Fig. 6

Evolution model of the dynamic centromeres in Brachypodium genus. Rooted in a common ancestral foundation, the absence of centromere sequences and structural conservations between these shared chromosomes of O. sativa and Brachypodium genus suggest rapid post-speciation differentiation and a complete turnover of centromeres. The centromere characteristics between B. distachyon and B. stacei exhibited notable distinctions at both localized and broad scales. B. distachyon exhibited lower copy numbers but greater diversity of satellite arrays, accompanied by a higher incidence of TE retrotransposon invasions within the centromeres. Conversely, B. stacei displayed higher copy numbers but lower polymorphisms of satellite arrays, with fewer TE invasions in the centromeres. In the tetraploid B. hybridum, centromeric repeats from its two diploid ancestors have merged but continue to exist independently without inter-subgenome transfer. The presence of chromosome-specific clusters of centromeric satellites suggests local chromosomal recombination-based centromere homogenization. Presumably, no intersubgenomic crosstalk appears to have occurred within the centromeric satellite repeats following allopolyploidization. The solid lines within the oval indicate the absence of crosstalk between the subgenomic centromeres in the tetraploid Brachypodium. Moreover, the positioning of CENH3 nucleosomes remains relatively stable, and epigenetic homeostasis of centromere is maintained within tetraploid Brachypodium species