Chromosome-wide regulation of meiotic crossover formation in Caenorhabditis elegans requires properly assembled chromosome axes.
Most sexually reproducing organisms depend on the regulated formation of crossovers, and the consequent chiasmata, to accomplish successful segregation of homologous chromosomes at the meiosis I division. A robust, chromosome-wide crossover control system limits chromosome pairs to one crossover in most meioses in the nematode Caenorhabditis elegans; this system has been proposed to rely on structural integrity of meiotic chromosome axes. Here, we test this hypothesis using a mutant, him-3(me80), that assembles reduced levels of meiosis-specific axis component HIM-3 along cohesin-containing chromosome axes. Whereas pairing, synapsis, and crossing over are eliminated when HIM-3 is absent, the him-3(me80) mutant supports assembly of synaptonemal complex protein SYP-1 along some paired chromosomes, resulting in partial competence for chiasma formation. We present both genetic and cytological evidence indicating that the him-3(me80) mutation leads to an increased incidence of meiotic products with two crossovers. These results indicate that limiting the amount of a major axis component results in a reduced capacity to communicate the presence of a (nascent) crossover and/or to discourage others in response.
Nabeshima
Kentaro
K
Department of Developmental Biology and Department of Genetics, Stanford University School of Medicine, Stanford, California 94305, USA.
Villeneuve
Anne M
AM
Hillers
Kenneth J
KJ
D000818:Animals; D017173:Caenorhabditis elegans / Q000235:genetics* / Q000502:physiology; D029742:Caenorhabditis elegans Proteins / Q000235:genetics / Q000502:physiology; D023902:Chromosome Pairing / Q000502:physiology; D002875:Chromosomes / Q000502:physiology*; D003434:Crossing Over, Genetic / Q000502:physiology*; D004268:DNA-Binding Proteins / Q000378:metabolism; D008040:Genetic Linkage; D008540:Meiosis / Q000502:physiology*; D009154:Mutation; D051135:Rad51 Recombinase; D014960:X Chromosome / Q000502:physiology
D029742:Caenorhabditis elegans Proteins; D004268:DNA-Binding Proteins; C121599:HIM-3 protein, C elegans; D051135:Rad51 Recombinase; C495148:rad-51 protein, C elegans