Lipo-random peptide mixtures to fight against bacterial plant diseases

Almost all major crops are severely affected by at least one important bacterial disease. Management of bacterial plant diseases vastly relies on copper bactericides. According to the European Food Safety Authority, the use of copper is of concern to public health and the environment, and copper compounds are due to be gradually phased out. Considering the lack of alternatives, there is an urgent need to develop novel technologies to manage bacterial plant diseases. We have recently introduced the random antimicrobial peptide mixture (RPM) approach to tackle pathogenic bacteria. We showed that unique RPMs consisting of random 20-mer combinations of one hydrophobic and one cationic amino acids have the potential to serve as crop protection agents¹. In the present study we explored the potential to improve RPM interaction with the cuticle covering the leaf surface and to improve their antimicrobial activity by conjugating palmitic acid to RPMs, generating lipo-random peptide mixtures (lipo-RPMs). Surprisingly, short lipo-RPMs, containing only 5 amino acids [combinations of L-phenylalanine (F) and D-lysine (dK)] showed strong antimicrobial activity both in vitro and in planta, without yielding phytotoxic or cytotoxic effects. We synthesized the 32 possible lipo-peptides (2⁵ combinations of F and dK) that compose this lipo-RPM and studied the antimicrobial activity of each one. This study showed differences among the various lipo-peptides and strengthened the occurrence of a synergistic interaction among them in the mixture. Our study demonstrates the potential of short lipo-RPMs as a novel technology for management of bacterial plant diseases.

¹Topman et al., Microbial Biotechnology (2018) 11(6), 1027– 1036