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，在有丝分裂和减数分裂期间，着丝粒复合体和纺锤体微管连接在一起以确保染色体分离。虽然着丝粒的功能是高度保守的，但存在不同类型的着丝粒。最近对非经典着丝粒物种的分析表明，除了单着丝粒外，元多着丝粒和不同类型的全新着丝粒也独立进化。具有完整中心或单中心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。对日本百合（Chionographis japonica, Liliales）的研究揭示了一种全新的中心粒组织类型。与所有其他被分析的全新中心物种拥有大量的小尺寸着丝粒单位不同，日本稻的全新中心粒由少量的超大尺寸的cenh3阳性卫星DNA阵列组成。为了阐明从单一中心到全新中心的转变，我们希望对全新中心的C. japonica和密切相关的单中心物种chamaelium luteum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，以下问题将被解决。全新中心的日本金丝桃和单中心的黄体金丝桃的着丝点组成不同吗？黄体原体的着丝粒重复序列是如何组织的？从单中心到全新中心的转变是否重新洗牌了粳稻的基因组？着丝粒重复序列的滚动圈扩增是否触发了全新着丝粒的形成？内着丝粒和周围着丝粒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?