Structure characteristics of mitochondrial genomes of Sitobion avenae and Diuraphis noxia

【Objective】 This study aimed to investigate the structure characteristics of mitochondrial genomes of Sitobion avenae and Diuraphis noxia， providing theoretical basis for effective identification and precise control of pests in the field. 【Method】 Based on mitochondrial genome sequences of Sitobion avenae and Diuraphis noxia， the comparative analysis of base composition， repetitive region sequence composition， and codon bias of their mitochondrial genomes of the 2 aphids was performed. 【Result】 The mitochondrial genomes of the 2 aphids were closed double-stranded circular molecules with total lengths of 15180 and 15784 bp， containing 22 tRNA genes， 13 protein-coding genes， 2 rRNA genes， 1 control region， and 1 repetitive region， and intergenic gaps and gene overlaps were found. AT contents in mitochondrial genomes of the 2 aphids were higher than 84%. All protein-coding genes of the 2 aphids employed the canonical ATN start codon and complete or incomplete stop codons TAA， TA， and T； 29 of the synonymous codons of the 2 aphids exhibited relative synonymous codon usage （RSCU） greater than 1， and the third base of these codons was A or U. The ratios of nonsynonymous substitution rate to synonymous substitution rate （Ka/Ks） of all protein-coding genes of mitochondrial genomes of Sitobion avenae and Diuraphis noxia were less than 1， and the ratio had an extremely significant positive correlation with AT content （P<0.01）. The repetitive regions were situated between tRNA- Glu and tRNA-Phe of mitochondrial genomes for the 2 aphids， and the sequence composition of the repetitive regions exhibited interspecific variation. The maximum likelihood phylogenetic tree based on protein-coding genes of mitochondrial genomes showed that Diuraphis noxia and Sitobion avenae were assigned to different clades. 【Conclusion】 The mitochondrial genomes of Sitobion avenae and Diuraphis noxia exhibit high AT contents and similar gene arrangement. Protein-coding genes are all subject to purifying selection.