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Open Access Research article

Novel variants of HMW glutenin subunits from Aegilops section Sitopsis species in relation to evolution and wheat breeding

Qian-Tao Jiang1, Jian Ma1, Yu-Ming Wei1, Ya-Xi Liu1, Xiu-Jin Lan1, Shou-Fen Dai1, Zhen-Xiang Lu2*, Shan Zhao1, Quan-Zhi Zhao1 and You-Liang Zheng3*

Author Affiliations

1 Triticeae Research Institute, Sichuan Agricultural University, Chengdu, Sichuan, 611130, China

2 Lethbridge Research Centre, Agriculture and Agri-Food Canada, Lethbridge, T1J 4B1, Canada

3 Key Laboratory of Southwestern Crop Germplasm Utilization, Ministry of Agriculture, Sichuan Agricultural University, Ya’an, Sichuan, 625014, China

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BMC Plant Biology 2012, 12:73  doi:10.1186/1471-2229-12-73

Published: 30 May 2012

Abstract

Background

High molecular weight glutenin subunits (HMW-GSs), encoded by the genes at Glu-1 loci in wheat and its related species, are significant in the determination of grain processing quality. However, the diversity and variations of HMW-GSs are relatively low in bread wheat. More interests are now focused on wheat wild relatives in Triticeae. The genus Aegilops represents an important germplasm for novel HWM-GSs and other useful genes for wheat genetic improvement.

Results

Six novel Glu-1 alleles and HMW-GSs were identified and characterized from three species of Aegilops section Sitopsis (S genome). Both open reading frames (ORFs) and promoter regions of these Glu-1 alleles were sequenced and characterized. The ORFs of Sitopsis Glu-1 genes are approximately 2.9 kb and 2.3 kb for x-type and y-type subunits, respectively. Although the primary structures of Sitopsis HMW-GSs are similar to those of previously reported ones, all six x-type or y-type subunits have the large fragment insertions. Our comparative analyses of the deduced amino acid sequences verified that Aegilops section Sitopsis species encode novel HMW-GSs with their molecular weights larger than almost all other known HMW-GSs. The Glu-1 promoter sequences share the high homology among S genome. Our phylogenetic analyses by both network and NJ tree indicated that there is a close phylogenetic evolutionary relationship of x-type and y-type subunit between S and D genome.

Conclusions

The large molecular weight of HMW-GSs from S genome is a unique feature identified in this study. Such large subunits are resulted from the duplications of repetitive domains in Sitopsis HMW-GSs. The unequal crossover events are the most likely mechanism of variations in glutenin subunits. The S genome-encoded subunits, 1Dx2.2 and 1Dx2.2* have independent origins, although they share similar evolutionary mechanism. As HMW-GSs play a key role in wheat baking quality, these large Sitopsis glutenin subunits can be used as special genetic resources for wheat quality improvement.