A novel, conserved and possibly functional motif "WHWGHTW" in mitochondrial transcription across Bilateria.

The animal mitogenomes which undergone a reductive evolution has an obvious loss of coding capacity compared to their known closest relatives, but it has not yet been fully investigated why and how the intergenic regions do not encode protein and have no known functions, are stably maintained, replicated, and transmitted by the genome. These relatively small intergenic regions may not be under neutral evolution and they may have functional and/or regulatory roles that have yet to be identified. Here, the distribution pattern, sequence content and location of a novel sequence motif of 'WWWGHTW' were bioinformatically investigated and characterised by constructing a sampling mitogenome dataset of 1889 species from 14 phyla representing the clade of Bilateria. This motif is reverse complementary of the previously described DmTTF binding sequence and found in the nd4L- (X) -trnT gene cluster. This cluster commonly exhibits a strand displacement region and an intergenic region among the bilaterian superphylums, particularly in Ecdysozoa. This motif may be accepted as a substrate providing binding sites for the specific interaction with transcription factors because of (i) its reverse complementarity of previously described DmTTF binding sequence, and (ii) the possession of G and T nucleotides in the fourth and sixth positions, (iii) the bias on T and G nucleotides instead of C and A in the degenerated positions. This suggestion is also supported by the presence of a strand displacement region in the nd4L- (X) -trnT gene cluster, particularly in Ecdysozoa consisting of the most rearranged mitogenomes among the bilaterian superphylums.

The first mitogenomes of the superfamily Pamphilioidea (Hymenoptera: Symphyta): Mitogenome architecture and phylogenetic inference.

The Pamphilioidea represents a small superfamily of the phytophagous suborder Symphyta (Hymenoptera). Here, nearly complete mitochondrial genomes (mitogenomes) of three pamphilioid species: Chinolyda flagellicornis (Pamphiliidae), Megalodontes spiraeae and M. cephalotes (Megalodontesidae) were newly sequenced using next generation sequencing and comparatively analysed with the previously reported symphytan mitogenomes. A positive AT skew (0.013) and a negative GC skew (-0.194) were found in pamphilioid mitogenome, and a deviation from strand asymmetry was also observed in the PCGs encoded on both strands. Several gene rearrangement events were observed in four tRNA gene clusters (WCY, IQM, ARNS1EF and TP clusters), which have not been reported from symphytan mitogenomes to date. As the most parsimonious explanation, compared with the inferred insect ancestral mitogenome architecture, the occurrence of gene rearrangements in pamphilioid mitogenomes requires totally five evolutionary steps, including four transpositions and one inversion. The predicted secondary structures of tRNAs, rrnS and rrnL genes are mostly consistent with reported hymenopteran species. Phylogenetic analyses recovered the monophyly of superfamily Pamphilioidea and indicated the relationship Tenthredinoidea + (Pamphilioidea + (Cephoidea + (Orussoidea + Apocrita))) with strong nodal supports.

The complete mitogenomes of Calameuta filiformis (Eversmann, 1847) and Calameuta idolon (Rossi, 1794) (Hymenoptera: Cephidae): The remarkable features of the elongated A+T rich region in Cephini.

Two complete mitogenomes of the stem borers, Calameuta filiformis and Calameuta idolon, and the complete A+T-rich region of Trachelus iudaicus (Hymenoptera: Cephidae), are reported. The mitogenomes of these species are the longest reported from hymenopterans to date. A remarkable increase in length of the A+T-rich region, the longest for Hymenoptera, was found and compared across the tribe Cephini. The presence of the tRNA- and rRNA-like sequences were reported in the A+T-rich region of sawflies and they were suggested to play a role in replication and/or transcription. The long and short tandem repeats were orderly located in both sides of the A+T-rich region producing stable secondary structures. We suggest that the short tandem repeats are likely to function as a replication fork barrier.

Two nearly complete mitogenomes of wheat stem borers, Cephus pygmeus (L.) and Cephus sareptanus Dovnar-Zapolskij (Hymenoptera: Cephidae): an unusual elongation of rrnS gene.

Two nearly complete mitochondrial genomes (mitogenomes) of wheat stem borers, Cephus pygmeus and Cephus sareptanus (Hymenoptera: Cephidae), were sequenced, characterised and compared with the previously known mitogenome of Cephus cinctus. The gene orders are mostly conserved, except for translocation of trnM and swapped position of trnI and trnQ. An A+T bias was found, but a deviation from strand asymmetry was also detected on the J strand. All protein coding genes (PCGs) are initiated by ATN codons, except for nad1, nad2 and atp8, and all are terminated with TAA, TA- or T- as a stop codon. The predicted secondary structures of rrnS and rrnL genes are mostly consistent with reported hymenopteran species. However, an unusual elongation in rrnS, not know elsewhere in the order, was discovered in Cephus species. Three autonomous sequences detected in domains I and II are mainly responsible for the length expansions.