Response analysis of host Spodoptera exigua larvae to infection by Heliothis virescens ascovirus 3h (HvAV-3h) via transcriptome

Heliothis virescens ascovirus 3 h (HvAV-3h), a dsDNA insect virus, belonging to the family Ascoviridae, can infect caterpillars of several Noctuidae species by ovipositing parasitoid wasps. In order to provide a comprehensive overview of the interactive responses of host larvae after infection by the ascovirus, a transcriptome analysis of Spodoptera exigua to HvAV-3h was conducted from 6 to 168 hours post infection (hpi). Approximately 101.64 Gb of RNA sequencing (RNA-seq) data obtained from infected and uninfected S. exigua larvae were used to perform a de novo transcriptome assembly, which generated approximately 62,258 S. exigua unigenes. Using differential gene expression analysis, it was determined that the majority of host transcripts were down-regulated beginning at 6 hpi and continuing throughout the infection period, although there was an increase in up-regulated unigene number during the 12 to 72 hpi stage. It is noteworthy that the most abundantly enriched pathways in KEGG annotation were Metabolism terms, indicating that the host larval metabolic mechanisms were highly influenced post HvAV-3h infection. In addition, the host cuticle protein encoding unigenes were highly down-regulated in most of the situations, suggesting that the host larval cuticle synthesis were inhibited by the viral infection.