Novel x-Type High-Molecular-Weight Glutenin Genes From Aegilops tauschii and Their Implications on the Wheat Origin and Evolution Mechanism of Glu-D1-1 Proteins
Zhang, Y., Li, X., Wang, A., An, X.L., Zhang, Q., Pei, Y-H, Gao, L., Ma, W., Appels, R. and Yan, Y. (2008) Novel x-Type High-Molecular-Weight Glutenin Genes From Aegilops tauschii and Their Implications on the Wheat Origin and Evolution Mechanism of Glu-D1-1 Proteins. Genetics, 178 (1). pp. 23-33.
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Two new x-type high-molecular-weight glutenin subunits with similar size to 1Dx5, designated 1Dx5* t and 1Dx5.1* t in Aegilops tauschii, were identified by SDS-PAGE, RP-HPLC, and MALDI-TOF-MS. The coding sequences were isolated by AS-PCR and the complete ORFs were obtained. Allele 1Dx5* t consists of 2481 bp encoding a mature protein of 827 residues with deduced M r of 85,782 Da whereas 1Dx5.1* t comprises 2526 bp encoding 842 residues with M r of 87,663 Da. The deduced M r's of both genes were consistent with those determined by MALDI-TOF-MS. Molecular structure analysis showed that the repeat motifs of 1Dx5* t were correspondingly closer to the consensus compared to 1Dx5.1* t and 1Dx5 subunits. A total of 11 SNPs (3 in 1Dx5* t and 8 in 1Dx5. 1* t) and two indels in 1Dx5* t were identified, among which 8 SNPs were due to C-Tor A-G transitions (an average of 73%). Expression of the cloned ORFs and N-terminal sequencing confirmed the authenticities of the two genes. Interestingly, several hybrid clones of 1Dx5* t expressed a slightly smaller protein relative to the authentic subunit present in seed proteins; this was confirmed to result from a deletion of 180 bp through illegitimate recombination as well as an in-frame stop codon. Network analysis demonstrated that 1Dx5* t, 1Dx2 t, 1Dx1.6 t, and 1Dx2.2* represent a root within a network and correspond to the common ancestors of the other Glu-D-1-1 alleles in an associated star-like phylogeny, suggesting that there were at least four independent origins of hexaploid wheat. In addition to unequal homologous recombination, duplication and deletion of large fragments occurring in Glu-D-1-1 alleles were attributed to illegitimate recombination.
|Publication Type:||Journal Article|
|Publisher:||Genetics Society of America|
|Copyright:||Copyright © 2008 by the Genetics Society of America.|
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