title: Cryptic paraflagellar rod in endosymbiont-containing kinetoplastid protozoa.
abstract: Cilia and flagella are central to many biological processes in a diverse range of organisms. The kinetoplastid protozoa are very appealing models for the study of flagellar function, particularly in the light of the availability of extensive trypanosomatid genome information. In addition to the highly conserved 9 + 2 axoneme, the kinetoplastid flagellum contains a characteristic paraflagellar rod structure (PFR). The PFR is necessary for full motility and provides support for metabolic regulators that may influence flagellar beating. However, there is an intriguing puzzle: one clade of endosymbiont-containing kinetoplastids apparently lack a PFR yet are as motile as species that possess a PFR and are able to attach to the invertebrate host epithelia. We investigated how these organisms are able to locomote despite the apparent lack of PFR. Here we have identified a PFR1 gene in the endosymbiont-bearing trypanosome Crithidia deanei. This gene is expressed in C. deanei and is able to partially complement a pfr1 null mutation in Leishmania mexicana cells, demonstrating that the encoded protein is functional. Careful reexamination of C. deanei flagellar ultrastructure revealed a greatly reduced PFR missed by many previous analyses. This affirms the PFR as a canonical organelle of kinetoplastids. Moreover, although PFR proteins have been conserved in evolution, primary sequence differences contribute to particular PFR morphotypes characteristic of different kinetoplastid species.
authors.affiliation: Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, United Kingdom. catarina.gadelha@path.ox.ac.uk
authors.forename: Catarina
authors.initials: C
authors.lastname: Gadelha
authors.forename: Bill
authors.initials: B
authors.lastname: Wickstead
authors.forename: Wanderley
authors.initials: W
authors.lastname: de Souza
authors.forename: Keith
authors.initials: K
authors.lastname: Gull
authors.forename: Narcisa
authors.initials: N
authors.lastname: Cunha-e-Silva
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002465:Cell Movement / Q000502:physiology*; D003421:Crithidia / Q000145:classification / Q000166:cytology* / Q000235:genetics* / Q000378:metabolism; D003599:Cytoskeleton / Q000378:metabolism / Q000648:ultrastructure; D005407:Flagella / Q000235:genetics / Q000378:metabolism / Q000648:ultrastructure*; D005816:Genetic Complementation Test; D016830:Kinetoplastida; D007894:Leishmania mexicana / Q000145:classification / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D015388:Organelles / Q000235:genetics / Q000378:metabolism / Q000648:ultrastructure*; D010802:Phylogeny; D015800:Protozoan Proteins / Q000235:genetics / Q000378:metabolism*; D016415:Sequence Alignment
chemical_list: C105582:PFR-2 protein, Leishmania; D015800:Protozoan Proteins