GENE EXPRESSION IN CELL ORGANELLES

内含子是如何进化的？它们是否发生在益生元世界的早期， 通过“外显子改组”有助于形成古老的基因，或者 它们作为移动的遗传元件插入基因中， 进化？对内含子进化的重要见解来自于 光合原生生物裸藻叶绿体基因组分析 gracilis，含有至少120个内含子， 内含子内内含子，称为“双内含子”，和复杂的双内含子 由顺序剪接的3或4个单独的内含子形成。 一 Euglena的第III组内含子和双内含子的详细研究是 提出了 具体目标包括：（1）表征额外的 III组内含子和双内含子及其RNA加工途径，（2） 选择性剪接的程度和重要性的测定 III组内含子，特别是选择性剪接是否导致 在来自单个基因的替代多肽产物中，（3） 第三组内含子和双内含子是如何进化的，通过一个 眼虫属近缘种Ⅲ组内含子的比较分析 （4）psbC双内含子orf458内一个基因的研究 基因座，以评估该基因是否可能在迁移或剪接中发挥作用， （5）开发了一个用于转化第三组内含子的系统， 裸藻叶绿体，以研究顺式和反式作用因子， 转基因质体中内含子和双内含子剪接，以及（6）尝试 开发一种体外III组内含子剪接系统。 这项工作是 解决的是关于宇宙起源的基本问题 内含子、剪接机制和可变剪接。

How have introns evolved? Did they occur early in the prebiotic world and contribute to the formation of ancient genes by "exon shuffling," or have they been inserted into genes as mobile genetic elements throughout evolution? Important insights into intron evolution have come from analysis of the chloroplast genome of the photosynthetic protist Euglena gracilis, which contains at least 120 introns, several introns-within-introns, known as "twintrons", and complex twintrons formed from 3 or 4 individual introns which are sequentially spliced. A detailed study of the group III introns and twintrons of Euglena is proposed. The specific aims include: (1) Characterization of additional group III introns and twintrons and their RNA processing pathways, (2) Determination of the extent and importance of alternative splicing of group III introns, and specifically whether alternative splicing results in alternative polypeptides products from a single gene, (3) A study of how group III introns and twintrons have evolved, addressed through a comparative analysis of group III introns in species related to Euglena gracilis, (4) Studies on a gene within a twintron, orf458 of the psbC locus, to assess if this gene may have a role in the mobility or splicing of group III introns, (5) Development of a system for transformation of Euglena chloroplasts, in order to study cis- and trans-acting factors in intron and twintron splicing in transgenic plastids, and (6) Attempts to develop an in vitro group III intron splicing system. This work is addressed at understanding fundamental question about the origins of introns, splicing mechanisms, and alternative splicing.