Analysis of Genes Expression of Spodoptera exigua Larvae upon AcMNPV Infection

Jae Young Choi,Jae Su Kim,Jong Yul Roh,Sang Woon Shin,Joo Hyun Lee,Zou Zhen,Yeon Ho Je,Yong Wang,Qin Liu,Xue Ying Tao,Subba Reddy Palli

doi:10.1371/journal.pone.0042462

Abstract

BackgroundThe impact of Autographa californica multicapsid nucleopolyhedrovirus (AcMNPV) infection on host gene expression in Spodoptera exigua 4th instar larvae was investigated through the use of 454 sequencing-based RNA-seq of cDNA libraries developed from insects challenged with active AcMNPV or heat-inactivated AcMNPV.Methodology/Principal FindingsBy comparing the two cDNA libraries, we show that 201 host genes are significantly up-regulated and 234 genes are significantly down-regulated by active AcMNPV infection. Down-regulated host genes included genes encoding antimicrobial peptides, namely three gloverin isoforms and an attacin, indicating that the viral infection actively repressed the expression of a portion of the host immune gene repertoire. Another interesting group of down-regulated host genes included genes encoding two juvenile hormone binding proteins and a hexamerin, all of which are involved in juvenile hormone regulation. The expression of these genes was enhanced by the topical application of Juvenile Hormone III (JHIII) in the insects challenged with heat-inactivated AcMNPV. However, infection with the active virus strongly suppresses the expression of these three genes, regardless of the absence or presence of JHIII.Conclusions/SignificanceUsing RNA-seq, we have identified groups of immune-regulated and juvenile hormone-regulated genes that are suppressed by infection with active AcMNPV. This information and further studies on the regulation of host gene expression by AcMNPV will provide the tools needed to enhance the utility of the virus as an effective protein expression system and as an insecticide.

Highlights

Baculoviruses are large DNA viruses that primarily infect insects
454 sequencing results and contig assembly As described in the Methods, cDNA libraries from Spodoptera exigua larvae challenged with active Autographa californica multicapsid nucleopolyhedrovirus (AcMNPV) or heat-inactivated AcMNPV were subjected to a 1/8-plate production run on the 454 GS-FLX sequencing instrument, resulting in 77,616 and 74,928 reads, respectively
Files containing these data were deposited in the Short Read Archive of the National Center for Biotechnology Information (NCBI) with accession numbers of SRX110132 (AcMNPV-challenged) and SRX110248, respectively

Summary

Introduction

Baculoviruses are large DNA viruses that primarily infect insects. Most baculoviruses are quite host-specific, infecting only a single species or a few closely related species, except for Autographa californica multicapsid nucleopolyhedrovirus (AcMNPV), which can infect a wide range of lepidopteran insects [1]. To identify the effect of AcMNPV infection on the expression of host transcripts in Spodoptera exigua larvae, we used 454 sequencing to analyse the transcriptome. To confirm the expression profiles of the UP and DOWN gene categories, total RNA was isolated from 5th instar larvae 12 hpi with active or heatinactivated AcMNPV.

Results

Conclusion