Molecular mechanism of plant elicitor daphnetin-carboxymethyl chitosan nanoparticles against Ralstonia solanacearum by activating plant system resistance

The exploration of biopolymer-based materials to avoid hazardous chemicals in agriculture has gained enormous importance for sustainable crop protection. Due to its good biocompatibility and water solubility, carboxymethyl chitosan (CMCS) has been widely applied as a pesticide carrier biomaterial. However, the mechanism by which carboxymethyl chitosan-grafted natural product nanoparticles induce tobacco systemic resistance against bacterial wilt remains largely unknown. In this study, water-soluble CMCS-grafted daphnetin (DA) nanoparticles ([email protected]) were successfully synthesized, characterized, and assessed for the first time. The grafting rate of DA in CMCS was 10.05 %, and the water solubility was increased. In addition, [email protected] significantly increased the activities of CAT, PPO and SOD defense enzymes, activated the expression of PR1 and NPR1, and suppressed the expression of JAZ3. [email protected] could induce immune responses against R. solanacearum in tobacco, including increases in defense enzymes and overexpression of pathogenesis-related (PR) proteins. The application of [email protected] effectively suppressed the development of tobacco bacterial wilt in pot experiments, and the control efficiency was as high as 74.23 %, 67.80 %, 61.67 % at 8, 10, and 12 days after inoculation. Additionally, [email protected] has excellent biosafety. Therefore, this study highlighted the application of [email protected] in manipulating tobacco to generate defense responses against R. solanacearum, which can be attributed to systemic resistance.