Quorum Sensing Inhibition Attenuates the Virulence of the Plant Pathogen Ralstonia solanacearum Species Complex
journal contributionposted on 2020-11-11, 06:44 authored by Ayaka Yoshihara, Mika Shimatani, Megumi Sakata, Chika Takemura, Wakana Senuma, Yasufumi Hikichi, Kenji Kai
Strains of Ralstonia solanacearum species complex (RSSC) cause “bacterial wilt” on a wide range of plant species and thus lead to marked economic losses in agriculture. Quorum sensing (QS), a bacterial cell–cell communication mechanism, controls the virulence of RSSC strains by regulating the production of extracellular polysaccharide (EPS) and secondary metabolites, biofilm formation, and cellular motility. R. solanacearum strain OE1-1 employs (R)-methyl 3-hydroxymyristate (3-OH MAME) as a QS signal, which is synthesized by the PhcB methyltransferase and sensed by the PhcS/PhcRQ two-component system. We describe the design, synthesis, and biological evaluation of inhibitors of the phc QS system. Initial screening of a small set of QS signal analogues revealed that methyl 3-hydroxy-8-phenyloctanoate, named, PQI-1 (phc quorum sensing inhibitor-1), inhibited biofilm formation by strain OE1-1. To improve its inhibitory activity, the derivatives of PQI-1 were synthesized, and their QS inhibition activities were evaluated. PQIs-2–5 evolved from PQI-1 more strongly inhibited not only biofilm formation but also the production of ralfuranone and EPS. Furthermore, RNA-Seq analysis revealed that the PQIs effectively inhibited QS-dependent gene expression and repression in strain OE1-1. On the other hand, the PQIs did not affect the canonical QS systems of the representative reporter bacteria. These antagonists, especially PQI-5, reduced wilting symptoms of the tomato plants infected with strain OE1-1. Taken together, we suggest that targeting the phc QS system has potential for the development of chemicals that protect agricultural crops from bacterial wilt disease.
EPSrepresentative reporter bacteriaRalstonia solanacearum speciesp hc q uorumsolanacearum strain OE 1-1PQIOHbiofilm formationRSSCQS-dependent gene expressionphc QS systemPlant Pathogen Ralstonia solanacear...QS inhibition activitiesMAMEQS signal analoguesmethyl 3- hydroxy -8-phenyloctanoatecanonical QS systemsstrain OE 1-1.