title: The lipopolysaccharide of Sinorhizobium meliloti suppresses defense-associated gene expression in cell cultures of the host plant Medicago truncatula.
abstract: In the establishment of symbiosis between Medicago truncatula and the nitrogen-fixing bacterium Sinorhizobium meliloti, the lipopolysaccharide (LPS) of the microsymbiont plays an important role as a signal molecule. It has been shown in cell cultures that the LPS is able to suppress an elicitor-induced oxidative burst. To investigate the effect of S. meliloti LPS on defense-associated gene expression, a microarray experiment was performed. For evaluation of the M. truncatula microarray datasets, the software tool MapMan, which was initially developed for the visualization of Arabidopsis (Arabidopsis thaliana) datasets, was adapted by assigning Medicago genes to the ontology originally created for Arabidopsis. This allowed functional visualization of gene expression of M. truncatula suspension-cultured cells treated with invertase as an elicitor. A gene expression pattern characteristic of a defense response was observed. Concomitant treatment of M. truncatula suspension-cultured cells with invertase and S. meliloti LPS leads to a lower level of induction of defense-associated genes compared to induction rates in cells treated with invertase alone. This suppression of defense-associated transcriptional rearrangement affects genes induced as well as repressed by elicitation and acts on transcripts connected to virtually all kinds of cellular processes. This indicates that LPS of the symbiont not only suppresses fast defense responses as the oxidative burst, but also exerts long-term influences, including transcriptional adjustment to pathogen attack. These data indicate a role for LPS during infection of the plant by its symbiotic partner.
authors.affiliation: Proteom und Metabolomforschung, Fakultät für Biologie, Universität Bielefeld, D-33501 Bielefeld, Germany.
authors.forename: Verena
authors.initials: V
authors.lastname: Tellström
authors.forename: Björn
authors.initials: B
authors.lastname: Usadel
authors.forename: Oliver
authors.initials: O
authors.lastname: Thimm
authors.forename: Mark
authors.initials: M
authors.lastname: Stitt
authors.forename: Helge
authors.initials: H
authors.lastname: Küster
authors.forename: Karsten
authors.initials: K
authors.lastname: Niehaus
mesh_terms: D002478:Cells, Cultured; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant / Q000187:drug effects* / Q000502:physiology; D008070:Lipopolysaccharides / Q000494:pharmacology*; D046913:Medicago truncatula / Q000166:cytology / Q000187:drug effects* / Q000235:genetics* / Q000382:microbiology; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D016962:Sinorhizobium meliloti; D043324:beta-Fructofuranosidase / Q000378:metabolism
chemical_list: D008070:Lipopolysaccharides; D010940:Plant Proteins; D043324:beta-Fructofuranosidase