Characterisation and chromosomal localisation of C-type low-molecular-weight glutenin subunits in the bread wheat cultivar Chinese Spring

Abstract

Low-molecular-weight glutenin subunits are classically divided into the B, C and D groups. Most attention has been paid to the characterisation of the B and D groups, whereas C subunits, although represented by a large number of protein components, have not been thoroughly characterised, mainly because they tend to separate with the gliadins in many fractionation procedures. Here we describe a procedure for obtaining a fraction strongly enriched in C subunits that has allowed us to determine the chromosomal location of these subunits in the bread wheat cultivar Chinese Spring. This analysis has shown that these subunits are coded on chromosome groups 1 and 6. Comparison between N-terminal amino acid sequencing of B and C subunits has shown that, whereas the former group includes mainly subunits with typical LMW-GS type sequences (76%), the C subunit group is made up almost completely of subunits with gliadin-like sequences (95%), including the alpha-type. These results indicate that the LMW-GSs are likely to be coded not only by the typical Glu-3 loci, but also by loci tightly linked to, and possibly included within, the Gli-1 and Gli-2 loci.

Characterization of low-molecular-weight glutenin genes in Aegilops tauschii

“…The LMW glutenins in the B group (40-50 kDa) are the most basic subunits, while the C-group subunits (30-40 kDa) have a wide range of pIs. It has been found by N-terminal amino sequencing that the C group of LMW glutenins contain up to 95% modified or mutant gliadins that have become incorporated into the polymer via disulfide bonding (Tao and Kasarda 1989;Lew et al 1992;Masci et al 2002). The D-group subunits are modified ω-gliadins (44-74 kDa) with at least one cysteine residue in their sequences, and they are the most acidic of all endosperm proteins (Masci et al 1991(Masci et al , 1993.…”

“…On the basis of N-terminal amino acid sequences, they can be divided into LMW-m, LMW-s, and LMW-i types (Kasarda et al 1988;Tao and Kasarda 1989;Lew et al 1992;Cloutier et al 2001). The LMW-s type have been found to be the predominant type by N-terminal sequencing of proteins and belongs to the B group of LMW glutenins (Lew et al 1992;Masci et al 2002). The LMWm type is the most predominant type found by gene sequencing and belong to both the B and C groups of LMW glutenins.…”

Identification of Specific Low-Molecular-Weight-Glutenin Subunits Related to Gluten Quality in Bread Wheats

“…It could be a γ-gliadin type subunit, because previous studies showed that a major C subunit of Norin 61 was encoded by Glu-D3 containing a γ-gliadin-like Nterminal amino acid sequence 13 . Other studies 11,12 revealed that most of the LMW-GSs in the C subunits shared a similarity of amino acid sequences to those of α-and γ-gliadins that carry a single additional cysteine residue involved in the formation of an intermolecular disulfide bond. Therefore, this LMW-GS could be encoded by the Gli-D1 locus tightly linked to Glu-D3 locus.…”

Length variation of i-type low-molecular-weight glutenin subunit genes in diploid wheats

“…The number of repeats, ranging between about 12 and 25, in the repetitive domain is mainly responsible for its length variation. Although the allelic variation of LMW-GS has been widely characterized at the protein level in wheat and its relatives [5,6,[18][19][20], the research on the genetic variation of LMW-GS at DNA level is still lacking.…”