title: Hydra meiosis reveals unexpected conservation of structural synaptonemal complex proteins across metazoans.
abstract: The synaptonemal complex (SC) is a key structure of meiosis, mediating the stable pairing (synapsis) of homologous chromosomes during prophase I. Its remarkable tripartite structure is evolutionarily well conserved and can be found in almost all sexually reproducing organisms. However, comparison of the different SC protein components in the common meiosis model organisms Saccharomyces cerevisiae, Arabidopsis thaliana, Caenorhabditis elegans, Drosophila melanogaster, and Mus musculus revealed no sequence homology. This discrepancy challenged the hypothesis that the SC arose only once in evolution. To pursue this matter we focused on the evolution of SYCP1 and SYCP3, the two major structural SC proteins of mammals. Remarkably, our comparative bioinformatic and expression studies revealed that SYCP1 and SYCP3 are also components of the SC in the basal metazoan Hydra. In contrast to previous assumptions, we therefore conclude that SYCP1 and SYCP3 form monophyletic groups of orthologous proteins across metazoans.
authors.affiliation: Department of Cell and Developmental Biology, Biocenter,  University of Würzburg, D-97074 Würzburg,  Germany.
authors.forename: Johanna
authors.initials: J
authors.lastname: Fraune
authors.forename: Manfred
authors.initials: M
authors.lastname: Alsheimer
authors.forename: Jean-Nicolas
authors.initials: JN
authors.lastname: Volff
authors.forename: Karoline
authors.initials: K
authors.lastname: Busch
authors.forename: Sebastian
authors.initials: S
authors.lastname: Fraune
authors.forename: Thomas C G
authors.initials: TC
authors.lastname: Bosch
authors.forename: Ricardo
authors.initials: R
authors.lastname: Benavente
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D015153:Blotting, Western; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000737:chemistry / Q000235:genetics; D004268:DNA-Binding Proteins; D015870:Gene Expression; D006829:Hydra / Q000235:genetics* / Q000378:metabolism; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D008540:Meiosis / Q000235:genetics*; D008854:Microscopy, Electron; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000145:classification / Q000235:genetics* / Q000378:metabolism; D010802:Phylogeny; D051381:Rats; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D013573:Synaptonemal Complex / Q000235:genetics* / Q000378:metabolism / Q000648:ultrastructure
chemical_list: D018076:DNA, Complementary; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; C078744:Sycp1 protein, rat; C085453:Sycp3 protein, rat