Complete mitochondrial genome of the small brown planthopper, Laodelphax striatellus (Delphacidae: Hemiptera), with a novel gene order.

We determined the first complete mitochondrial genome (mitogenome) sequence from a representative of the insect family Delphacidae, Laodelphax striatellus. The 16,513 bp long L. striatellus mitogenome encodes 13 putative proteins, two ribosomal RNAs, and 22 transfer RNAs, and contains a putative control region (or A+T-rich region). The nucleotide composition is biased toward adenine and thymine (77.2% A+T), and the amino acid composition is affected to a similar degree by the AT mutational bias. All 13 protein-coding genes (PCGs) start with a typical ATN initiation codon. Eight of 13 PCGs in L. striatellus have a complete termination codon (TAA), whereas the remaining five have incomplete termination codons. The anticodons of the L. striatellus tRNAs are identical to those in Drosophila yakuba, and all tRNAs except for tRNA(Ser-AGN) can be folded in the form of a typical cloverleaf structure. The A+T-rich region of L. striatellus was found between srRNA and tRNA(lle), and the entire region was 2040 bp long. The gene content of the L. striatellus mitogenome is identical to other completely sequenced insect mitogenomes, while the gene order is different from the common arrangement found in most insects: five tRNA genes and three PCGs in the L. striatellus mitogenome have changed positions relative to the ancestral arrangement of mitochondrial genes in D. yakuba. Besides describing the above contents, we also aligned the mitogenome sequence of L. striatellus with other hemipterans to analyse the phylogenetic relationships of Hemiptera. The results show that Heteroptera is the sister group to all other Hemiptera, and Cicadomorpha is the sister group to the clade Fulgoromorpha+Sternorrhyncha.