Proteogenomic Characterization of Novel x-Type High Molecular Weight Glutenin Subunit 1Ax1.1

Abstract

Analysis of Portuguese wheat (Triticum aestivum L.) landrace ‘Barbela’ revealed the existence of a new x-type high molecular weight-glutenin subunit (HMW-GS) encoded at the Glu-A1 locus, which we named 1Ax1.1. Using one-dimensional and two-dimensional electrophoresis and mass spectrometry, we compared subunit 1Ax1.1 with other subunits encoded at the Glu-A1 locus. Subunit 1Ax1.1 has a theoretical molecular weight of 93,648 Da (or 91,508 Da for the mature protein) and an isoelectric point (pI) of about 5.7, making it the largest and most acidic HMW-GS known to be encoded at Glu-A1. Specific primers were designed to amplify and sequence 2601 bp of the Glu-A1 locus from the ‘Barbela 28’ wheat genome. A very high level of identity was found between the sequence encoding 1Ax1.1 and those encoding other alleles of the locus. The major difference found was an insertion of 36 amino acids in the central repetitive domain.

Special HMW-GSs and their genes of Triticum turgidum subsp. dicoccoides accession D141 and the potential utilization in common wheat

“…Some researchers considered it should be 1Ax subunit if there was a HMW-GS at Glu-A1 locus of common wheat, because 1Ay gene is always silent (Payne et al 1981;Shewry et al 1992). In common wheat, the previously characterized HMW-GS alleles at Glu-A1 locus had five allelic forms, including null, 1Ax1, 1Ax2 * , 1Ax2 *B and 1Ax1.1, of which the former two allelic forms were most common (Anderson and Greene 1989;Halford et al 1992;Shewry et al 1992;Ribeiro et al 2013). However, 1Ay was present in the diploid and tetraploid wheats, even in the hexaploid T. zhukovskyi Men.…”

Characterization of novel high-molecular-weight glutenin subunits and their coding sequences in Aegilops markgrafii

“…The HMW-GS form an elastomeric polymer network, which provides a 'backbone' for interactions with other glutenin subunits and with gliadins, and this network is stabilized by interchain disulphide bonds (Shewry and Tatham, 1997). However, it is widely accepted that high glutamine content can also stabilize the polymeric structure of glutenin by forming more hydrogen bonds, which are also involved in determining the elastic properties of wheat dough (Belton, 1999;Ribeiro et al, 2013). A larger HMW-GS Cx1 means higher glutamine content and thus more stabilized glutenin polymeric structures and 'better' quality.…”

Genetic divergence for high-molecular weight glutenin subunits (HMW-GS) in indigenous landraces and commercial cultivars of bread wheat of Pakistan

“…More than half of the commercial cultivars carried this allele, indicating that breeders rigorously selected wheat cultivars with better quality that were indirectly coupled to the 2* allele (He et al, 2013). Ribeiro et al (2013) analyzed the Portuguese wheat landrace 'Barbela' and reported a new x-type HMW-GS encoded at the Glu-A1 locus that was named 1Ax1.1. Lan et al (2013) reported low-molecular weight glutenin subunits as the major components of glutenins, which were considered to be important for the end-use quality of wheat; however, Kaur et al (2013) reported the physico-chemical and rheological properties of Indian wheat cultivars varying in HMW-GS.…”