Transcriptome analysis and identification of P450 genes relevant to imidacloprid detoxification in Bradysia odoriphaga

Chengyu Chen,Xiwu Gao,Cuicui Wang,Xueyan Shi,Ying Liu

doi:10.1038/s41598-018-20981-2

Chengyu Chen, Xiwu Gao + Show 3 more

Open Access

https://doi.org/10.1038/s41598-018-20981-2

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Journal: Scientific Reports	Publication Date: Feb 7, 2018
Citations: 20	License type: open-access

Affiliation: China Agricultural University

Abstract

Pesticide tolerance poses many challenges for pest control, particularly for destructive pests such as Bradysia odoriphaga. Imidacloprid has been used to control B. odoriphaga since 2013, however, imidacloprid resistance in B. odoriphaga has developed in recent years. Identifying actual and potential genes involved in detoxification metabolism of imidacloprid could offer solutions for controlling this insect. In this study, RNA-seq was used to explore differentially expressed genes in B. odoriphaga that respond to imidacloprid treatment. Differential expression data between imidacloprid treatment and the control revealed 281 transcripts (176 with annotations) showing upregulation and 394 transcripts (235 with annotations) showing downregulation. Among them, differential expression levels of seven P450 unigenes were associated with imidacloprid detoxification mechanism, with 4 unigenes that were upregulated and 3 unigenes that were downregulated. The qRT-PCR results of the seven differential expression P450 unigenes after imidacloprid treatment were consistent with RNA-Seq data. Furthermore, oral delivery mediated RNA interference of these four upregulated P450 unigenes followed by an insecticide bioassay significantly increased the mortality of imidacloprid-treated B. odoriphaga. This result indicated that the four upregulated P450s are involved in detoxification of imidacloprid. This study provides a genetic basis for further exploring P450 genes for imidacloprid detoxification in B. odoriphaga.

Highlights

The sciarid fly Bradysia odoriphaga is a serious crop pest with a wide range of more than 30 plant species from seven families[1,2]
The over-expression of some P450 genes has been proven to be associated with increased metabolism of imidacloprid, including CYP6G1 (Drosophila melanogaster), CYP6D1 (Musca domestica), CYP6ER1, CYP6AY1 (Nilaparvata lugens), and CYP6CM1vQ (Bemisia tabaci)[20,21,22,23]
Illumina sequencing and de novo assembly were performed by merging all samples of B. odoriphaga in the treatment and control groups, resulting in the generation of 43,453 total unigenes, a total length of 55,884,005 bp, an N50 length of 1,995 bp, and a mean length of 1,286.08 bp

Summary

Introduction

The sciarid fly Bradysia odoriphaga is a serious crop pest with a wide range of more than 30 plant species from seven families[1,2]. With the wide application of imidacloprid for B. odoriphaga control, increased imidacloprid resistance has recently developed in field populations of B. odoriphaga[13,14,15]. In order to delay imidacloprid resistance development in B. odoriphaga, it is crucial to identify the imidacloprid detoxification metabolism related genes in B. odoriphaga, and figure out the mechanism of imidacloprid detoxification. The pathways by which imidacloprid is metabolized and detoxified in insects have been reported widely, highlighting the principal roles of cytochrome P450 enzyme and elevated gene expression levels of P450s in imidacloprid detoxification[16,17]. Elevated P450s enzyme activity was found to be related with imidacloprid insensitivity in B. odoriphaga larvae in our previous study, which is currently the only report about the imidacloprid detoxification mechanism in B. odoriphaga[14]. Transcriptome sequencing is an efficient way to uncover information about functional genes and differentially expressed genes in insects after insecticide treatment[27,28]

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