Comparative Analysis of Two Pear Pests, Cacopsylla jukyungi and Cacopsylla burckhardti (Hemiptera: Psyllidae), Based on Complete Mitochondrial Genomes and Comparison to Confamilial Species

Mitochondrial genome sequences have been used in diverse fields of biology. In this study, we sequenced the complete mitochondrial genomes (mitogenome) of two pear pests: Cacopsylla jukyungi, the most damaging insect pest to commercial pears in South Korea, and Cacopsylla burckhardti (Hemiptera: Psyllidae). The two mitogenomes were compared to confamilial species to accumulate genetic information and understand evolutionary characteristics of the family Psyllidae. The 15,438 bp-and 14,799 bp-long complete mitogenomes of C. jukyungi and C. burckhardti, respectively, had many features typical of insect mitogenomes; however, at 1283 bp, the C. jukyungi mitogenome had an unusually long A+T-rich region, which was composed of two identical 540-bp repeat sequences. Among the intergenic spacer regions, the one located at the ND1 and trnS2 junction was relatively well conserved in length (mostly within 23-36 bp). This region had a high sequence identity in all Psyllidae, possessing a 5-bp consensus sequence (CGGTA), which is speculated to have a functional role. Though the A+T-rich region in available Psyllidae mitogenomes varied substantially in length (662-1430 bp) and sequence divergence, all species had a conserved sequence stretch at the 3'-end of srRNA, which is also speculated to have a functional role. Genetic divergence among genes indicated the lowest variability in srRNA, lrRNA, and COI, whereas ATP8 and ND6 showed the highest variability at both family and genus (Cacopsylla) levels. Our data provide evidence that the family Psyllidae, including current C. jukyungi and C. burckhardti, have evolutionary unique features that were previously undetected, along with the unique A+T-rich region structure in C. jukyungi.