TaGS-D1, an ortholog of rice OsGS3, is associated with grain weight and grain length in common wheat

The OsGS3 gene plays a principal role in controlling grain weight and grain length in rice. However, the function of an orthologous gene TaGS in wheat has not been analyzed to date. In the present study, we cloned the gDNA of TaGS gene, designated TaGS-D1, with four exons and three introns on chromosome 7DS by a comparative genomics approach. The cDNA of TaGS-D1 is 255 bp, and it encodes 85 amino acids. We also found a plant-specific organ size regulation domain in the deduced polypeptide, indicating that TaGS-D1, like OsGS3, does not belong to the PEBP family. DNA sequencing of the TaGS-D1 locus revealed no diversity in the coding sequence of exons, but there was a single nucleotide polymorphism (SNP) in the first intron, and 30 SNPs, a 40-bp InDel and a 3-bp InDel were found in the second intron between genotypes with higher and lower thousand grain weights (TGW). Based on the 40-bp InDel, a co-dominant STS marker, designated GS7D, was developed to discriminate the two alleles. GS7D was 8.0 cM from Xbarc184 located on chromosome 7DS by linkage mapping. A QTL for TGW and grain length at GS7D locus explained up to 16.3 and 7.7 %, respectively, of the phenotypic variances in a RIL population derived from Doumai/Shi 4185 grown in Shijiazhuang and Beijing. One hundred and seventy-five Chinese wheat cultivars were genotyped with GS7D, indicating that TaGS-D1 was significantly associated with grain weight. The allelic distribution at the TaGS-D1 locus showed that the frequencies of TaGS-D1a were high in cultivars from Serbia, Japan, Australia, Canada, and the Northeastern Spring Wheat and Northern Winter Wheat Regions of China.