RELATIONSHIP BETWEEN SEQUENCE POLYMORPHISM OF GSP-1 AND PUROINDOLINES IN TRITICUM AESTIVUM AND AEGILOPS TAUSCHII

Authors: MASSA, ALICIA - WASHINGTON STATE UNIV; Morris, Craig

Submitted to: International Gluten Workshop
Publication Type: Proceedings
Publication Acceptance Date: 9/8/2003
Publication Date: 6/1/2004
Citation: Massa, A.N., Morris, C.F. 2004. Relationship between sequence polymorphism of gsp-1 and puroindolines in triticum aestivum and aegilops tauschii. International Gluten Workshop. pp.461-464.

Interpretive Summary: Grain Softness Protein-1 (Gsp-1) is similar to puroindolines a and b, the genes that control hardness and softness in wheat grain. Primary interest in Gsp-1 stems from the unique properties of this family of proteins, and their usefulness in phylogenetic studies. Hexaploid wheat was formed through one or more rare crossbreeding events between a wild AABB-genome species and a DD-genome-bearing grass, Aegilops tauschii. Surveys of Ae. tauschii have indicated a much greater degree of gene and protein sequence changes for the two puroindoline genes compared to those found in wheat. Among the 50 Ae. tauschii accessions sequenced in this study, a total of 7 genetic differences throughout the Gsp-D1 gene were found, resulting in a total of 4 amino acid differences. Each unique gene sequence was assigned an allele. None of the unique Gsp-D1 gene sequences exactly matched those found in Chinese Spring. Consequently, one interpretation is that none of these Ae. tauschii accessions embody the specific ancestral relative of wheat. The Gsp-D1b allele was most similar to wheat, differing by only 1 nucleotide and 1 amino acid. Relative abundance of each gene type was documented.

Technical Abstract: Grain Softness Protein-1 (Gsp-1) has evolved to define a set of homoeologous genes which are closely related to the indolines'most notably, puroindolines a and b; and closely co-located in chromosome 5DS at the Hardness locus. Indolines appear in most taxa of Triticeae and Aveneae. Primary interest in Gsp-1 stems from the unique properties of this family of proteins, and their utility in phylogenetic studies. Hexaploid wheat (Triticum aestivum L.) was formed through one or more rare hybridization events between a wild AABB tetraploid species and a DD genome-bearing Aegilops tauschii. Surveys of Ae. tauschii accessions have indicated a much greater degree of nucleic acid and protein sequence polymorphism for the two puroindoline genes compared to that found in wheat. Among the 50 Ae. tauschii accessions sequenced in this study, a total of 7 polymorphic nucleotide positions throughout the Gsp-D1 gene were found, resulting in a total of 4 amino acid differences. Each unique gene sequence was assigned an allele (i.e. 'b' through 'h'). None of the unique Gsp-D1 gene sequences exactly matched those found in Chinese Spring. Consequently, one interpretation is that none of these Ae. tauschii accessions embody the specific ancestral D-genome donor of wheat. The Gsp-D1b allele was most similar to Chinese Spring, differing by only 1 nucleotide and 1 amino acid. Alleles b, c, d and e were relatively common with 8 to 14 accessions each, whereas alleles f, g and h had 2 accessions each. The allelic variation within subsp. tauschii was greater than the observed in subsp. strangulata, which is also in agreement with the morphological variation observed for subsp. tauschii.