Genomic analysis of nucleopolyhedrosis virus NPV strains from gram pod borer Helicoverpa armigera

Abstract

Helicoverpa armigera nucleopolyhedrovirus HearNPV (Baculoviridae), is a rod newlineshaped, single nucleocapsid alphabaculovirus with circular closed, double stranded DNA newlinegenomes. It has proved to have excellent insecticidal propriety for control of H. armigera newline(Lepidoptera) larvae on number of crops. The NPVs produce large, polyhedron-shaped newlineocclusion bodies containing many virions, are further designated as single nucleopcapsid or newlinemultinucleocapsid. NPVs that are isolated from different insects in the field populations differ newlinefrom one another with regard to virulence against respective insects. The gram pod borer, H. newlinearmigera is an important pest that feeds on a number of agricultural and other economically newlineimportant plants. Helicoverpa armigera has developed a resistance to all groups of chemical newlineinsecticides. In order to mitigate the resistance developed, several options have been explored newlinefor the control of this devastating pest. Among them, NPVs are considered as one of the most newlinepromising larvicidal agents against such pests. HearNPV to control H. armigera was one of newlinethe first commercially available baculoviral pesticides, and has been successfully used to newlinecontrol the pest in agricultural crops. In order to properly manage this pest, a complete newlinegenome sequence would be invaluable. The variation identified by these comparative newlinegenomics helps to us to identify the genes responsible for increased virulence and these newlineapproaches will be a valuable addition to understand the virulence factor of HNPV. newlineThe present study is the first report on the complete genome of HearNPV of the newlineIndian isolate. In this study, we sequenced and analyzed most virulent strain of H. armigera newline(HearNPV-L1) isolate from Ludhiana, Punjab, India. The HearNPV-L1 isolate showed high newlineinsecticidal activity against third instar larvae of H. armigera in the laboratory conditions, newlinehaving lowest LC50 values compared to several isolates, viz., Hingoli, Nanded, Nagpur, newlineBengaluru, Faridkot, Manasa, Sriganganagar and Hyderabad obtained from other parts of theThe four conserved gene regions were characterized using species specific primers and newlinevalidated four genes by adopting a Hot-Start PCR in HearNPV L1 isolate of India. We newlineanalyzed their protein data and explained the comparative study with the whole genome. newlineThese chosen genes play a crucial role in insecticidal activity and establish successful newlineinfection to target insects, their conserved sequences not only will help in designing robust newlineprimers but also in the reliable identification of HearNPV in the baculovirus sample. The newlineLigand and receptor will plays a key role in dictating the mechanism (e.g., agonism vs newlineantagonism). In order to understand and validate the mechanism at structural level, the newlineinteraction study was performed by using the virulent genes as ligand and the receptor newlineHaSCP-2 using different docking tools. Structural analysis of the virulent genes of HearNPVL1 showed the binding affinity of ligand receptor interaction of the complex Pif and HaSCP2 newlineis having high binding affinity. This confirmed the highest virulent gene helps in increase in newlineinfectivity of Helicoverpa armigera.