Isolation and characterization of wheat ω-gliadin genes

Abstract

The DNA sequences of two full-length wheat ω-gliadin prolamin genes (ωF20b and ωG3) containing significant 5´ and 3´ flanking DNA sequences are reported. The ωF20b DNA sequence contains an open reading frame encoding a 30,460-Dalton protein, whereas the ωG3 sequence would encode a putative 39,210-Dalton protein except for a stop codon at amino-acid residue position 165. These two ω-gliadin genes are closely related and are of the ARQ-/ARE-variant type as categorized by the derived N-terminal amino-acid sequences and aminoacid compositions. The ω-gliadins were believed be related to the ω-secalins of rye and the C-hordeins of barley, and analyses of these complete ω-gliadin sequences confirm this close relationship. Although the ω-type sequences from all three species are closely related, in this analysis the rye and barley ω-type sequences are the most similar in a pairwise comparison. A comparison of ω-gliadin flanking sequences with respect to that of their orthologs and with respect to wheat gliadin genes suggests the conservation of flanking DNA necessary for gene function. Sequence data for members of all major wheat prolamin families are now available.

Development and characteristics of ω-gliadin-free wheat genotypes

“…As a result, codons of particular amino acids may turn into stop codons, down-regulating structural gene expression leading to pseudogenes. An example is glutamine codon-CAA or CAG-that may change to stop codons UAA or UAG by a C [ T transition (Hsia and Anderson 2001). Such mutations are more probable for gluten protein genes, especially those coding x-gliadins, because of their extremely high glutamine contents (average 40 %).…”

Molecular Cloning and Identification of Novel ω-gliadin Genes fromTriticumSpecies

“…However, few ω-gliadin genes are cloned (Hsia and Anderson 2001;Masoudi-Nejad et al 2002;Matsuo et al 2005;Hassani et al 2008;Chen et al 2011;Zhuang et al 2012;Waga and Skoczowski 2014), possibly because their coding sequence includes a large repetitive domain, which hampers gene cloning (Anderson et al 2009). In this study, we have cloned 13 distinct sequences of ω-gliadins in T. urartu (AA), T. monococcum ssp.…”

“…Pseudogenes are known to be common in cereal prolamine gene families, such as wheat α-gliadins (Anderson 1991) and ω-gliadins (Hsia and Anderson 2001). ω-Gliadin genes particularly tend to be inactivate when they become large in size (Anderson et al 2009).…”

“…Previously reported study suggested that lack of cysteines prevents polypeptides from forming the gluten polymer (Wieser 2007). Up to now, only a few ω-gliadin gene sequences have been reported (Hsia and Anderson 2001;Masoudi-Nejad et al 2002;Matsuo et al 2005;Hassani et al 2008;Chen et al 2011;Zhuang et al 2012;Waga and Skoczowski 2014). This is probably because a large repetitive domain in the coding sequence hampers the cloning of ω-gliadin gene (Anderson et al 2009).…”

“…The general protein structure of a ω-gliadin is simple: a 19-residue putative signal peptide followed by a 10-11-residue non-repetitive N-terminus, a repetitive region encompassing 90-96% of the protein and a 10-11 residue C-terminus (Hsia and Anderson 2001). The ω-gliadins are composed almost entirely of a repetitive domain bracketed by short unique sequences generally lacking both cysteine and methionine, and are therefore 'sulfur-poor' polypeptides (Anderson et al 2009).…”