Novel LMW glutenin subunit genes from wild emmer wheat (Triticum turgidum ssp. dicoccoides) in relation to Glu-3 evolution

Characterization of novel LMW-i genes with nine cysteine residues from Chinese wheat landraces (Triticum aestivum L.) and analysis of their functional properties on dough mixing

The low-molecular-weight glutenin subunits (LMW-GS) with extra cysteine numbers have attracted great research interest for their potential quality value. In this study, 14 LMW-i type genes (YD1-YD14) were isolated from three types of Chinese wheat landraces; and nine of 14 genes (YD1-YD9) had nine cysteines, and the other five genes contained eight cysteines. Phylogenic analysis suggested that all 14 LMW-i genes were related to Glu-A3-1 variants Glu-A3-17/FJ 549934 and Glu-A3-15/FJ 549932. Six randomly selected genes, five genes including YD 1 with nine cysteines and the remaining one with eight cysteines, were successfully expressed in bacteria as mature proteins with a molecular mass of ~ 46 kDa. These proteins were traced to corresponding seed storage proteins for having similar elution times in reverse phase high-performance liquid chromatography (RP-HPLC) profiles. Mass spectrometry verified that bacterial expressed protein pET-30a-YD1 was LMW-i. Dough mixing experiments for incorporation of 50 mg pET-30a-YD1 proteins into the base flour of weak gluten wheat cv. "Chuannong 16" indicated that the dough strength of mixing flours was noticeably weaker than that of the control, which was reflected by mixing parameters in 8-min curve width, peak width, peak height, mixing time, and right of peak slope. The results suggested that the LMW-i genes with nine cysteine residues in the present study contributed to inferior quality properties for wheat flour.

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The online version contains supplementary material available at 10.1007/s13205-021-03044-8.

The genetic diversity of group-1 homoeologs and characterization of novel LMW-GS genes from Chinese Xinjiang winter wheat landraces (Triticum aestivum L.)

Group-1 homoelog genes in wheat genomes encode storage proteins and are the major determinants of wheat product properties. Consequently, understanding the genetic diversity of group-1 homoelogs and genes encoding storage proteins, especially the low-molecular-weight glutenins (LMW-GSs), within wheat landrace genomes is necessary to further improve the quality of modern wheat crops. The genetic diversity of group-1 homoelogs in 75 Xinjiang winter wheat landraces was evaluated by Diversity Arrays Technology (DArT) markers. These data were used to select 15 landraces for additional LMW-GS gene isolation. The genetic similarity coefficients among landraces were highly similar regardless if considering the diversity markers on 1A, 1B, and 1D chromosomes individually or using all of the markers together. These similarities were evinced by the generation of four similar cluster dendrograms that comprised 11-15 landrace groups, regardless of the dataset used to generate the dendrograms. A total of 105 LMW-GS sequences corresponding to 79 unique genes were identified overall by using primers designed to target Glu-A3 and Glu-B3 loci, and 54 mature proteins were predicted from the unique LMW-GS genes. Nine novel chimeric LMW-GS genes were also identified, of which, one was recombinant for -i/-m, one for -s/-m, and seven for -m/-m parent genes, respectively. Phylogenetic analysis separated all of the LMW-GSs into three clades that were supported by moderate bootstrap values (> 70%). The clades corresponded to LMW-GS genes primarily harboring different N-terminals. These results provide useful information for better understanding the evolutionary genetics of the important Glu-3 locus of wheat, and they also provide new novel gene targets that can potentially be exploited to improve wheat quality.

Enriching LMW-GS alleles and strengthening gluten properties of common wheat through wide hybridization with wild emmer

Two advanced lines (BAd7-209 and BAd7-213) with identical high-molecular-weight glutenin subunit composition were obtained via wide hybridization between low-gluten cultivar chuannong16 (CN16) and wild emmer D97 (D97). BAd7-209 was better than BAd7-213, and both of them were much better than CN16 in a dough quality test. We found that BAd7-209 had more abundant and higher expression levels of low-molecular-weight glutenin subunit (LMW-GS) proteins than those of BAd7-213. Twenty-nine novel LMW-GS genes at Glu-A3 locus were isolated from BAd7-209, BAd7-213 and their parents. We found that all 29 LMW-GS genes possessed the same primary structure shared by other known LMW-GSs. Twenty-seven genes encode LMW-m-type subunits, and two encode LMW-i-type subunits. BAd7-209 had a higher number of LMW-GS genes than BAd7-213, CN16, and D97. Two wild emmer genes MG574329 and MG574330 were present in the two advanced lines. Most of the LMW-m-type genes showed minor nucleotide variations between wide hybrids and their parents that could be induced through the wide hybridization process. Our results demonstrated that the wild emmer LMW-GS alleles could be feasibly transferred and integrated into common wheat background via wide hybridization and the potential value of the wild emmer LMW-GS alleles in breeding programs designed to improve wheat flour quality.

Characterization of novel LMW glutenin subunit genes at the Glu-M3 locus from Aegilops comosa

We report the characterization of seven novel low-molecular-weight glutenin subunit (LMW-GS) genes from Aegilops comosa (2n = 2x = 14, MM). We found that all seven LMW-GS genes possessed the same primary structure shared by other known LMW-GSs. Three genes (comosa-M1, comosa-M2, and comosa-M3) encode LMW-m-type subunits, two (comosa-I1 and comosa-I2) encode LWM-i-type subunits, and two (comosa-L1 and comosa-L2) encode LWM-l-type subunits. The comosa-M1 possessed seven cysteine residues, which resulted from a single-nucleotide polymorphism (SNP) of the G-A transition in the fifth position of the N-terminal sequence. Two l-type subunits, comosa-L1 and comosa-L2, contained nine cysteine residues with an extra cysteine residue located in the signal peptide and repetitive domain. In addition, a long insertion of 13 residues (LGQQPQ8/LVQQPQ8) was present in the end of the C-terminal II. Phylogenetic analysis implied that the comosa-L2 may be the intermediate type during the evolution of LMW-l and LMW-i-type genes. Our results demonstrated that the novel LMW-GSs, such as comosa-M1, comosa-L1, and comosa-L2, may have positive effects on dough properties.