title: The glutamine synthetase gene family in Populus.
abstract: BACKGROUND
  Glutamine synthetase (GS; EC: 6.3.1.2, L-glutamate: ammonia ligase ADP-forming) is a key enzyme in ammonium assimilation and metabolism of higher plants. The current work was undertaken to develop a more comprehensive understanding of molecular and biochemical features of GS gene family in poplar, and to characterize the developmental regulation of GS expression in various tissues and at various times during the poplar perennial growth.
  
  
  RESULTS
  The GS gene family consists of 8 different genes exhibiting all structural and regulatory elements consistent with their roles as functional genes. Our results indicate that the family members are organized in 4 groups of duplicated genes, 3 of which code for cytosolic GS isoforms (GS1) and 1 which codes for the choroplastic GS isoform (GS2). Our analysis shows that Populus trichocarpa is the first plant species in which it was observed the complete GS family duplicated. Detailed expression analyses have revealed specific spatial and seasonal patterns of GS expression in poplar. These data provide insights into the metabolic function of GS isoforms in poplar and pave the way for future functional studies.
  
  
  CONCLUSIONS
  Our data suggest that GS duplicates could have been retained in order to increase the amount of enzyme in a particular cell type. This possibility could contribute to the homeostasis of nitrogen metabolism in functions associated to changes in glutamine-derived metabolic products. The presence of duplicated GS genes in poplar could also contribute to diversification of the enzymatic properties for a particular GS isoform through the assembly of GS polypeptides into homo oligomeric and/or hetero oligomeric holoenzymes in specific cell types.
authors.affiliation: Departamento de Biología Molecular y Bioquímica, Instituto Andaluz de Biotecnología, Universidad de Málaga, 29071-Málaga, Spain.
authors.forename: Vanessa
authors.initials: V
authors.lastname: Castro-Rodríguez
authors.forename: Angel
authors.initials: A
authors.lastname: García-Gutiérrez
authors.forename: Javier
authors.initials: J
authors.lastname: Canales
authors.forename: Concepción
authors.initials: C
authors.lastname: Avila
authors.forename: Edward G
authors.initials: EG
authors.lastname: Kirby
authors.forename: Francisco M
authors.initials: FM
authors.lastname: Cánovas
mesh_terms: D055028:Comparative Genomic Hybridization; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D020131:Genes, Duplicate; D005974:Glutamate-Ammonia Ligase / Q000235:genetics*; D007527:Isoenzymes / Q000235:genetics; D005810:Multigene Family; D010802:Phylogeny; D032107:Populus / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D012621:Seasons
chemical_list: D007527:Isoenzymes; D005974:Glutamate-Ammonia Ligase