Harpin_Pss encapsulation in chitosan nanoparticles for improved bioavailability and disease resistance in tomato

Harpin_Pss, an elicitor from Pseudomonas syringae pv. syringae, induces systemic acquired resistance in non-host plants, providing resistance to phytopathogens. Poor assimilation of harpin_Pss is a major constraint in foliar application as biopesticide. We, therefore, prepared harpin_Pss-loaded chitosan nanoparticles (H-CSNPs) to improve permeability and bio-availability of harpin_Pss in tomato. H-CSNPs showed high encapsulation efficiency (90%), improved stability (p < 0.01) and bioavailability of harpin_Pss (p < 0.01). Treatment with H-CSNPs resulted in sustained induction of peroxidase, phenylalanine ammonia lyase and decreased Rhizoctonia solani infection (p < 0.05). Transcripts of several genes involved in defense response were differentially expressed in harpin_Pss, CSNPs and H-CSNPs treatments. While, genes involved in jasmonic acid (JA) metabolism were up-regulated during harpin_Pss and H-CSNP spray treatments, indicating the role of JA pathway in triggering harpin-mediated defense responses. Furthermore, the entry of CSNPs into the cell and localization of harpin_Pss into chloroplast was tracked using rhodamine-labelled CSNPs encapsulated with GFP tagged harpin_Pss. The results of this study indicate use of H-CSNPs is effective for sustained-release of harpin_Pss and provides resistance for prolonged duration.