Comparative Transcriptome Analysis of Bombyx mori (Lepidoptera) Larval Hemolymph in Response to Autographa californica Nucleopolyhedrovirus in Differentially Resistant Strains

Xin-Yi Ding,Xia Sun,Chun-Xiao Zhao,Mu-Wang Li,Yun-Hui Kong,Xue-Yang Wang,Sheng Qin

doi:10.3390/pr9081401

Abstract

Bombyx mori nucleopolyhedrovirus (BmNPV) is a kind of pathogen that causes huge economic losses to silkworm production. Although Autographa californica nucleopolyhedrovirus (AcMNPV) and BmNPV are both baculoviruses, the host domains of these two viruses have almost no intersection in nature. Recently, it has been found that some silkworms could be infected by recombinant AcMNPV through a puncture, which provided valuable material for studying the infection mechanism of baculovirus to silkworm. In this study, comparative transcriptomics was used to analyse the hemolymph of two differentially resistant strains following AcMNPV inoculation. There were 678 DEGs in p50 and 515 DEGs in C108 following viral infection. Among them, the upregulation and downregulation of DEGs were similar in p50; however, the upregulated DEGs were nearly twice as numerous as the downregulated DEGs in C108. The DEGs in different resistant strains differed by GO enrichment. Based on KEGG enrichment, DEGs were mainly enriched in metabolic pathways in p50 and the apoptosis pathway in C108. Moreover, 13 genes involved in metabolic pathways and 11 genes involved in the apoptosis pathway were analysed. Among the DEGs involved in apoptosis, the function of BmTex261 in viral infection was analysed. The BmTex261 showed the highest expression in hemolymph and a significant response to viral infection in the hemolymph of C108, indicating that it is involved in anti-AcMNPV infection. This was further validated by the significantly decreased expression of viral gene lef3 after overexpression of BmTex261 in BmN cells. The results provide a theoretical reference for the molecular mechanism of resistance to BmNPV in silkworms.

Highlights

IntroductionBombyx mori (B. mori), is one of the most important insects in developing countries because of the silkworm cocoon, which is used in the medical and food industries [1,2,3,4]
All silkworms (100%) infected with AcMNPV showed this phenomenon (Figure 1A), in contrast to the p50 infected with Bombyx mori nucleopolyhedrovirus (BmNPV)
Infection with AcMNPV in silkworm individuals was determined at different durations in a previous study; the peak of AcMNNPV proliferation occurred at 36 h after inoculation with bud virus (BV)-eGFP (1.0 × 108 pfu/mL) in p50 strains [37], and this time point was selected for further sample preparation

Summary

Introduction

Bombyx mori (B. mori), is one of the most important insects in developing countries because of the silkworm cocoon, which is used in the medical and food industries [1,2,3,4]. Silkworm infection by pathogens is a common problem. BmNPV causes serious losses, and the underlying defence mechanism is still unclear. AcMNPV is another representative baculovirus in insects and similar to BmNPV, except in the embedded ways [5]. Both of them have strict host domains and generally do not cross-infect other host domains, but studies have found that AcMNPV can infect silkworms by puncturing [6]. This study further discussed the mechanism of the

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