Linear element formation and their role in meiotic sister chromatid cohesion and chromosome pairing.

Fission yeast does not form synaptonemal complexes in meiotic prophase. Instead, linear elements appear that resemble the axial cores of other eukaryotes. They have been proposed to be minimal structures necessary for proper meiotic chromosome functions. We examined linear element formation in meiotic recombination deficient mutants. The rec12, rec14 and meu13 mutants showed altered linear element formation. Examination of rec12 and other mutants deficient in the initiation of meiotic recombination revealed that occurrence of meiosis-specific DNA breaks is not a precondition for the formation of linear elements. The rec11 and rec8 mutants exhibited strongly impaired linear elements with morphologies specific for these meiotic cohesin mutants. The rec10 and rec16/rep1 mutants lack linear elements completely. The region specificity of loss of recombination in the rec8, rec10 and rec11 mutants can be explained by their defects in linear element formation. Investigation of the rec10 mutant showed that linear elements are basically dispensable for sister chromatid cohesion, but contribute to full level pairing of homologous chromosomes.