Epigenetic Variation in the Arabidopsis Genome

表观遗传信息，以差异胞嘧啶甲基化和替代染色质结构的形式，在真核基因表达的调控中起着核心作用。在某些情况下，可选择的表观遗传修饰可以通过减数分裂遗传，从而打开了表观遗传变异在产生表型和基因组多样性方面发挥作用的可能性。这个项目是对开花植物拟南芥表观遗传变异的两个例子的调查。第一个要研究的表观遗传系统涉及复杂的BAL基因组位点，其中包含近缘病原菌防御基因和散布的转座元件。有缺陷的Bal表观遗传等位基因导致该基因座的几个基因过度表达，并赋予发育和病原体防御表型。这项研究将探索导致这种基因表达失调的基因座上的分子变化，以及Bal等位基因不寻常的亚稳定行为。该项目的第二个目标是描述一类新发现的非LTR反转录转座子，该反转录转座子由在某些拟南芥品系中表观遗传沉默但在另一些品系中不存在的成员组成。我们将研究这种自然表观遗传变异的机制基础和意义。种群中个体生物的略有不同的形式是这些个体的遗传潜力和环境之间相互作用的结果。同样重要的是表观遗传变化，它不涉及DNA序列的变化，而是这些遗传信息的包装。该项目利用小型开花植物拟南芥中可用的实验工具来研究表观遗传变化在遗传中的作用以及个体和品系之间的形态多样性控制。

Epigenetic information, in the form of differential cytosine methylation and alternative chromatin structures, plays a central role in the modulation of eukaryotic gene expression. In some cases, alternative epigenetic modifications can be inherited through meiosis, opening up the possibility that epigenetic variation plays a role in generating phenotypic and genomic diversity. This project is an investigation of two examples of epigenetic variation in the flowering plant Arabidopsis thaliana. The first epigenetic system to be investigated involves the complex BAL genomic locus, which contains paralogous pathogen defense genes and interspersed transposable elements. The defective bal epigenetic allele leads to overexpression of several genes from the locus and confers both developmental and pathogen defense phenotypes. The research will probe the molecular changes at the locus that cause this mis-regulation of gene expression, as well as the unusual metastable behavior of the bal allele. The second objective of the project is to characterize a newly discovered class of non-LTR retrotransposons, comprised of members that are epigenetically silenced in some strains of Arabidopsis but not others. The mechanistic basis and significance of this natural epigenetic variation will be investigated.The slightly different forms of individual organisms in a population result from the interaction between the genetic potential of those individuals and the environment. Also important are epigenetic changes, which do not involve alterations in DNA sequence but rather the packaging of this genetic information. This project takes advantage of the experimental tools available in the small flowering plant Arabidopsis to study the role of epigenetic changes in inheritance and the control of morphological diversity among individuals and strains.