Proposal of International Gluten Research Group
Abstract In a scenario of climate change and rapidly rising urban populations demanding processed foods, it is necessary to develop new wheat cultivars combining high yield potential, disease resistance, and stability for yield and processing quality, even under heat or drought stress conditions. Allelic variation for gluten proteins (glutenin subunits and gliadins) is a major determinant of differences in dough viscoelastic properties observed between cultivars of both bread wheat and durum wheat. Technical difficulties in allelic identification due to the complexity of the protein profile produced by each cultivar and the use of different nomenclature systems in different laboratories has historically interfered with information exchange between research groups, a situation exacerbated by the vast number of possible profiles found in different cultivars due to the multi-allelic nature of the principal loci encoding gluten proteins (Glu-1, Glu-2, Glu-3, Gli-1 and Gli-2). For the Glu-3 alleles, we have collaborated to unify criteria across laboratories and to compare four different methods of allelic identification (SDS-PAGE, 2-DE, MALDI-TOF-MS and PCR), and have shown that the four methods can be regarded as complementary techniques for allelic identification. We seek to continue addressing remaining analytical challenges, place the findings in the context of the Catalogue of Gene Symbols for Wheat, and, with unified criteria, initiate work to define better the relationship between specific gluten proteins and processing quality attributes. Therefore, we propose a new system to share materials through public gene banks in collaboration with the Catalogue, and the formation of a wider international group aimed at facilitating the resolution of the remaining problems in the field. We also propose to extend our collaboration by forming a wheat quality expert working group under the Wheat Initiative.
Current Status of Glu-3 Allele Nomenclature
It has been shown that allelic variation for the high-molecular-weight glutenin subunits (HMW-GSs) and low-molecular-weight glutenin subunits (LMW-GSs) affects the properties of dough made with different wheat cultivars. LMW-GS composition in common wheat is one of the critical determinants of gluten properties (Branlard et al. 2001; Eagles et al. 2006; Gupta et al. 1994; Liu et al. 2005; Maruyama-Funatsuki et al. 2005). Gupta and Shepherd (1990) assigned the individual LMW-GSs to Glu-A3, Glu-B3 and Glu-D3 loci and selected standard cultivars that covered the allelic variation observed. However, subsequent use of Glu-3 nomenclature has not been consistent among laboratories, due to the complexity of the LMW-GSs, different separation methods and different standard cultivars used by researchers (Branlard et al. 2003; Ikeda et al. 2006; Singh et al. 1990). It is necessary to unify the various Glu-3 allelic nomenclature systems in use, to allow information to be shared regarding the effects of individual alleles on gluten properties and to be applied in breeding programs aimed at improving gluten properties. In previous studies, four laboratories plus an international institution shared cultivars and compared results. We confirmed that there were inconsistencies to identify Glu3 alleles between laboratories due to differences of separation and identification methods (Ikeda et al. 2008). Using 2-DE analysis, we found new Glu-3 alleles among these materials (Ikeda et al. 2009). Combining SDS-PAGE, 2-DE, MALDITOF-MS and PCR analyses, we showed that a combination of methods was required to identify certain alleles, and that these methods would be especially useful when characterizing new alleles. We also recommended 30 cultivars as standards for the determination of LMW-GS alleles (Liu et al. 2010).