Local chromosome context is a major determinant of crossover pathway biochemistry during budding yeast meiosis

Meiotic chromosomes are divided into regions of enrichment and depletion for meiotic chromosome axis proteins, in budding yeast Hop1 and Red1. These proteins are important for formation of Spo11-catalyzed DSB, but their contribution to crossover recombination is undefined. By studying meiotic recombination initiated by the sequence-specific VMA1-derived endonuclease (VDE), we show that meiotic chromosome structure helps to determine the biochemical mechanism by which recombination intermediates are resolved to form crossovers. At a Hop1-enriched locus, most VDE-initiated crossovers required the MutL{gamma} resolvase, which forms most Spo11-initiated crossovers. In contrast, at a locus with lower Hop1 occupancy, most VDE-initiated crossovers were MutL{gamma}-independent. In pch2 mutants, the two loci displayed similar Hop1 occupancy levels, and also displayed similar MutL{gamma}-dependence of VDE-induced crossovers. We suggest that meiotic and mitotic recombination pathways coexist within meiotic cells, with features of meiotic chromosome structure partitioning the genome into regions where one pathway or the other predominates.