Department of Microbiology, University of Manitoba, Winnipeg, MB, Canada R3T 2N2.
Fungal Genet Biol. 2013 Apr;53:71-83. doi: 10.1016/j.fgb.2013.01.005. Epub 2013 Feb 9.
Comparative sequence analysis of the mitochondrial small subunit ribosomal RNA (rns) gene among species of Ophiostoma, Grosmannia, Ceratocystiopsis and related taxa provides an overview of the types of introns that have invaded this gene within the ophiostomatoid fungi. The rns gene appears to be a reservoir for a number of group I and group II introns along with intron-associated open reading frames such as homing endonucleases and reverse transcriptases. This study uncovered two twintrons, one at position mS917 where a group ID intron encoding a LAGLIDADG ORF invaded another ORF-less group ID intron. Another twintron complex was detected at position mS1247 here a group IIA1 intron invaded the open reading frame embedded within a group IC2 intron. Overall the distribution of the introns does not appear to follow evolutionary lineages suggesting the possibility of rare horizontal gains and frequent losses. Results of this study will make a significant contribution to the understanding of the complexity of the mitochondrial intron landscape, and offer a resource to those annotating mitochondrial genomes. It will also serve as a resource to those that bioprospect for ribozymes and homing endonucleases.
种间比较序列分析小亚基核糖体 RNA (rns) 基因在奥氏蜜环菌、 Grosmannia、 Ceratocystiopsis 和相关分类群中，概述了入侵该基因的内含子类型。rns 基因似乎是许多 I 组和 II 组内含子以及内含子相关开放阅读框（如归巢内切酶和逆转录酶）的储存库。本研究揭示了两个双内含子，一个位于 mS917 位置，一个编码 LAGLIDADG ORF 的 I 组内含子入侵了另一个无 ORF 的 I 组内含子。在 mS1247 位置检测到另一个双内含子复合物，一个 IIA1 内含子入侵了嵌入在 IC2 内含子中的开放阅读框。总体而言，内含子的分布似乎不遵循进化谱系，这表明存在罕见的水平获得和频繁的丢失的可能性。本研究的结果将对理解线粒体内含子景观的复杂性做出重大贡献，并为那些注释线粒体基因组的人提供资源。它也将为那些寻找核酶和归巢内切酶的人提供资源。
