Harpin-loaded chitosan nanoparticles induced defense responses in tobacco

Abstract

Phytopathogens entry into plant cell is restricted by several chemical substances which hamper the natural ecosystem and are expensive. Induction of defense responses in plants by elicitors is a better alternative approach to combat phytopathogens. Controlled and steady release of elicitors from nanoparticles core will improve the bioavailability and alleviate the repeated application of molecules that triggers the hypersensitive response (HR) in plants. Here we reported the efficacy of chitosan-harpin as nanoparticles in eliciting defense responses in tobacco wherein harpin (30 ng/mL) loaded chitosan nanoparticles (H-CSNPs) were prepared by ionotropic gelation method using chitosan and sodium tripolyphosphate (TPP). The nanoparticles were spherical and possess a size of about ∼160 nm with a zeta potential of 30.2 ± 0.7 mV. The FT-IR and XRD studies confirmed the formation of chitosan nanoparticles. The encapsulation efficiency of harpin was 85% and steady release was observed up to 4 h in releasing kinetics. Topical application of H-CSNPs resulted histopathological evidences which coincided with the induction HR specific marker genes viz., pathogenises related proteins and induction of defense enzymes. The harpin at nanogram concentrations with chitosan improved the bioavailability than the harpin or chitosan alone in the tobacco plant.

Keywords

• Chitosan nanoparticles (CSNPs)
• Harpin
• Ionotropic gelation
• Hypersensitive response (HR)
• Reactive oxygen species (ROS)