Chromosomal fusions, but not chromosomal inversions, activate a PCH-2 dependent checkpoint that promotes crossover formation in .

Meiotic crossovers promote accurate chromosome segregation during gametogenesis. In , a highly conserved AAA ATPase, PCH-2, ensures that homologous chromosomes have at least one crossover, preventing meiotic defects. PCH-2 localizes to meiotic chromosomes and this localization is extended when there are defects in meiotic recombination, suggesting a role in responding to defects. Here, we show that, unlike in other systems, PCH-2 does not persist on meiotic chromosomes when there are chromosomal inversions but does persist when there are whole chromosome fusions. Moreover, this persistence correlates with an increase in crossovers, demonstrating that PCH-2's localization to chromosomes promotes crossover formation.