关键词: 斑翅草螽, 线粒体基因组, 序列分析, 基因间隔序列, 相对密码子使用频率

Abstract: The mitochondrial genome (mitogenome) of Ruspolia dubia (Orthoptera: Conocephalinae) contains a short control region with 70 bp in length. So, the mitogenome of Conocephalus maculates come from Conocephalinae was sequenced by using long-PCR and sub-PCR techniques. The mitogenome of C. maculates is 15 898 bp in size, its A+T content is 72.05% and the genome organization follows the ancestral insect gene arrangement. All protein-coding genes (PCGs) start with a typical ATN codon, while nine of the 13 PCGs end with TAA or TAG, and the remainder have incomplete termination codons T. Except for trnS^AGN, all 21 tRNAs have the typical clover-leaf structures. According to the unusual Type-9 of Steinberg et al. (1997), the DHU arm of trnS^AGN forms a simple 7-nt loop and the anticodon stem has nine base-pairs with a bulged nucleotide in the middle in contrast to the normal five base-pairs. The main differences between C. maculatus and other orthopteran mitogenomes was that two novel larger intergenic spacers (78 bp and 360 bp) between trnS^UCN and nad1, nad1 and trnL^CUN, respectively. The intergenic spacer between nad1 and trnL^CUN has been labeled unidentified open reading frame (UORF) because N strand comprises an open reading frame (103 amino acids) complete with start and termination codons (ATT/TAA). The usage of synonymous codon markedly is correlated with the nucleotide at the 3rd codon position, but has no relation to the anticodon of mitogenome tRNA. Generally, for all codons with their relative synonymous codon usage (RSCU) more than 1, the 3rd codon positions are A or T. Noncanonical matches of G-U base pairs accounts for the overwhelming majority of total unmatched base pairs in the orthopteran mitogenome tRNAs. The results suggest that the G-U may be one cognitive base pairing in mitogenome. The C. maculates mitogenome sequences, as well as the previously determined orthopteran mitogenomes, provide sequence source to reconstruct Orthoptera evolutionary history.

Key words: Conocephalus maculates, mitochondrial genome, sequence analysis, intergenic spacer, relative synonymous codon usage (RSCU)