Search

Given mitochondrion is the 'energy and oxygen usage factories', adaptive signatures of mitochondrial genes have been extensively investigated in vertebrates from different altitudes, but few studies focus on insects. Here, we sequenced the complete mitochondrial genome (mitogenome) of Dolycoris. baccarum living in the Tibetan Plateau (DBHC, ∼3200 m above sea level (asl)) and conducted a detailed comparative analysis with another D. baccarum mitogenome (DBQY) from relatively low altitude (∼1300 m asl). All the 37 mitochondrial genes were highly conserved and under purifying selection, except for two mitochondrial protein-coding genes (MPCGs) (atp6 and nad5) that showed positively selected signatures. We therefore further examined non-synonymous substitutions in atp6 and nad5, by sequencing more individuals from three populations with different altitudes. We found that these non-synonymous substitutions were polymorphic in these populations, likely due to relaxed selection constraints in different altitudes. Purifying selection in all mitochondrial genes may be due to their functional importance for the precision of ATP production usually. Length difference in mitochondrial control regions between DBHC and DBQY was also conversed at the population level, indicating that sequence size adjustments in control region may be associated with adaptation to divergent altitudes. Quantitatively real-time PCR analysis for 12 MPCGs showed that gene expression patterns had a significant change between the two populations, suggesting that expression levels of MPCGs could be modulated by divergent environmental pressures (e.g. oxygen content and ambient temperature). These results provided an important guide for further uncovering genetic mechanisms of ecological adaptation in insects. [ABSTRACT FROM AUTHOR]

To better understand the diversity and phylogeny of Scarabaeidae, we sequenced and annotated the nearly complete mitochondrial genome (mitogenome) of Amphimallon solstitiale (Coleoptera: Scarabaeidae: Melolonthinae). This mitogenome was 13,755 bp long and encoded 13 protein-coding genes (PCGs), 19 transfer RNA genes (tRNAs) and two ribosomal RNA unit genes. The A. solstitiale mitogenome with an A + T content of 69.45% presented a positive AT-skew (0.052) and a negative GC-skew (−0.236). Eleven PCGs started with a typical ATN codon, whereas the remaining two PCGs used CAC (cox1) and GTT (cox2) as the initial codon. All tRNAs had a typical secondary cloverleaf structure, except for trnS1 which lacked the dihydrouridine arm. The Bayesian phylogenetic analysis based on mitogenomic data recovered a phylogeny within Scarabaeidae as (Echirinae + (Scirtifomia + (Aphodiinae + (Melolonthinae + (Rutelinae + Cetoniinae))))). [ABSTRACT FROM AUTHOR]