title: Transcriptomics of actinorhizal symbioses reveals homologs of the whole common symbiotic signaling cascade.
abstract: Comparative transcriptomics of two actinorhizal symbiotic plants, Casuarina glauca and Alnus glutinosa, was used to gain insight into their symbiotic programs triggered following contact with the nitrogen-fixing actinobacterium Frankia. Approximately 14,000 unigenes were recovered in roots and 3-week-old nodules of each of the two species. A transcriptomic array was designed to monitor changes in expression levels between roots and nodules, enabling the identification of up- and down-regulated genes as well as root- and nodule-specific genes. The expression levels of several genes emblematic of symbiosis were confirmed by quantitative polymerase chain reaction. As expected, several genes related to carbon and nitrogen exchange, defense against pathogens, or stress resistance were strongly regulated. Furthermore, homolog genes of the common and nodule-specific signaling pathways known in legumes were identified in the two actinorhizal symbiotic plants. The conservation of the host plant signaling pathway is all the more surprising in light of the lack of canonical nod genes in the genomes of its bacterial symbiont, Frankia. The evolutionary pattern emerging from these studies reinforces the hypothesis of a common genetic ancestor of the Fabid (Eurosid I) nodulating clade with a genetic predisposition for nodulation.
authors.affiliation: Equipe Rhizogenèse, Institut de Recherche pour le Développement, UMR Diversité Adaptation et Développement des Plantes, 34394 Montpellier cedex 5, France.
authors.forename: Valérie
authors.initials: V
authors.lastname: Hocher
authors.forename: Nicole
authors.initials: N
authors.lastname: Alloisio
authors.forename: Florence
authors.initials: F
authors.lastname: Auguy
authors.forename: Pascale
authors.initials: P
authors.lastname: Fournier
authors.forename: Patrick
authors.initials: P
authors.lastname: Doumas
authors.forename: Petar
authors.initials: P
authors.lastname: Pujic
authors.forename: Hassen
authors.initials: H
authors.lastname: Gherbi
authors.forename: Clothilde
authors.initials: C
authors.lastname: Queiroux
authors.forename: Corinne
authors.initials: C
authors.lastname: Da Silva
authors.forename: Patrick
authors.initials: P
authors.lastname: Wincker
authors.forename: Philippe
authors.initials: P
authors.lastname: Normand
authors.forename: Didier
authors.initials: D
authors.lastname: Bogusz
mesh_terms: D029661:Alnus / Q000235:genetics / Q000382:microbiology; D029401:Betulaceae / Q000235:genetics* / Q000382:microbiology*; D030541:Databases, Genetic; D015536:Down-Regulation / Q000235:genetics; D040161:Frankia / Q000502:physiology*; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant / Q000235:genetics; D008565:Membrane Proteins / Q000378:metabolism; D008954:Models, Biological; D008969:Molecular Sequence Data; D020411:Oligonucleotide Array Sequence Analysis; D010940:Plant Proteins / Q000378:metabolism; D055170:Plant Root Nodulation / Q000235:genetics; D015203:Reproducibility of Results; D012689:Sequence Homology, Nucleic Acid; D015398:Signal Transduction / Q000235:genetics*; D013559:Symbiosis / Q000235:genetics*; D014158:Transcription, Genetic; D015854:Up-Regulation / Q000235:genetics
chemical_list: D008565:Membrane Proteins; D010940:Plant Proteins; C045625:nodulin