Plastid origins

The evolution of plastids (chloroplasts) from cyanobacterial endosymbionts was an event of profound significance in the history of eukaryotic life. The so-called primary endosymbiotic origin of plastids, which is generally believed to have happened only once, afforded eukaryotes the ability to harness the energy of sunlight, a capacity that subsequently spread to distantly related organisms by additional eukaryote-eukaryote endosymbioses. This chapter provides an overview of recent genomics-enabled advances in our understanding of plastid evolution. The emerging picture is one of unexpected complexity in which mergers between various combinations of hosts and endosymbionts have given rise to modern-day eukaryotic phototrophs with mosaic gene repertoires.