title: Msh4 and Msh5 function in SC-independent chiasma formation during the streamlined meiosis of Tetrahymena.
abstract: ZMM proteins have been defined in budding yeast as factors that are collectively involved in the formation of interfering crossovers (COs) and synaptonemal complexes (SCs), and they are a hallmark of the predominant meiotic recombination pathway of most organisms. In addition to this so-called class I CO pathway, a minority of crossovers are formed by a class II pathway, which involves the Mus81-Mms4 endonuclease complex. This is the only CO pathway in the SC-less meiosis of the fission yeast. ZMM proteins (including SC components) were always found to be co-occurring and hence have been regarded as functionally linked. Like the fission yeast, the protist Tetrahymena thermophila does not possess a SC, and its COs are dependent on Mus81-Mms4. Here we show that the ZMM proteins Msh4 and Msh5 are required for normal chiasma formation, and we propose that they have a pro-CO function outside a canonical class I pathway in Tetrahymena. Thus, the two-pathway model is not tenable as a general rule.
authors.affiliation: Department of Chromosome Biology and Max F. Perutz Laboratories, Center for Molecular Biology, University of Vienna, A-1030 Vienna, Austria.
authors.forename: Anura
authors.identifier: http://orcid.org/0000-0002-3675-2146
authors.initials: A
authors.lastname: Shodhan
authors.affiliation: Department of Chromosome Biology and Max F. Perutz Laboratories, Center for Molecular Biology, University of Vienna, A-1030 Vienna, Austria.
authors.forename: Agnieszka
authors.initials: A
authors.lastname: Lukaszewicz
authors.affiliation: Research Institute of Molecular Pathology, A-130 Vienna, Austria IMBA, Institute of Molecular Biotechnology of the Austrian Academy of Sciences, A-1030 Vienna, Austria.
authors.forename: Maria
authors.initials: M
authors.lastname: Novatchkova
authors.affiliation: Department of Chromosome Biology and Max F. Perutz Laboratories, Center for Molecular Biology, University of Vienna, A-1030 Vienna, Austria josef.loidl@univie.ac.at.
authors.forename: Josef
authors.initials: J
authors.lastname: Loidl
mesh_terms: D003434:Crossing Over, Genetic; D053903:DNA Breaks, Double-Stranded; D016054:DNA, Protozoan / Q000378:metabolism; D055786:Gene Knockout Techniques; D008540:Meiosis; D009154:Mutation / Q000235:genetics; D010802:Phylogeny; D015800:Protozoan Proteins / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D013573:Synaptonemal Complex / Q000378:metabolism*; D013768:Tetrahymena / Q000166:cytology* / Q000378:metabolism*
chemical_list: D016054:DNA, Protozoan; D015800:Protozoan Proteins
keywords: DSB repair; crossover pathways; meiosis; recombination; synaptonemal complex