Analysis of the chloroplast large subunit ribosomal RNA gene from 17 Chlamydomonas taxa. Three internal transcribed spacers and 12 group I intron insertion sites.
Analysis of the chloroplast large subunit ribosomal RNA gene from 17 Chlamydomonas taxa. Three internal transcribed spacers and 12 group I intron insertion sites.
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17 个衣藻类群叶绿体大亚基核糖体 RNA 基因的分析。
DOI：
10.1006/jmbi.1993.1402
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发表时间：
1993
影响因子：
5.6
通讯作者：
Lemieux,C
中科院分区：
文献类型：
--
作者：
Turmel,M;Gutell,RR;Mercier,JP;Otis,C;Lemieux,C
先前关于两种远缘绿藻真配子衣藻和莱茵衣藻叶绿体大亚基 rRNA 基因的报道表明 I 组内含子的分布存在差异，并表明内部转录间隔区的不同排列。为了深入了解这两种类型的插入序列的起源，我们对另外 15 个衣藻门的叶绿体 L 基因进行了测序，并表征了它们编码的成熟大亚基 rRNA 物种以及 C 指定的那些。莱茵哈特氏菌 rrnL.这些分析揭示了在所有 17 个类群中存在共享相同位置的三个内部转录间隔区，以及代表 12 个插入位点的总共 39 个 I 组内含子的存在。在这些插入位点中，仅在非衣藻中鉴定出一个。衣藻内含子的分布变化很大，并且在许多方面与叶绿体 rRNA 序列比较推导出的系统发育不一致。该系统发育的特点是衣藻门的两个主要谱系形成姐妹群。由于绿藻/陆地植物谱系中的早期分支生物没有显示叶绿体 rDNA 内含子，因此衣藻中的所有内含子插入位置似乎都是最近起源的，其中一些位置是在两个主要衣藻谱系分歧之后出现的。值得注意的是，与 rRNA 基因中大多数 I 组内含子插入位置相对应的 rRNA 区域已被指定了功能角色，表明它们位于核糖体的暴露区域。基于暴露的rRNA区域和内含子插入位点之间的这种显着相关性，我们推测自剪接反应的逆转在rRNA基因中发现的多个内含子插入位置的创建以及衣藻叶绿体基因组中其他地方的I组内含子的增殖中发挥了重要作用。
Previous reports on the chloroplast large subunit rRNA genes of the two distantly related green algaeChlamydomonas eugametosandChlamydomonas reinhardtiiindicate differences in the distribution of group I introns and suggest a different arrangement of internal transcribed spacers. To provide insights into the origin of these two types of intervening sequences, we have undertaken the sequencing of the chloroplastrrnL genes of 15 additionalChlamydomonastaxa and have characterized the mature large subunit rRNA species they encode in addition to those specified by theC. reinhardtii rrnL. These analyses disclosed the presence of three internal transcribed spacers sharing the same positions in all of the 17 taxa as well as the presence of a total of 39 group I introns representing 12 insertion sites. Of these insertion sites, only one has been identified in non-Chlamydomonastaxa. The distribution ofChlamydomonasintrons is highly variable and, in many respects, is not consistent with the phylogeny deduced from chloroplast rRNA sequence comparisons. This phylogeny features two main lineages ofChlamydomonastaxa forming sister groups. Because earlier branching organisms in the green algal/land plant lineage display no chloroplast rDNA introns, it appears that all of the intron insertion positions inChlamydomonasare of recent origins, with some of the positions having arisen subsequent to the divergence of the two mainChlamydomonaslineages. Remarkably, the rRNA regions corresponding to most of the group I intron insertion positions in rRNA genes have been assigned functional roles suggesting that they lie in exposed regions of the ribosome. On the basis of this striking correlation between exposed rRNA regions and intron insertion sites, we speculate that the reversal of the self-splicing reaction has played a major role in the creation of the multiple intron insertion positions found in rRNA genes as well as in the proliferation of group I introns elsewhere in theChlamydomonaschloroplast genome.