Research Projects

Helicoverpa armigera, a major polyphagous insect pest, poses a significant threat to a wide range of economically important crops due to its aggressive feeding behaviour and adaptability. During herbivory, H.armigera secretes salivary and oral proteins that directly interact with host plant tissues. These secretory effectors and elicitor have been implicated in either activating or suppressing plant immune responses, thereby facilitating successful infestation. Amongst the characterized effectors, PPI5, HAS1, and HARP1 target distinct nodes in jasmonic acid (JA) and salicylic acid (SA) signalling. PPI5, a peptidyl-prolyl isomerase, inhibits ER stress- mediated immune signalling by binding to and supressing the expression and enzymatic activity of the ER-localized cyclophilin GhFKBP17-2, resulting in the downregulation of JA and SA responses (Wang et al., 2024). HAS1, a member of the venom R-like protein family conserved in other noctuid insects (Spodoptera, Mamestra) and carnivorous parasitic wasps, supresses JA-dependent defence by directly interacting with MYC3 and MYC4 transcription factors, thereby inhibiting JA-responsive gene expression (Chen et al., 2023). HARP1 targets JAZ repressors, preventing their SCF-COI1 mediated degradation and blocking downstream JA-signalling. Homologs of HARP1 are also found across Noctuidae, including REPAT38 in Spodoptera exigua, which similarly binds JAZ proteins, represses JA signaling, and enhances evolutionary strategy among both herbivorous and carnivorous insects to suppress host immune responses through effector-mediated interference with hormone signalling and transcriptional regulation (Chen et al., 2019). However, the effectors identified so far are known to function primarily when the host plants are cotton, Arabidopsis and tobacco. In contrast, the specific biological roles of many salivary and oral secretions of H. armigera remain largely unknown and uncharacterized during its feeding on chickpea. Despite increasing evidence highlighting the importance of insect- derived salivary effectors and elicitors in modulating host immunity, the specific identity, biological activity, and molecular targets of these proteins remain largely unexplored, particularly. H.armigera-Cicer arietinum interaction. Understanding these mechanisms is essential for developing targeted pest management strategies and enhancing crop resistance. This proposal arises from the need to isolate, identify and functionally characterize the salivary and oral effector and elicitors of H. armigera using activity based proteomics and transcriptomics, impact of in planta overexpression of effector on plant defense, effect of dsRNA of effector on insect vigour and to investigate their interaction with host plant defence signalling pathways.