Lipopeptide families at the interface between pathogenic and beneficialPseudomonas-plant interactions

Lipopeptides (LPs) are a prominent class of molecules among the steadily growing spectrum of specialized metabolites retrieved fromPseudomonas, in particular soil-dwelling and plant-associated isolates. Among the multiple LP families, pioneering research focussed on phytotoxic and antimicrobial cyclic lipopeptides (CLPs) of the ubiquitous plant pathogenPseudomonas syringae(syringomycin and syringopeptin). Their non-ribosomal peptide synthetases (NRPSs) are embedded in biosynthetic gene clusters (BGCs) that are tightly co-clustered on a pathogenicity island. Other members of theP. syringaegroup (Pseudomonas cichorii) and some species of thePseudomonas aspleniigroup andPseudomonas fluorescenscomplex have adopted these biosynthetic strategies to co-produce their own mycin and peptin variants, in some strains supplemented with an analogue of theP. syringaelinear LP (LLP), syringafactin. This capacity is not confined to phytopathogens but also occurs in some biocontrol strains, which indicates that these LP families not solely function as general virulence factors. We address this issue by scrutinizing the structural diversity and bioactivities of LPs from the mycin, peptin, and factin families in a phylogenetic and evolutionary perspective. BGC functional organization (including associated regulatory and transport genes) and NRPS modular architectures in known and candidate LP producers were assessed by genome mining.