title: Identification of potential transcriptional regulators of actinorhizal symbioses in Casuarina glauca and Alnus glutinosa.
abstract: BACKGROUND
  Trees belonging to the Casuarinaceae and Betulaceae families play an important ecological role and are useful tools in forestry for degraded land rehabilitation and reforestation. These functions are linked to their capacity to establish symbiotic relationships with a nitrogen-fixing soil bacterium of the genus Frankia. However, the molecular mechanisms controlling the establishment of these symbioses are poorly understood. The aim of this work was to identify potential transcription factors involved in the establishment and functioning of actinorhizal symbioses.
  
  
  RESULTS
  We identified 202 putative transcription factors by in silico analysis in 40 families in Casuarina glauca (Casuarinaceae) and 195 in 35 families in Alnus glutinosa (Betulaceae) EST databases. Based on published transcriptome datasets and quantitative PCR analysis, we found that 39% and 26% of these transcription factors were regulated during C. glauca and A. glutinosa-Frankia interactions, respectively. Phylogenetic studies confirmed the presence of common key transcription factors such as NSP, NF-YA and ERN-related proteins involved in nodule formation in legumes, which confirm the existence of a common symbiosis signaling pathway in nitrogen-fixing root nodule symbioses. We also identified an actinorhizal-specific transcription factor belonging to the zinc finger C1-2i subfamily we named CgZF1 in C. glauca and AgZF1 in A. glutinosa.
  
  
  CONCLUSIONS
  We identified putative nodulation-associated transcription factors with particular emphasis on members of the GRAS, NF-YA, ERF and C2H2 families. Interestingly, comparison of the non-legume and legume TF with signaling elements from actinorhizal species revealed a new subgroup of nodule-specific C2H2 TF that could be specifically involved in actinorhizal symbioses. In silico identification, transcript analysis, and phylogeny reconstruction of transcription factor families paves the way for the study of specific molecular regulation of symbiosis in response to Frankia infection.
authors.forename: Issa
authors.initials: I
authors.lastname: Diédhiou
authors.forename: Alexandre
authors.initials: A
authors.lastname: Tromas
authors.forename: Maïmouna
authors.initials: M
authors.lastname: Cissoko
authors.forename: Krystelle
authors.initials: K
authors.lastname: Gray
authors.forename: Boris
authors.initials: B
authors.lastname: Parizot
authors.forename: Amandine
authors.initials: A
authors.lastname: Crabos
authors.forename: Nicole
authors.initials: N
authors.lastname: Alloisio
authors.forename: Pascale
authors.initials: P
authors.lastname: Fournier
authors.forename: Lorena
authors.initials: L
authors.lastname: Carro
authors.forename: Sergio
authors.initials: S
authors.lastname: Svistoonoff
authors.forename: Hassen
authors.initials: H
authors.lastname: Gherbi
authors.forename: Valérie
authors.initials: V
authors.lastname: Hocher
authors.forename: Diaga
authors.initials: D
authors.lastname: Diouf
authors.forename: Laurent
authors.initials: L
authors.lastname: Laplaze
authors.forename: Antony
authors.initials: A
authors.lastname: Champion
mesh_terms: D029661:Alnus / Q000382:microbiology; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D004269:DNA, Bacterial / Q000235:genetics / Q000378:metabolism; D018076:DNA, Complementary / Q000235:genetics / Q000378:metabolism; D040161:Frankia / Q000235:genetics* / Q000378:metabolism; D019684:Magnoliopsida / Q000382:microbiology*; D008969:Molecular Sequence Data; D018517:Plant Roots / Q000378:metabolism / Q000382:microbiology; D017422:Sequence Analysis, DNA; D013559:Symbiosis / Q000235:genetics*
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D018076:DNA, Complementary