Analysis of cluster-type holocentromeres - a novel centromere-type identified in the Liliales genus Chionographis – How to get from mono- to holocentricity?

着丝粒是一个特殊的染色体区域，着丝粒复合体在这里组装，纺锤体微管附着，以确保有丝分裂和减数分裂过程中的染色体分离。着丝粒的功能是高度保守的，但存在着丝粒的不同类型。最近对非经典着丝粒物种的分析表明，除了单着丝粒外，偏多着丝粒和不同类型的全着丝粒都是独立进化的。具有全着丝点或单着丝点染色体结构的密切相关物种的存在为研究着丝粒类型的进化提供了独特的可能性。我们对中国百合目的研究发现了一种新的全丝点组织。与所有其他具有大量小着丝粒单位的被分析的全着丝粒物种不同，日本绒毛虫的全着丝粒由少量百万碱基大小的CENH3阳性卫星DNA阵列组成。为了阐明从单着丝点到全着丝点的转变，我们希望对日本全着丝点藻和与之密切相关的单着丝点种黄毛藻进行比较分析。使用不同的分子、细胞遗传学和生物信息学工具的组合，将解决以下问题。在全着丝点和单着丝点黄体中，动粒组成是否存在差异？着丝粒重复序列在黄曲霉中是如何组织的？从单着丝点到全着丝点的转变是否重新洗牌了日本血吸虫的基因组？着丝粒重复序列的滚环扩增是否触发了全着丝粒的形成？着丝粒内侧和着丝粒周围组蛋白修饰的改变是否与着丝粒类型的转变有关？

The centromere is a specialized chromosomal region where the kinetochore complex assembles and spindle microtubules attach to ensure chromosome segregation during mitosis and meiosis. Different types of centromeres exist, although the function of the centromere is highly conserved. Recent analyses of species with non-classical centromeres demonstrated that in addition to monocentromeres, meta-polycentromeres and different types of holocentromeres independently evolved. The existence of closely related species with either holocentric or monocentric chromosome architecture offers a unique possibility for investigating the evolution of centromere types. Our study of Chionographis japonica (Liliales) revealed a new type of holocentromere organization. Unlike all other analyzed holocentric species possessing numerous small-sized centromere units, the holocentromere of C. japonica is composed of a low number of megabase-sized CENH3-positive satellite DNA arrays. To shed light on the transition from mono-to-holocentricity, we wish to perform a comparative analysis between holocentric C. japonica and the closely related monocentric species Chamaelirium luteum. Using a combination of different molecular, cytogenetic and bioinformatic tools, the following questions will be addressed. Does the kinetochore composition differ between holocentric C. japonica and monocentric C. luteum? How are the centromeric repeat arrays organized in C. luteum? Did the transition from mono-to-holocentricity reshuffle the genome of C. japonica? Did rolling circle amplification of centromeric repeats trigger the formation of a holocentromere? Did changes of inner centromere and pericentromeric histone modifications relate to the transition of centromere types?