The Evolutionary Journey of the Sterol Synthesis Pathways in Eukaryotes

Sterols play key roles in eukaryotic cell membrane stability and dynamics, as signaling molecules, and as precursors in sterol-based metabolic pathways, including the production of steroid hormones. The sterol biosynthetic pathway, based on a common set of core reactions, has been subject to intense diversification in each major eukaryotic clade. As a result, these organisms display a bewildering panoply of sterol-derived compounds that correlate with their multiple lifestyles and adaptations. In this work, we provide new insights on sterol synthesis evolution and diversification in extant eukaryotes, with a special focus on algae and plants. In particular, we provide detailed information on the sterol synthesis pathway in bryophytes. A comprehensive phylogenetic analysis of bryophyte sterol biosynthetic enzymes suggests that duplications and divergence of the final enzymes of the canonical sterol pathway are taking place in this group.