Meiotic Recombination in C. elegans Initiates by a Conserved Mechanism and Is Dispensable for Homologous Chromosome Synapsis

TLDR

Chromosome segregation at meiosis I relies on homolog pairing and crossing‑over, which in most eukaryotes culminates in synaptonemal complex formation, and in budding yeast recombination initiates via double‑strand breaks that are thought essential for SC assembly. The study investigates whether the DSB‑initiated recombination mechanism is conserved and whether homologous chromosome synapsis depends on recombination in *C. elegans*. The authors examine this by testing the conservation of the recombination initiation mechanism and the synapsis dependence in *C.

Abstract

Chromosome segregation at meiosis I depends on pairing and crossing-over between homologs. In most eukaryotes, pairing culminates with formation of the proteinaceous synaptonemal complex (SC). In budding yeast, recombination initiates through double-strand DNA breaks (DSBs) and is thought to be essential for SC formation. Here, we examine whether this mechanism for initiating meiotic recombination is conserved, and we test the dependence of homologous chromosome synapsis on recombination in C. elegans. We find that a homolog of the yeast DSB-generating enzyme, Spo11p, is required for meiotic exchange in this metazoan, and that radiation-induced breaks partially alleviate this dependence. Thus, initiation of recombination by DSBs is apparently conserved. However, homologous synapsis is independent of recombination in the nematode, since it occurs normally in a C. elegans spo-11 null mutant.