The complete mitochondrial genome of Sympiezomias velatus (Coleoptera: Curculionidae)

Candidate Chemosensory Genes Identified in the Adult Antennae of Sympiezomias velatus and Binding Property of Odorant-Binding Protein 15

Chemosensory genes play important roles in insect behaviors and have thus become potential molecular targets for pest control based on the manipulation of chemoreception-driven behaviors. The great gray weevil Sympiezomias velatus (Chevrolat) (Coleoptera: Curculionidae) is an important agricultural pest that causes serious economic losses to many crops in China, but its chemosensory genes have not been reported. Here we assembled the antennal transcriptomes of female and male adult S. velatus and revealed the major chemosensory genes necessary for olfaction. A total of 138 candidate chemosensory genes in six families were identified, including 41 encoding odorant-binding proteins (OBPs), 11 encoding chemosensory proteins (CSPs), 62 encoding odorant receptors (ORs), 15 encoding gustatory receptors (GRs), six encoding ionotropic receptors (IRs), and three encoding sensory neuron membrane proteins (SNMPs). We analyzed their phylogenetic relationship based on the amino acid sequences of these chemosensory-related protein families in S. velatus and other insects, and the expression profiles based on their antennal transcriptomes. Chemosensory genes that show antenna-abundant/specific or sex-biased expression were observed, suggesting that these genes might have functions in olfaction. Furthermore, we chose an antenna-abundant OBP belonging to ABPX subfamily, SvelOBP15, to investigate its binding property. The results showed that among 33 tested compounds, SvelOBP15 displayed high binding affinities (Ki = 7.36-12.94 μmol/L) with farnesol, nerolidol, limonene and diisobutyl phthalate, indicating that SvelOBP15 plays olfactory roles by binding and transporting specific plant volatiles. These findings will help us better understand the olfactory systems of S. velatus, and provide a basis for functional elucidation of these chemosensory genes.

The complete mitochondrial genome of Lixus subtilis Boheman, 1835 (Coleoptera, Curculionidae) and its phylogenetic implications

The first complete mitochondrial genome of Lixus subtilis Boheman is reported in this study. The circular genome is 15,223 bp long, including a standard set of 21 transfer RNAs (tRNAs), 2 ribosomal RNAs (rRNAs), 13 protein-coding genes, and a non-coding control region. The trnI gene was not found in the L. subtilis mitogenome. All tRNAs had the typical cloverleaf structure, except for trnS1, which lacked the dihydrouridine arm. The phylogenetic tree of 13 Curculionidae species based on the concatenated nucleotide sequences of complete mitochondrial genomes strongly supported that L. subtilis is closely related to Curculioninae and Molytinae.

Population genomics and phylogeography of the boll weevil, Anthonomus grandis Boheman (Coleoptera: Curculionidae), in the United States, northern Mexico, and Argentina

The boll weevil, Anthonomus grandis Boheman (Coleoptera: Curculionidae), is an important pest of commercial cotton across the Americas. In the United States, eradication of this species is complicated by re-infestations of areas where eradication has been previously successful and by the existence of morphologically similar variants that can confound identification efforts. To date, no study has applied a high-throughput sequencing approach to better understand the population genetic structure of the boll weevil. Furthermore, only a single study has investigated genetic relationships between populations in North and South America. We used double digest restriction site-associated DNA sequencing (ddRADseq) to resolve the population genomic structure of the boll weevil in the southern United States, northern Mexico, and Argentina. Additionally, we assembled the first complete mitochondrial genome for this species and generated a preliminary whole genome assembly, both of which were used to improve the identification of informative loci. Downstream analyses revealed two main lineages-one consisting of populations found geographically west of the Sierra Madre Occidental mountain range and the second consisting of populations found to the east-were revealed, and both were sub-structured. Population geographic structure was consistent with the isolation by distance model, indicating that geogrpahic distance is likely a primary mechanism driving divergence in this species. Boll weevil populations from Argentina were found to be more closely related to the eastern lineage, suggesting a recent colonization of South America by the eastern lineage, but additional sampling across Mexico, Central America and South America is needed to further clarify their origin. Finally, we uncovered an instance of population turnover or replacement, highlighting the temporal instability of population structure.

Mitogenome Analysis of Four Lamiinae Species (Coleoptera: Cerambycidae) and Gene Expression Responses by Monochamus alternatus When Infected with the Parasitic Nematode, Bursaphelenchus mucronatus

We determined the mitochondrial gene sequence of Monochamus alternatus and three other mitogenomes of Lamiinae (Insect: Coleoptera: Cerambycidae) belonging to three genera (Aulaconotus, Apriona and Paraglenea) to enrich the mitochondrial genome database of Lamiinae and further explore the phylogenetic relationships within the subfamily. Phylogenetic trees of the Lamiinae were built using the Bayesian inference (BI) and maximum likelihood (ML) methods and the monophyly of Monochamus, Anoplophora, and Batocera genera was supported. Anoplophora chinensis, An. glabripennis and Aristobia reticulator were closely related, suggesting they may also be potential vectors for the transmission of the pine wood pathogenic nematode (Bursaphelenchus xylophilus) in addition to M. alternatus, a well-known vector of pine wilt disease. There is a special symbiotic relationship between M. alternatus and Bursaphelenchus xylophilus. As the native sympatric sibling species of B. xylophilus, B. mucronatus also has a specific relationship that is often overlooked. The analysis of mitochondrial gene expression aimed to explore the effect of B. mucronatus on the energy metabolism of the respiratory chain of M. alternatus adults. Using RT-qPCR, we determined and analyzed the expression of eight mitochondrial protein-coding genes (COI, COII, COIII, ND1, ND4, ND5, ATP6, and Cty b) between M. alternatus infected by B. mucronatus and M. alternatus without the nematode. Expression of all the eight mitochondrial genes were up-regulated, particularly the ND4 and ND5 gene, which were up-regulated by 4-5-fold (p < 0.01). Since longicorn beetles have immune responses to nematodes, we believe that their relationship should not be viewed as symbiotic, but classed as parasitic.

