Concerted Evolution of Duplicate Control Regions in the Mitochondria of Species of the Flatfish Family Bothidae (Teleostei: Pleuronectiformes)

Mitogenomes of flatfishes (Pleuronectiformes) exhibit the greatest diversity of gene rear-rangements in teleostean fishes. Duplicate control regions (CRs) have been found in the mito-genomes of two flatfishes, Samariscus latus (Samaridae) and Laeops lanceolata (Bothidae), which is rare in teleosts. It has been reported that duplicate CRs have evolved in a concerted fashion in fishes and other animals, however, whether concerted evo-lution exists in flatfishes remains unknown. In this study, based on five newly sequenced and six previously reported mitogenomes of lefteye flounders in the Bothidae, we explored whether duplicate CRs and concerted evolution exist in these species. Results based on the present study and previous reports show that four out of eleven bothid species examined have duplicate CRs of their mitogenomes. The core regions of the duplicate CRs of mitogenomes in the same species have identical, or nearly identical, sequences when compared to each other. This pattern fits the typical characteristics of concerted evolution. Additionally, phylogenetic and ancestral state reconstruction analysis also provided evidence to support the hypothesis that duplicate CRs evolved concertedly. The core region of concerted evolution is situated at the conserved domains of the CR of the mitogenome from the termination associated sequences (TASs) to the conserved sequence blocks (CSBs). Commonly, this region is con-sidered to regulate mitochondrial replication and transcription. Thus, we hypothesize that the cause of concerted evolution of the duplicate CRs in the mtDNAs of these four bothids may be related to some function of the conserved sequences of the CRs during mitochondrial rep-lication and transcription. We hope our results will provide fresh insight into the molecular mechanisms related to replication and evolution of mitogenomes.

硬骨鱼类的鳎鱼类线粒体基因组展现出最丰富的基因重排多样性。在两种鳎鱼类，即 Samariscus latus（沙鳎科）和 Laeops lanceolata（鳎科），其线粒体基因组中发现了重复的控制区（CRs），这在辐鳍鱼类中极为罕见。已有报道指出，重复的CRs在鱼类及其他动物中协同进化，然而，在鳎鱼类中是否存在协同进化仍是一个未解之谜。在本研究中，基于五份新测序及六份先前报道的鳎科左侧目鳎鱼线粒体基因组，我们探讨了这些物种中是否存在重复的CRs以及协同进化。本研究结果与先前报道相结合，显示在所考察的十一种鳎鱼中，有四种物种的线粒体基因组存在重复的CRs。同一物种中重复的CRs的核心区域在相互比较时显示出相同的，或几乎相同的，序列。这种模式符合协同进化的典型特征。此外，系统发育和祖先状态重建分析也为重复CRs协同进化的假说提供了证据。协同进化的核心区域位于线粒体CR的保守域，从终止相关序列（TASs）至保守序列块（CSBs）。通常，这一区域被认为调节线粒体复制和转录。因此，我们假设这四种鳎鱼线粒体DNA中重复CRs的协同进化可能与CRs保守序列在线粒体复制和转录中的某些功能有关。我们希望我们的研究结果将为线粒体基因组复制和进化的分子机制提供新的见解。