Centromeres attach chromosomes to spindle microtubules during cell division and, despite this conserved role, show paradoxically rapid evolution and are typified by complex repeats. We used long-read sequencing to generate the Col-CEN Arabidopsis thaliana genome assembly that resolves all five centromeres. The centromeres consist of megabase-scale tandemly repeated satellite arrays, which support CENTROMERE SPECIFIC HISTONE H3 (CENH3) occupancy and are densely DNA methylated, with satellite variants private to each chromosome. CENH3 preferentially occupies satellites that show the least amount of divergence and occur in higher-order repeats. The centromeres are invaded by ATHILA retrotransposons, which disrupt genetic and epigenetic organization. Centromeric crossover recombination is suppressed, yet low levels of meiotic DNA double-strand breaks occur that are regulated by DNA methylation. We propose that Arabidopsis centromeres are evolving through cycles of satellite homogenization and retrotransposon-driven diversification.

 摘 要 

在细胞分裂过程中，着丝粒会将染色体附着在纺锤体微管上，尽管这种过程比较保守，但却表现出反常的快速演化，并且以复杂的重复序列为特征。本文中，作者利用长读长测序技术获得了拟南芥的Col-CEN参考基因组组装，解析了所有五条染色体上的着丝粒序列。着丝粒由兆级的串联重复卫星阵列组成，支持着丝粒特异性组蛋白H3（CENH3）的占据，并且DNA甲基化程度很高，且每个染色体都具有特异性的卫星阵列变体。CENH3会优先占据分化程度最小且以高阶重复出现的卫星阵列。着丝粒受到ATHILA逆转录转座子的侵入，这破坏了普通遗传和表观遗传的组织。着丝粒交叉（crossover）重组受到抑制，但减数分裂DNA双链断裂的水平较低，受到DNA甲基化的调节。作者认为，拟南芥着丝粒是通过卫星均质化和逆转录转座子驱动的多样化进行演化。