An Autographa californica nucleopolyhedrovirus-encoded microRNA, AcMNPV-miR-4, downregulates the expression of host gene alg-2

Autographa california multiple nucleopolyhedrovirus (AcMNPV)-encoded microRNAs (miRNAs) that regulate viral genes to achieve infection have been reported previously. Here, we report another AcMNPV encoded miRNA, AcMNPV-miR-4 (Ac-miR-4), which downregulated the host gene, apoptosis-linked gene (alg-2). This regulation was verified by dual-luciferase reporter assays. The effects of Ac-miR-4 on virus infection were assessed. The results showed that the production of infectious budded virions (BV) was decreased and the occlusion-derived virion (ODV) embedding into polyhedra was delayed when Sf9 cells were administered an overdose of Ac-miR-4. All these findings suggest that Ac-miR-4 prolongs cell lifespan and reduces virus virulence at a relatively early stage but increases ODV at a very late stage. This finding may be attributed to the downregulation effects of alg-2, which lead to weakened ALG-2 related functions, such as cell apoptosis, vesicle budding and protein transport.

Automated summary

This study identified a microRNA encoded by Autographa california multiple nucleopolyhedrovirus (AcMNPV) that regulates viral genes and host genes to affect virus infection. The microRNA, called AcMNPV-miR-4, downregulates the host gene alg-2, leading to an extended cell lifespan and reduced virus virulence in the early stage of infection. However, in the late stage, it increases the production of a specific virus structure.