Characterization of novel LMW-GS genes at Glu-D3 locus on chromosome 1D in Aegilops tauschii

Potential of Aegilops sp. for Improvement of Grain Processing and Nutritional Quality in Wheat (Triticum aestivum)

Wheat is one of the most important staple crops in the world and good source of calories and nutrition. Its flour and dough have unique physical properties and can be processed to make unique products like bread, cakes, biscuits, pasta, noodles etc., which is not possible from other staple crops. Due to domestication, the genetic variability of the genes coding for different economically important traits in wheat is narrow. This genetic variability can be increased by utilizing its wild relatives. Its closest relative, genus Aegilops can be an important source of new alleles. Aegilops has played a very important role in evolution of tetraploid and hexaploid wheat. It consists of 22 species with C, D, M, N, S, T and U genomes with high allelic diversity relative to wheat. Its utilization for wheat improvement for various abiotic and biotic stresses has been reported by various scientific publications. Here in, for the first time, we review the potential of Aegilops for improvement of processing and nutritional traits in wheat. Among processing quality related gluten proteins; high molecular weight glutenins (HMW GS), being easiest to study have been explored in highest number of accessions or lines i.e., 681 belonging to 13 species and selected ones like Ae. searsii, Ae. geniculata and Ae. longissima have been linked with improved bread making quality of wheat. Gliadins and low molecular weight glutenins (LMW GS) have also been extensively explored for wheat improvement and Ae. umbellulata specific LMW GS have been linked with wheat bread making quality improvement. Aegilops has been explored for seed texture diversity and proteins like puroindolins (Pin) and grain softness proteins (GSP). For nutrition quality improvement, it has been screened for essential micronutrients like Fe, Zn, phytochemicals like carotenoids and dietary fibers like arabinoxylan and β-glucan. Ae. kotschyi and Ae. biuncialis transfer in wheat have been associated with higher Fe, Zn content. In this article we have tried to compile information available on exploration of nutritional and processing quality related traits in Aegilops section and their utilization for wheat improvement by different approaches.

Allelic variation of LMW-GS composition in Chinese wheat landraces of the Yangtze-River region detected by MALDI-TOF-MS

Low molecular weight glutenin subunits are important components of wheat storage proteins, which play an important role in determining end-use quality of common wheat. A newly established matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) procedure was used to analyze 478 landraces of bread wheat collected from the Yangtze-River region in China. Results indicated that 17 alleles at three loci: Glu-A3, Glu-B3 and Glu-D3 were identified, resulting in 87 different allele combinations. Of the 17 alleles detected at all the Glu-3 loci, five belonged to Glu-A3, seven to Glu-B3 and five to Glu-D3 locus. MALDI-TOF-MS indicated Glu-A3a/c was present in 72.8%, Glu-A3b in 8.4%, Glu-A3d in 8.4%, Glu-A3f in 5.2% and Glu-A3e in 3.6% lines. Seven types of alleles were identified at the Glu-B3 locus: Glu-B3d/i (25.5%), Glu-B3b (21.3%), Glu-B3c (16.9%), Glu-B3h (13.8%), Glu-B3f (8.4%), Glu-B3a (8.2%), and Glu-B3g (5.2%). Five types of Glu-D3 alleles were detected: Glu-D3a (58.4%), Glu-D3c (22.6%), Glu-D3d (15.5%), Glu-D3b (3.3%) and Glu-D3f (0.2%). Four new alleles that showed abnormal MALDI-TOF spectrum patterns were identified at the Glu-A3 and Glu-B3 loci. A detailed study is needed to further characterize these alleles and their potential usage for wheat improvement.

PCR-based isolation and identification of full-length low-molecular-weight glutenin subunit genes in bread wheat (Triticum aestivum L.)

Low-molecular-weight glutenin subunits (LMW-GSs) are encoded by a multi-gene family and are essential for determining the quality of wheat flour products, such as bread and noodles. However, the exact role or contribution of individual LMW-GS genes to wheat quality remains unclear. This is, at least in part, due to the difficulty in characterizing complete sequences of all LMW-GS gene family members in bread wheat. To identify full-length LMW-GS genes, a polymerase chain reaction (PCR)-based method was established, consisting of newly designed conserved primers and the previously developed LMW-GS gene molecular marker system. Using the PCR-based method, 17 LMW-GS genes were identified and characterized in Xiaoyan 54, of which 12 contained full-length sequences. Sequence alignments showed that 13 LMW-GS genes were identical to those found in Xiaoyan 54 using the genomic DNA library screening, and the other four full-length LMW-GS genes were first isolated from Xiaoyan 54. In Chinese Spring, 16 unique LMW-GS genes were isolated, and 13 of them contained full-length coding sequences. Additionally, 16 and 17 LMW-GS genes in Dongnong 101 and Lvhan 328 (chosen from the micro-core collections of Chinese germplasm), respectively, were also identified. Sequence alignments revealed that at least 15 LMW-GS genes were common in the four wheat varieties, and allelic variants of each gene shared high sequence identities (>95%) but exhibited length polymorphism in repetitive regions. This study provides a PCR-based method for efficiently identifying LMW-GS genes in bread wheat, which will improve the characterization of complex members of the LMW-GS gene family and facilitate the understanding of their contributions to wheat quality.

[Cloning and phylogenetic analysis of low-molecular-weight glutenin subunit genes at Glu-B3 locus in common wheat relative species]

The common wheat relative species are important germplasm for wheat breeding. In the present study, novel allelic variants at Glu-B3 locus were cloned to provide gene resources for wheat quality improvement. Four Glu-B3-locus specific primer sets LB1F/LB1R, LB2F/LB2R, LB3F/LB3R, and LB4F/LB4R were employed to isolate novel allelic variants of GluB3-1, GluB3-2, GluB3-3, and GluB3-4 from seven common wheat relative species, i.e., T. durum, T. dicoccum, T. dicoccoides, Aegilops longissima, Ae. searsii, Ae. Bicornis, and Ae. speltoides, and the software MEGA 4 was used to construct a phylogenetic tree. In total, 16 novel allelic variants of GluB3-1, GluB3-3, and GluB3-4 genes were isolated from the seven common wheat relative species, designated GluB3-16, GluB3-35, GluB3-36, GluB3-37, GluB3-46, GluB3-47, GluB3-48, GluB3-49, GluB3-410, GluB3-411, GluB3-412, GluB3-413, GluB3-414, GluB3-415, GluB3-416 and GluB3-417, respectively. In detail, GluB3-16 was cloned from T. dicoccoides with LB1F/LB1R, and the molecular weight of the de-duced amino acid was 39.2 kDa. GluB3-35, GluB3-36, and GluB3-37 were isolated from T. durum and T. dicoccum with the primer set LB3F/LB3R, and the molecular weights of their deduced peptides were 44.5 kDa (GluB3-36) and 44.6 kDa (GluB3-35 and GluB3-37). The molecular weight of deduced peptides of GluB3-4 ranged from 38.6 kDa (GluB3-414) to 42.5 kDa (GluB3-413). All the 16 new allelic variants showed a single open reading frame (ORF), and their deduced amino-acid sequences had a typical sequence structure of LMW-GS. The allelic variants at Glu-B3 locus identified in com-mon wheat relative species provide potential gene resources for wheat quality breeding and gene transformation. The results suggested that these Glu-B3 genes originated from different evolution processes.