Abstract
Meiotic chromosomes efficiently transduce information along their length to regulate the distribution of genetic exchanges (crossovers). However, the mode of signal transduction remains unknown. A conserved protein interface called the synaptonemal complex forms between the parental chromosomes. The synaptonemal complex exhibits liquid-like behaviors, suggesting that the diffusion of signaling molecules along its length could coordinate crossover formation. Here, we directly test the feasibility of such a mechanism by tracking a component of the synaptonemal complex (SYP-3) and a conserved regulator of exchanges (ZHP-3) in live Caenorhabditis elegans gonads. While we find that both proteins diffuse within the synaptonemal complex, ZHP-3 diffuses 4- and 9-fold faster than SYP-3 before and after crossover designation, respectively. We use these measurements to parameterize a physical model for signal transduction. We find that ZHP-3, but not SYP-3, can explore the lengths of chromosomes on the time scale of crossover designation, consistent with a role in the spatial regulation of exchanges. Given the conservation of ZHP-3 paralogues across eukaryotes, we propose that diffusion along the synaptonemal complex may be a conserved mechanism of meiotic regulation. More broadly, our work explores how diffusion compartmentalized by condensates could regulate crucial chromosomal functions.