Structure And Function Analysis Of Grain Weight Gene TaGW2 Of The New Wheat Variety "Yannong 1212"

Wheat is one of the most important food crops,being of great importance for world food security.With the area of arable land constantly decreasing,the soil environment being damaged,natural disasters happening frequently and the population increasing,it is imperative to improve wheat production capacity.Thousand-grain weight is one of the three factors that make up wheat yield and has great impact on wheat yield.To date,conventional methods remain the most widely used wheat breeding methods in China.These methods have long hybrid breeding cycle,large workload and bottleneck in yield breakthrough.In recent years,with the development of molecular breeding technology,new ideas have been brought to wheat breeding.Modern molecular biology methods,e.g.genetic basis studies for controlling wheat grain weight,related gene cloning,benificial allelic variants discovering and functional marker development are of great significance for high yield breeding in wheat.The new wheat variety Yannong 1212 was released by the Yantai Academy of Agricultural Sciences.It has excellent traits such as high yield and disease resistance.However,little is known about the molecular basis of its theoretical basis and action mechanism of these traits.which limits the potential use of this variety in futhrure wheat breeding programs.OsGW2 controls grain width and weight in rice.Therefore,its wheat homology gene,TaGW2 was selected as a candidate gene in this study and was cloned and characterized.The function of TaGW2 in Yannong1212 and Yannong15 was studied to detect the benificial alleles.The main results were as following:(1)TaGW2 gene sequences in A,B,and D subgenomes of Yannong 1212 and Yannong 15(except for the intron 6)were cloned.(2)By comparing the sequences of Yannong 1212 and Yannong 15,several new nucleotide polymorphisms(SNPs)were found.One single SNP was found in the exon sequence of the A subgenome,located at 923 th,resulting in the amino acid sequence change.Two SNPs were found in the exon sequence of the B subgenome,One was at80 th,which caused amino acid sequence change.One was at 567 th,which did not cause amino acid sequence change.No SNP was found in exomesof the Dsubgenome.(3)The TaGW2 gene is composed of 8 exons and 7 introns.It has the same structure as GW2 of monocotyledonous species of Poaceae.It has a full-length cDNA of 1275 bp and encodes 424 amino acids.The positions 61-103 amino acid region is a RING-type domain giving it the protein E3 ubiquitin ligase activity.(4)Using Yannong 1212 and Yannong 15 as parents,210 individual plants of F2 population were generated molecular markers were designed for each SNP,to analyze the genotype of each individual plant.Correlation analysis between genotype and kernel weight showed that mutations in TaGW2 gene B subgenome significantly increased kernel weight.Thousand kernel weights of “EE” and “Ee” genotypes were increased by 3.83 g and 2.74 g compared to “ee” genotype.(5)Using the SNP marker to verify another 12 wheat varieties,none of the target fragments were amplified using the TAGW2-Y1212-B primer set,and all of the target fragments were amplified using the TAGW2-Y15-B primer combination,indicating that the SNP may occurred in low frequency and that it is possibley the unique beneficial mutant allele in Yannong 1212.The results of this study indicate that TaGW2 gene is related to wheat grain weight and may have the same mechanism of action as the rice GW2 gene,providing a theoretical basis for future high-yield breeding in wheat.