title: Expansion of the gamma-gliadin gene family in Aegilops and Triticum.
abstract: BACKGROUND
  The gamma-gliadins are considered to be the oldest of the gliadin family of storage proteins in Aegilops/Triticum. However, the expansion of this multigene family has not been studied in an evolutionary perspective.
  
  
  RESULTS
  We have cloned 59 gamma-gliadin genes from Aegilops and Triticum species (Aegilops caudata L., Aegilops comosa Sm. in Sibth. & Sm., Aegilops mutica Boiss., Aegilops speltoides Tausch, Aegilops tauschii Coss., Aegilops umbellulata Zhuk., Aegilops uniaristata Vis., and Triticum monococcum L.) representing eight different genomes: Am, B/S, C, D, M, N, T and U. Overall, 15% of the sequences contained internal stop codons resulting in pseudogenes, but this percentage was variable among genomes, up to over 50% in Ae. umbellulata. The most common length of the deduced protein, including the signal peptide, was 302 amino acids, but the length varied from 215 to 362 amino acids, both obtained from Ae. speltoides. Most genes encoded proteins with eight cysteines. However, all Aegilops species had genes that encoded a gamma-gliadin protein of 302 amino acids with an additional cysteine. These conserved nine-cysteine gamma-gliadins may perform a specific function, possibly as chain terminators in gluten network formation in protein bodies during endosperm development. A phylogenetic analysis of gamma-gliadins derived from Aegilops and Triticum species and the related genera Lophopyrum, Crithopsis, and Dasypyrum showed six groups of genes. Most Aegilops species contained gamma-gliadin genes from several of these groups, which also included sequences from the genera Lophopyrum, Crithopsis, and Dasypyrum. Hordein and secalin sequences formed separate groups.
  
  
  CONCLUSIONS
  We present a model for the evolution of the gamma-gliadins from which we deduce that the most recent common ancestor (MRCA) of Aegilops/Triticum-Dasypyrum-Lophopyrum-Crithopsis already had four groups of gamma-gliadin sequences, presumably the result of two rounds of duplication of the locus.
authors.affiliation: Wageningen UR Plant Breeding, Wageningen UR, P,O, Box 16, Wageningen, NL-6700 AA, The Netherlands.
authors.forename: Svetlana V
authors.initials: SV
authors.lastname: Goryunova
authors.forename: Elma M J
authors.initials: EM
authors.lastname: Salentijn
authors.forename: Nadejda N
authors.initials: NN
authors.lastname: Chikida
authors.forename: Elena Z
authors.initials: EZ
authors.lastname: Kochieva
authors.forename: Ingrid M
authors.initials: IM
authors.lastname: van der Meer
authors.forename: Luud J W J
authors.initials: LJ
authors.lastname: Gilissen
authors.forename: Marinus J M
authors.initials: MJ
authors.lastname: Smulders
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D016000:Cluster Analysis; D019143:Evolution, Molecular; D020440:Gene Duplication; D014644:Genetic Variation; D018745:Genome, Plant / Q000235:genetics; D005903:Gliadin / Q000145:classification / Q000235:genetics*; D008957:Models, Genetic; D008969:Molecular Sequence Data; D005810:Multigene Family; D010802:Phylogeny; D006109:Poaceae / Q000235:genetics*; D011544:Pseudogenes / Q000235:genetics; D012641:Selection, Genetic; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid; D014908:Triticum / Q000235:genetics*
chemical_list: D005903:Gliadin