Abstract
The complete 16,043 bp mitochondrial genome (mitogenome) of Bactrocera minax (Diptera: Tephritidae) has been sequenced. The genome encodes 37 genes usually found in insect mitogenomes. The mitogenome information for B. minax was compared to the homologous sequences of Bactrocera oleae, Bactrocera tryoni, Bactrocera philippinensis, Bactrocera carambolae, Bactrocera papayae, Bactrocera dorsalis, Bactrocera correcta, Bactrocera cucurbitae and Ceratitis capitata. The analysis indicated the structure and organization are typical of, and similar to, the nine closely related species mentioned above, although it contains the lowest genome-wide A+T content (67.3%). Four short intergenic spacers with a high degree of conservation among the nine tephritid species mentioned above and B. minax were observed, which also have clear counterparts in the control regions (CRs). Correlation analysis among these ten tephritid species revealed close positive correlation between the A+T content of zero-fold degenerate sites (P0FD), the ratio of nucleotide substitution frequency at P0FD sites to all degenerate sites (zero-fold degenerate sites, two-fold degenerate sites and four-fold degenerate sites) and amino acid sequence distance (ASD) were found. Further, significant positive correlation was observed between the A+T content of four-fold degenerate sites (P4FD) and the ratio of nucleotide substitution frequency at P4FD sites to all degenerate sites; however, we found significant negative correlation between ASD and the A+T content of P4FD, and the ratio of nucleotide substitution frequency at P4FD sites to all degenerate sites. A higher nucleotide substitution frequency at non-synonymous sites compared to synonymous sites was observed in nad4, the first time that has been observed in an insect mitogenome. A poly(T) stretch at the 5′ end of the CR followed by a [TA(A)]n-like stretch was also found. In addition, a highly conserved G+A-rich sequence block was observed in front of the poly(T) stretch among the ten tephritid species and two tandem repeats were present in the CR.
Highlights
The family Tephritidae, generally known as ‘‘true’’ fruit flies, includes 471 genera and 4257 species distributed throughout the temperate and tropical areas of the world
Some hosts are endemic to southern China and the eastern Himalayan region [5] but B. minax has been reported on the kumquat Fortunella crassifolia [6] and the boxthorn Lycium chinense [2]
White and Wang [7] designated a lectotype of B. minax and assigned the species to the Bactrocera (Tetradacus); in addition, they indicated that Bactrocera citri Chen, collected from China in 1940, should be placed in synonymy with B. minax
Summary
The family Tephritidae, generally known as ‘‘true’’ fruit flies, includes 471 genera and 4257 species distributed throughout the temperate and tropical areas of the world. The fruit fly Bactrocera minax Enderlein (Diptera: Tephritidae), generally known as the Chinese citrus fruit fly, has been a serious pest of commercial citrus crops in China for more than half a century [2]. This species has been recorded in southern China, India (West Bengal and Sikkim) and Bhutan [2,3] wild and cultivated citrus species [4]. A wide variety of questions about the biology and phylogeny of B. minax have been addressed with the aid of molecular tools These studies could have used two main sources of genetic data; namely, nuclear sequence data and, most frequently, mitochondrial sequence data. The molecule contains at least one sequence of variable length known as the A+T-rich region or control region
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