Abstract
As a major noncoding fragment, the control region (CR) of mtDNA is responsible for the initiation of mitogenome transcription and replication. Several structural features of CR sequences have been reported in many insects. However, comprehensive analyses on the structural organization and phylogenetic utility, as well as the role of tandem replications (TRs) on length variation, high A+T content, and shift of base skew of CR sequences are poorly investigated in hemipteran insects. In this study, we conducted a series of comparative analyses, using 116 samples covering all 11 infraorders of the five currently recognized monophyletic groups in the Hemiptera. Several structural elements (mononucleotide stretches containing conserved sequence blocks (CSBs), TRs, and GA-rich region) were identified in the mitochondrial control region in hemipteran insects, without showing a consistent location. The presence and absence of certain specific structural elements in CR sequences show the various structural organizations of that segment among the five monophyletic groups, which indicates the diversification of the control region’s structural organization in Hemiptera. Among the many groups within Hemiptera, eight monophyletic groups and three consistent phylogenetic trees were recovered, using CSBs datasets by maximum likelihood and Bayesian methods, which suggests the possible utility of CR sequences for phylogenetic reconstruction in certain groups of Hemiptera. Statistical analyses showed that TRs may contribute to the length variation, high AT content, and the shift of base skewing of CR sequences toward high AT content in the Hemiptera. Our findings enrich the knowledge of structural organization, phylogenetic utility, and roles of tandem replication of hemipteran CR, and provide a possible framework for mitochondrial control region analyses in hemimetabolous insects.
Highlights
The control region (CR) is a requisite part of the mitogenome, which is called an “A+T-rich region” for its extraordinarily high A+T content in insects [1]
Our analyses reveal that CR sequences consist of several structural elements without obvious conserved and variable domains in Hemiptera insects (Figure 1), which implies that the CR of hemipteran insects belongs to the Group 2 control region, as described previously [5]
Our results have shown that the structural organization of CR sequences have diversified, due to the presence and absence of certain specific structural elements among the five monophyletic groups (Sternorrhyncha, Fulgoromorpha, Cicadomorpha, Heteroptera and Coleorrhyncha)
Summary
The control region (CR) is a requisite part of the mitogenome, which is called an “A+T-rich region” for its extraordinarily high A+T content in insects [1]. Phylogenetic analyses on bioluminescent Elateridae species proposed again that the CR might be used as a suitable marker for phylogenetic reconstruction [16] These studies on the phylogenetic potential of CR just focus on holometabolous insects, and relevant research on hemimetabolous groups has not been reported up until now. In order to assess the role of TRs on length variation of CR sequences, the total TR length, synthesizing the information about the number, repeat unit size, and copy number variation of the structural element must be taken into account It is still unknown whether the occurrence of TRs contributes to high AT content and base skewing of CR sequences toward high AT content. The evaluation of TR’s roles on the AT content and base skewing of CR sequences toward high AT content will help us trace the potential molecular mechanism or evolutionary clues leading to this heavy base bias of CR sequences
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