Analysis of Chromosome Cohesion in Arabidopsis

在有丝分裂和减数分裂过程中，染色体内聚在染色体分离中起着核心作用。REC8/ scc1样蛋白是有丝分裂和减数分裂内聚复合体的组成部分，是内聚释放的调控点。对多种生物的研究表明，姐妹染色单体内聚是一种高度保守的机制，着丝粒与染色体臂、有丝分裂与减数分裂之间以及不同物种之间的内聚存在重要差异。早期的研究在拟南芥中发现了四种REC8/ scc1样蛋白（SYN1-4）。其中一种蛋白质SYN1对减数分裂至关重要，而SYN2和SYN4可能参与有丝分裂。第四个拟南芥内聚蛋白SYN3似乎在植物核仁中具有新的作用。该项目涉及许多旨在更好地了解拟南芥黏结蛋白的研究。(1)通过免疫定位实验和突变株分析，确定SYN2、SYN3和SYN4的功能。特别是SYN3在核仁中的作用将被研究。(2)通过透射电镜（TEM）研究syn1植物轴向元件的形成和免疫电镜（TEM）研究syn1在减数分裂染色体上的分布，进一步研究syn1在减数分裂过程中同源染色体配对和突触中的作用。(3)通过酵母双杂交筛选和突变体分析，确定与SYN1相互作用和/或影响其在染色体上分布的蛋白，并研究其在染色体内聚中的作用。总之，这些研究将有助于深入了解拟南芥SCC1/ rec8样黏结蛋白在减数分裂和有丝分裂中的具体作用，并有助于填补我们对植物黏结蛋白的一般理解的空白。最后，它们将对姐妹染色单体内聚过程、生物体控制这一重要过程的不同方式以及内聚蛋白的潜在新作用产生新的见解。

Chromosome cohesion plays a central role in chromosome segregation during both mitosis and meiosis. The REC8/SCC1-like proteins are integral components of the mitotic and meiotic cohesion complexes and appear to be the regulatory point for the release of cohesion. Studies in a variety of organisms indicate that while sister chromatid cohesion is a highly conserved mechanism, important differences exist in cohesion at the centromeres verses chromosome arms, between mitosis and meiosis and across different species. Earlier studies identified four REC8/SCC1-like proteins in Arabidopsis (SYN1-4). One of these proteins, SYN1 is essential for meiosis while SYN2 and SYN4 may participate in mitosis. The fourth Arabidopsis cohesin protein, SYN3, appears to have a novel role in the plant nucleolus. This project involves a number of studies designed to better understand the Arabidopsis cohesin proteins. (1) Immunolocalization experiments and the analysis of mutant plants will be conducted to determine the function(s) of SYN2, SYN3 and SYN4. In particular the role of SYN3 in the nucleolus will be investigated. (2) Transmission electron microscopy (TEM) studies to examine axial element formation in syn1 plants and immuno-TEM studies to examine the distribution of SYN1 on meiotic chromosomes will be conducted to further investigate the role of SYN1 in homologous chromosome pairing and synapsis during meiosis . (3) Proteins that interact with SYN1 and/or influence its distribution on chromosomes will be identified through yeast two hybrid screens and mutant analysis and their role in chromosome cohesion investigated. Together these studies will provide insight into the specific roles of the Arabidopsis SCC1/REC8-like cohesin proteins in meiosis and mitosis and help fill a void in our understanding of plant cohesin proteins in general. Finally, they will yield new insights into the process of sister chromatid cohesion, different ways organisms control this important process and potentially new roles for the cohesin proteins.