Pan-centromere landscape and dynamic evolution in Brassica plants.

Abstract

The centromere paradox, in which functionally conserved centromeres exhibit rapid evolution, has long intrigued geneticists and evolutionary biologists. Despite its importance, the centromeric landscape remains poorly understood due to the lack of complete assemblies. Here we dissect the dynamic evolution of Brassica centromeres by generating telomere-to-telomere genome assemblies from seven morphotypes of B. rapa (AA) and the two tetraploids B. juncea (AABB) and B. napus (AACC). Pan-centromere analysis reveals that Brassica centromeres are extensively invaded by retrotransposons and show remarkable diversity in size and structure. While A- and C-genome centromeres feature distinct patterns of satellites, B-genome centromeres are devoid of satellites. 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 Brassica centromere structures. These insights will illuminate plant centromere evolution and guide the design of crop synthetic chromosomes.