title: An evolutionary balance: conservation vs innovation in ciliate membrane trafficking.
abstract: As most of eukaryotic diversity lies in single-celled protists, they represent unique opportunities to ask questions about the balance of conservation and innovation in cell biological features. Among free-living protists the ciliates offer ease of culturing, a rich array of experimental approaches, and versatile molecular tools, particularly in Tetrahymena thermophila and Paramecium tetraurelia. These attributes have been exploited by researchers to analyze a wealth of cellular structures in these large and complex cells. This mini-review focuses on 3 aspects of ciliate membrane dynamics, all linked with endolysosomal trafficking. First is nutrition based on phagocytosis and maturation of food vacuoles. Secondly, we discuss regulated exocytosis from vesicles that have features of both dense core secretory granules but also lysosome-related organelles. The third topic is the targeting, breakdown and resorption of parental nuclei in mating partners. For all 3 phenomena, it is clear that elements of the canonical membrane-trafficking system have been retained and in some cases repurposed. In addition, there is evidence that recently evolved, lineage-specific proteins provide determinants in these pathways.
authors.affiliation: Department of Biology, Millsaps College, Jackson, Mississippi.
authors.forename: Sabrice
authors.initials: S
authors.lastname: Guerrier
authors.affiliation: Department of Biology, University of Konstanz, Konstanz, Germany.
authors.forename: Helmut
authors.initials: H
authors.lastname: Plattner
authors.affiliation: Department of Cell Biology, University of Alberta, Canada.
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Richardson
authors.affiliation: Department of Cell Biology, University of Alberta, Canada.
authors.forename: Joel B
authors.initials: JB
authors.lastname: Dacks
authors.affiliation: Department of Molecular Genetics and Cell Biology, The University of Chicago, Chicago, Illinois.
authors.forename: Aaron P
authors.initials: AP
authors.lastname: Turkewitz
mesh_terms: D000818:Animals; D005089:Exocytosis / Q000502:physiology; D006801:Humans; D008247:Lysosomes / Q000378:metabolism / Q000502:physiology; D008566:Membranes / Q000378:metabolism*; D016805:Paramecium tetraurelia / Q000378:metabolism; D010587:Phagocytosis / Q000502:physiology; D021381:Protein Transport / Q000502:physiology*; D015800:Protozoan Proteins / Q000378:metabolism; D022142:Secretory Vesicles / Q000378:metabolism; D016808:Tetrahymena thermophila / Q000378:metabolism
chemical_list: D015800:Protozoan Proteins
keywords: 
  SNARE
  ; Alveolate; Rab GTPase
  ; autophagy; calcium signaling; nucleophagy; vesicles