title: Identification of the meiotic toolkit in diatoms and exploration of meiosis-specific SPO11 and RAD51 homologs in the sexual species Pseudo-nitzschia multistriata and Seminavis robusta.
abstract: BACKGROUND
  Sexual reproduction is an obligate phase in the life cycle of most eukaryotes. Meiosis varies among organisms, which is reflected by the variability of the gene set associated to the process. Diatoms are unicellular organisms that belong to the stramenopile clade and have unique life cycles that can include a sexual phase.
  
  
  RESULTS
  The exploration of five diatom genomes and one diatom transcriptome led to the identification of 42 genes potentially involved in meiosis. While these include the majority of known meiosis-related genes, several meiosis-specific genes, including DMC1, could not be identified. Furthermore, phylogenetic analyses supported gene identification and revealed ancestral loss and recent expansion in the RAD51 family in diatoms. The two sexual species Pseudo-nitzschia multistriata and Seminavis robusta were used to explore the expression of meiosis-related genes: RAD21, SPO11-2, RAD51-A, RAD51-B and RAD51-C were upregulated during meiosis, whereas other paralogs in these families showed no differential expression patterns, suggesting that they may play a role during vegetative divisions. An almost identical toolkit is shared among Pseudo-nitzschia multiseries and Fragilariopsis cylindrus, as well as two species for which sex has not been observed, Phaeodactylum tricornutum and Thalassiosira pseudonana, suggesting that these two may retain a facultative sexual phase.
  
  
  CONCLUSIONS
  Our results reveal the conserved meiotic toolkit in six diatom species and indicate that Stramenopiles share major modifications of canonical meiosis processes ancestral to eukaryotes, with important divergences in each Kingdom.
authors.affiliation: Stazione Zoologica Anton Dohrn, Villa Comunale 1, 80121, Naples, Italy. shrikant.patil@szn.it.
authors.forename: Shrikant
authors.initials: S
authors.lastname: Patil
authors.affiliation: Department of Biology, Protistology and Aquatic Ecology, Ghent University, 9000, Ghent, Belgium. saramoeys@hotmail.com.|Department of Plant Systems Biology, Flanders Institute for Biotechnology (VIB), 9052, Ghent, Belgium. saramoeys@hotmail.com.|Department of Plant Biotechnology and Bioinformatics, Ghent University, 9052, Ghent, Belgium. saramoeys@hotmail.com.
authors.forename: Sara
authors.initials: S
authors.lastname: Moeys
authors.affiliation: Facultad de Ciencias Biológicas, Instituto Milenio de Oceanografía, Pontificia Universidad Católica de Chile, Santiago, Chile. pvondassow@bio.puc.cl.|UMI 3614, Evolutionary Biology and Ecology of Algae, CNRS-UPMC Sorbonne Universités, PUCCh, UACH, Station Biologique de Roscoff, Roscoff, France. pvondassow@bio.puc.cl.
authors.forename: Peter
authors.initials: P
authors.lastname: von Dassow
authors.affiliation: Department of Biology, Protistology and Aquatic Ecology, Ghent University, 9000, Ghent, Belgium. mahuy@psb.vib-ugent.be.|Department of Plant Systems Biology, Flanders Institute for Biotechnology (VIB), 9052, Ghent, Belgium. mahuy@psb.vib-ugent.be.|Department of Plant Biotechnology and Bioinformatics, Ghent University, 9052, Ghent, Belgium. mahuy@psb.vib-ugent.be.
authors.forename: Marie J J
authors.initials: MJ
authors.lastname: Huysman
authors.affiliation: The Genome Analysis Centre (TGAC), Norwich Research Park, Norwich, NR4 7UH, UK. daniel.mapleson@tgac.ac.uk.
authors.forename: Daniel
authors.initials: D
authors.lastname: Mapleson
authors.affiliation: Department of Plant Systems Biology, Flanders Institute for Biotechnology (VIB), 9052, Ghent, Belgium. lieven.deveylder@psb.vib-ugent.be.|Department of Plant Biotechnology and Bioinformatics, Ghent University, 9052, Ghent, Belgium. lieven.deveylder@psb.vib-ugent.be.
authors.forename: Lieven
authors.initials: L
authors.lastname: De Veylder
authors.affiliation: Stazione Zoologica Anton Dohrn, Villa Comunale 1, 80121, Naples, Italy. remo.sanges@szn.it.
authors.forename: Remo
authors.initials: R
authors.lastname: Sanges
authors.affiliation: Department of Biology, Protistology and Aquatic Ecology, Ghent University, 9000, Ghent, Belgium. wim.vyverman@ugent.be.
authors.forename: Wim
authors.initials: W
authors.lastname: Vyverman
authors.affiliation: Stazione Zoologica Anton Dohrn, Villa Comunale 1, 80121, Naples, Italy. marina.montresor@szn.it.
authors.forename: Marina
authors.initials: M
authors.lastname: Montresor
authors.affiliation: Stazione Zoologica Anton Dohrn, Villa Comunale 1, 80121, Naples, Italy. mariella.ferrante@szn.it.
authors.forename: Maria Immacolata
authors.initials: MI
authors.lastname: Ferrante
mesh_terms: D018797:Cell Cycle Proteins / Q000235:genetics; D017377:Diatoms / Q000235:genetics* / Q000502:physiology*; D015870:Gene Expression; D008540:Meiosis / Q000235:genetics*; D010802:Phylogeny; D011506:Proteins / Q000235:genetics; D012098:Reproduction; D013573:Synaptonemal Complex
chemical_list: D018797:Cell Cycle Proteins; D011506:Proteins