Genetic diversity and architectural dynamics of soybean centromeres

Centromere function is fundamental and conserved across eukaryotes, despite highly divergent DNA sequences, even among closely related species. These regions often contain rapidly evolving repeats and retrotransposons, yet play a crucial role in chromosome segregation. Soybean, which harbors two distinct types of centromeric satellite repeats, is an ideal model for studying centromeric repeat organization and function.

Here we generate the complete map of centromeric satellite repeats revealing the organizational patterns of different types of centromeric satellite repeats within centromeres. These maps are constructed using three recently available telomere-to-telomere soybean genomes. We find that certain centromeric satellite repeats exhibit chromosome-specific evolutionary trajectories and may serve distinct functional roles in centromere activity. We further analyze the potential relationship between centromere-specific histones H3 (CENH3) and centromeric satellite repeats, identifying consensus motifs associated with CENH3-binding sites. We also analyze the higher-order tandem repeats of the centromere and propose a hypothetical model of centromeric DNA replication.

We conclude that CentGm-1 and CentGm-4 evolve independently. The observation that completely identical CentGm-4 sequences consistently appear on the same chromosome across different soybean varieties indicates a stronger chromosome-specific preference for CentGm-4. We propose a model in which replication templates within the centromere region originate from multiple CENH3-nucleosome complexes bound to CentGm sequences. Both CentGm-1 and CentGm-4 contain similar motifs with the potential to bind CENH3 protein. The findings provide a new insight into the mechanisms behind centromere diversity and dynamics.