Molecular Characterization of Chitin Synthase Gene in Tetranychus cinnabarinus (Boisduval) and Its Response to Sublethal Concentrations of an Insecticide.

Tianrong Xin,Jing Wang,Jia Chen,Zhenzhen Li,Bin Xia,Zhiwen Zou

doi:10.3390/insects12060501

Abstract

Simple SummaryIn this study, we identified chitin synthase 1 gene (TcCHS1) from Tetranychus cinnabarinus (Boisduval) and then explored the gene expression levels of TcCHS1 at different developmental stages of T. cinnabarinus. We also investigated the effects of sublethal concentrations of diflubenzuron on the toxicities and survivals of T. cinnabarinus eggs and larvae as well as TcCHS1 expression levels. Our results demonstrated that TcCHS1 was essential for growth and development, and diflubenzuron exposure affected chitin metabolism. This work was undertaken to establish a foundation for further research on the functions of chitin synthase. It will provide a new target for controlling of T. cinnabarinus in the agricultural ecosystem.The carmine spider mite, Tetranychus cinnabarinus (Boisduval), is one of the most important acarine pest species. At present, its control remains primarily dependent on using various chemical insecticides/acaricides in agricultural crops worldwide. To clarify the mechanism whereby T. cinnabarinus responds to insecticide exposure, we identified the chitin synthase 1 gene (TcCHS1) and then explored the gene expression levels of TcCHS1 at different developmental stages of T. cinnabarinus. We also investigated the effects of sublethal concentrations of diflubenzuron on the toxicities and survivals of T. cinnabarinus eggs and larvae as well as TcCHS1 expression levels. The full-length cDNA sequence contains an open reading frame (ORF) of 4881 nucleotides that encoded for a 1474 amino acid residues protein. The predicted TcCHS1 protein had a molecular mass of 168.35 kDa and an isoelectric point of 6.26, and its amino acid sequence contained all the signature motifs (EDR, QRRRW and TWGTR) of chitin synthases. The results of phylogenetic analyses demonstrated that the putative CHS1 amino acid sequence of T. cinnabarinus revealed high similarities with chitin synthases in other insects and mites. Additionally, at the molecular level, transcriptional analysis by real-time quantitative PCR in different developmental stages of T. cinnabarinus revealed that TcCHS1 mRNA was expressed in all stages, and highest in eggs and female adults, but lowest in deutonymphs. Furthermore, the results of toxicity bioassays indicated that diflubenzuron treatment resulted in high mortality rates in eggs and larvae of T. cinnabarinus. The mRNA expression levels of TcCHS1 from the eggs and larvae of T. cinnabarinus were up-regulated in response to sublethal concentrations of diflubenzuron exposures. Together, all these results demonstrate that diflubenzuron has ovicidal and larvicidal effects and TcCHS1 may play an important role in the growth and development of T. cinnabarinus and may disrupt the chitin biosynthesis, thereby controlling T. cinnabarinus populations.

Highlights

Insects must periodically undergo several molting processes in order to allow growth and development, and during the molting process, they digest the old cuticle and produce the new one by chitin degradation and synthesis simultaneously [1]
CHS1 expression of Tribolium castaneum was different in the developmental stages and highest in the prepupal to young pupal stages; this result is consistent with a major role for this gene in chitin synthesis associated with pupal and adult cuticles [16]
The full-length cDNA of chitin synthase 1 (TcCHS1) from T. cinnabarinus was cloned and characterized in this study, and it belonged to the CHS1 gene family by phylogenetic analysis

Summary

Introduction

Insects must periodically undergo several molting processes in order to allow growth and development, and during the molting process, they digest the old cuticle and produce the new one by chitin degradation and synthesis simultaneously [1]. The chitin synthases of many insects and mites have been cloned and characterized, such as Aedes aegypti [5], Drosophila melanogaster [6], Anopheles quadrimaculatus [7], Spodoptera exigua [8], Locusta migratoria manilensis [9], Ostrina funracalis [10], Anopheles gambiae [11], Leptinotarsa decemlineata [12], Panonychus citri [13], and Tetranychus urticae [14] These results revealed that the CHSs are usually classified into CHS1 (CHS-A) and CHS2 (CHS-B) [15]. Chitin biosynthesis is essential for arthropod growth and development, and the CHS of the chitin biosynthesis pathway represents a potentially desirable target for developing a new strategy for arthropod pest management in agricultural systems because chitin is absent in plants and vertebrate animals [16]

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