Chimeric Origins of Ochrophytes and Haptophytes Revealed Through an Ancient Plastid Proteome
Plastids are supported by a wide range of proteins encoded within the nucleus and imported from the cytoplasm. These plastid-targeted proteins may originate from the endosymbiont, the host, or other sources entirely. Here, we identify and characterise 770 plastid-targeted proteins that are conserved across the ochrophytes, a major group of algae including diatoms, pelagophytes and kelps, that possess plastids derived from red algae. We show that the ancestral ochrophyte plastid proteome was an evolutionary chimera, with 25% of its phylogenetically tractable nucleus-encoded proteins deriving from green algae. We additionally show that functional mixing of host and plastid proteomes, such as through dual-targeting, is an ancestral feature of plastid evolution. Finally, we detect a clear phylogenetic signal from one ochrophyte subgroup, the lineage containing pelagophytes and dictyochophytes, in plastid-targeted proteins from another major algal lineage, the haptophytes. This may represent a possible serial endosymbiosis event deep in eukaryotic evolutionary history.
- Author (aut): Dorrell, Richard G.
- Author (aut): Gile, Gillian
- Author (aut): McCallum, Giselle
- Author (aut): Meheust, Raphael
- Author (aut): Bapteste, Eric P.
- Author (aut): Klinger, Christen M.
- Author (aut): Brillet-Gueguen, Loraine
- Author (aut): Freeman, Katalina
- Author (aut): Richter, Daniel J.
- Author (aut): Bowler, Chris
- Contributor (ctb): College of Liberal Arts and Sciences