Multiple Independent Losses of Photosynthetic Ability in Eukaryotic Evolution and the Metabolism of Non-Photosynthetic Plastids

Abstract

Multiple independent losses of photosynthesis have occurred among several unrelated eukaryotic lineages including red and green algae, land plants, alveolates, stramenopiles, cryptophytes and euglenophytes. Most plastid genomes of non-photosynthetic eukaryotes do not contain genes associated with photosynthesis, but they usually encode at least one gene product involved in an essential non-photosynthetic metabolic pathway. Complete loss of plastid genome and simultaneous retention of plastid compartment is rare, and complete plastid loss is documented only for few alveolate species. Non-photosynthetic plastids are often involved in essential fatty acid, isoprenoid, Fe-S cluster, and heme synthesis.