Plastid Complexity in Dinoflagellates: A Picture of Gains, Losses, Replacements and Revisions

Abstract

Dinoflagellates are exemplars of plastid complexity and evolutionary possibility. Their ordinary plastids are extraordinary, and their extraordinary plastids provide a window into the processes of plastid gain and integration. No other plastid-bearing eukaryotic group possesses so much diversity or deviance from the basic traits of this cyanobacteria-derived endosymbiont. Although dinoflagellate plastids provide a major contribution to global carbon fixation and energy cycles, they show a remarkable willingness to tinker, modify and dispense with canonical function. The archetype dinoflagellate plastid, the peridinin plastid, has lost photosynthesis many times, has the most divergent organelle genomes of any plastid, is bounded by an atypical plastid membrane number and uses unusual protein trafficking routes. Moreover, dinoflagellates have gained new endosymbionts many times, representing multiple different stages of the processes of organelle formation. New insights into dinoflagellate plastid biology and diversity also suggest that it is timely to revise notions of the origin of the peridinin plastid.