The glutamine synthetase (GS2) genes in relation to grain protein content of durum wheat

Abstract

Glutamine synthetase (GS2) is a key enzyme in plant nitrogen metabolism responsible of the first step of ammonium assimilation and transformation into glutamine (an essential compound in the amino acid-biosynthetic pathway). The goal of the present study was to isolate and characterize GS2 genes and to assess the linkage with grain protein content (GPC), an important quantitative trait controlled by multiple genes. Here, we report the isolation of the complete glutamine synthetase gene sequences and their localization on the two homeologous chromosome 2A and 2B in durum wheat cvs. Ciccio and Svevo characterized by a different grain protein content. GS2-A2 located on 2A chromosome is comprised of 13 exons separated by 12 introns, and the allele sequence in the two cultivars were different for an insertion of 5 bp located in the third exon in the cv. Ciccio. The GS2-B2 has the same intron/exon structure, but the two cultivars differ for the insertion of a 33-bp sequence located in the second intron of the cv. Svevo. Specific primers were designed in the polymorphic region and amplified in a recombinant inbred line mapping population. The study localized GS genes (GS2-A2, GS2-B2 GSe, GSr) on chromosomes 2A, 2B, 4A, and 4B, where four significant QTLs for GPC were also located.

Allelic Variants of Glutamine Synthetase and Glutamate Synthase Genes in a Collection of Durum Wheat and Association with Grain Protein Content

“…The phenotypic variation ranged from 4.1 to 9.2%. Although significant results were previously reported [10], no significant correlation was instead outlined by the regression analysis between GPC and the 33 bp indel of the GS2-B2 gene, likely due to the fact that an unequal distribution of alleles occur in the collection of genotypes. Glutamine synthetase plays a key role in the use of absorbed nitrogen, process of primary importance for plant growth.…”

“…Based on the genomic sequences of the two homoeologous genes GS2-2A and GS2-2B previous isolated [10], several pairs of specific genomic primers reported in Table S1 were drawn. These were amplified and screened for genomic variations in the entire collection of tetraploid wheat (see Materials and Methods).…”

“…On the other hand, two different polymorphisms were identified on the 2B homoelogous chromosome: a repeated 5 bp microsatellite (GATTA) and a 33 bp indel, respectively, located in the first and second introns of the GS2-2B gene. Figure 1 shows peaks corresponding to MITE deletion in the second intron of the GS2-2A gene (peak at 480 bp, and the 33 bp deletion/insertion of the GS2-2B gene (473 and 507 bp, respectively) [10]. We ran a regression analysis between the GS2 allelic variants and the GPC in the described tetraploid wheat collection evaluated in three replicated field experiments.…”

QTL detection for wheat kernel size and quality and the responses of these traits to low nitrogen stress

“…In addition, TaSus2 could influence the responses of KL and KW to N stress, but it had no effect on the response of per-plant yield (Cui et al 2014a). Glutamine synthetase (GS2) is a key enzyme involved in plant N metabolism that is responsible for the first step of ammonium assimilation and transformation into glutamine; thus, it plays a key roles in the growth, N use and yield potential of cereal crops, including wheat (Gadaleta et al 2011;Li et al 2011). Polyphenol oxidase (PPO) activity is highly correlated with the undesirable browning of wheat-based end products, especially Asian noodles (He et al 2007;Liu et al 2012).…”

Identification and Expression Analysis of Glutamine Synthetase Genes in Ramie (Boehmeria nivea L. Gaud)

“…Genetic studies in rice [10][11][12], maize [8,13] and wheat [14] have demonstrated the colocalization of QTLs for GS protein or activity with QTLs in the mapped GS genes that are related to agronomic traits. In higher plants, GS influences and determines the growth and developmental periods of plants, such as the period of grain development and filling in rice [15], wheat [7] and maize [16]; the senescence process in wheat [7]; and the vegetative process in rice and barley [9,17].…”