Cell Density-Regulated Adhesins Contribute to Early Disease Development and Adhesion in Ralstonia solanacearum

Mariama D. Carter, Devanshi Khokhani, Caitilyn Allen

Research output: Contribution to journalArticlepeer-review

4 Scopus citations

Abstract

Adhesins (adhesive proteins) help bacteria stick to and colonize diverse surfaces and often contribute to virulence. The genome of the bacterial wilt pathogen Ralstonia solanacearum (Rs) encodes dozens of putative adhesins, some of which are upregulated during plant pathogenesis. Little is known about the role of these proteins in bacterial wilt disease. During tomato colonization, three putative Rs adhesin genes were upregulated in a DphcA quorum-sensing mutant that cannot respond to high cell densities: radA (Ralstonia adhesin A), rcpA (Ralstonia collagen-like protein A), and rcpB. Based on this differential gene expression, we hypothesized that adhesins repressed by PhcA contribute to early disease stages when Rs experiences a low cell density. During root colonization, Rs upregulated rcpA and rcpB, but not radA, relative to bacteria in the stem at mid-disease. Root attachment assays and confocal microscopy with DrcpA/B and DradA revealed that all three adhesins help Rs attach to tomato seedling roots. Biofilm assays on abiotic surfaces found that Rs does not require RadA, RcpA, or RcpB for interbacterial attachment (cohesion), but these proteins are essential for anchoring aggregates to a surface (adhesion). However, Rs did not require the adhesins for later disease stages in planta, including colonization of the root endosphere and stems. Interestingly, all three adhesins were essential for full competitive fitness in planta. Together, these infection stage-specific assays identified three proteins that contribute to adhesion and the critical first host-pathogen interaction in bacterial wilt disease.

Original languageEnglish (US)
JournalApplied and environmental microbiology
Volume89
Issue number2
DOIs
StatePublished - Feb 2023

Bibliographical note

Funding Information:
This material is based upon work supported by the National Science Foundation Graduate Research Fellowship under grant no. DGE-1747503. Any opinion, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation. We gratefully acknowledge Sarah Swanson, University of Wisconsin-Madison Department of Botany, and Jonathon M. Jacobs, Ohio State University Department of Plant Pathology, for their technical help with confocal microscopy. We also thank Corri D. Hamilton, University of British Colombia Department of Microbiology and Immunology, for designing the iolG quantitative PCR primers.

Funding Information:
This material is based upon work supported by the National Science Foundation Graduate Research Fellowship under grant no. DGE-1747503. Any opinion, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation.

Publisher Copyright:
Copyright © 2023 American Society for Microbiology. All Rights Reserved.

Keywords

  • Ralstonia solanacearum
  • adhesin
  • adhesion
  • bacterial wilt
  • biofilm
  • cohesion
  • plant pathogens
  • soil-borne pathogen
  • tomato

PubMed: MeSH publication types

  • Journal Article
  • Research Support, U.S. Gov't, Non-P.H.S.

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