Lipo-Random peptide mixtures for managing bacterial plant diseases

Bacterial diseases affect all major crops causing significant yield and food lost. To date, the management of bacterial plant diseases vastly relies on copper bactericides, but the use of copper is of concern to public health and the environment, and copper compounds are due to be gradually phased out. Therefore, there is an urgent need to develop novel technologies to manage bacterial plant diseases. Recently we introduced the random peptide mixture (RPM) approach to tackle pathogenic bacteria¹. We showed that antimicrobial RPMs, consisting of random 20-mer combinations of cationic and hydrophobic amino acids have the potential to be used for crop protection purposes. In the present study we conjugated palmitic acid in order to explore the potential to improve RPMs interaction with the cuticle and to improve their antimicrobial activity, generating lipo-random peptide mixtures (lipo-RPMs). The addition of palmitic acid preserved the antimicrobial activity in vitro and in planta in the lipo-RPM-FdK5+p (a 5-mer RPM composed of L-phenylalanine and D-lysine with palmitic acid at the N-terminus). No phytotoxic or cytotoxic effects were detected for this lipo-RPM. The 32 individual lipo-peptides that composes the FdK5+p mixture were synthetized and studied to understand the effect of the ratio between hydrophobic and cationic amino acids on antimicrobial activity. Based on these results we generated improved 5-mer lipo-RPMs with powerful antimicrobial effect. Furthermore, individual lipo-peptides were shown to possess a synergistic effect. Our study demonstrates the potential of lipo-RPMs as novel tools for the management of bacterial plant diseases.

¹Topman et al., 11, 1027-1036 (2018)