title: Transcriptome analysis of a bacterially induced basal and hypersensitive response of Medicago truncatula.
abstract: Research using the well-studied model legume Medicago truncatula has largely focused on rhizobium symbiosis, while little information is currently available for this species on pathogen-induced transcriptome changes. We have performed a transcriptome analysis of this species with the objective of studying the basal (BR, no visible symptoms) and hypersensitive response (HR, plant cell death) in its leaves at 6 and at 24 h after infection by HR-negative (hrcC mutant) and HR-inducing Pseudomonas syringae pv. syringae strains, respectively. Although there were no visible symptoms at the BR, the alterations in gene expression were comparable to those found with the HR. Both responses resulted in the transcriptional alteration of hundreds of plant genes; however, the responses in the HR were usually more intense. The reactions to HR-inducing and HR-negative bacterial strains were significantly overlapping. Parallel up- or down-regulation of genes with the same function occurred frequently. However, some plant processes were regulated in one direction; for example, most of the protein synthesis-related genes were activated and all of the photosynthetic/chloroplast genes were suppressed during BR. The possible roles of several functional classes (e.g., cell rescue, signaling, defense, cell death, etc.) of transcriptionally altered genes are discussed. The results of the comparison with available mycorrhizal and nodule expression data show that there is a significant overlap between nodulation and the leaf defense response and that during the early stage of the nodulation in roots, Sinorhizobium meliloti induces a fluctuation in the transcription of BR- and HR-responsive genes.
authors.affiliation: Plant Protection Institute of the Hungarian Academy of Sciences, Herman O. 15, P.O. Box 102, Budapest, Hungary. zboz@nki.hu
authors.forename: Zoltán
authors.initials: Z
authors.lastname: Bozsó
authors.forename: Nicolas
authors.initials: N
authors.lastname: Maunoury
authors.forename: Agnes
authors.initials: A
authors.lastname: Szatmari
authors.forename: Peter
authors.initials: P
authors.lastname: Mergaert
authors.forename: Péter G
authors.initials: PG
authors.lastname: Ott
authors.forename: László R
authors.initials: LR
authors.lastname: Zsíros
authors.forename: Erika
authors.initials: E
authors.lastname: Szabó
authors.forename: Eva
authors.initials: E
authors.lastname: Kondorosi
authors.forename: Zoltán
authors.initials: Z
authors.lastname: Klement
mesh_terms: D001425:Bacterial Outer Membrane Proteins / Q000235:genetics; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant; D005798:Genes, Bacterial; D017343:Genes, Plant; D054884:Host-Pathogen Interactions / Q000235:genetics / Q000502:physiology; D046913:Medicago truncatula / Q000235:genetics* / Q000378:metabolism / Q000382:microbiology*; D009154:Mutation; D038821:Mycorrhizae / Q000502:physiology; D020411:Oligonucleotide Array Sequence Analysis; D010935:Plant Diseases / Q000235:genetics / Q000382:microbiology; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D055170:Plant Root Nodulation / Q000235:genetics / Q000502:physiology; D044224:Pseudomonas syringae / Q000235:genetics / Q000472:pathogenicity; D015398:Signal Transduction / Q000235:genetics; D013559:Symbiosis / Q000235:genetics / Q000502:physiology; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
chemical_list: D001425:Bacterial Outer Membrane Proteins; D010940:Plant Proteins; D014157:Transcription Factors; C077559:hrpH protein, Pseudomonas syringae