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.
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 Mr of 85,782 Da whereas 1Dx5.1*t comprises 2526 bp encoding 842 residues with Mr of 87,663 Da. The deduced Mr'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-T or 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, 1Dx2t, 1Dx1.6t, 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.
Zhang
Yanzhen
Y
Key Laboratory of Genetics and Biotechnology, College of Life Sciences, Capital Normal University, Beijing, China.
Li
Xiaohui
X
Wang
Aili
A
An
Xueli
X
Zhang
Qian
Q
Pei
Yuhe
Y
Gao
Liyan
L
Ma
Wujun
W
Appels
Rudi
R
Yan
Yueming
Y
D000595:Amino Acid Sequence; D001483:Base Sequence; D005075:Biological Evolution; D003001:Cloning, Molecular; D004926:Escherichia coli; D017353:Gene Deletion; D017343:Genes, Plant; D005822:Genetic Vectors; D005983:Glutens / Q000737:chemistry / Q000235:genetics*; D008969:Molecular Sequence Data; D008970:Molecular Weight; D016366:Open Reading Frames / Q000235:genetics; D010802:Phylogeny; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics*; D020641:Polymorphism, Single Nucleotide / Q000235:genetics; D021122:Protein Subunits / Q000737:chemistry / Q000235:genetics; D014908:Triticum / Q000235:genetics*
D010940:Plant Proteins; D021122:Protein Subunits; D005983:Glutens; C037302:glutenin