Specific modulation of the root immune system by a community of commensal bacteria

Paulo J.P.L. Teixeira, Nicholas R. Colaianni, Theresa F. Law, Jonathan M. Conway, Sarah Gilbert, Haofan Li, Isai Salas-González, Darshana Panda, Nicole M. Del Risco, Omri M. Finkel, Gabriel Castrillo, Piotr Mieczkowski, Corbin D. Jones, Jeffery L. Dangl*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

46 Scopus citations


Plants have an innate immune system to fight off potential invaders that is based on the perception of nonself or modified-self molecules. Microbe-associated molecular patterns (MAMPs) are evolutionarily conserved microbial molecules whose extracellular detection by specific cell surface receptors initiates an array of biochemical responses collectively known as MAMP-triggered immunity (MTI). Well-characterized MAMPs include chitin, peptidoglycan, and flg22, a 22-amino acid epitope found in the major building block of the bacterial flagellum, FliC. The importance of MAMP detection by the plant immune system is underscored by the large diversity of strategies used by pathogens to interfere with MTI and that failure to do so is often associated with loss of virulence. Yet, whether or how MTI functions beyond pathogenic interactions is not well understood. Here we demonstrate that a community of root commensal bacteria modulates a specific and evolutionarily conserved sector of the Arabidopsis immune system. We identify a set of robust, taxonomically diverse MTI suppressor strains that are efficient root colonizers and, notably, can enhance the colonization capacity of other tested commensal bacteria. We highlight the importance of extracellular strategies for MTI suppression by showing that the type 2, not the type 3, secretion system is required for the immunomodulatory activity of one robust MTI suppressor. Our findings reveal that root colonization by commensals is controlled by MTI, which, in turn, can be selectively modulated by specific members of a representative bacterial root microbiota.

Original languageAmerican English
Article numbere2100678118
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number16
StatePublished - 20 Apr 2021
Externally publishedYes

Bibliographical note

Funding Information:
ACKNOWLEDGMENTS. We thank Dr. Ka-Wai Ma and Dr. Paul Schulze-Lefert for providing the gentamycin-resistant Pseudomonas viridiflava strain OTU5 p5.e6 and for sharing their bacteria colonization protocol and unpublished transcriptome data; Schulze-Lefert laboratory members for comments on the manuscript; the J.L.D. laboratory microbiome group for useful discussions; and Prof. Sarah Grant for comments and suggestions on the manuscript. This work was supported by NSF Grant IOS-1917270 and by Office of Science (Biological and Environmental Research), US Department of Energy Grant DE-SC0014395 (to J.L.D.) J.L.D is an Investigator of the Howard Hughes Medical Institute (HHMI), supported by the HHMI. P.J.P.L.T. was supported by The Pew Latin American Fellows Program in the Biomedical Sciences. N.R.C. was supported by NIH Training Grant T32GM135123.

Publisher Copyright:
© 2021 National Academy of Sciences. All rights reserved.


  • Flg22
  • MAMP
  • Plant immunity
  • Root microbiome
  • SynCom


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