Characterization of <i>Ferredoxin-Dependent Glutamine-Oxoglutarate Amidotransferase (Fd-GOGAT)</i> Genes and Their Relationship with Grain Protein Content QTL in Wheat

<div><p>Background</p><p>In higher plants, inorganic nitrogen is assimilated via the glutamate synthase cycle or GS-GOGAT pathway. GOGAT enzyme occurs in two distinct forms that use NADH (NADH-GOGAT) or Fd (Fd-GOGAT) as electron carriers. The goal of the present study was to characterize wheat <i>Fd-GOGAT</i> genes and to assess the linkage with grain protein content (GPC), an important quantitative trait controlled by multiple genes.</p><p>Results</p><p>We report the complete genomic sequences of the three homoeologous A, B and D Fd-GOGAT genes from hexaploid wheat (<i>Triticum aestivum</i>) and their localization and characterization. The gene is comprised of 33 exons and 32 introns for all the three homoeologues genes. The three genes show the same exon/intron number and size, with the only exception of a series of indels in intronic regions. The partial sequence of the Fd-GOGAT gene located on A genome was determined in two durum wheat (<i>Triticum turgidum</i> ssp. <i>durum</i>) cvs Ciccio and Svevo, characterized by different grain protein content. Genomic differences allowed the gene mapping in the centromeric region of chromosome 2A. QTL analysis was conducted in the Svevo×Ciccio RIL mapping population, previously evaluated in 5 different environments. The study co-localized the <i>Fd-GOGAT-A</i> gene with the marker GWM-339, identifying a significant major QTL for GPC.</p><p>Conclusions</p><p>The wheat Fd-GOGAT genes are highly conserved; both among the three homoeologous hexaploid wheat genes and in comparison with other plants. In durum wheat, an association was shown between the <i>Fd-GOGAT</i> allele of cv Svevo with increasing GPC - potentially useful in breeding programs.</p>