TtsI, a Key Regulator of Rhizobium Species NGR234 Is Required for Type III-Dependent Protein Secretion and Synthesis of Rhamnose-Rich Polysaccharides

Article Article scientifique Article TtsI, a Key Regulator of Rhizobium Species NGR234 Is Required for Type III-Dependent Protein Secretion and Synthesis of Rhamnose-Rich Polysaccharides eng 2004-09 author Marie Corinne 506697 author Deakin William James 507597 author Ojanen-Reuhs Tuula author Diallo Ericka 516600 author Reuhs Brad author Broughton William John 22724 Administration de la faculté des sciences (SIAD) author Perret Xavier 643804 958-966 10.1094/MPMI.2004.17.9.958 15384486 0894-0282 Formation of nitrogen-fixing nodules on legume roots by Rhizobium sp. NGR234 requires an array of bacterial factors, including nodulation outer proteins (Nops) secreted through a type III secretion system (TTSS). Secretion of Nops is abolished upon inactivation of ttsI (formerly y4xI), a protein with characteristics of two-component response regulators that was predicted to activate transcription of TTSS-related genes. During the symbiotic interaction, the phenotype of NGRΩttsI differs from that of a mutant with a nonfunctional secretion machine, however. This indicated that TtsI regulates the synthesis of other symbiotic factors as well. Conserved sequences, called tts boxes, proposed to act as binding sites for TtsI, were identified not only within the TTSS cluster but also in the promoter regions of i) genes predicted to encode homologs of virulence factors secreted by pathogenic bacteria, ii) loci involved in the synthesis of a rhamnose-rich component (rhamnan) of the lipopolysaccharides (LPS), and iii) open reading frames that play roles in plasmid partitioning. Transcription studies showed that TtsI and tts boxes are required for the activation of TTSS-related genes and those involved in rhamnose synthesis. Furthermore, extraction of polysaccharides revealed that inactivation of ttsI abolishes the synthesis of the rhamnan component of the LPS. The phenotypes of mutants impaired in TTSS-dependent protein secretion, rhamnan synthesis, or in both functions were compared to assess the roles of some of the TtsI-controlled factors during symbiosis. Dewey 580 45 Département des sciences végétales 163 false Molecular plant-microbe interactions 17 9 872b685d-af4a-4b22-bbb2-7fd552fa55df Article (Published version) Public Marie_MPMI_200417958.pdf 454816 application/pdf CC BY-4.0 3966c20e859a657bdfb825e80fa8809a8d0d2281d432c25f25b812d7db1736af openAccess Faculté des sciences / Section de biologie / Département des sciences végétales

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TtsI, a Key Regulator of Rhizobium Species NGR234 Is Required for Type III-Dependent Protein Secretion and Synthesis of Rhamnose-Rich Polysaccharides	Molecular plant-microbe interactions			2004	84	280

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