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SUMMARY:Multiple mechanisms limit meiotic crossovers - Raphael Mercier\, V
 ersailles INRA
DTSTART:20150423T120000Z
DTEND:20150423T130000Z
UID:TALK58902@talks.cam.ac.uk
CONTACT:38889
DESCRIPTION:Meiotic crossovers (COs) have two important roles\, shuffling 
 genetic information and ensuring proper chromosome segregation. Despite th
 eir importance and a large excess of precursors (i.e DNA double strand-bre
 aks\, DSBs)\, the number of meiotic COs is tightly regulated\, typically o
 ne to three per chromosome pair [1]. Nevertheless\, the mechanisms that en
 sure DSBs repair mostly as non-crossovers\, and the evolutionary forces th
 at impose this constraint\, are poorly understood. Following a specific ge
 netic screen\, we identified several proteins that antagonize crossover fo
 rmation in Arabidopsis Thaliana. This includes very conserved proteins suc
 h the helicase FANCM and its two co-factors MHF1 and MHF2 [2\,3]\, the BLM
 -like helicases\, the TOPOISOMERASE3a (TOP3α) [4] and the AAA-ATPase FIDG
 ETIN-LIKE1. Strikingly\, the concomitant disruption of several of these ac
 tivities led to a nine fold increase in CO frequency\, without affecting c
 hromosome segregation and fertility. This shows that several parallel path
 ways actively limit CO formation and supports the idea that crossover numb
 er is restricted not because of mechanical constraints but likely because 
 of long-term costs of recombination. Furthermore\, this demonstrates how m
 anipulating a few genes holds great promise for increasing recombination f
 requency in plant breeding programs.\n\n \n\n1. Mercier R\, Mézard C\, Je
 nczewski E\, Macaisne N\, Grelon M (2014) The Molecular Biology of Meiosis
  in Plants. Annu Rev Plant Biol 66: 1–31.\n\n2. Girard C\, Crismani W\, 
 Froger N\, Mazel J\, Lemhemdi A\, Horlow C\, Mercier R (2014) FANCM-associ
 ated proteins MHF1 and MHF2\, but not the other Fanconi anemia factors\, l
 imit meiotic crossovers. Nucleic Acids Res 42: 9087–9095.\n\n3. Crismani
  W\, Girard C\, Froger N\, Pradillo M\, Santos JL\, Chelysheva L\, Copenha
 ver GP\, Horlow C\, Mercier R (2012) FANCM Limits Meiotic Crossovers. Scie
 nce 336: 1588–1590.\n\n4. Séguéla-Arnaud M\, Crismani W\, Larchevêque
  C\, Mazel J\, Froger N\, Choinard S\, Lemhemdi A\, Macaisne N\, Van Leene
  J\, Gevaert K\, et al. (2015) Multiple mechanisms limit meiotic crossover
 s: TOP3α and two BLM homologs antagonize crossovers in parallel to FANCM.
  Proc Natl Acad Sci 201423107. 
LOCATION:Department of Plant Sciences\, Large Lecture Theatre
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