Transcriptional Regulation of a Chitinase Gene by 20-Hydroxyecdysone and Starvation in the Oriental Fruit Fly, Bactrocera dorsalis

Wen-Jia Yang,Jin-Jun Wang,Rui-Ying Zhang,Kang-Kang Xu,Wei Dou

doi:10.3390/ijms141020048

Wen-Jia Yang, Jin-Jun Wang + Show 3 more

Open Access

https://doi.org/10.3390/ijms141020048

Copy DOI

Abstract

Insect chitinases are hydrolytic enzymes that are required for the degradation of glycosidic bonds of chitin. In this study, we identified and characterized a full-length cDNA of the chitinase gene (BdCht2) in the oriental fruit fly, Bactrocera dorsalis. The cDNA contains an open reading frame (ORF) of 1449 bp that encodes 483 amino acid residues and 126- and 296-bp non-coding regions at the 5′- and 3′-ends, respectively. The BdCht2 genome has four exons and three introns. The predicted molecular mass of the deduced BdCht2 is approximately 54.3 kDa, with an isoelectric point of 5.97. The 977 bp 5′ flanking region was identified and the transcription factor binding sites were predicted. Bioinformatic analyses showed that the deduced amino acid sequence of BdCht2 had 34%–66% identity to that of chitinases identified in other insect species. Quantitative real-time PCR (qPCR) analyses indicated that BdCht2 was mainly expressed during the larval-pupal and pupal-adult transitions. The tissue-specific expression showed that the highest expression was in the integument, followed by the fat body and other tissues. Moreover, the expression of BdCht2 was upregulated significantly upon 20-hydroxyecdysone (20E) at different dose injections after 8 h compared to that of the control. Starvation also increased the expression of BdCht2 in the third-instar larvae and was suppressed again by re-feeding the insects. These results suggest that BdCht2 plays an important role in the molting process of B. dorsalis larvae and can be regulated by 20E.

Highlights

Chitin is found in fungi, nematodes and arthropods and plays key roles in maintaining morphology and protecting organisms against external attacks [1,2]
The full-length cDNA sequence of BdCht2 (GenBank accession number: JN100105) is 1871 bp with an open reading frame (ORF) of 1449 bp, which encodes a protein of 483 amino acids with a predicted molecular mass of approximately 54.3 kDa and an isoelectric point of 5.97
The BdCht2 cDNA has a molecular structure consisting of a single peptide, a single catalytic domain and no chitin binding domain (CBD), which is similar to the domain architecture of

Summary

Introduction

Chitin is found in fungi, nematodes and arthropods and plays key roles in maintaining morphology and protecting organisms against external attacks [1,2]. Chitin is a vital component of the cuticles of the epidermis and trachea, as well as the peritrophic matrix (PM) in the midgut lumen [3,4]. Some chitin in the old cuticle and PM are degraded and replaced by the newly synthesized chitin [5]. Chitin synthesis is catalyzed by chitin synthases (CHSs), which are cataloged into two classes: CHS1 and CHS2. Chitin degradation is hydrolyzed by the chitinase, which catalyzes the random hydrolysis of N-acetyl-β-D-glucosamine β-1,4-glycosidic linkages in chitin and chitodextrins. Insect chitinases belong to the family 18 glycosyl hydrolases, based on the conservation of amino acid sequences and many conserved motifs [6]

Results

Discussion

Conclusion