title: The search for the missing link: a relic plastid in Perkinsus?
abstract: Perkinsus marinus (Phylum Perkinsozoa) is a protozoan parasite that has devastated natural and farmed oyster populations in the USA, significantly affecting the shellfish industry and the estuarine environment. The other two genera in the phylum, Parvilucifera and Rastrimonas, are parasites of microeukaryotes. The Perkinsozoa occupies a key position at the base of the dinoflagellate branch, close to its divergence from the Apicomplexa, a clade that includes parasitic protista, many harbouring a relic plastid. Thus, as a taxon that has also evolved toward parasitism, the Perkinsozoa has attracted the attention of biologists interested in the evolution of this organelle, both in its ultrastructure and the conservation, loss or transfer of its genes. A review of the recent literature reveals mounting evidence in support of the presence of a relic plastid in P. marinus, including the presence of multimembrane structures, characteristic metabolic pathways and proteins with a bipartite N-terminal extension. Further, these findings raise intriguing questions regarding the potential functions and unique adaptation of the putative plastid and/or plastid genes in the Perkinsozoa. In this review we analyse the above-mentioned evidence and evaluate the potential future directions and expected benefits of addressing such questions. Given the rapidly expanding molecular/genetic resources and methodological toolbox for Perkinsus spp., these organisms should complement the currently established models for investigating plastid evolution within the Chromalveolata.
authors: Department of Microbiology and Immunology, School of Medicine, University of Maryland, IMET, Baltimore, MD 21202-3101, USA. jfernandez-robledo@som.umaryland.edu
authors: José A
authors: JA
authors: Fernández Robledo
authors: Elisabet
authors: E
authors: Caler
authors: Motomichi
authors: M
authors: Matsuzaki
authors: Patrick J
authors: PJ
authors: Keeling
authors: Dhanasekaran
authors: D
authors: Shanmugam
authors: David S
authors: DS
authors: Roos
authors: Gerardo R
authors: GR
authors: Vasta
mesh_terms: D056893:Alveolata / Q000235:genetics* / Q000472:pathogenicity / Q000648:ultrastructure*; D000595:Amino Acid Sequence; D000818:Animals; D019143:Evolution, Molecular; D006801:Humans; D008854:Microscopy, Electron; D008954:Models, Biological; D008969:Molecular Sequence Data; D010125:Ostreidae / Q000469:parasitology; D018087:Plastids / Q000235:genetics* / Q000648:ultrastructure*; D016415:Sequence Alignment; D014481:United States