Abstract:

The classical phenomenon of meiotic crossover interference is a one-dimensional spatial patterning process that produces evenly spaced crossovers. Here, quantitative analysis of diagnostic molecules along budding yeast chromosomes reveals that that interference sets up not one, but two interdigitated patterns of related periodicities (\~450nm and \~900nm). Both patterns comprise spatially clustered assemblies of crossover recombination, chromosome axis and synaptonemal complex proteins ("triads"), which manifest as either focal (\~450nm) or domainal (\~900nm) signals. Functionally, the two sets of triads correspond, respectively, to canonical crossovers and a previously mysterious minority set of crossovers, and thus, in toto, account for all detected events. Triad spacings and spreading are economically and synthetically explained by the hypothesis that patterning is mediated by mechanical forces along prophase chromosome axes. Intensity levels of domainal triad components are further modulated, dynamically, by the conserved protein remodeler Pch2/TRIP13.One Sentence Summary We find that the classical meiotic phenomenon of crossover interference establishes not one, but two related spatial patterns along prophase chromosomes, both marked by closely spaced assemblies of recombination, axis and synaptonemal complex components ("triads"), which correspond to sites of canonical and minority crossovers respectively.Competing Interest StatementThe authors have declared no competing interest.