Ralfuranones contribute to mushroom‐type biofilm formation by Ralstonia solanacearum strain OE1‐1. (10th October 2017)

• Record Type: Journal Article
• Authors: Mori, Yuka; Hosoi, Yuki; Ishikawa, Shiho; Hayashi, Kazusa; Asai, Yu; Ohnishi, Hideyuki; Shimatani, Mika; Inoue, Kanako; Ikeda, Kenichi; Nakayashiki, Hitoshi; Nishimura, Yasuyo; Ohnishi, Kouhei; Kiba, Akinori; Kai, Kenji; Hikichi, Yasufumi
• Is Part Of: Molecular plant pathology. Volume 19:Number 4(2018)
• Page Start: 975
• Page End: 985
• Publication Date: 2017-10-10
• Subjects: mushroom‐type biofilm -- ralfuranones -- Ralstonia solanacearum -- virulence; Plant diseases -- Molecular aspects -- Periodicals; Plant-pathogen relationships -- Molecular aspects -- Periodicals; 571.936
• DOI: 10.1111/mpp.12583
• Languages: English
• ISSNs: 1464-6722

Abstract

Summary: After invasion into intercellular spaces of tomato plants, the soil‐borne, plant‐pathogenic Ralstonia solanacearum strain OE1‐1 forms mushroom‐shaped biofilms (mushroom‐type biofilms, mBFs) on tomato cells, leading to its virulence. The strain OE1‐1 produces aryl‐furanone secondary metabolites, ralfuranones (A, B, J, K and L), dependent on the quorum sensing (QS) system, with methyl 3‐hydroxymyristate (3‐OH MAME) synthesized by PhcB as a QS signal. Ralfuranones are associated with the feedback loop of the QS system. A ralfuranone productivity‐deficient mutant (Δ ralA ) exhibited significantly reduced growth in intercellular spaces compared with strain OE1‐1, losing its virulence. To analyse the function of ralfuranones in mBF formation by OE1‐1 cells, we observed cell aggregates of R. solanacearum strains statically incubated in tomato apoplast fluids on filters under a scanning electron microscope. The Δ ralA strain formed significantly fewer microcolonies and mBFs than strain OE1‐1. Supplementation of ralfuranones A, B, J and K, but not L, significantly enhanced the development of mBF formation by Δ ralA . Furthermore, a phcB ‐ and ralA ‐deleted mutant (Δ phcB / ralA ) exhibited less formation of mBFs than OE1‐1, although a QS‐deficient, phcB ‐deleted mutant formed mBFs similar to OE1‐1. Supplementation with 3‐OH MAME significantly reduced the formation of mBFs by Δ phcB / ralA . The application of each ralfuranone significantly increased the formation of mBFs by Δ phcB / ralA supplied with 3‐OH MAME. Together, our findings indicate that ralfuranones are implicated not only in the development of mBFs by strain OE1‐1, but also in the suppression of QS‐mediated negative regulation of mBF formation.