A second ‘overexpression’ allele at the Glu-B1 high-molecular-weight glutenin locus of wheat: sequence characterisation and functional effects

Abstract

Bread is one of the major constituents of the human diet and wheat (Triticum aestivum L.) is the most important cereal for bread making. The gluten proteins (glutenins and gliadins) are recognised as important components affecting the processing quality of wheat flour. In this research, we investigated a particular glutenin subunit allele in an Australian cultivar, H45. Based on protein and DNA assays, the Glu-B1 allele of H45 seems to be Glu-B1al, an allele that includes a functional duplication of a gene encoding an x-type high-molecular-weight glutenin subunit, and is thought to increase dough strength through overexpression of that subunit. Yet H45 does not have the dough properties that would be expected if it carries the Glu-B1al allele. After confirming that H45 overexpresses Bx subunits and that it has relatively low un-extractable polymeric protein (an indicator of weak dough), we cloned and sequenced two Bx genes from H45. The sequences of the two genes differ from each other, and they each differ by four single-nucleotide polymorphisms (SNPs) from the sequence that has been reported for the Glu-B1al x-type glutenin genes of the Canadian wheat cultivar Glenlea. One of the SNPs leads to an extra cysteine residue in one of the subunits. The presence of this additional cysteine may explain the dough properties of H45 through effects on cross-linkage within or between glutenin subunits. We propose that the Glu-B1 allele of H45 be designated Glu-B1br, and we present evidence that Glu-B1br is co-inherited with low un-extractable polymeric protein.

Quality properties and expression profiling of protein disulfide isomerase genes during grain development of three spring wheat near isogenic lines

“…It is generally accepted that HMW-GS 5+10 can produce superior dough quality compared to 2+12 subunits (SARKAR et al, 2014). Possible reasons include the number and position of cysteine residues (WEEGELS et al, 1996;PIROZI et al, 2008), the accumulation rate differences during grain development (XU et al, 2006;GAO et al, 2012;LIU et al, 2012;WANG et al, 2013) and the formation of inter-or intra-molecular disulfide bonds which can stabilize the structure and increase the number of glutenin macropolymer (ALTENBACH et al, 2007;LAUDENCIA-CHINGCUANCO et al, 2007;SHEWRY et al, 2009;LI et al, 2010). Our results from this work further confirmed that CB037-B with HMW-GS 5+10 subunits has higher GMP content and better mixing property and breadmaking quality than CB037-A with 2+12 subunits (Table 1 and Figure 2).…”

Molecular cloning and characterization of six novel HMW‐GS genes from Aegilops speltoides and Aegilops kotschyi

“…Gao et al. () gave a plausible explanation for the weak strength of H45 by suggesting that the extra cysteine found in H45 sequences might act as a chain terminator. However, there is some evidence that in most cases, HMW glutenin subunits with extra numbers of cysteine residues are positively associated with improved processing quality in bread wheat varieties (Lafiandra et al.…”

A Cross between Bread Wheat and a 2D(2R) Disomic Substitution Triticale Line Leads to the Formation of a Novel Disomic Addition Line and Provides Information of the Role of Rye Secalins on Breadmaking Characteristics

“…In bread wheat it has been widely demonstrated that number of subunits in addition to the number and distribution of cysteine residues, available for intermolecular bonds, are responsible for differences of breadmaking quality of different wheat varieties, as also mentioned in the introduction. Results have been obtained that show that additional cysteines not always influence positively the bread-making quality of flour, as in the case of the 1Dx5 subunit [66][67][68]. On the basis of the rheological data obtained we can hypothesize that the additional cysteine present in the 1Ry subunit contributes to modulate differently the size distribution of glutenin polymers, producing a dough with a very large extensibility.…”