Details

Autor(en) / Beteiligte

• Daniels, Ruth
• De Vos, Dirk E.
• Desair, Jos
• Raedschelders, Gert
• Luyten, Ellen
• Rosemeyer, Viola
• Verreth, Christel
• Schoeters, Eric
• Vanderleyden, Jos
• Michiels, Jan

Titel

The cin Quorum Sensing Locus of Rhizobium etli CNPAF512 Affects Growth and Symbiotic Nitrogen Fixation

Ist Teil von

• The Journal of biological chemistry, 2002-01, Vol.277 (1), p.462-468

Ort / Verlag

United States: Elsevier Inc

Erscheinungsjahr

2002

Quelle

MEDLINE

Beschreibungen/Notizen

• Rhizobium etli CNPAF512 produces an autoinducer that inhibits growth of Rhizobium leguminosarum bv. viciae 248 and activates theAgrobacterium tumefaciens tra reporter system. Production of this compound in R. etli is dependent on two genes, named cinR and cinI, postulated to code for a transcriptional regulator and an autoinducer synthase, respectively. NMR analysis of the purified molecule indicates that the R. etli autoinducer produced by CinI is a saturated long chain 3-hydroxy-acyl-homoserine lactone, abbreviated as 3OH-(slc)-HSL. Usingcin-gusA fusions, expression ofcinI and cinR was shown to be growth phase-dependent. Deletion analysis of the cinIpromoter region indicates that a regulatory element negatively controlscinI expression. Mutational analysis revealed that expression of the cinI gene is positively regulated by the CinR/3OH-(slc)-HSL complex. Besides 3OH-(slc)-HSL, R. etliproduces at least six other autoinducer molecules, for which the structures have not yet been revealed, and of which the synthesis requires the previously identified raiI andraiR genes. At least three different autoinducers, including a compound co-migrating with 3OH-(slc)-HSL, are produced inR. etli bacteroids isolated from bean nodules. This is further substantiated by the observation that cinI andcinR are both expressed under symbiotic conditions. Acetylene reduction activity of nodules induced by the cinmutants was reduced with 60–70% compared with wild-type nodules, indicating that the R. etli 3OH-(slc)-HSL is involved in the symbiotic process. This was further confirmed by transmission electron microscopy of nodules induced by the wild type and thecinI mutant. Symbiosomes carrying cinI mutant bacteroids did not fully differentiate compared with wild-type symbiosomes. Finally, it was observed that the cinRgene and raiR control growth of R. etli.