Rec8 Cohesin-mediated Axis-loop chromatin architecture is required for meiotic recombination

During meiotic prophase, cohesin-dependent axial structures are formed in the synaptonemal complex (SC). However, the functional correlation between these structures and cohesion remains elusive. Here, we examined the formation of cohesin-dependent axial structures in the fission yeast Schizosaccharomyces pombe. This organism forms atypical SCs composed of linear elements (LinEs) resembling the lateral elements of SC but lacking the transverse filaments. Hi-C analysis using a highly synchronous population of meiotic S. pombe cells revealed that the axis-loop chromatin structure formed in meiotic prophase was dependent on the Rec8 cohesin complex. In contrast, the Rec8-mediated formation of the axis-loop structure occurred in cells lacking components of LinEs. To dissect the functions of Rec8, we identified a rec8-F204S mutant that lost the ability to assemble the axis-loop structure without losing cohesion of sister chromatids. This mutant showed defects in the formation of the axis-loop structure and LinE assembly and thus exhibited reduced meiotic recombination. Collectively, our results demonstrate that the Rec8-dependent axis-loop structure provides a structural platform essential for LinE assembly, facilitating meiotic recombination of homologous chromosomes, independently of its role in sister chromatid cohesion.