A polydnaviral genome of Microplitis bicoloratus bracovirus and molecular interactions between the host and virus involved in NF-κB signaling

Abstract

Polydnaviruses (PDVs) play a critical role in altering host gene expression to induce immunosuppression. However, it remains largely unclear how PDV genes affect host genes. Here, the complete genome sequence of Microplitis bicoloratus bracovirus (MbBV), which is known to be an apoptosis inducer, was determined. The MbBV genome consisted of 17 putative double-stranded DNA circles and 179 fragments with a total size of 336,336 bp and contained 116 open reading frames (ORFs). Based on conserved domains, nine gene families were identified, of which the IκB-like viral ankyrin (vank) family included 28 members and was one of the largest families. Among the 116 ORFs, 13 MbBV genes were expressed in hemocytes undergoing MbBV-induced apoptosis and further analyzed. Three vank genes (vank86, vank92, vank101) were expressed in hemocytes collected from Spodoptera litura larvae parasitized by M. bicoloratus, in which host NF-κB/IκBs, including relish, dorsal, and cactus, were also persistently expressed. When Spli221 cells were infected with MbBV viral particles, mRNA levels of host and viral NF-κB/IκB genes were persistent and also varied in Spli221 cells undergoing virus-induced pre-apoptosis cell from 1 to 5 hours postinfection. Both were then expressed in a time-dependent expression in virus-induced apoptotic cells. These data show that viral IκB-like transcription does not inhibit host NF-κB/IκB expression, suggesting that transcription of these genes might be regulated by different mechanisms.

Regulation of the Larval Transcriptome of Diatraea saccharalis (Lepidoptera: Crambidae) by Maternal and Other Factors of the Parasitoid Cotesia flavipes (Hymenoptera: Braconidae)

“…Some caspases and Ca +2 -dependent molecules (caspase activators), such as calpain and calcineurin, were up-regulated in D. saccharalis larvae parasitized and pseudoparasitized by C. flavipes (Mattson and Chan, 2003; Humeau et al, 2017). Apoptosis of High Five cells was induced in the presence of viral protein associated with Microplitis bicoloratus Chen (Hymenptera: Braconidae) and Toxoneuron nigriceps (Viereck) (Hymenoptera: Braconidae), through their interaction with cell proteins that activate caspases (Yu et al, 2016; Salvia et al, 2017). Cotesia flavipes also regulated Ca +2 channels, Ca +2 modulators and Ca +2 -dependent molecules, altering several physiological processes ranging from cell proliferation to apoptosis activation.…”

Symbiotic bracovirus of a parasite manipulates host lipid metabolism via tachykinin signaling

“…The life cycle of PDVs is generally divided into two parts: one is in their primary host (the wasp), in which the viral DNAs are dramatically replicated only in the nuclei of ovarian calyx cells of female wasps, and the other is in their secondary host (usually a caterpillar), in which the viruses integrate into host genome and subsequently express the numerous virulence genes to regulate the host physiology [26,27,31]. To date, the genomes of nine BV species and five IV species have been fully sequenced [25,[32][33][34][35][36][37][38][39][40][41]. These studies provided comprehensive information on PDV genes and have accelerated functional investigations of individual virus genes.…”

Spodoptera litura cyclophilin A is required for Microplitis bicoloratus bracovirus‐induced apoptosis during insect cellular immune response

“…PDVs are a family of viruses that spread through a symbiotic relationship with host parasitic wasps and are divided into two genera: Bracovirus (BV) and Ichnovirus (IV). M. bicoloratus inject their eggs into the hemocoel of S. litura larvae, passing on the MbBV in the process and spreading the infection (Falabella et al, ; Strand & Burke, ; Yu et al, ). The viral genome is then integrated into the host chromosomes, and the viral genes involved in the inhibition of the host immune response are expressed, ensuring the proper development of the wasp larvae (Albrecht et al, ; Annaheim & Lanzrein, ; Strand & Burke, ; Yu et al, ).…”