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

Abstract

This paper reports the characterization of the low-molecular-weight (LMW) glutenin gene family of Aegilops tauschii (syn. Triticum tauschii), the D-genome donor of hexaploid wheat. By analysis of bacterial artificial chromosome (BAC) clones positive for hybridization with an LMW glutenin probe, seven unique LMW glutenin genes were identified. These genes were sequenced, including their untranslated 3' and 5' flanking regions. The deduced amino acid sequences of the genes revealed four putative active genes and three pseudogenes. All these genes had a very high level of similarity to LMW glutenins characterized in hexaploid wheat. The predicted molecular weights of the mature proteins were between 32.2 kDa and 39.6 kDa, and the predicted isoelectric points of the proteins were between 7.53 and 8.06. All the deduced proteins were of the LMW-m type. The organization of the seven LMW glutenin genes appears to be interspersed over at least several hundred kilo base pairs, as indicated by the presence of only one gene or pseudogene per BAC clone. Southern blot analysis of genomic DNA of Ae. tauschii and the BAC clones containing the seven LMW glutenin genes indicated that the BAC clones contained all LMW glutenin-hybridizing bands present in the genome. Two-dimensional gel electrophoresis of an LMW glutenin extract from Ae. tauschii was conducted and showed the presence of at least 11 distinct proteins. Further analysis indicated that some of the observed proteins were modified gliadins. These results suggest that the actual number of typical LMW glutenins may in fact be much lower than previously thought, with a number of modified gliadins also being present in the polymeric fraction.

A Novel Chimeric Low-Molecular-Weight Glutenin Subunit Gene From the Wild Relatives of Wheat Aegilops kotschyi and Ae. juvenalis: Evolution at the Glu-3 Loci

“…Since the previous reported LMW-GS genes were from different Triticum and Aegilops genomes ( Johal et al 2004;An et al 2006), there contained considerable SNP variations in the repetitive and C-terminal domains. A total of 20 SNPs resulted from point mutation, but indel variations were detected among the four cloned LMW-m-type genes, which scattered in the different domains, except the signal peptide and N-terminal domains (Table 1).…”

“…In the past, an increasing number of LMW-GS genes have been isolated and characterized from common wheat (D'Ovidio and Masci 2004) and high allelic variations have been identified at the Glu-3 locus (Gianibelli et al 2002;Yanet al 2003a,b,c;An et al 2005;Li et al 2006). A recent focus has been to isolate new LMW-GS genes from wheat related species, e.g., Triticum boeoticum (Lee et al 1999), T. monoccocum , Aegilops tauschii ( Johal et al 2004;Pei et al 2007), and T. dicoccoides (Q. Li et al 2008).…”

“…The gene sizes vary, depending mainly on the number of repeats in the repetitive domain, normally ranging from 12 to 25 amino acid residues. The extensive allelic variation among both LMW-GS and HMW-GS genes are due mainly to single nucleotide polymorphisms (SNPs) and insertions/deletions (indels) of repetitive units ( Johal et al 2004;Yan et al 2004;An et al 2006;Zhang et al 2006;Li et al 2008). It was speculated that the genetic mechanisms for these variations may result from unequal crossing over and slippage during replication and dot mutation (Anderson and Greene 1989;D'Ovidio et al 1996;An et al 2006).…”

Sequences variation and classification of B-hordein genes in hull-less barley from the Qinghai-Tibet Plateau

“…vulgare [10,18], H. brevisubulatum [11] and H. chilense [17], and a LMW-GS from Aegilops tauschii (AY585355) [25] (Fig. 2).…”

Characterization of low-molecular-weight glutenin subunit genes of Aegilops section Sitopsis and comparative analysis with those of wheat (Triticum aestivum L.) and some Aegilops species

“…It not only contributes the entire D genome of wheat, but also has been proposed as B genome ancestor. Consequently, extensive studies on novel LMW-GS gene mining have also been conducted in Aegilops genus, such as species containing D, C, M, N, U genomes (Ciaffi et al 1999;Gianibelli et al 2002;Johal et al 2004;Huang et al 2005;Wang et al 2011;Li et al 2008Li et al , 2010. However, little information is available about the LMW-GS genes in Sitopsis section, the putative B genome donor of wheat.…”