The deletion of the AcMNPV ac124 gene resulted in a decrease in chitinase transcription.

The Autographa californica multiple nucleopolyhedrovirus (AcMNPV) ac124 gene has been previously characterized as a viral pathogenicity factor. In this study, an ac124-knockout virus (vAc124KO) was generated to examine the role of the ac124 gene in the context of the AcMNPV genome during infection. Our results showed that the absence of ac124 does not affect the production of budded virus (BV) and occlusion bodies (OBs) in infected Sf9 cells. Western blotting analysis showed that the deletion of ac124 does not affect the temporal expression and the relative levels of GP64, VP39, P6.9, and polyhedrin. qRT-PCR analysis showed that the transcription level of chitinase but not the adjacent cathepsin in vAc124KO infected cells was significantly lower than that of the vAcWT infected cells from 24 to 96 h p.i. Luciferase assays showed that the overexpression of Ac124 could significantly improve the ability of chitinase promoter to initiate reporter genes. Based on the above data, we hypothesize that Ac124 binds to the promoter of chitinase to regulate the expression of chitinase gene.