Allelic Variation Of Wx Proteins And Their Effects On Starch Content And Composition In Chinese Wheat Landraces

Wheat starch major component as 53%-70%of dry weight of bread wheat seeds,which is one of the important factors affecting wheat yield and quality.Wheat starch is composed of amylose and amylopectin.Amylose content is controlled by granule bound starch synthase(GBSS),granule bound starch synthase(GBSS)has two isozymes:Granule-bound starch synthase I(GBSS I)and granule-bound starch synthase II(GBSS II).Granule-bound starch synthase I(GBSS I)is also known as Wx protein.In this study,the Wx protein composition of 786 accessions of Chinese wheat landraces was investigated by using SDS-PAGE.The molecular markers specific for null Wx alleles were used to verify the molecular characteristics of this loci.The effects of deletion of Wx protein on starch content and physicochemical properties were further explored.The main results are listed as following:1.The Wx protein composition of 786 accessions of Chinese wheat landraces were characterized by using SDS-PAGE.The results showed that 13 accessions of Chinese wheat landraces lack the expression of Wx-A1 protein,25 accessions miss the Wx-B1 protein.The results showed that Chinese wheat landraces had polymorphism at Wx loci,and these accessions could be used to modify starch composition in wheat quality breeding.2.The genes encoding null Wx protein were verified by the markers specific for null Wx alleles.The results indicated that it is consistent with that of SDS-PAGE in most accessions,while the results between molecular marker and SDS-PAGE are contrary in three accessions;we conclude that these accessions may have novel structural characteristics which has led to the lack of Wx proteins.3.The total starch content of the accessions with different Wx protein composition was measured.The results showed that the variation of the total starch content of these accessions was not significant.SPSS statistical analysis and is consistent with previous studies.The amylose starch content of the accessions with different Wx protein composition was measured.The results showed that lack the expression of Wx protein affected a decrease in amylose content in different degrees.The amylose content of the Wx-B1 protein accessions is lower than that of the accessions lacking the Wx-A1 protein,and the amylose content of the Wx-A1 protein is lower than the amylose content of the normal accessions.SPSS statistical analysis amylose content of different Wx protein accessions,the results showed that the lack of Wx-A1 protein and the lack of Wx-B1 protein accessions amylose content difference in level 0.05,and Wx protein normal difference in level O.Ol.We can conclude that the effect of Wx-B1 protein on amylose content is slightly greater than that of Wx-A1 protein on amylose content.4.The gelatinization temperature of the accessions with different Wx proteincompositions was measure by Q20 Differential Scanning Calorimeter.The results indicated that the accessions with higher amylose content exhibit the higher gelatinization temperature positively related to amylose content.Statistical analysis support the amylose content and gelatinization temperature were correlated.