Crossover interference mediates multiscale patterning along meiotic chromosomes

Meiotic crossover interference is a one-dimensional spatial patterning process that produces evenly-spaced crossovers. Quantitative analysis of diagnostic molecules along budding yeast chromosomes reveals that this process sets up two interdigitated patterns, of shorter and longer periodicity, by "two-tiered" patterning. Both tiers comprise clustered assemblies of three types of molecules ("triads") representing the three major components of meiotic chromosomes (crossover recombination, axes, and the synaptonemal complex). One tier of triads occurs at sites of majority ("canonical") crossovers. Second tier triads are more widely spaced but also exhibit interference, dependent on the same functions as canonical crossover interference. Diverse lines of evidence suggest that second tier triads arise at sites of previously mysterious "minority" crossovers. Finally, conserved protein remodeler Pch2/TRIP13 modulates the abundance of triad components, specifically in longer periodicity triads, dynamically in real time. Potential roles of triad structure, mechanisms of two-tiered patterning, and the nature of minority crossovers are discussed.