Application of phage display: development of tools to fight against Xylella fastidiosa

Xylella fastidiosa is a phytopathogen infecting a wide array of plants, whose spread and effect on agricultural economy worry governments around the world. Despite many researches, its biology and in-planta behavior are still partially known and there is no curative treatments to date. In this study, we focus on a lipase/esterase called LesA, which is highly secreted by Xf, and also involved in the bacteria’s virulence. This uncharacterized enzyme of 42 kD size, comprises a rigid 7 alpha-helixes LID domain, similar to lipases from other phytopathogens  like X. oryzae. We aim to find molecules able to bind LesA specifically and with a high affinity, to develop tools  against Xf. Peptides able to recognize LesA could be used  as a biomarker of Xf infection. Inhibition of an essential virulence factor could also delay Xf spread inside the host as well as emergence of symptoms. This delay may give time for plants to take an advantage on bacteria and defend themselves with a natural and appropriate defense response from its immunity, helping to fight against the disease. For this purpose, we use phage display technology to screen among a large bank of peptides those able to interact with our target enzyme. More than a billion of different peptides are expressed on surface of bacteriophages, but few will be selected by biopanning for their ability to bind the target. The resulting population of peptides will be tested by ELISA to quantify their specificity to LesA. Among the best candidates, we will select those with the additional ability to inhibit LesA and we will test them on various biological models (bacterial culture media, in-planta…).