title: RNA Seq analysis of the Eimeria tenella gametocyte transcriptome reveals clues about the molecular basis for sexual reproduction and oocyst biogenesis.
abstract: BACKGROUND
  The protozoan Eimeria tenella is a common parasite of chickens, causing avian coccidiosis, a disease of on-going concern to agricultural industries. The high prevalence of E. tenella can be attributed to the resilient oocyst stage, which is transmitted between hosts in the environment. As in related Coccidia, development of the eimerian oocyst appears to be dependent on completion of the parasite's sexual cycle. RNA Seq transcriptome profiling offers insights into the mechanisms governing the biology of E. tenella sexual stages (gametocytes) and the potential to identify targets for blocking parasite transmission.
  
  
  RESULTS
  Comparisons between the sequenced transcriptomes of E. tenella gametocytes and two asexual developmental stages, merozoites and sporozoites, revealed upregulated gametocyte transcription of 863 genes. Many of these genes code for proteins involved in coccidian sexual biology, such as oocyst wall biosynthesis and fertilisation, and some of these were characterised in more depth. Thus, macrogametocyte-specific expression and localisation was confirmed for two proteins destined for incorporation into the oocyst wall, as well as for a subtilisin protease and an oxidoreductase. Homologues of an oocyst wall protein and oxidoreductase were found in the related coccidian, Toxoplasma gondii, and shown to be macrogametocyte-specific. In addition, a microgametocyte gamete fusion protein, EtHAP2, was discovered.
  
  
  CONCLUSIONS
  The need for novel vaccine candidates capable of controlling coccidiosis is rising and this panel of gametocyte targets represents an invaluable resource for development of future strategies to interrupt parasite transmission, not just in Eimeria but in other Coccidia, including Toxoplasma, where transmission blocking is a relatively unexplored strategy.
authors.affiliation: Queensland Tropical Health Alliance Research Laboratory, Australian Institute of Tropical Health and Medicine, James Cook University, Cairns Campus, McGregor Road, Smithfield, QLD, 4878, Australia. robert.walker1@jcu.edu.au.|Institute of Parasitology, University of Zurich, Winterthurerstrasse 266a, CH-8057, Zürich, Switzerland. robert.walker1@jcu.edu.au.
authors.forename: Robert A
authors.initials: RA
authors.lastname: Walker
authors.affiliation: College of Public Health, Medical and Veterinary Sciences, James Cook University, Cairns Campus, McGregor Road, Smithfield, QLD, 4878, Australia. philippasharman@gmail.com.
authors.forename: Philippa A
authors.initials: PA
authors.lastname: Sharman
authors.affiliation: College of Public Health, Medical and Veterinary Sciences, James Cook University, Cairns Campus, McGregor Road, Smithfield, QLD, 4878, Australia. kate.miller1@jcu.edu.au.
authors.forename: Catherine M
authors.initials: CM
authors.lastname: Miller
authors.affiliation: Institute of Parasitology, University of Zurich, Winterthurerstrasse 266a, CH-8057, Zürich, Switzerland. christoph.lippuner@dkf.unibe.ch.|Department of Farm Animal, University of Zurich, Winterthurerstrasse, CH-8057, Zürich, Switzerland. christoph.lippuner@dkf.unibe.ch.
authors.forename: Christoph
authors.initials: C
authors.lastname: Lippuner
authors.affiliation: Functional Genomics Center Zurich, Winterthurerstrasse, CH-8057, Zürich, Switzerland. michal.okoniewski@gmail.com.
authors.forename: Michal
authors.initials: M
authors.lastname: Okoniewski
authors.affiliation: Institute of Parasitology, University of Zurich, Winterthurerstrasse 266a, CH-8057, Zürich, Switzerland. ramon.eichenberger@uzh.ch.
authors.forename: Ramon M
authors.initials: RM
authors.lastname: Eichenberger
authors.affiliation: Institute of Parasitology, University of Zurich, Winterthurerstrasse 266a, CH-8057, Zürich, Switzerland. chandra.ramakrishnan@uzh.ch.
authors.forename: Chandra
authors.initials: C
authors.lastname: Ramakrishnan
authors.affiliation: Apicomplexes et Immunité Mucosale, INRA, UMR1282, Infectiologie et Santé Publique, F-37380, Nouzilly, France. nicholas.smith@jcu.edu.au.|Université François Rabelais de Tours, UMR1282, Infectiologie et Santé Publique, F-37000, Tours, France. nicholas.smith@jcu.edu.au.
authors.forename: Fabien
authors.initials: F
authors.lastname: Brossier
authors.affiliation: Institute of Parasitology, University of Zurich, Winterthurerstrasse 266a, CH-8057, Zürich, Switzerland. deplazesp@access.uzh.ch.
authors.forename: Peter
authors.initials: P
authors.lastname: Deplazes
authors.affiliation: Institute of Parasitology, University of Zurich, Winterthurerstrasse 266a, CH-8057, Zürich, Switzerland. adrian.hehl@uzh.ch.
authors.forename: Adrian B
authors.initials: AB
authors.lastname: Hehl
authors.affiliation: Queensland Tropical Health Alliance Research Laboratory, Australian Institute of Tropical Health and Medicine, James Cook University, Cairns Campus, McGregor Road, Smithfield, QLD, 4878, Australia. nicholas.smith@jcu.edu.au.
authors.forename: Nicholas C
authors.initials: NC
authors.lastname: Smith
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002645:Chickens / Q000469:parasitology; D003048:Coccidiosis / Q000469:parasitology / Q000473:pathology; D016786:Eimeria tenella / Q000235:genetics* / Q000254:growth & development; D018503:Genome, Protozoan; D052940:Merozoites / Q000378:metabolism; D008856:Microscopy, Fluorescence; D008969:Molecular Sequence Data; D033661:Oocysts / Q000378:metabolism; D010088:Oxidoreductases / Q000235:genetics / Q000378:metabolism; D015800:Protozoan Proteins / Q000235:genetics / Q000378:metabolism; D012313:RNA / Q000737:chemistry / Q000302:isolation & purification; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics; D016415:Sequence Alignment; D017423:Sequence Analysis, RNA; D034101:Sporozoites / Q000378:metabolism; D059467:Transcriptome
chemical_list: D015800:Protozoan Proteins; D011994:Recombinant Proteins; D012313:RNA; D010088:Oxidoreductases