Baculovirus-mediated RNAi Inhibits The Transcription Of The Overexpression Of Cytochrome P450Gene In Cotton Bollworm

The resistance to chemical pesticides of major agricultural pests is increasingly getting worse due to the widespread use of them. Cytochrome P450monooxygenases of Helicoverpa armigera (H. armigera) whose activity is related to the resistance of pests to chemical pesticides and phyto toxin play an important role in the detoxification process in vivo. RNAi is an emerging biotechnique using dsRNA to induce post-transcriptional silence of the target genes, which can result in the silence of target genes in many living beings.We selected the pyre thro id-resistant genes of H. armigera Cytochrome P450including CYP9A14, CYP9A17, CYP9A12, CYP6B7and also the CYP6AE14which is related to the resistance of phytotoxin gossypol as targets to be silent by a baculovirus-media ted RNAi. By using the inverted repeat sequence of CYP9A14, CYP9A14t, CYP9A17, CYP9A17t, CYP9A12, CYP6B7, CYP6AE14, we constructed a series of recombinant Helicoverpa armigera nucleopolyhedroviruses (HaNPVs). High-titer budded viruses, generated by the recombinant viruses infecting HzAM1cells, were injected into the hemolymph of cypermethrin-resistant H. armigera larvae. When the resistant larvae were infected with the recombinant virus of vHaBac-CYP9A14t, the level of the CYP9A14transcript in the midgut was significantly decreased. When the resistant larvae were infected with the recombinant viruses of vHaBac-CYP9A17t or vHaBac-CYP6AE14, the level of the CYP9A17or CYP6AE14transcripts in the midgut were considerably dwindled. When resistant larvae were infected with the recombinant viruses of vHaBac-CYP9A14, vHaBac-CYP9A17, vHaBac-CYP9A12, vHaBac-CYP6B7or the control virus vHaBac-EGFP, the level of the corresponding transcripts in the midgut had not been changed.Bioassay results showed that the combination of cypermethrin and HaNPVs can significantly enhance the infectivity of the cypermethrin-resistant H. armigera larvae. Whereas, the combination of cypermethrin and vHaBac-CYP9A14t had the similar synergic effect as the combination of cypermethrin and the control virus vHaBac-EGFP. The combination of cypermethrin and mixed viruses of vHaBac-CYP9A14t and vHaBac-CYP9A17t had the similar synergic effect as the combination of cypermethrin and the control virus too.Our experiments showed that it is feasible to interfere H. armigera genes by HaNPV vector. Thereby, our study opened a new avenue for the study of gene functions of H. armigera and other insects, and offered a new way for the control of the resistant H. armigera and other agricultural pests by combining pyrethroid pesticides with baculoviruses. At the same time, we proposed a theoretical basis and a broader perspective for the universal application of RNAi in H. armigera and other agricultural pests control...