NEXT GENERATION ECOFRIENDLY CONTROL OF GRAM NEGATIVE PLANT PATHOGENIC BACTERIA: VIRULENCE INHIBITING PEPTIDES AND POLYPHENOLS FROM NO-FOOD PLANT BIOMASS

Plant diseases caused by bacteria may be highly destructive under adverse environmental conditions or in the case of quarantine pathogens. Bacterial diseases of plants still remain a challenging issue, basically relying on the use of copper and antibiotics, the latter not allowed in EU for plant protection. Given the negative ecotoxicological profile of copper, alternatives to its use are urgently needed, to meet the demands concerning agro-industry productivity and environmental protection. Here we propose an innovative strategy, based on the use of newly designed peptides and of plant polyphenols extracted from no-food biomass by a “green chemistry” process, targeting bacterial pathogenicity and virulence mechanisms, but not viability, thus avoiding the risk to develop any resistance. Both virulence inhibiting peptides (VIPs) and plant polyphenol extracts affect the TTSS and QS functionality, both in vitro and in planta, at concentrations of 30-60 μM, using Pseudomonas savastanoi, P. syringae pv. tabaci and P. syringae pv. actinidiae as model systems. Their effectiveness was demonstrated by pathogenicity trials and by bacterial gene expression studies, through real time PCR and several promoter-reporter systems. VIPs effectiveness was also demonstrated in Nicotiana tabacum and Actinidia chinensis stably transformed for VIPs expression, when challenged by P. syringae pv. tabaci and pv. actinidiae, respectively. No negative side-effects and no toxicity have been found on soil microflora, on model organisms and microorganisms, on biomimetic cellular membranes, as well as on Ca-ATPase pumps.