title: New insights into the origin of the B genome of hexaploid wheat: evolutionary relationships at the SPA genomic region with the S genome of the diploid relative Aegilops speltoides.
abstract: BACKGROUND
  Several studies suggested that the diploid ancestor of the B genome of tetraploid and hexaploid wheat species belongs to the Sitopsis section, having Aegilops speltoides (SS, 2n = 14) as the closest identified relative. However molecular relationships based on genomic sequence comparison, including both coding and non-coding DNA, have never been investigated. In an attempt to clarify these relationships, we compared, in this study, sequences of the Storage Protein Activator (SPA) locus region of the S genome of Ae. speltoides (2n = 14) to that of the A, B and D genomes co-resident in the hexaploid wheat species (Triticum aestivum, AABBDD, 2n = 42).
  
  
  RESULTS
  Four BAC clones, spanning the SPA locus of respectively the A, B, D and S genomes, were isolated and sequenced. Orthologous genomic regions were identified as delimited by shared non-transposable elements and non-coding sequences surrounding the SPA gene and correspond to 35,268, 22,739, 43,397 and 53,919 bp for the A, B, D and S genomes, respectively. Sequence length discrepancies within and outside the SPA orthologous regions are the result of non-shared transposable elements (TE) insertions, all of which inserted after the progenitors of the four genomes divergence.
  
  
  CONCLUSIONS
  On the basis of conserved sequence length as well as identity of the shared non-TE regions and the SPA coding sequence, Ae speltoides appears to be more evolutionary related to the B genome of T. aestivum than the A and D genomes. However, the differential insertions of TEs, none of which are conserved between the two genomes led to the conclusion that the S genome of Ae. speltoides has diverged very early from the progenitor of the B genome which remains to be identified.
authors.affiliation: UMR INRA 1165 - CNRS 8114 UEVE - Unité de Recherche en Génomique Végétale, 2, rue Gaston Crémieux, CP5708, 91057 Evry cedex, France. jsalse@clermont.inra.fr
authors.forename: Jérome
authors.initials: J
authors.lastname: Salse
authors.forename: Véronique
authors.initials: V
authors.lastname: Chagué
authors.forename: Stéphanie
authors.initials: S
authors.lastname: Bolot
authors.forename: Ghislaine
authors.initials: G
authors.lastname: Magdelenat
authors.forename: Cécile
authors.initials: C
authors.lastname: Huneau
authors.forename: Caroline
authors.initials: C
authors.lastname: Pont
authors.forename: Harry
authors.initials: H
authors.lastname: Belcram
authors.forename: Arnaud
authors.initials: A
authors.lastname: Couloux
authors.forename: Soazic
authors.initials: S
authors.lastname: Gardais
authors.forename: Aurélie
authors.initials: A
authors.lastname: Evrard
authors.forename: Béatrice
authors.initials: B
authors.lastname: Segurens
authors.forename: Mathieu
authors.initials: M
authors.lastname: Charles
authors.forename: Catherine
authors.initials: C
authors.lastname: Ravel
authors.forename: Sylvie
authors.initials: S
authors.lastname: Samain
authors.forename: Gilles
authors.initials: G
authors.lastname: Charmet
authors.forename: Nathalie
authors.initials: N
authors.lastname: Boudet
authors.forename: Boulos
authors.initials: B
authors.lastname: Chalhoub
mesh_terms: D022202:Chromosomes, Artificial, Bacterial; D003001:Cloning, Molecular; D004251:DNA Transposable Elements; D004171:Diploidy; D019143:Evolution, Molecular; D018745:Genome, Plant / Q000235:genetics*; D010802:Phylogeny; D010940:Plant Proteins; D006109:Poaceae / Q000235:genetics*; D017422:Sequence Analysis, DNA; D014908:Triticum / Q000235:genetics*
chemical_list: D004251:DNA Transposable Elements; D010940:Plant Proteins; C105777:storage protein activator