Plant lectin-like antibacterial proteins from phytopathogensPseudomonas syringaeandXanthomonas citri
The genomes ofPseudomonas syringaepv.syringae642 andXanthomonas citripv.malvacearumLMG 761 each carry a putative homologue of the plant lectin-like bacteriocin (llpA) genes previously identified in the rhizosphere isolatePseudomonas putidaBW11M1 and the biocontrol strainPseudomonas fluorescensPf-5. The respective purified recombinant proteins, LlpAPss642 and LlpAXcm761, display genus-specific antibacterial activity across species boundaries. The inhibitory spectrum of theP. syringaebacteriocin overlaps partially with those of theP. putidaandP. fluorescensLlpAs. Notably,Xanthomonas axonopodispv.citristr. 306 secretes a protein identical to LlpAXcm761. The functional characterization of LlpA proteins from two different phytopathogenic γ-proteobacterial species expands the lectin-like bacteriocin family beyond thePseudomonasgenus and suggests its involvement in competition among closely related plant-associated bacteria with different lifestyles.