in Homo sapiens and the sei-1 gene previously identified as a functional homologue of BSCL2 in Saccharomyces cerevisiae. Though our results suggest that sei-1 may be a highly divergent homologue of BSCL2 / seipin rather than an unrelated protein, the divergence suggests that researchers may need to be cautious applying results obtained in Saccharomyces spp.. Visual abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=145 SRC="FIGDIR/small/683490v1_ufig1.gif" ALT="Figure 1"> View larger version (41K): org.highwire.dtl.DTLVardef@1d380c5org.highwire.dtl.DTLVardef@ab2432org.highwire.dtl.DTLVardef@1d56cb5org.highwire.dtl.DTLVardef@d3fcbc_HPS_FORMAT_FIGEXP M_FIG C_FIG

bioinformatics↗

bioRxiv2021

Within-Arctic horizontal gene transfer as a driver of convergent evolution in distantly related microalgae

The Arctic Ocean is being impacted by warming temperatures, increasing freshwater and highly variable ice conditions. The microalgal communities underpinning Arctic marine food webs, once thought to be dominated by diatoms, include a phylogenetically diverse range of small algal species, whose biology remains poorly understood. Here, we present genome sequences of a cryptomonad, a haptophyte, a chrysophyte, and a pelagophyte, isolated from the Arctic water column and ice. Comparing protein family distributions and sequence similarity across a densely-sampled set of algal genomes and transcriptomes, we note striking convergences in the biology of distantly related small Arctic algae, compared to non-Arctic relatives; although this convergence is largely exclusive of Arctic diatoms. Using high-throughput phylogenetic approaches, incorporating environmental sequence data from Tara Oceans, we demonstrate that this convergence was partly explained by horizontal gene transfers (HGT) between Arctic species, in over at least 30 other discrete gene families, and most notably in ice-binding domains (IBD). These Arctic-specific genes have been repeatedly transferred between Arctic algae, and are independent of equivalent HGTs in the Antarctic Southern Ocean. Our data provide insights into the specialized Arctic marine microbiome, and underlines the role of geographically-limited HGT as a driver of environmental adaptation in eukaryotic algae.

evolutionary biology↗