Azadirachtin-A from Azadirachtaindica Impacts Multiple Biological Targets in CottonBollworm Helicoverpa armigera

摘要

Azadirachtin-A (AzaA) from the Indian neem tree (Azadirachta indica) has insecticidal properties; however, its molecular mechanism remains elusive. The “targeted and nontargeted proteomic profiling”, metabolomics, matrix-assisted laser desorption/ionization time of flight (MALDI-TOF) imaging, gene expression, and in silico analysis provided clues about its action on Helicoverpa armigera. Fourth instar H. armigera larvae fed on AzaA-based diet (AzaD) suffered from significant mortality, growth retardation, reduced larval mass, complications in molting, and prolonged development. Furthermore, death of AzaD-fed larvae was observed with various phenotypes like bursting, blackening, and half-molting. Liquid chromatography–mass spectrometry (LC–MS) data showed limited catabolic processing of ingested AzaA and dramatic alternations of primary metabolism in H. armigera. MALDI-TOF imaging indicated the presence of AzaA in midgut of H. armigera. In the gut, out of 79 proteins identified, 34 were upregulated, which were related to digestion, immunity, energy production, and apoptosis mechanism. On the other hand, 45 proteins were downregulated, including those from carbohydrate metabolism,lipid metabolism, and energy transfer. In the hemolymph, 21 upregulatedproteins were reported to be involved in immunity, RNA processing,and mRNA-directed protein synthesis, while 7 downregulated proteinswere implicated in energy transfer, hydrolysis, lipid metabolism,defense mechanisms, and amino acid storage-related functions. Subsequently,six target proteins were identified using labeled AzaA that interactedwith whole insect proteins. In silico analysis suggests that AzaAcould be efficiently accommodated in the hydrophobic pocket of juvenilehormone esterase and showed strong interaction with active site residues,indicating plausible targets of AzaA in H. armigera. Quantitative polymerase chain reaction analysis suggested differentialgene expression patterns and partly corroborated the proteomic results.Overall, data suggest that AzaA generally targets more than one proteinin H. armigera and hence could be apotent biopesticide.