Heliocoverpa armigera single nucleocapsid nucleopolyhedrovirus induces Hz-AM1 cell cycle arrest at the G2 phase with accumulation of cyclin B1

The cell cycle phase distributions of Hz-AM1 cells grown in monolayer culture were G1 = 49.7 ± 3.3%, S = 22.7 ± 3.8% and G2/M = 27.8 ± 4.2% without >4N DNA content. The culture doubling time was about 40 h and the duration of the G1, S and G2/M phases was estimated to be 10, 14 and 16 h, respectively. HaSNPV infection of Hz-AM1 cells resulted in both unsynchronized and synchronized G1 phase arrest at G2/M phase. HaSNPV infection also resulted in the appearance of more than 4N DNA content, which accumulated to the highest levels 72 h post-infection. We also found that the expression level of cyclin B1 increased significantly after 16 h post-infection, while cyclin A did not show any change. This observation supports the Hz-AM1-infected arrest at the G2/M phage. Cytoplasm location of cyclin B1 indicated that the Hz-AM1 cell cycle arrest was at the G2 phase.