Prevalence and environmental abundance of the TSET complex in cosmopolitan algal groups

Classical cell biology paradigms are largely established on animal, fungal, and plant models which constitute a small fraction of eukaryotic diversity. Some important cellular machinery has been historically overlooked due to their absence from animals and fungi, e.g., the membrane-trafficking complex TSET involved in plant cell division and endocytosis. Here, we document TSET complexes in distantly related photosynthetic eukaryotic groups (green algae, red algae, haptophytes, cryptophytes, and stramenopiles including diatoms). 3D modeling predicts that at least some stramenopile-encoded subunits share conserved structural features with plant orthologues, and gene expression analysis from the diatom <i>Phaeodactylum tricornutum</i> shows that they are co-expressed with endomembrane trafficking proteins. Finally, diatom TSET genes are detectable in <i>meta</i>-transcriptomic data from <i>Tara</i> Oceans, suggesting functional roles in the wild. These results support the importance of integrating non-model organisms into our understanding of eukaryotic cell biology, as they may reveal underappreciated protein complexes essential for cellular and ecosystem functions.