Full-Length Transcriptome Profiling of Coridius chinensis Mitochondrial Genome Reveals the Transcription of Genes with Ancestral Arrangement in Insects.

Coridius chinensis (Hemiptera: Dinidoridae) is a medicinal insect. Its mitochondrial gene arrangement is consistent with that of Drosophila melanogaster and Erthesina fullo , the two insects with well-studied mitochondrial transcription. To investigate whether the structural consistency of mitochondrial genes leads to similarities in transcription and post-transcriptional processing, we improved the gene annotation and constructed a quantitative transcription map for the C. chinensis mitochondrial genome (mitogenome) using full-length transcriptome sequencing. The size of this mitogenome was 16,214 bp and the proposed model of mitochondrial transcription was similar to that of Drosophila . Both strands were nearly entirely transcribed except for the antisense genes downstream of trnS2 on N strand. The expression of cytochrome c subunit genes is higher than that of NADH-dehydrogenase subunit genes. The post-transcriptional cleavage process followed the "tRNA punctuation" model, and both the "reverse cleavage" model in Drosophila and "forward cleavage" model in E. fullo were found in C. chinensis . In addition, we found that long non-coding RNAs from the control region contained tandem repeats. Polyadenylation was performed after CCA triplet at the 3' end of tRNA. The isoform diversity of lrRNA was identified. Our study sheds light on the transcriptional regulation and RNA processing of insect mitogenomes with the putative ancestral gene arrangement.