Versatile role of Pseudomonas fuscovaginae cyclic lipopeptides in plant and microbial interactions

Abstract

Pseudomonas fuscovaginae is the most prominent bacterial sheath rot pathogen, causing sheath brown rot disease in rice. This disease occurs worldwide and it is characterized by typical necrotic lesions on the sheath, as well as a reduction in the number of emitted panicles and filled grains. P. fuscovaginae has been shown to produce syringotoxin and fuscopeptin cyclic lipopeptides (CLPs), which have been linked to pathogenicity. In this study, we investigated the role of P. fuscovaginae UPB0736 CLPs in plant pathogenicity, antifungal activity and swarming motility. To do so, we sequenced the strain to obtain a single-contig genome and we constructed deletion mutants in the biosynthetic gene clusters responsible for the synthesis of CLPs. We show that UPB0736 produces a third CLP of 13 amino acids, now named asplenin, and we link this CLP with the swarming activity of the strain. We could then show that syringotoxin is particularly active against Rhizoctonia solani in vitro. By testing the mutants in planta we investigated the role of both fuscopeptin and syringotoxin in causing sheath rot lesions. We proved that the presence of these two CLPs considerably affected the number of emitted panicles, although their number was still significantly affected in the mutants deficient in both fuscopeptin and syringotoxin. These results reveal the importance of CLPs in P. fuscovaginae pathogenicity, but also suggest that other pathogenicity factors may be involved.

Charting the Lipopeptidome of Nonpathogenic Pseudomonas

“…A lipotridecapeptide BGC is present in the type strains of P. fuscovaginae and P. asplenii (Asplenii SG), known coproducers of Mycin and Peptin CLPs (syringotoxin and fuscopeptin, respectively, [ 16 ]) (Table S4K). This LP apparently corresponds to N5 (renamed asplenin) detected in other Asplenii-SG rhizosphere isolates ( 15 , 51 ). We identified candidate producers of four other Asplenin members with a potential eight-membered macrocycle but different AA sequences (LP13a to d; Table S4L).…”

“…Only few nonphytopathogenic “dual producers” are known to cosynthesize CLPs belonging to two chemically distinct families ( 11 , 12 ). Strains carrying clustered biosynthetic gene clusters (BGCs) of the Mycin and Peptin families, along with a third BGC for either an LLP of the Syringafactin family ( 13 ), the LLP thanafactin ( 14 ), or asplenin ( 15 ), are confined to particular taxonomic (sub)groups harboring both pathogenic and phytobeneficial isolates ( Table S2 ) ( 16 , 17 ). Biosynthesis of the cyclic lipononapeptides of the Mycin family requires the activity of a didomain enzyme for chlorination and incorporation of a terminal chlorothreonine ( 18 ).…”

Does regulation hold the key to optimizing lipopeptide production in Pseudomonas for biotechnology?

“…In addition, syringotoxin is also toxic to the rice sheath blight pathogen Rhizoctonia solani AG1-1A. Asplenin is needed for swarming motility ( Ferrarini et al, 2022b ). The syringotoxin and fuscopeptin BGCs in P. fuscovaginae UPB0736 are completely devoid of luxR type regulatory genes, while three luxR genes (termed luxR1 , luxR2 and luxR3 by ( Ferrarini et al, 2022b ) and renamed here as asp3 , asp4 and asp1 ) are situated upstream of the asplenin BGC, and one luxR gene ( aspR2 ) downstream of the last NRPS gene of this cluster ( Figure 3 ).…”

“…Asplenin is needed for swarming motility ( Ferrarini et al, 2022b ). The syringotoxin and fuscopeptin BGCs in P. fuscovaginae UPB0736 are completely devoid of luxR type regulatory genes, while three luxR genes (termed luxR1 , luxR2 and luxR3 by ( Ferrarini et al, 2022b ) and renamed here as asp3 , asp4 and asp1 ) are situated upstream of the asplenin BGC, and one luxR gene ( aspR2 ) downstream of the last NRPS gene of this cluster ( Figure 3 ). Phylogenetic analysis reveals that AspR3 and AspR1 cluster in the same clade as the LuxR1 regulators situated upstream of the BGCs in mono-producers, while AspR2 and AspR4 cluster with the LuxR2 regulators downstream of the BGCs in mono-producers ( Figure 9 ).…”

Stereomeric Lipopeptides from a Single Non-Ribosomal Peptide Synthetase as an Additional Source of Structural and Functional Diversification in Pseudomonas Lipopeptide Biosynthesis

“…To date, comparative analysis of epi-active and epi-inactive E/C-domains have not revealed unambiguous correlations with specific variations in the amino acid sequence of the active site in dual E/C-domains, thus preventing fail-safe D/L-configurational attribution based on genomic data alone. Therefore, full determination of CLiP structure still necessitates the use of extensive chemical structure analysis and, in some cases, chemical synthesis [ 30 ]. This need is now further underscored by the discovery of configurational flexibility within a single NRPS assembly line.…”