Peptidyl prolyl cis/trans isomerase from Pseudomonas fluorescens encapsulated into biodegradable natural polymers: A potential plant protection agent inducing plant resistance to fungal pathogens

Intensive use of pesticides causes pollution of terrestrial and water ecosystems negatively influencing on the bio-diversity and human health. Use of bioactive compounds, such as elicitors, able to boost non-specific plant im-munity, is a promising alternative to chemical treatments of crops. MF3, a protein from Pseudomonas fluorescens, is able to induce resistance in various crops thus protecting them from a range of plant pathogens, but can be de-stroyed under field conditions by UV radiation and proteolytic enzymes of plant and microbial origin. MF3 en-capsulation in biodegradable polymers, such as poly-3-hydroxybutyrate (PHB) and sodium alginate (ALG) has been shown earlier to shield it against adverse external factors. In this study, we examined the protecting effi-ciency of both MF3 complexes on three model plant-pathogen systems: "wheat -Parastagonospora nodorum" (1), "rice - Magnaporthe oryzae" (2), and "cucumber - Cladosporium cucumerinum" (3). Both MF3-ALG and MF3-PHB complexes demonstrated a significant disease suppression level varying between 55-80 and 40-60 % in the models 1 and 3, respectively; in the model 2, they completely blocked disease development. A significant protective activity of ALG alone was observed in all three models. For the models 1 and 2, a synergistic interaction between MF3 and ALG in relation to the disease suppression was validated. In several cases (free and encapsulated MF3 in the model 1 and MF3-ALG complex in the model 2), a possible translaminar protective activity was shown. The obtained results confirmed a principal possibility to develop environmentally safe biopesticides based on the MF3 encapsulated in PHB or ALG.