The family Toxoderidae (Mantodea) contains an ecologically diverse group of praying mantis species that have in common greatly elongated bodies. In this study, we sequenced and compared the complete mitochondrial genomes of two Toxoderidae species, Paratoxodera polyacantha and Toxodera hauseri, and compared their mitochondrial genome characteristics with another member of the Toxoderidae, Stenotoxodera porioni (KY689118). The lengths of the mitogenomes of T. hauseri and P. polyacantha were 15,616 bp and 15,999 bp, respectively, which is similar to that of S. porioni (15,846 bp). The size of each gene as well as the A+T-rich region and the A+T content of the whole genome were also very similar among the three species as were the protein-coding genes, the A+T content and the codon usages. The mitogenome of T. hauseri had the typical 22 tRNAs, whereas that of P. polyacantha had 26 tRNAs including an extra two copies of trnA-trnR. Intergenic regions of 67 bp and 76 bp were found in T. hauseri and P. polyacantha, respectively, between COX2 and trnK; these can be explained as residues of a tandem duplication/random loss of trnK and trnD. This non-coding region may be synapomorphic for Toxoderidae. In BI and ML analyses, the monophyly of Toxoderidae was supported and P. polyacantha was the sister clade to T. hauseri and S. porioni.
The non-reducing disaccharide trehalose is widely distributed among various organisms. It plays a crucial role as an instant source of energy, being the major blood sugar in insects. In addition, it helps countering abiotic stresses. Trehalose synthesis in insects and other invertebrates is thought to occur via the trehalose-6-phosphate synthase (TPS) and trehalose-6-phosphate phosphatase (TPP) pathways. In many insects, the TPP gene has not been identified, whereas multiple TPS genes that encode proteins harboring TPS/OtsA and TPP/OtsB conserved domains have been found and cloned in the same species. The function of the TPS gene in insects and other invertebrates has not been reviewed in depth, and the available information is quite fragmented. The present review discusses the current understanding of the trehalose synthesis pathway, TPS genetic architecture, biochemistry, physiological function, and potential sensitivity to insecticides. We note the variability in the number of TPS genes in different invertebrate species, consider whether trehalose synthesis may rely only on the TPS gene, and discuss the results of in vitro TPS overexpression experiment. Tissue expression profile and developmental characteristics of the TPS gene indicate that it is important in energy production, growth and development, metamorphosis, stress recovery, chitin synthesis, insect flight, and other biological processes. We highlight the molecular and biochemical properties of insect TPS that make it a suitable target of potential pest control inhibitors. The application of trehalose synthesis inhibitors is a promising direction in insect pest control because vertebrates do not synthesize trehalose; therefore, TPS inhibitors would be relatively safe for humans and higher animals, making them ideal insecticidal agents without off-target effects.
The mitochondrial genome of Hoplobatrachus rugulosus (Anura: Dicroglossidae) is a circular molecule of 20,309 bp in length, containing 39 genes (including the extra copy of ND5 and tRNA(Met) genes). The following four distinctive features are observed: the cluster of rearranged tRNA genes (TPF tRNA gene cluster), the translocation of tRNA(Leu(CUN)) and ND5 genes, the tandem duplication of tRNA(Met) genes (Met1 and Met2), and the duplicated d-loop-ND5 regions.
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