Pancentromere landscape and dynamic evolution in Brassica plants
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Centromere paradox where functionally conserved centromeres exhibit rapid evolution has long intrigued geneticists and evolutionary biologists. Despite its importance, centromeric landscape remains poorly understood due to its assembling challenge. Here, we dissect the dynamic evolution of Brassica centromeres by generating telomere-to-telomere assemblies from seven morphotypes of B. rapa (AA) and two tetroploids B. juncea (AABB) and B. napus (AACC). Pan-centromere analysis reveal that Brassica centromeres are extensively invaded by retrotransposons and show remarkable diversity in size and structure. While A- and C-genome centromeres are featured by distinct patterns of satellites, B-genome centromeres are devoid of satellites. Interestingly, the centromeric satellite expansion in the C-genome is reminiscent of the layered expansions observed in human centromeres. Accordingly, we propose a working model of centromere evolution reconstructing the key evolutionary events leading to current centromere structures. These insights will illuminate plant centromere evolution and guide the design of crop synthetic chromosomes.
