Function analysis and application of IAP1/2 of Autographa californica multiple nucleopolyhedrovirus

The baculovirus Autographa californica multiple nucleopolyhedrovirus (AcMNPV) possesses two genes, iap1 and iap2, which encode the inhibitors of apoptosis proteins (IAP). One previous work showed that transient expression of Ac-IAP1 was capable of inducing apoptosis of Sf9 cells, but others demonstrated that Ac-IAP1 had anti-apoptosis activity against apoptosis induced by HearNPV in Tn-Hi5 cells. So the function of Ac-IAP1 remained unclear. To further define the function of Ac-IAPs, we used a Bac-to-Bac baculovirus expression system to generate two recombinant baculoviruses, AcMNPV-iap1-egfp and AcMNPV-iap2-egfp. Function analysis showed that Ac-IAP1 could induce the apoptosis process of Sf9 cells in a dose-dependent manner, even in the medium starvation mode. However, Ac-IAP2 could promote cell proliferation and the BIR2 domain in Ac-IAP2 played an important role in anti-apoptotic ability. Moreover, an insecticidal potency test showed that the larvae of Helicoverpa armigera in the AcMNPV-iap2-egfp group had a higher mortality rate (61.11%) and a lower pupation rate, although the time of death and pupation were delayed, compared with those in AcMNPV-egfp and AcMNPV-iap1-egfp groups, which confirmed that the recombinant virus AcMNPV-iap2-egfp had better insecticidal efficiency. This study confirmed the function of Ac-IAPs and developed a useful AcMNPV-iap2-egfp, which provided the experimental basis for the mechanistic analysis of Ac-IAPs and the theoretical foundation for using and modifying AcMNPV.