Chromosome-Level Genome Assembly of Cyrtotrachelus buqueti and Mining of Its Specific Genes

Background: The most severe insect damage to bamboo shoots is the bamboo-snout beetle (Cyrtotrachelus buqueti). Bamboo is a perennial plant that has significant economic value. C. buqueti also plays a vital role in the degradation of bamboo lignocellulose and causing damage. The genome sequencing and functional gene annotation of C. buqueti are of great significance to reveal the molecular mechanism of its efficient degradation of bamboo fiber and the development of the bamboo industry.Results: The size of C. buqueti genome was close to 600.92 Mb by building a one paired-end (PE) library and k-mer analysis. Then, we developed nine 20-kb SMRTbell libraries for genome sequencing and got a total of 51.12 Gb of the original PacBio sequel reads. Furthermore, after filtering with a coverage depth of 85.06×, clean reads with 48.71 Gb were obtained. The final size of C. buqueti genome is 633.85 Mb after being assembled and measured, and the contig N50 of C. buqueti genome is 27.93 Mb. The value of contig N50 shows that the assembly quality of C. buqueti genome exceeds that of most published insect genomes. The size of the gene sequence located on chromosomes reaches 630.86 Mb, accounting for 99.53% of the genome sequence. A 1,063 conserved genes were collected at this assembled genome, comprising 99.72% of the overall genes with 1,066 using the Benchmark Uniform Single-Copy Orthology (BUSCO). Moreover, 63.78% of the C. buqueti genome is repetitive, and 57.15% is redundant with long-term elements. A 12,569 protein-coding genes distributed on 12 chromosomes were acquired after function annotation, of which 96.18% were functional genes. The comparative genomic analysis results revealed that C. buqueti was similar to D. ponderosae. Moreover, the comparative analysis of specific genes in C. buqueti genome showed that it had 244 unique lignocellulose degradation genes and 240 genes related to energy production and conversion. At the same time, 73 P450 genes and 30 GST genes were identified, respectively, in the C. buqueti genome.Conclusion: The high-quality C. buqueti genome has been obtained in the present study. The assembly level of this insect’s genome is higher than that of other most reported insects’ genomes. The phylogenetic analysis of P450 and GST gene family showed that C. buqueti had a vital detoxification function to plant chemical components.

Mathematical Model and microCT-Based Kinematic Analysis of the Rostrum Mouthparts in Cyrtotrachelus buqueti Guer (Coleoptera: Curculionidae)

To uncover the chewing mechanism of Cyrtotrachelus buqueti Guer, a mathematical model was created and a kinematic analysis of its rostrum mouthparts was conducted for, to our knowledge, the first time. To reduce noise and improve the quality of scanning electron micrographs of the weevil's mouthparts, nonlocal means and integral nonlocal means algorithms were proposed. Additionally, based on a comparison and analysis of five classical edge detection algorithms, a multiscale edge detection algorithm based on the B-spline wavelet was used to obtain the boundaries of structural features. The least squares method was used to analyze the data of the mouthparts to fit the mathematical model and fitted curves were obtained using Gaussian equations. The results show that curvature and concave–convex variations of the weevil's mouthparts can highlight fluctuations in friction effects when it chews bamboo shoots, which is helpful in preventing debris from bamboo shoots or other debris from sticking to the mouthpart surfaces. Moreover, this paper highlights the utility of micro-computed tomography (microCT) for three-dimensional (3D) reconstruction and a flowchart is suggested. The reconstructed slices were 9.0 μm thick and an accurate 3D rendered model was obtained from a series of microCT slices. Finally, a real model of the rostrum mouthparts was analyzed using finite-element analysis. The results provide a biological template for the design of a novel bionic drilling mechanism.

Design of bionic foldable wing mimicking the hind wings of the C. buqueti bamboo weevil

The bamboo weevil, Cyrtotrachelus buqueti, has excellent flight ability and strong environmental adaptability. When it flies, its fore wings and hind wings are unfolded, whereas when it crawls, its fore wings are closed, and its flexible hind wings are regularly folded under the fore wings. In this paper, the hind wing folding/unfolding pattern of C. buqueti is analyzed and a new bionic foldable wing with rigid–flexible coupling consisting of a link mechanism and a wing membrane is constructed. The movement of the link at the wing base mimics the contraction of a muscle in the thorax that triggers scissor-like motion and the deployment of the veins. Elastic hinges are used to mimic the rotational motion of the wing base and the vein joints. The static/dynamic characteristics of bionic foldable wings are further analyzed, and the LS-DYNA software is used to investigate rigid–flexible coupling dynamics. The elastic deformation of the wing membrane, kinematic characteristics of the linkage mechanism, and modes of the whole system are calculated. Static analysis of the structure reveals that the foldable wing has excellent stiffness characteristics and load-bearing capacity. The bionic foldable wing is constructed using 3D printing technology, and its folding and unfolding performance is tested. Evaluation of its performance shows that the bionic wing has a large fold ratio and can achieve stable folding and unfolding motions. A slightly tighter assembly between the pin and the hinge hole ensures that the wing does not fold back during flapping.

Bioinformatic and biochemical analysis of the key binding sites of the pheromone binding protein of Cyrtotrachelus buqueti Guerin-Meneville (Coleoptera: Curculionidea)

The bamboo snout beetle Cyrtotrachelus buqueti is a widely distributed wood-boring pest found in China, and its larvae cause significant economic losses because this beetle targets a wide range of host plants. A potential pest management measure of this beetle involves regulating olfactory chemoreceptors. In the process of olfactory recognition, pheromone-binding proteins (PBPs) play an important role. Homology modeling and molecular docking were conducted in this study for the interaction between CbuqPBP1 and dibutyl phthalate to better understand the relationship between PBP structures and their ligands. Site-directed mutagenesis and binding experiments were combined to identify the binding sites of CbuqPBP1 and to explore its ligand-binding mechanism. The 3D structural model of CbuqPBP1 has six a-helices. Five of these a-helices adopt an antiparallel arrangement to form an internal ligand-binding pocket. When docking dibutyl phthalate within the active site of CbuqPBP1, a CH-π interaction between the benzene ring of dibutyl phthalate and Phe69 was observed, and a weak hydrogen bond formed between the ester carbonyl oxygen and His53. Thus, Phe69 and His53 are predicted to be important residues of CbuqPBP1 involved in ligand recognition. Site-directed mutagenesis and fluorescence assays with a His53Ala CbuqPBP1 mutant showed no affinity toward ligands. Mutation of Phe69 only affected binding of CbuqPBP1 to cedar camphor. Thus, His53 (Between α2 and α3) of CbuqPBP1 appears to be a key binding site residue, and Phe69 (Located at α3) is a very important binding site for particular ligand interactions.