Abstract
The lepidopteran model silkworm, Bombyx mori, is an important economic insect. Viruses cause serious economic losses in sericulture; thus, the economic importance of these viruses heightens the need to understand the antiviral pathways of silkworm to develop antiviral strategies. Insect innate immunity pathways play a critical role in the outcome of infection. The RNA interference (RNAi), NF-kB-mediated, immune deficiency (Imd), and stimulator of interferon gene (STING) pathways, and Janus kinase/signal transducer and activator of transcription (JAK/STAT) pathway are the major antiviral defense mechanisms, and these have been shown to play important roles in the antiviral immunity of silkworms. In contrast, viruses can modulate the prophenol oxidase (PPO), phosphatidylinositol 3-kinase (PI3K)/protein kinase B (Akt), and the extracellular signal-regulated kinase (ERK) signaling pathways of the host to elevate their proliferation in silkworms. In this review, we present an overview of the current understanding of the main immune pathways in response to viruses and the signaling pathways modulated by viruses in silkworms. Elucidation of these pathways involved in the antiviral mechanism of silkworms furnishes a theoretical basis for the enhancement of virus resistance in economic insects, such as upregulating antiviral immune pathways through transgenic overexpression, RNAi of virus genes, and targeting these virus-modulated pathways by gene editing or inhibitors.
Highlights
Virus infection poses a serious threat to human health and agricultural production
Further experiments revealed that BmPGRP-S2 was a secreted protein, which may recognize a certain viral component and transmit the signal to downstream molecules, and its overexpression increased the expression of BmImd, BmRelish, and antimicrobial peptide (AMP) and decreased silkworm mortality after Bombyx mori cytoplasmic polyhedrosis virus (BmCPV) infection [19] (Figure 1B)
The BmEGFR plays an important role in Bombyx mori nucleopolyhedrovirus (BmNPV) infection, which participates in the activation of extracellular signal-regulated kinase (ERK) and phosphatidylinositol 3-kinase (PI3K)/Akt pathways by the virus
Summary
Virus infection poses a serious threat to human health and agricultural production. As the only fully domesticated insect, the lepidopteran model silkworm, Bombyx mori, is economically important for silk production. The antiviral defense mechanism of silkworms mainly relies on innate immunity, including the RNA interference (RNAi), NF-kB-mediated pathways, and Janus kinase/signal transducer and activator of transcription (JAK/STAT) pathway [19, 21,22,23,24]. Bmo-miR-2819 can downregulate the ie-1 gene of BmNPV to suppress viral multiplication [39]; bmo-miR-278-3p could decrease target gene IBP2 expression and increase BmCPV mRNA, it is downregulated and IBP2 is upregulated in BmCPV-infected silkworms [40].
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