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Abstract

The brown algae, a eukaryotic lineage belonging to the stramenopiles, have evolved multicellularity independently of animals and land plants for over a billion years, becoming the third most complex multicellular lineage in the planet. Despite their importance, we still know very little about how these organism function at the molecular level. In order to shed light into the molecular bases of development processes underlying their complex body plans, we are employing tissue specific and single-cell RNA sequencing across a range of brown algal species. This Atlas of expression will illuminate how multicellularity emerged and evolved in this group of eukaryotes. In particular, we are focusing on the model Ectocarpus to unveil critical transcriptional regulatory networks and functional modules pivotal in multicellularity formation. Furthermore, Ectocarpus harbors an dsDNA endogenous giant virus that replicates exclusively in reproductive organ cells. The reasons behind this restricted viral proliferation and the cell-type specific response during virus-algae interaction have remained elusive. We are employing single-cell transcriptomics to investigate the dynamics and cell-type specific interactions during viral infection in Ectocarpus. Our findings illuminate the molecular mechanisms underlying multicellularity formation and cell-type specific responses during viral infection in brown algae, offering fresh insights into the roles of cell differentiation in the evolution of multicellular organisms and providing a valuable resource for comprehensive investigations into brown algae-pathogen interactions.