Abstract
Baculoviruses have already been used for insect pest control, but the slow killing speed limits their further promotion and application. Here we provide a strategy for improving baculovirus insecticidal activity using Helicoverpa armigera nucleopolyhedrovirus (HearNPV) to express double-stranded RNAs (dsRNAs) targeting cotton bollworm (Helicoverpa armigera) juvenile hormone (JH)-related genes. Droplet-feeding bioassays show that the 50% lethal concentration (LC50) values of recombinant baculoviruses expressing the dsRNA of JH acid methyl transferase gene (HaJHAMT) and the JH acid binding protein gene (HaJHBP) were 1.24 × 104 polyhedral inclusion bodies (PIB)/mL and 2.26 × 104 PIB/mL, respectively. Both were much lower than the control value (8.12 × 104 PIB/mL). Meanwhile, the LT50 of recombinant baculovirus expressing dsRNA of HaJHBP was only 54.2% of the control value, which means that larval death was accelerated. Furthermore, the mRNA level of target genes was reduced in recombinant baculovirus-treated cotton bollworm larvae. Transcription of several key genes involved in hormone signaling pathways—for example, ecdysone receptor gene (HaEcR)—was also altered. This study establishes a new strategy for pest management by interfering with insect hormone-related gene expression via baculoviruses, and the engineered baculoviruses have great potential application in cotton production.
Highlights
Insect pests cause large crop losses worldwide through direct damage and the transmission of plant diseases [1]
Our results demonstrate that the recombinant Helicoverpa armigera nucleopolyhedrovirus (HearNPV) obtained in this study had significantly improved insecticidal activity
In order to obtain the recombinant baculovirus expressing double-stranded RNAs (dsRNAs) by the Bac-to-Bac system, the donor vectors, in which dsRNA expression was under the control of the p10 promoter and op166
Summary
Insect pests cause large crop losses worldwide through direct damage and the transmission of plant diseases [1]. Baculoviruses, which are arthropod-specific viruses, have been successfully applied for agriculture and forestry pest management. They are safe for people and wildlife because of their extremely narrow host range [4,5]. Baculoviruses can cause epidemics in insect populations and be effective in the environment for a long time [6]. The genome sequences of some notable baculoviruses were determined, and many strategies have been developed to improve their killing action and stability through recombinant DNA technology [2,8]. Recombinant baculovirus expressing an insect-specific toxin from the scorpion Androctonus australis and straw itch mite Pyemotes tritici showed improved insecticidal activity [10,11]
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