ABC transporter BmWh2 enhances antiviral defense against baculovirus in silkworm via ATG upregulation

Abstract

Baculoviruses are widely used as biological pesticides for pest control. Bombyx mori nucleopolyhedrovirus (BmNPV) is a typical baculovirus that causes serious economic losses in the sericulture. ATP-binding cassette (ABC) transporters are widely distributed in various organisms, from viruses to humans, and play important roles in multiple biological processes. However, their roles in the interactions between viruses and insect hosts remain largely unknown. In this study, we used molecular cloning, reverse transcription-PCR, and quantitative PCR (qPCR) to investigate the function of the silkworm ABC transporter BmWh2 during BmNPV infection. The results showed that BmWh2 was upregulated after BmNPV infection. In BmE cells, knockout of BmWh2 significantly increased viral DNA content, while overexpression of BmWh2 had the opposite effects, indicating that BmWh2 could inhibit BmNPV proliferation. A transgenic vector overexpressing BmWh2 was constructed under the control of the A4 promoter, and two transgenic silkworm lines A4Wh2–1/2 were generated via embryo microinjection. qPCR analysis confirmed that the expression level of BmWh2 in A4Wh2 silkworms was significantly increased. After oral infection with BmNPV, the mortality of A4Wh2–2 was 24 % lower than that of non-transgenic WT, and the viral DNA content in A4Wh2–2 was 8 % of that in WT. The mRNA levels of ATG6 and ATG8 were increased in both BmE cells overexpressing BmWh2 and A4Wh2 silkworms, implying that BmWh2 inhibited viral proliferation by increasing ATG expression. This study is the first report of an ABC transporter involved in antiviral immunity in B. mori, providing a theoretical reference for pesticide resistance.