Complete mitochondrial genome of the olive weevil, Dyscerus cribripennis (Coleoptera: Curculionidae)

The olive weevil Dyscerus cribripennis (Coleoptera: Curculionidae) is an uncontrollable noxious insect to Olea europaea. The 15,977 bp complete mitochondrial genome of D. cribripennis contained 13 protein-coding genes (PCGs), 2 ribosomal RNA genes (rRNAs), 21 transfer RNA genes (tRNAs), and a control region (GenBank accession number MW023069). The trnI was not found in the D. cribripennis mitogenome. The phylogenetic analysis based on mitogenomes showed that D. cribripennis is closed related with Hylobitelus xiaoi.

The complete mitochondrial genome of the tea weevil, Myllocerinus aurolineatus (Coleoptera: Curculionidae)

The tea weevil, Myllocerinus aurolineatus (Voss), is a serious pest of tea plants. We have obtained and annotated the complete mitochondrial genome of M. aurolineatus (GenBank accession No. MH197100). The entire mt genome is 17,762 bp long with an A + T content of 75.45%. The mt genome of M. aurolineatus encodes all 37 genes that are typically found in animal mt genomes, consists of 13 protein-coding genes, 2 ribosomal RNA and 22 transfer RNA genes. The gene order is consistent with other weevil mt genomes in Entiminae, within a typical gene order of “RANSEF”. Phylogenetic analysis was performed using 13 protein-coding genes among 18 weevils showed that M. aurolineatus is closely related to another Entiminae species, Sympiezomias velatus.

The complete mitochondrial genome of a walnut weevil, Alcidodes juglans Chao (Coleoptera: Curculionidae)

The walnut weevil, Alcidodes juglans Chao (Coleoptera: Curculionidae), is an important agricultural pest and distributed widely in China. The complete mitochondrial genome of A. juglans is 15,638 bp long, and consists of 13 protein-coding genes (PCGs), two ribosomal RNA genes, 21 transfer RNA (tRNA) genes and a putative control region (GenBank accession No. MH819192). The trnI gene has not been observed in the A. juglans mitogenome. The nucleotide composition is significantly biased (A, G, C, and T was 38.35%, 10.02%, 14.96%, and 36.67%, respectively) with A + T contents of 75.02%. All of the 21 tRNAs have the typical cloverleaf structure, with an exception for trnS₁ (AGN). All PCGs are initiated by ATN codons, except for cox1 with AAT instead. Ten PCGs use a common stop codon of TAA or TAG, whereas the remaining three were terminated with a single T. The phylogenetic relationships based on neighbour-joining method showed that A. juglans is closely related to Naupactus xanthographus, which is in accordance with the traditional morphological classification.

Complete mitochondrial genome of the bamboo snout beetle, Cyrotrachelus buqueti (Coleoptera: Curculionidae)

The bamboo snout beetle Cyrotrachelus buqueti (Coleoptera: Curculionidae) is a destructive forest pest and distributed widely in Southeast Asia. The 15,035 bp complete mitochondrial genome of the species consists of 13 protein-coding genes (PCGs), two ribosomal RNA genes (rRNAs), 21 transfer RNA genes (tRNAs) and a control region (GenBank accession no. MG674390). The trnl gene was not found in the C. buqueti mitogenome. The gene order and the orientation of C. buqueti were similar to those found in other Coleoptera species. The nucleotide composition was significantly biased (A, G, C, and T was 38.18%, 10.10%, 16.16%, and 35.56%, respectively) with A + T contents of 73.74%. ATG, ATA, ATT, AAT, and TTG were initiation codons and TAA, TAG, and T were termination codons. All the 21 tRNAs displayed a typical cloverleaf secondary structure, except for trnS1 which lacked the dihydrouridine arm. Phylogenetic analysis was performed using 13 PCGs with 14 other beetles showed that C. buqueti is closely related to Eucryptorhynchus brandti, which agree with the traditional classification.

The complete mitochondrial genome of Enallagma cyathigerum (Odonata: Coenagrionidae) and phylogenetic analysis

To better understand the diversity and evolution of Odonata, we sequenced and annotated the complete mitochondrial genome (mitogenome) of Enallagma cyathigerum. This mitogenome was 16,661 bp in size and encoded the typical 37 genes, i.e. 13 protein-coding genes (PCGs), 22 transfer RNA genes (tRNAs) and two ribosomal RNA genes. The nucleotide composition of the E. cyathigerum mitogenome was significantly biased toward A and T, with an A + T content of 74.2%. Eleven PCGs started with a typical ATN codon, whereas the remaining two PCGs (nad1 and nad3) used TTG as the initial codon. All the 22 tRNAs had a typical secondary cloverleaf structure. The Bayesian phylogenetic analysis based on the concatenated nucleotide sequences of 13 PCGs strongly supported the sister relationship of E. cyathigerum and two Ischnura species from the same family Coenagrionidae. The phylogenetic tree strongly supported the monophyly of each of the two suborders (Zygoptera and Anisoptera) and recovered a phylogeny of Zygoptera + (Anisoptera + Anisozygoptera).