Nucleolar Cdc14 Splitting Reflects Recombination Context and Meiotic Chromosome Dynamics

Chromosome dynamics, recombination, and nucleolar organization intersect during meiotic prophase I, yet how recombination context influences nucleolar architecture remains unclear. We analyzed the nucleolar pool of Cdc14 in Saccharomyces cerevisiae under matched prophase-I gating. In a recombination-competent reference ( ndt80Δ ), Cdc14–mCherry formed a predominant single focus with occasional, reversible two-focus episodes that Nop56–GFP placed within the nucleolar compartment (“nucleolar splitting”). Splitting rose sharply in dmc1Δ ndt80Δ and remained high in spo11–y135f dmc1Δ ndt80Δ , demonstrating that elevated DSB formation is not required and pointing instead to homolog-engagement state as the key variable. Population checkpoint readouts did not map onto the phenotype: Hop1 phosphorylation was strong in dmc1Δ , weak/transient in ndt80Δ , and undetectable in spo11–y135f , yet splitting was high in dmc1Δ and spo11–y135f and low in ndt80Δ . Persistence metrics showed that events concentrated early and waned in ndt80Δ , whereas dmc1Δ and spo11 backgrounds retained activity into later windows, consistently across thresholds. We propose that nucleolar splitting reflects rheological responses of a nucleolar condensate to chromosome-scale forces that vary with homolog engagement. This view is consistent with DSB-independent contributions from telomere clustering into the bouquet configuration, telomere-led rapid prophase movements, and centromere coupling/pairing as routes that shape force transmission to the rDNA territory. In this sense, the nucleolus emerges as a mesoscale, mechanically sensitive readout of meiotic chromosome dynamics.