title: Virulence quenching with a prenylated isoflavanone renders the Malagasy legume Dalbergia pervillei resistant to Rhodococcus fascians.
abstract: The phytopathogenic Actinomycete Rhodococcus fascians induces leafy galls on a wide range of hosts, causing major economical losses in the ornamentals industry. Although differences in the responsivity occur within species, no plant tested so far could be considered resistant to R. fascians strain D188 infection. Here, we observed that members of the genus Dalbergia, which belong to the Fabaceae, did not develop leafy galls when challenged with R. fascians and we set out to unravel the mechanism of this recalcitrance. Whereas organic extracts of Dalbergia tissues exhibited toxicity towards the bacteria, more importantly, dichloromethane bark extracts inhibited the induction of bacterial virulence gene expression without any apparent loss of viability, illustrating that resistance is likely multifactorial. The virulence quencher was identified as a new prenylated isoflavanone, termed perbergin, and specifically targeted the AttR regulon (a LysR-type transcriptional regulator) which is imperative for the switch of R. fascians from an epiphytic to a pathogenic lifestyle. The mode of action of perbergin demonstrated that just like in Gram-negative host-microbe interactions, also in Gram-positive phytopathogens autoregulation is being targeted by the plant as an efficient means of defence. Moreover, the identification of perbergin opens the path to disease control in affected nurseries.
authors.affiliation: Laboratoire de Biotechnologie Végétale, Université Libre de Bruxelles, 12 rue des Professeurs Jeener et Brachet, Gosselies, Belgium.
authors.forename: Sanda
authors.initials: S
authors.lastname: Rajaonson
authors.forename: Olivier M
authors.initials: OM
authors.lastname: Vandeputte
authors.forename: Danny
authors.initials: D
authors.lastname: Vereecke
authors.forename: Martin
authors.initials: M
authors.lastname: Kiendrebeogo
authors.forename: Eliane
authors.initials: E
authors.lastname: Ralambofetra
authors.forename: Caroline
authors.initials: C
authors.lastname: Stévigny
authors.forename: Pierre
authors.initials: P
authors.lastname: Duez
authors.forename: Christian
authors.initials: C
authors.lastname: Rabemanantsoa
authors.forename: Adeline
authors.initials: A
authors.lastname: Mol
authors.forename: Billo
authors.initials: B
authors.lastname: Diallo
authors.forename: Marie
authors.initials: M
authors.lastname: Baucher
authors.forename: Mondher
authors.initials: M
authors.lastname: El Jaziri
mesh_terms: D000900:Anti-Bacterial Agents / Q000302:isolation & purification / Q000494:pharmacology; D035782:Dalbergia / Q000737:chemistry* / Q000382:microbiology; D015964:Gene Expression Regulation, Bacterial; D007529:Isoflavones / Q000302:isolation & purification / Q000494:pharmacology*; D015394:Molecular Structure; D039821:Monoterpenes / Q000302:isolation & purification / Q000494:pharmacology*; D024301:Plant Bark / Q000737:chemistry; D010936:Plant Extracts / Q000494:pharmacology; D010941:Plant Tumors / Q000382:microbiology; D054876:Prenylation; D012240:Rhodococcus / Q000187:drug effects / Q000235:genetics / Q000472:pathogenicity*; D014774:Virulence
chemical_list: C560203:3-(2,3-dihydroxy-4-methoxyphenyl)-8-(3,7-dimethylocta-2,6-dienyl)-5,7-dihydroxy-2,3-dihydrochromen-4-one; D000900:Anti-Bacterial Agents; D007529:Isoflavones; D039821:Monoterpenes; D010936:Plant Extracts; C065753:isoflavanone