Transcriptome Responses of the Host Trichoplusia ni to Infection by the Baculovirus Autographa californica Multiple Nucleopolyhedrovirus

Abstract

Productive infection of Trichoplusia ni cells by the baculovirus Autographa californica multiple nucleopolyhedrovirus (AcMNPV) leads to expression of ϳ156 viral genes and results in dramatic cell remodeling. How the cell transcriptome responds to viral infection was unknown due to the lack of a reference genome and transcriptome for T. ni. We used an ϳ60-Gb RNA sequencing (RNA-seq) data set from infected and uninfected T. ni cells to generate and annotate a de novo transcriptome assembly of approximately 70,322 T. ni unigenes (assembled transcripts), representing the 48-h infection cycle. Using differential gene expression analysis, we found that the majority of host transcripts were downregulated after 6 h postinfection (p.i.) and throughout the remainder of the infection. In contrast, 5.7% (4,028) of the T. ni unigenes were upregulated during the early period (0 to 6 h p.i.), followed by a decrease through the remainder of the infection cycle. Also, a small subset of genes related to metabolism and stress response showed a significant elevation of transcript levels at 18 and 24 h p.i. but a decrease thereafter. We also examined the responses of genes belonging to a number of specific pathways of interest, including stress responses, apoptosis, immunity, and protein trafficking. We identified specific pathway members that were upregulated during the early phase of the infection. Combined with the parallel analysis of AcMNPV expression, these results provide both a broad and a detailed view of how baculovirus infection impacts the host cell transcriptome to evade cellular defensive responses, to modify cellular biosynthetic pathways, and to remodel cell structure. IMPORTANCEBaculoviruses are insect-specific DNA viruses that are highly pathogenic to their insect hosts. In addition to their use for biological control of certain insects, baculoviruses also serve as viral vectors for numerous biotechnological applications, such as mammalian cell transduction and protein expression for vaccine production. While there is considerable information regarding viral gene expression in infected cells, little is known regarding responses of the host cell to baculovirus infection. In these studies, we assembled a cell transcriptome from the host Trichoplusia ni and used that transcriptome to analyze changes in host cell gene expression throughout the infection cycle. The study was performed in parallel with a prior study of changes in viral gene expression. Combined, these studies provide an unprecedented new level of detail and an overview of events in the infection cycle, and they will stimulate new experimental approaches to understand, modify, and utilize baculoviruses for a variety of applications.

Digital gene expression analysis of Helicoverpa armigera in the early stage of infection with Helicoverpa armigera nucleopolyhedrovirus

“…Genes involved in sugar transportation and carbon metabolism were also found to be up-regulated in the interactions of BmNPV-B. mori and AcMNPV-S. frugiperda (Choi et al, 2012;Nguyen et al, 2013;Sagisaka et al, 2010); genes that encoded proteins associated with mitochondria and energy/metabolism, including NADH dehydrogenase and ATP synthase, were also induced in the interaction of AcMNPV-T. ni (Chen et al, 2014). No NPV-encoded genes have been linked to energy metabolism (Chen et al, 2001;Nguyen et al, 2013).…”

“…The large number of DEGs and noticeably higher numbers of down-regulated DEGs (718) GO and KEGG analysis were performed for the investigation of DEG enrichment. In the reported systems of NPV-insect interactions, genes with roles in the stress response, apoptosis, immunity, transcription and translation regulation, protein trafficking, signal transduction, energy generation, endocrine modulation and cytoskeleton rearrangement were primarily enriched and clustered (Bao et al, 2009;Chen et al, 2014;Gatehouse et al, 2009;Nguyen et al, 2013;Popham 15 et al, 2010;Sagisaka et al, 2010;Salem et al, 2011). In this study, genes termed in "catalytic activity" and "metabolic process" were primarily induced by infection with HearNPV, which might facilitate NPV infection and multiplication due to increased nutrition and energy supply through digestion from host storage.…”

“…Their increased transcriptional levels were reduced concomitant with the infection (Chen et al, 2014), resulting in the collapse of host defense reactions and successful NPV infection. Manipulation of host defense reactions may be an important strategy for HearNPV and is critical for further colonization.…”

Trichoplusia ni Kinesin-1 Associates with Autographa californica Multiple Nucleopolyhedrovirus Nucleocapsid Proteins and Is Required for Production of Budded Virus

“…To enable a more detailed analysis of the interaction between kinesin-1 and AcMNPV nucleocapsid proteins, transformed cell lines expressing tagged forms of KLC or KHC were developed. The sequences of T. ni KHC and KLC were originally identified by high-throughput transcriptome sequencing (RNA-seq) analysis of T. ni cells (42). The cDNAs were cloned, and constructs expressing KHC and KLC tagged with either the HA or the Myc epitope tag at both the N and C termini were made ( Fig.…”

“…The T. ni KHC and KLC sequences were initially determined from a transcriptome analysis of a T. ni Tnms42 cell (42). To clone KLC and KHC cDNA, total RNA was isolated from Tn5B1 cells using the TRIzol reagent (Ambion).…”