The gene space in wheat: the complete γ-gliadin gene family from the wheat cultivar Chinese Spring

The complete set of unique gamma-gliadin genes is described for the wheat cultivar Chinese Spring using a combination of expressed sequence tag (EST) and Roche 454 DNA sequences. Assemblies of Chinese Spring ESTs yielded 11 different gamma-gliadin gene sequences. Two of the sequences encode identical polypeptides and are assumed to be the result of a recent gene duplication. One gene has a 3' coding mutation that changes the reading frame in the final eight codons. A second assembly of Chinese Spring gamma-gliadin sequences was generated using Roche 454 total genomic DNA sequences. The 454 assembly confirmed the same 11 active genes as the EST assembly plus two pseudogenes not represented by ESTs. These 13 gamma-gliadin sequences represent the complete unique set of gamma-gliadin genes for cv Chinese Spring, although not ruled out are additional genes that are exact duplications of these 13 genes. A comparison with the ESTs of two other hexaploid cultivars (Butte 86 and Recital) finds that the most active genes are present in all three cultivars, with exceptions likely due to too few ESTs for detection in Butte 86 and Recital. A comparison of the numbers of ESTs per gene indicates differential levels of expression within the gamma-gliadin gene family. Genome assignments were made for 6 of the 13 Chinese Spring gamma-gliadin genes, i.e., one assignment from a match to two gamma-gliadin genes found within a tetraploid wheat A genome BAC and four genes that match four distinct gamma-gliadin sequences assembled from Roche 454 sequences from Aegilops tauschii, the hexaploid wheat D-genome ancestor.