Allelic Variation and Genetic Diversity at HMW Glutenin Subunits Loci in Yunnan, Tibetan and Xinjiang Wheat

Allelic variation and genetic diversity at HMW glutenin subunits loci, Glu-A1, Glu-B1and Glu-D1 were investigated in 64 accessions of three unique wheats of western Chinausing sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE). Two HMWglutenin patterns (i.e., null, 7+8, 2+12 and null, 7, 2+12) in 34 Yunnan wheataccessions, 3 HMW glutenin patterns (i.e., null, 7+8, 2+12; null, 6+8, 2+12 andnull, 7+8, 2) in 24 Tibetan accessions and 1 HMW glutenin pattern (null, 7, 2+12) in6 Xinjiang wheat accessions were found. The Tibetan accession TB18 was found to be witha rare subunit 2 encoded by Glu-D1. A total of 4 (i.e., Glu-A1c, Glu-B1a, Glu-B1b andGlu-D1a), 5 (i.e., Glu-A1c, Glu-B1d, Glu-B1b, Glu-D1a and Glu-D1) and 3 alleles (i.e.,Glu-A1c, Glu-B1a and Glu-D1a) at Glu-1 locus were identified among Yunnan, Tibetan andXinjiang unique wheat accessions, respectively. For Yunnan wheat, Tibetan wheat andXinjiang wheat, the Neis mean genetic variation indexes were 0.1574, 0.1366 and 0,respectively, which might indicate the higher genetic diversity at HMW glutenin subunitsloci of Yunnan and Tibetan wheat accessions as compared to that of Xinjiang wheataccessions. Among the three genomes of hexaploid wheats of western China, the highestNeis genetic variation index was appeared in B genome with the mean value of 0.2674,while the indexes for genomes A and D were 0 and 0.0270, respectively. It might bereasonable to indicate that Glu-B1 showed the highest, Glu-D1 the intermediate and Glu-A1 always the lowest genetic diversity.

Isolation and Molecular Characterization of High Molecular Weight Glutenin Subunit Genes 1Bx13 and 1By16 from Hexaploid Wheat

The high molecular weight glutenin subunit （HMW-GS） pair 1Bx13＋1By16 are recognized to positively correlate with bread-making quality; however, their molecular data remain unknown. In order to reveal the mechanism by which 1By16 and 1Bx13 creates high quality, their open reading frames （ORFs） were amplified from common wheat Atlas66 and Jimai 20 using primers that were designed based on published sequences of HMW glutenin genes. The ORF of 1By16 was 2220bp, deduced into 738 amino acid residues with seven cysteines including 59 hexapeptides and 22 nanopeptides motifs. The ORF of 1Bx13 was 2385bp, deduced into 795 amino acid residues with four cysteines including 68 hexapeptides, 25 nanopeptides and six tripepUdes motifs. We found that 1By16 was the largest y-type HMW glutenin gene described to date in common wheat. The 1By16 had 36 amino acid residues inserted in the central repetitive domain compared with 1By15. Expression in bacteria and western-blot tests confirmed that the sequence cloned was the ORF of HMW-GS 1By16, and that 1Bx13 was one of the largest 1Bx genes that have been described so far in common wheat, exhibiting a hexapeptide （PGQGQQ） insertion in the end of central repetitive domain compared with 1Bx7. A phylogenetic tree based on the deduced full-length amino acid sequence alignment of the published HMW-GS genes showed that the 1By16 was clustered with Glu-1B-2, and that the 1Bx13 was clustered with Glu-1B-1 alleles.

A genetic evidence of chromosomal fragment from bridge parent existing in substitution lines between two common wheat varieties

Locating of important agronomic genes onto chromosome is helpful for efficient development of new wheat varieties. Wheat chromosome substitution lines between two varieties have been widely used for locating genes because of their distinctive advantages in genetic analysis, compared with the aneuploid genetic materials. Apart from the substituted chromosome, the other chromosomes between the substitution lines and their recipient parent should be identical, which eases the gene locating practice. In this study, a set of chromosome substitution lines with cv. Wichita （WI） as the recipient parent and cv. Cheyenne （CNN） as the donor parent were studied for the composition of high molecular weight glutenin subunits （HMW-GS） as well as a range of agronomic important traits. Results revealed that the substitution lines of WI（CNN5D）, WI（CNN6A） and WI（CNN7B） had higher plant heights than the two parents of WI and CNN, and WI（CNN3D） had later maturity than the parents. By sodium dodecyl sulfate polyacrylamide gel electrophoresis （SDS-PAGE） and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry （MALDI-TOF-MS） analysis, a substitution line WI（CNN5B） was found to contain different HMW-GS patterns from its two parents, in which 1 By9 was replaced by 1 By8 on chromosome 1BL. Simple sequence repeat （SSR） analysis confirmed that the variation on 1BL in WI（CNN5B） was originated from Chinese Spring （CS）. It is concluded that chromosomal fragments from bridge material and donor parent were quite often retained in intracultivaral chromosome substitution lines except the substituting chromosomes.

Molecular Characterization of Two Silenced y-type Genes for Glu-B1 in Triticum aestivum ssp.yunnanese and ssp.tibetanum

The high molecular weight glutenin subunits （HMW-GSs） are a major class of common wheat storage proteins. The breadmaking quality of common wheat flour is influenced by the composition of HMW-GSs. In the present study, two unexpressed 1 By genes from Triticum aesitvum L.ssp.yunnanese AS332 and T. aesitvum ssp.tibetanurn AS908 were respectively cloned and characterized. The results indicated that both of the silenced 1By genes in AS332 and AS908 were 1Byg. In contrast to previously reported mechanisms for silenced genes lAx and lay, which was due to the insertion of transposon elements or the presence of premature stop codon via base substitution of C→T transition in trinucleotides CAA or CAG, the silence of 1By9 genes was caused by premature stop codons via the deletion of base A in trinucleotide CA.A, which lead to frameshift mutation and indirectly produced several premature stop codons （TAG） downstream of the coding sequence.