Molecular Characterisation Of ?-gliadin Genes In Wheat A Genome And The Effect On Wheat Gluten Quality

As one of the major food crops around the world,wheat can be made into many different types of food such as bread,steamed bread and cake due to the influence of the gliadin proteins in the wheat grains to the gluten quality.However,the gene encoding the gliadin as one multi-gene family has the characteristics of multiple copies and high similarity in DNA sequence,plus common wheat as one heterologous hexaploidy with a large genome and complex genetic background,these have led difficulties to the identification and analysis of the multi-gene family.In view of the factors above,we used the Triticum urartu,whose genome has already been sequenced and was considered as the ancestor specie of the A genome of the common wheat,as the research material to detect the ?-gliadin mult-gene family and its influence to the gluten quality of the common wheat.Ninety-nine ?-gliadin genes were characterized by PCR amplification and result of alignment in this research.Then the result of multi-alignment and the construction of the phylogenetic tree using these genes showed that two categories could be divided roughly,one contained three subgroups while another contained one which had never been reported from the Triticum urartu and were considered as one new multi-gene branch of the ?-gliadin genes.On the basis of above,the characteristics of the expression level among the four subgroups of the 99 ?-gliadin genes were studied and showed three expression patterns,the high level of the expression,the middle level of the expression and the low level of the expression,corresponded to the subgroup one,the subgroup two and the subgroup four with three,respectively.Based on the different expression patterns,bisulfite sequencing assay was used to research the level of methylation in the promoter region,the result showed that the level of methylation in the promoter region of group 1 and 2 was much lower than that of group 4 which did not contain the core cis-acting element of the expression of gliadin genes,the Prolamin-box.It was comprehensively indicated that the expression of the ?-gliadin genes was regulated by the methylation level and the cis-acting element in their promoter region.RNA-seq method and the processing quality of 120 different wheat cultivars were detected for studying the influence of the wheat gluten quality from the ?-gliadin genes.The correlation analysis between the transcription level and the gluten quality was carried out.The result showed that the expression of the ?-gliadin genes negatively related to the BEM,the forming time and the stable time of the dough,generally had a negative effect on the gluten quality of wheat.Meanwhile,one genome-wide association study of the transcription level of the ?-gliadin genes in the 120 different wheat cultivars have indicated 86 significant effective SNP site that influence the expression of the ?-gliadin genes,of which 67 sites were located in the homologous chromosome of group one while three sites were on the chromosome of 6A and the 16 sites remaining were distributed on the chromosomes of 2A,3D,4A,5A,5B,7A,7B and 7D respectively.