| Wheat is one of the most widely cultivated and consumed cereal crops in the world. The yield and quality of wheat have a decisive influence on the quality of human life. The wheat production and consumption of China rank first in the world, but the quality is not satisfied, mainly for the poor quality of the secondary processing. The secondary processing quality of wheat is mainly determined by the characteristics of glutenin in storage protein, which is determined by the composition characteristics of high and low molecular weight glutenin subunit(LMW-GS). Many researches have shown that low molecular weight gluten subunits mainly affect the viscosity of wheat dough and ductility, which is the essence for bread-making and play an important role in the determination of end-use quality of common wheat,and high molecular weight glutenin subunits(HMW-GSs) decide the elasticity of wheat dough. Identification of novel glutenin resources,and accurate and fast identification of LMW-GS composition have been a challenge in modern wheat breeding. The wheat landraces derived from the Yangtze-River region possess rich allelic variations of gluten and new gluten genes. In the present study, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry(MALDI-TOF-MS) procedure was used to analyze 478 landraces of bread wheat collected from the Yangtze-River region of China,and a high molecular weight gluten subunit gene 1Dy12.7 was cloned, the main results were as follows: 1. Allelic variation of LMW-GS composition in wheat landraces of the Yangtze-River regionIn the current, a newly established MALDI-TOF-MS procedure was used to analyse 478 landraces of bread wheat collected from the Yangtze-River region of China. Results indicated that 17 alleles at three loci: Glu-A3, Glu-B3 and Glu-D3 were identified,resulting in 87 different allele combinations. Out of the 17 alleles detected at all the Glu-3 loci, five belonged to Glu-A3, seven to Glu-B3 and five to Glu-D3 locus. MALDI-TOF-MS indicated Glu-A3a/c was present in 72.80% of the landraces, Glu-A3 b in 8.37%,Glu-A3 d in 8.37%,Glu-A3 f in 5.23% and Glu-A3 e in 3.56%. Seven types of alleles were identified at the Glu-B3 locus: Glu-B3d/i(25.52%), Glu-B3b(21.34%), Glu-B3c(16.95%), Glu-B3h(13.81%), Glu-B3f(8.37%), Glu-B3a(8.16%), and Glu-B3g(5.23%). Five types of Glu-D3 alleles were detected: Glu-D3a(58.37%), Glu-D3c(22.59%), Glu-D3d(15.48%), Glu-D3b(3.35%) and Glu-D3f(0.21%). Four new alleles represented by abnormal MALDI-TOF-MS spectrum patterns were identified at the Glu-A3 and the Glu-B3 locus: Glu-A3d1, Glu-A3d2, Glu-A3d3, Glu-B3 p. More detailed studies are needed in order to further characterize these alleles and find their potential usage for wheat improvement. 2. Molecular cloning of HMW-GS gene 1Dy12.7A novel Glu-1Dy HMW-GS gene,designated as 1Dy12.7,was identified and cloned from Chinese wheat landrace Luosimai. The 1Dy12.7 gene was deposited as the NCBInr Acc. KR262519. The full open reading frame of 1Dy12.7 was 1977 bp, coding for 658 amino acid residues. The encoding protein possesses four representative primary regions of HMW-GS(a signal peptide, a N-terminal domain, a central repetitive domain, and a C-terminal domain). The deduced molecular weight of 1Dy12.7 subunit(68,400 Da) was dramatically consistent with the result identified by MALDI-TOF-MS(68,407 Da). Comparing with the most similar Glu-1Dy alleles previously published, the 1Dy12.7 gene sequence had a total of 17 SNPs and 2 Indels. The secondary structure prediction indicated that 1Dy12.7 subunit has similar proportion of α-helix, β-turn, and β-bend to those of 1Dy10(X12929). The phylogenetic analysis illustrated that the x- and y-type subunits of glutenins were well separated, and 1Dy12.7 were clustered with the other Glu-1Dy alleles. The results revealed that 1Dy12.7 subunit have potential to strengthen gluten polymer interactions, and is valuable genetic resource for wheat quality breeding. |
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