Abstract
In the present study, we determined the complete mitochondrial DNA (mtDNA) sequence of Apis cerana, the Asiatic cavity-nesting honeybee. We present here an analysis of features of its gene content and genome organization in comparison with Apis mellifera to assess the variation within the genus Apis and among main groups of Hymenoptera. The size of the entire mt genome of A. cerana is 15,895 bp, containing 2 ribosomal RNA genes, 13 protein-coding genes, 22 transfer RNA (tRNA) genes and one control region. These genes are transcribed from both strands and have a nucleotide composition high in A and T. The contents of A+T of the complete genomes are 83.96% for A. cerana. The AT bias had a significant effect on both the codon usage pattern and amino acid composition of proteins. There are a total of 3672 codons in all 13 protein-coding genes, excluding termination codons. The most frequently used amino acid is Leu (15.52%), followed by Ile (12.85%), Phe (10.10%), Ser (9.15%) and Met (8.96%). Intergenic regions in the mt genome of A. cerana are 705 bp in total. The order and orientation of the gene arrangement pattern is identical to that of A. mellifera, except for the position of the tRNA-Ser(AGN) gene. Phylogenetic analyses using concatenated amino acid sequences of 13 protein-coding genes, with three different computational algorithms (NJ, MP and ML), all revealed two distinct groups with high statistical support, indicating that A. cerana and A. mellifera are two separate species, consistent with results of previous morphological and molecular studies. The complete mtDNA sequence of A. cerana provides additional genetic markers for studying population genetics, systematics and phylogeographics of honeybees.
Highlights
The Asiatic honeybee, Apis cerana Fabricius (Hymenoptera: Apidae), is an important honeybee species in Asian countries
The A. cerana mt genome shows a novel arrangement within Hymenoptera compared with the ancestral pancrustacean mt genome organization [36]
A rearrangement is classified as an inversion when the transfer RNA (tRNA) is found on the opposite strand and as shuffling when the tRNA gene is on the same mt stand but in a different position compared with the ancestral organization [37]
Summary
The Asiatic honeybee, Apis cerana Fabricius (Hymenoptera: Apidae), is an important honeybee species in Asian countries. We determined the complete nucleotide sequence of the A. cerana mt genome, we performed phylogenetic analyses using selected Hymenoptera species. The mt genome of A. cerana contains 13 protein-coding genes
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