Analysis Of Wx Gene Sequences From Diploid Species Of Three Wheat Related Genera

The content and composition of starch plays an important role in determining the processing quality and end-use of wheat flours although its account for about 70%of total grain weight.The amylose/amylopectin ratio is an important factor affecting starch properties.Waxy protein(GBSSI)is the sole enzyme that directly affects the expression of amylose in grain.Allelic variation at the Wx locus of common wheat has been studied in detail.However,limited Wx genes has been isolated from wheat wild relative species distantly related to wheat genera Wx gene is rarely reported.For example,no full length Wx gene sequence has been isolated from diploid species of Eremopyrum,Psathyrostachys and Henrardia genera.In this study,eight complete Wx gene sequences has been isolated and sequenced from eight accessions belonging to three wheat related generas.The main results are as follows:1.The two Wx genes from Er.bonaepartis were 2,776 bp in nucleotide lengths.The two Wx proteins shared the same deduced amino acid sequences although they showed four single nucleotide polymorphism(SNP)in nucleotides.One SNP leading to one amino acid substitution was occurred in the two Wx genes from Er.triticeum although both of them were 2,750 bp in DNA sequences.Divergence times evaluation suggested that the divergence time of four Wx genes from two Eremopyrum species with Wx-A~u1d from T.urartu was the shortest,with 2.42 million years ago(MYA)and 3.42 MYA,respectively.SIFT Blank analysis indicated that the two or three amino acid substitutions(82 F?L,234L?P and 305 A?S)between the two Wx protein from two Er.triticeum accessions probably have deleterious affect on Wx protein activity,and two Wx protein from two Er.Bonaepartis accessions have normal activity.2.The two Wx genes from two Ps.juncea accessions were 2,820 bp and 2,834 bp,respectively.A total of 17 SNPs were occurred in exons,and more insertion or deletion(INDELs)on sixth and seventh introns were found.In the deduced amino acid sequences,there were five amino acid substitutions between the two protein.Divergence times evaluation suggested that the nucleotide sequences of two Wx from Ps.juncea showed the shortest divergence times with the Wx from H.vulgare by 2.86 MYA.It is speculated that two amino acid substitutions(163 I?Y and 237 L?P)in the two Wx of Ps.juncea may affect Wx protein activity through SIFT Blank analysis.3.The Wx genes from two He.persica accessions were 2,778 bp and 2,773 bp,respectively.There were 20 SNPs in exon regions and INDELs in the second,fourth and ninth introns.In the deduced amino acid sequence,the two Wx proteins showed only two amino acid substitutions.Divergence times evaluation suggested that the nucleotide sequences of two Wx from He.persica had the shortest divergence times with S.cereale by2.28 MYA.SIFT Blank analysis suggested that no substitution was found to have deleterious effects on the Wx proteins from two He.persica accessions.4.In short,the Wx genes from three wheat related wild genera were about 2,800 bp in nucleotide lengths.Compared with the Wx from common wheat,the sequence identity in exon regions is ranged from 93.01-95.59%,and it is only varied from 67.98-76.24%in the introns.SNPs in exons and INDELs in introns were mainly responsible for the sequence divergence among them.5.Cluster analysis and estimated of divergence times showed the Wx genes from Ns genome of Ps.juncea were closer to the Wx from H genome of H.vulgare.Similarly,the Wx from Fs genome of Er.triticeum and O genome of He.persica were closer to A genome of common wheat.However,the Wx genes from Xe genome of Eremopyrum were distantly related to the Wx genes from other wheat wild species.