Ralstonia solanacearum requires F-box-like domain-containing type III effectors to promote disease on several host plants

Aurélie Angot, Nemo Peeters, Esther Lechner, Fabienne Vailleau, Catherine Baud, Laurent Gentzbittel, Elodie Sartorel, Pascal Genschik, Christian Boucher, Stéphane Genin

Research output: Contribution to journalArticlepeer-review

162 Citations (Scopus)

Abstract

The phytopathogenic bacterium Ralstonia solanacearum encodes a family of seven type III secretion system (T3SS) effectors that contain both a leucine-rich repeat and an F-box domain. This structure is reminiscent of a class of typical eukaryotic proteins called F-box proteins. The latter, together with Skp1 and Cullin1 subunits, constitute the SCF-type E3 ubiquitin ligase complex and control specific protein ubiquitinylation. In the eukaryotic cell, depending on the nature of the polyubiquitin chain, the ubiquitin-tagged proteins either see their properties modified or are doomed for degradation by the 26S proteasome. This pathway is essential to many developmental processes in plants, ranging from hormone signaling and flower development to stress responses. Here, we show that these previously undescribed T3SS effectors are putative bacterial F-box proteins capable of interacting with a subset of the 19 different Arabidopsis Skp1-like proteins like bona fide Arabidopsis F-box proteins. A R. solanacearum strain in which all of the seven GALA effector genes have been deleted or mutated was no longer pathogenic on Arabidopsis and less virulent on tomato. Furthermore, we found that GALA7 is a host-specificity factor, required for disease on Medicago truncatula plants. Our results indicate that the GALA T3SS effectors are essential to R. solanacearum to control disease. Because the F-box domain is essential to the virulence function of GALA7, we hypothesize that these effectors act by hijacking their host SCF-type E3 ubiquitin ligases to interfere with their host ubiquitin/proteasome pathway to promote disease.

Original languageEnglish
Pages (from-to)14620-14625
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume103
Issue number39
DOIs
Publication statusPublished - 26 Sep 2006
Externally publishedYes

Keywords

  • Plant pathogen
  • SCF complex
  • Type III secretion system
  • Virulence

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