RNA Splicing in Chloroplasts: Mechanism and Function of Group I Introns

叶绿体基因组包含大约100个基因; 其正确表达是必要的 光合作用和叶绿体发育。 一个关键步骤 在一些叶绿体基因的表达是RNA 剪接是一种将位于细胞内部的序列 切除内含子，并切除编码序列（外显子）。 精确地重新连接。 比较序列分析表明 大多数叶绿体内含子可以被分类为I组或 然而，第二组的直接信息很少， 叶绿体中RNA剪接的机制。 在这里，结果 这表明：（1）至少有一个核 RRN的有效剪接需要基因产物 （2）23 S前体RNA在衣原体体内的表达。 能够在体外自我剪接。 初步证据显示， 还提出，这表明psbA基因的内含子， 的光系统II和其他未鉴定的I组内含子， 衣原体能够自我剪接。研究是 建议尽可能阐明机制， 叶绿体I组内含子剪接的控制。 无论是在 体外（自剪接）和体内（遗传）方法将 被利用。 了解RNA剪接的机制和控制， 叶绿体的重要性至少有两个原因。 的 首先是由于植物是主要来源 生物学上有用的能量。 植物获得 通过光合作用的过程， 至少部分依赖于 叶绿体编码的基因。 其次，有许多 关于起源、功能和 真核生物中内含子的剪接;反式作用 因素是特别感兴趣的，因为它们可能 调节内含子相关过程的作用。 虽然 叶绿体基因组与细胞核共同进化， 植物细胞的线粒体基因组，它有一个独特的 起源和许多独特的特征。 因此， 一个有用的来源，一个新的基本信息， 涉及内含子的分子过程。

The chloroplast genome contains on the order of 100 genes; the proper expression of which are necessary for photosynthesis and chloroplast development. A critical step in the expression of a number of chloroplast genes is RNA splicing; the process where internally-located sequences (introns) are excised, and coding sequences (exons) are precisely religated. Comparative sequence analysis suggests that most chloroplast introns can be classified as Group I or Group II, however, there is very little direct information on the mechanism of RNA splicing in chloroplasts. Here, results are presented which indicate that (1) at least one nuclear gene product is required for efficient splicing of the rrn 23S intron of Chlamydomonas in vivo and, (2) 23S preRNA is capable of self-splicing in vitro. Preliminary evidence is also presented which suggests that introns of the psbA gene of Photosystem II and other unidentified Group I introns in Chlamydomonas are capable of self-splicing. Studies are proposed to elucidate, as far as possible, the mechanism and control of splicing of chloroplast Group I introns. Both in vitro (self-splicing) and in vivo (genetic) approaches will be utilized. Understanding the mechanism and control of RNA splicing in chloroplasts is important for at least two reasons. The first is due to the fact that plants are the primary source of biologically useful energy on this planet. Plants obtain energy through the process of photosynthesis, which is dependent, at least in part, on the expression and regulation of chloroplast-encoded genes. Secondly, there are many unanswered questions concerning the origin, function, and splicing of introns in eucaryotes; the role of trans-acting factors are of particular interest because of their probable role in regulating intron-related processes. Although the chloroplast genome has coevolved with the nuclear and mitochondrial genomes of plant cells, it has a distinct origin and many unique characteristics. Therefore, could be a useful source a new basic information on cellular and molecular processes that involve introns.