title: Composition and functional analysis of low-molecular-weight glutenin alleles with Aroona near-isogenic lines of bread wheat.
abstract: BACKGROUND
  Low-molecular-weight glutenin subunits (LMW-GS) strongly influence the bread-making quality of bread wheat. These proteins are encoded by a multi-gene family located at the Glu-A3, Glu-B3 and Glu-D3 loci on the short arms of homoeologous group 1 chromosomes, and show high allelic variation. To characterize the genetic and protein compositions of LMW-GS alleles, we investigated 16 Aroona near-isogenic lines (NILs) using SDS-PAGE, 2D-PAGE and the LMW-GS gene marker system. Moreover, the composition of glutenin macro-polymers, dough properties and pan bread quality parameters were determined for functional analysis of LMW-GS alleles in the NILs.
  
  
  RESULTS
  Using the LMW-GS gene marker system, 14-20 LMW-GS genes were identified in individual NILs. At the Glu-A3 locus, two m-type and 2-4 i-type genes were identified and their allelic variants showed high polymorphisms in length and nucleotide sequences. The Glu-A3d allele possessed three active genes, the highest number among Glu-A3 alleles. At the Glu-B3 locus, 2-3 m-type and 1-3 s-type genes were identified from individual NILs. Based on the different compositions of s-type genes, Glu-B3 alleles were divided into two groups, one containing Glu-B3a, B3b, B3f and B3g, and the other comprising Glu-B3c, B3d, B3h and B3i. Eight conserved genes were identified among Glu-D3 alleles, except for Glu-D3f. The protein products of the unique active genes in each NIL were detected using protein electrophoresis. Among Glu-3 alleles, the Glu-A3e genotype without i-type LMW-GS performed worst in almost all quality properties. Glu-B3b, B3g and B3i showed better quality parameters than the other Glu-B3 alleles, whereas the Glu-B3c allele containing s-type genes with low expression levels had an inferior effect on bread-making quality. Due to the conserved genes at Glu-D3 locus, Glu-D3 alleles showed no significant differences in effects on all quality parameters.
  
  
  CONCLUSIONS
  This work provided new insights into the composition and function of 18 LMW-GS alleles in bread wheat. The variation of i-type genes mainly contributed to the high diversity of Glu-A3 alleles, and the differences among Glu-B3 alleles were mainly derived from the high polymorphism of s-type genes. Among LMW-GS alleles, Glu-A3e and Glu-B3c represented inferior alleles for bread-making quality, whereas Glu-A3d, Glu-B3b, Glu-B3g and Glu-B3i were correlated with superior bread-making quality. Glu-D3 alleles played minor roles in determining quality variation in bread wheat. Thus, LMW-GS alleles not only affect dough extensibility but greatly contribute to the dough resistance, glutenin macro-polymers and bread quality.
authors.affiliation: Institute of Crop Science, National Wheat Improvement Center, Chinese Academy of Agricultural Sciences (CAAS), 12 Zhongguancun South Street, Beijing, 100081, China.
authors.forename: Xiaofei
authors.initials: X
authors.lastname: Zhang
authors.forename: Hui
authors.initials: H
authors.lastname: Jin
authors.forename: Yan
authors.initials: Y
authors.lastname: Zhang
authors.forename: Dongcheng
authors.initials: D
authors.lastname: Liu
authors.forename: Genying
authors.initials: G
authors.lastname: Li
authors.forename: Xianchun
authors.initials: X
authors.lastname: Xia
authors.forename: Zhonghu
authors.initials: Z
authors.lastname: He
authors.forename: Aimin
authors.initials: A
authors.lastname: Zhang
mesh_terms: D000483:Alleles; D001939:Bread / Q000032:analysis*; D001947:Breeding; D018744:DNA, Plant / Q000235:genetics; D004591:Electrophoresis, Polyacrylamide Gel; D005983:Glutens / Q000032:analysis* / Q000235:genetics*; D008970:Molecular Weight; D017422:Sequence Analysis, DNA; D014908:Triticum / Q000145:classification / Q000235:genetics*
chemical_list: D018744:DNA, Plant; D005983:Glutens; C037302:glutenin