Integrative transcriptomic and metabolomic analyses reveals the toxicity and mechanistic insights of bioformulated chitosan nanoparticles against Magnaporthe oryzae

Rice blast, an extremely destructive disease caused by the filamentous fungal pathogen Magnaporthe oryzae, poses a global threat to the production of rice (Oryza sativa L.). The emerging trend of reducing dependence on chemical fungicides for crop protection has increased interest in exploring bioformulated nanomaterials as a sustainable alternative antimicrobial strategy for effectively managing plant diseases. Herein, we used physiomorphological, transcriptomic, and metabolomic methods to investigate the toxicity and molecular action mechanisms of moringa-chitosan nanoparticles (M-CNPs) against M. oryzae. Our results demonstrate that M-CNPs exhibit direct antifungal properties by impeding the growth and conidia formation of M. oryzae in a concentration-dependent manner. Propidium iodide staining indicated concentration-dependent significant apoptosis (91.33%) in the fungus. Ultrastructural observations revealed complete structural damage in fungal cells treated with 200 mg/L M-CNPs, including disruption of the cell wall and destruction of internal organelles. Transcriptomic and metabolomic analyses revealed the intricate mechanism underlying the toxicity of M-CNPs against M. oryzae. The transcriptomics data indicated that exposure to M-CNPs disrupted various processes integral to cell membrane biosynthesis, aflatoxin biosynthesis, transcriptional regulation, and nuclear integrity in M. oryzae., emphasizing the interaction between M-CNPs and fungal cells. Similarly, metabolomic profiling demonstrated that exposure to M-CNPs significantly altered the levels of several key metabolites involved in the integral components of metabolic pathways, microbial metabolism, histidine metabolism, citrate cycle, and lipid and protein metabolism in M. oryzae. Overall, these findings demonstrated the potent antifungal action of M-CNPs, with a remarkable impact at the physiological and molecular level, culminating in substantial apoptotic-like fungal cell death. This research provides a novel perspective on investigating bioformulated nanomaterials as antifungal agents for plant disease control.