South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, 510650, China.
World J Microbiol Biotechnol. 2012 Jan;28(1):371-80. doi: 10.1007/s11274-011-0829-9. Epub 2011 Jul 7.
The full-length cytochrome c oxidase subunit I gene (cox1) containing a group I intron was isolated from an important medical fungus Cordyceps militaris (Cordycipitaceae). The open reading frame (ORF) of 1,593 nucleotides encoded a predicted protein COX1 of 530 amino acids. The group I intron encoded a putative homing endonuclease (HE) with two LAGLIDADG motifs. RT-PCR and Northern analysis showed a mature transcript of spliced cox1. Both 5'exon-intron and intron-3'exon junctions were also found by RT-PCR, suggesting the possible presence of unspliced cox1 RNA in total RNA. Sequence comparison by BLASTn showed that the coding region of cox1 (CRcox1) of C. militaris had significant similarities to those of related species (such as Cordyceps bassiana and C. brongniartii), while the intron had no significant homologous sequences of Cordycipitaceae fungi in NCBI database. The phylogenetic tree based on the CRcox1 confirmed the present taxonomic status of related species, but the cox1 introns were phylogenetically distinct. Compared to C. bassiana and C. brongniartii, the cox1 intron of C. militaris exhibited specific splicing site and different intronic ORF. The analysis of the folding RNA structures of the known cox1 introns from Cordyceps species showed different base pairs and conserved regions (P1-P10) in their structures. The present results provide useful information on the studies of cox1 intron splicing and Cordyceps evolution.
从重要药用真菌蛹虫草（虫草科）中分离出全长细胞色素 c 氧化酶亚基 I 基因（cox1），该基因包含一个 I 组内含子。开放阅读框（ORF）为 1593 个核苷酸，编码 530 个氨基酸的预测蛋白 COX1。I 组内含子编码具有两个 LAGLIDADG 基序的假定归巢内切酶（HE）。RT-PCR 和 Northern 分析显示剪接cox1 的成熟转录本。通过 RT-PCR 还发现了 5'外显子-内含子和内含子-3'外显子接头，这表明在总 RNA 中可能存在未剪接的 cox1 RNA。BLASTn 序列比较表明，蛹虫草 cox1 的编码区（CRcox1）与相关物种（如蛹虫草和大团囊虫草）具有显著相似性，而内含子在 NCBI 数据库中与虫草科真菌没有显著同源序列。基于 CRcox1 的系统发育树证实了相关物种的现有分类地位，但 cox1 内含子在系统发育上是不同的。与蛹虫草和大团囊虫草相比，蛹虫草的 cox1 内含子表现出特定的剪接位点和不同的内含子 ORF。对来自虫草属物种的已知 cox1 内含子的折叠 RNA 结构的分析表明，其结构中存在不同的碱基对和保守区（P1-P10）。本研究结果为 cox1 内含子剪接和虫草属进化的研究提供了有用的信息。
