Characterization and Role of SAR Elements Flanking the HSC80Locus of Tomato

真核生物，特别是陆生植物中染色质组织、核结构和基因表达之间的关系是一个复杂而未解决的问题。染色体结构域由附着在染色体支架上的染色质环组成，可能为基因表达提供一个特殊的环境。支持这一假设的是，在植物基因组不同位点插入的转基因表达水平非常低。支架附着区（Scaffold Attachment Regions， SAR）是结合核支架并锚定环结构域的DNA元件。我们发现番茄的HSC80基因两侧有SAR区，这表明在体内，这些SAR元件与支架存在关联。假定的环结构域将与同一区域的dna i超敏图进行比较。利用转基因植物，我们将确定两侧的SARs对于HSC80-Gus嵌合基因和甘露糖合成酶(Mas)- gus嵌合基因的位置无关、拷贝数依赖的表达是否必要。为了避免选择偏差，我们将描述非直接选择的Mas-Gus转基因的表达模式。我们将通过与携带卡那霉素抗性基因的单独T-DNA共转化获得嵌合Gus基因的非选择性插入。一段时间以来，人们已经清楚，在发育过程中和不同组织中基因表达的程序化调控太过复杂，无法完全用顺式和反式因子来解释。一个越来越被接受的观点是，染色体结构在某种程度上对基因表达的精确控制中起着一定的作用，这项工作的成功完成将使我们对可能的调节机制有更深入的了解。

The relationship between chromatin organization, nuclear architecture and gene expression in all eukaryotes and, specifically, in terrestrial plants is a complex and unresolved question. Chromosomal domains, consisting of chromatin loops attached to the chromosomal scaffold, may provide a specialized environment for gene expression. Supporting this hypothesis, transgenes inserted at different loci in a plant genome very in expression levels. Scaffold Attachment Regions (SAR) are DNA elements that bind to the nuclear scaffolds and could anchor loop domains. We have discovered that the HSC80 gene of tomato is flanked by SAR regions, suggesting that, in vivo, the association of these SAR elements with the scaffold. The putative loop domain will be compared to a DNAase I-hypersensitivity map of the same region. Using transgenic plants, we will determine whether flanking SARs are necessary for position-independent, copy-number- dependent expression of a HSC80-Gus chimeric gene and of a mannopine synthase (Mas)-Gus chimeric gene. To avoid a selection bias, we will characterize the expression pattern of Mas-Gus transgenes that were not directly selected. We will obtain unselected insertion of the chimeric Gus gene by co-transformation with a separate T-DNA carrying the kanamycin resistance gene. %%% It has been clear for some time that the programmed regulation of gene expression during development and in different tissues is too complex to be totally explained by cis and trans acting factors. One idea which has become more and more acceptable is that chromosome structure somehow plays a part in such precise control of gene expression and the information which should result from the successful completion of this work will give greater insight into possible mechanisms of regulation.