A Potent Plant-Derived Chitinase: Structural Informatics and Insecticidal Activity against Helicoverpa armigera.

Helicoverpa armigera (cotton bollworm) is a globally distributed lepidopteran pest that causes estimated annual agricultural losses exceeding 5 billion USD. While chemical pesticides remain the primary control strategy, their prolonged use has led to significant environmental contamination, development of widespread insecticide resistance, and non-target organism toxicity. These limitations underscore the critical need for plant-derived biopesticides that offer target specificity, environmental biodegradability, and sustainable pest management solutions without promoting resistance development. Here, we elucidate the insecticidal potential of Nelumbo nucifera Chitinase (NnChi) against the insect H. armigera through structural informatics and in-vivo insecticidal bioassays. SDS-PAGE showed a single band of ~32 kDa, and LC-MS/MS analysis depicted a fragment of 10 amino acids with 100% identity with Family 19 Class I Chitinase of Mangifera indica. NnChi-predicted structure revealed its two domains (ChB D, Cat D) connected through linker region and docking analysis of both these domains with (GlcNAc)₄ showing binding affinities of -5.6 kcal/mol and -7.0 kcal/mol, respectively. MD simulation (100 ns) showed that 4 residues (RQCR) of ChB D and 4 residues (NRIP) of Cat D contributed to binding with (GlcNAc)₄. To the best of our knowledge, we are reporting the molecular interactions of both domains (ChB D and Cat D) with (GlcNAc)₄ via simulation studies for the first time. These computational findings were further verified through insecticidal assay. Significant larval mortality of H. armigera was observed from 3^rd-6^th instar against 15 µg/g NnChi treatment. Among life cycle parameters, larval and pupal duration, adult eclosion, larval and pupal weight are significantly decreased in a concentration-dependent manner as compared to control. Our integrated structural-functional characterization demonstrates that NnChi exhibits significant insecticidal activity against Helicoverpa armigera. These findings establish NnChi as a promising biopesticide candidate worthy of further investigation.