Comparative Genomics of A Rice Centromere

着丝粒是细胞学上（视觉上）定义的具有高度保守功能的实体。它负责染色体姐妹染色单体的内聚，是着丝点组装的位置，着丝点是一种蛋白质结构，在细胞分裂期间将染色体连接到纺锤体纤维。在大多数多细胞真核生物中，着丝粒嵌入异染色质中，异染色质是一种紧密堆积的DNA形式，并且与大量缺失基因的长束卫星重复序列有关。因此，着丝粒传统上被认为是一个高度异色和基因沉默的染色体区域。最近对水稻8号染色体着丝粒（Cen8）和人类新着丝粒（新形成的着丝粒区）的研究表明，着丝粒起源于基因区。本项目将以水稻Cen8为模型，重点研究着丝粒的进化。具体来说，该项目将开发基于细菌人工染色体（BAC）的物理图谱，该图谱跨越6个二倍体野生水稻品种的Cen8，并从6个着丝粒中每一个产生大约1兆碱基的DNA序列。六个着丝粒的功能边界将用细胞遗传学和分子方法确定。比较序列分析将揭示与6个着丝粒相关的结构重排和序列分化。将探讨cen8相关基因的表达和进化，以了解这些基因如何适应独特的染色体结构域。这个项目的结果将揭示着丝粒的进化，也将为研究位于异染色质和重组抑制染色体结构域的基因的进化奠定基础。项目成果序列数据和基因注释结果将通过GenBank、项目网站（可通过http://www.omap.org/访问）和Gramene等社区数据库（http://www.gramene.org）向公众开放。

The centromere is a cytologically (visually) defined entity with highly conserved functions. It is responsible for chromosomal sister chromatid cohesion and is the site for the assembly of kinetochore, a protein structure which links chromosomes to spindle fibers during cell division. In most multicellular eukaryotes, the centromeres are embedded within heterochromatin, a tightly packed form of DNA, and are associated with long tracts of satellite repeats in which genes are largely absent. Thus, the centromere is traditionally viewed as a highly heterochromatic and genetically silent chromosomal domain. Recent research work from the centromere of rice chromosome 8 (Cen8) as well as the neocentromeres (newly forming centromeric regions) from humans suggest that centromeres originated from genic regions. This project will focus on centromere evolution using rice Cen8 as a model. Specifically, this project will develop bacterial artificial chromosome (BAC)-based physical maps that span Cen8 in six diploid wild rice species and produce approximately one megabase of DNA sequence from each of the six centromeres. The functional boundary of the six centromeres will be determined using cytogenetic and molecular methods. The structural rearrangements and sequence divergence associated with the six centromeres will be revealed by comparative sequence analysis. Expression and evolution of Cen8-associated genes will be explored to understand how such genes adapt to a unique chromosomal domain. The results from this project will shed light on centromere evolution and will also build a foundation to study the evolution of genes located in heterochromatic and recombinationally-suppressed chromosomal domains. Access to Project OutcomesSequence data and gene annotation results will be made available to the public through GenBank, the project website (accessible through http://www.omap.org/) and community databases such as Gramene (http://www.gramene.org).