Structural and Functional Analysis of Wheat Gene Encoding the Fd Glutamine:2-Oxoglutarate Amidotransferase (Fd-GOGAT) in Wheat

Durum wheat (Triticum turgidum L. var. durum) is one of the most important cereal crops grown worldwide and provides most of the proteins in human diet. Seed storage proteins are directly related to the nutritional and technological value of the derived products. We focused on Fd-GOGAT gene as one of the potential candidate genes for determining grain protein content (GPC), as located on chromosome group 2, where a major GPC QTL is reported. Using a barley FD-GOGAT sequence as an initial query, we extracted and assembled 454-reads of cv. Chinese Spring (http://www.cerealsdb.uk.net/search_reads.htm). From the single 454 reads we were able to assemble the three orthologous genes from the three hexaploid genomes. PCR primer pairs were designed for the three distinct GOGAT hexaploid sequences and used to identify genome assignments using DNA from Chinese Spring nulli-tetrasomic lines for the group 2 chromosomes. The wheat Fd-GOGAT is comprised of 33 exons and 32 introns. Consensus exon/introns boundaries were determined using grass EST sequences aligned to the genomic sequence. The intron borders matched the canonical plant intron borders (GT…AG) for all 32 introns. We also sequenced the FD-GOGAT gene in two durum wheat cultivars, Ciccio and Svevo, with different grain protein content. The two cultivars differ for 10 SNPs and several Indels ; an insertion of 8 bp was used to map the gene and verify the correlation with the QTL for GPC located in the centromeric region of 2A chromosome.