Jiang Pei, Li Hu, Song Fan, Cai Yao, Wang Jianyun, Liu Jinpeng, Cai Wanzhi
Department of Entomology, China Agricultural University, Beijing 100193, China.
Markey Cancer Center, University of Kentucky, Lexington, KY 40536, USA.
Int J Mol Sci. 2016 Jun 16;17(6):951. doi: 10.3390/ijms17060951.
Most assassin bugs are predators that act as important natural enemies of insect pests. Mitochondrial (mt) genomes of these insects are double-strand circular DNAs that encode 37 genes. In the present study, we explore the duplication and rearrangement of tRNA genes in the mt genome of Reduvius tenebrosus, the first mt genome from the subfamily Reduviinae. The gene order rearranges from CR (control region)-trnI-trnQ-trnM-ND2 to CR-trnQ-trnI2-trnI1-trnM-ND2. We identified 23 tRNA genes, including 22 tRNAs commonly found in insects and an additional trnI (trnI2), which has high sequence similarity to trnM. We found several pseudo genes, such as pseudo-trnI, pseudo-CR, and pseudo-ND2, in the hotspot region of gene rearrangement (between the control region and ND2). These features provided evidence that this novel gene order could be explained by the tandem duplication/random loss (TDRL) model. The tRNA duplication/anticodon mutation mechanism further explains the presence of trnI2, which is remolded from a duplicated trnM in the TDRL process (through an anticodon mutation of CAT to GAT). Our study also raises new questions as to whether the two events proceed simultaneously and if the remolded tRNA gene is fully functional. Significantly, the duplicated tRNA gene in the mitochondrial genome has evolved independently at least two times within assassin bugs.
大多数猎蝽是捕食性昆虫，是害虫的重要天敌。这些昆虫的线粒体（mt）基因组是编码37个基因的双链环状DNA。在本研究中，我们探索了暗黑猎蝽（Reduvius tenebrosus）mt基因组中tRNA基因的重复和重排，暗黑猎蝽是红蝽亚科（Reduviinae）的首个mt基因组。基因顺序从CR（控制区）-trnI-trnQ-trnM-ND2重排为CR-trnQ-trnI2-trnI1-trnM-ND2。我们鉴定出23个tRNA基因，包括昆虫中常见的22个tRNA以及另外一个与trnM具有高度序列相似性的trnI（trnI2）。我们在基因重排的热点区域（控制区和ND2之间）发现了几个假基因，如假trnI、假CR和假ND2。这些特征提供了证据，表明这种新的基因顺序可以用串联重复/随机丢失（TDRL）模型来解释。tRNA重复/反密码子突变机制进一步解释了trnI2的存在，它是在TDRL过程中由一个重复的trnM重塑而来（通过反密码子从CAT突变为GAT）。我们的研究还提出了新的问题，即这两个事件是否同时发生，以及重塑的tRNA基因是否具有完全功能。值得注意的是，线粒体基因组中重复的tRNA基因在猎蝽中至少独立进化了两次。
