Functional Validation of Glutamine synthetase and Glutamate synthase Genes in Durum Wheat near Isogenic Lines with QTL for High GPC

Abstract

Durum wheat (Triticum turgidum L. ssp. durum) is a minor crop grown on about 17 million hectares of land worldwide. Several grain characteristics determine semolina’s high end-use quality, such as grain protein content (GPC) which is directly related to the final products’ nutritional and technological values. GPC improvement could be pursued by considering a candidate gene approach. The glutamine synthetase (GS)/glutamate synthase (GOGAT) cycle represents a bottleneck in the first step of nitrogen assimilation. QTL for GPC have been located on all chromosomes, and several major ones have been reported on 2A and 2B chromosomes, where GS2 and Fd-GOGAT genes have been mapped. A useful and efficient method to validate a putative QTL is the constitution of near-isogenic lines (NILs) by using the marker found to be associated to that QTL. Here, we present the development of two distinct sets of heterogeneous inbred family (HIF)- based NILs segregating for GS2 and Fd-GOGAT genes obtained from heterozygous lines at those loci, as well as their genotypic and phenotypic characterizations. The results allow the validation of the previously identified GPC QTL on 2A and 2B chromosomes, along with the role of these key genes in GPC control.

Yield-Related QTL Clusters and the Potential Candidate Genes in Two Wheat DH Populations

“…One GPC QTL on 2AS (50.0-56.3 MB) without yield penalty was suggested to be used in wheat breeding. A suggested candidate gene, Fd-GOGAT_2A (TraesCS2A01G130600; 2A: 78.3 Mb), for a GPC QTL, was 20 Mb beyond the QTL [ 67 , 82 ].…”

“…TaSUS2-2B (TraesCS2B01G194200; 2B: 171.0Mb) was inside of the 2B.2 QTL cluster and may contribute to the phenotypes [ 83 ]. GS2-B2 (TraesCS2B01G528300; 722.6 Mb) was 1 Mb beyond cluster 2B.3 and may contribute to the phenotypes [ 67 , 78 ]. A dwarfing gene Rht4 was close to a SSR marker WMC317 (4BL: 784.3 Mb) [ 43 ], 60 Mb beyond the 2B.3 QTL cluster.…”

“…It was also reported that natural variants of GPC1-A1 have the same role as GPC1-B1 [ 65 , 66 ]. Recently, GPC QTL was further validated on 2A and 2B, and Fd-GOGAT_2A and GS2-B2 (glutamine synthetase) were suggested as candidates for those QTL, respectively [ 67 ].…”

Wheat glutamine synthetase TaGSr-4B is a candidate gene for a QTL of thousand grain weight on chromosome 4B

“…Yu et al ( 2021 ) found that sulphur regulates the GS activity in wheat leaves to increase NUE and grain yield (Yu et al 2021 ). TaGS2-A1 , B1 and D1 were mapped on group 2 and GS-2B were suggested as a candidate gene for grain protein content (GPC) QTL on 2B (Li et al 2011 ; Nigro et al 2020 ). TaGS1 was mapped in group 6 chromosomes, while TaGSr and TaGSe were in group 4 (Bernard et al 2008 ; Nigro et al 2019 ; Wang et al 2020 ).…”

Wheat Breeding through Genetic and Physical Mapping 2

“…The results presented would support a reconsideration of the ABA-WDS family as a member of the LEA superfamily. The same candidate-gene approach was reported by Nigro et al [9] as validating the involvement of glutamine synthetase and glutamate synthase genes in the control of high GPC in durum wheat. A useful and efficient method of validating a putative QTL is the constitution of near-isogenic lines (NILs), by using the marker found to be associated with QTL.…”