Of ¦Á-gliadin And Wheat Breeding

In order to exploitα-gliadin composition and possible relationship with wheat breeding,one hundred and fifty-eightα-gliadin open reading frames were cloned and sequenced from wheat relative grasses,the somatic hybrid wheat introgression lineâ…¡-12 and its biparents.Out of them,sixty-threeα-gliadin open reading frames were characterized from diploid Agropyron elongatum and Elymus sibiricus.About 90%of these sequences contained an internal stop codon(TAG or TAA)or frameshift,the former maily due to the change from C to T in glutamine(CAG or CAA).Aligned with reportedα-gliadin sequences,signal peptide domain,repetitive domain and C-terminal region were significantly identical,but both polyglumatine domains different.Most of the amino acid differences could be attributed to varieties of SNPs and sequences involving complete codons,or frameshift changes.Two new types of motifs GRV and RV were found in repetitive domains of the first three codons.Novel types of motifs,including(Q)₃AR(Q)₅,(Q)₂AR(Q)₅,(Q)₃A,were characterized in the first polyglumatine region.Some ghadins with odd number of cysteine residues were discovered in both N- and C- terminal unique domain,α-gliadin of E.sibiricus contained two types of known CD epitode in potential real gene,whereas,those of diploid Agropyron elongatum has only one type in pseudogenes,no in potential real ones.Phylogenetic analysis showed thatα-gliadins from diploid Agropyron elongatum were comprised of several subfamilies,which were closely related to those from decaploid Agropyron elongatum;while that from E.sibiricus were more homologous to those from other Triticum species.Ninety-fiveα-gliadin open reading frames were cloned and sequenced from somatic hybrid wheat introgression lineâ…¡-12 and its parents Triticum aestivum cv. Jinan177(JN177)and decaploid Agropyron elongatum.The data showed the composition and origin of theα-gliadin gene inâ…¡-12 included:(1)most that were homologous to those of JN177;(2)a few derived direct from decaploid A.elongatum; (3)some new genes that were created via point mutation,unequal,crossover or slippage of a parental gene.Therefore,Novelα-gliadin genes were found to originate via point mutation,unequal crossover or slippage of a parental gene,demonstrating new genes could be rapidly created through somatic hybridization in a manner similar to that previously shown for HMW-GS genes.A particular quality attribute of interest was the presence or absence of celiac disease(CD)epitopes.These were found to be 4 times more common amongα-gliadin genes from the parent wheat JN177 than from decaploid A.elongatum.Although four types of CD-epitopes were found in introgression lineâ…¡-12,the number of the genes encoded CD-epitopes was lower than in JN177,due to the occurrence of pseudogenes.We discussed the benefit of theseα-gliadins to wheat breeding.The number and the locus of cysteine residues inα- gliadin gene play very important role in flour quality.In order to investigate their function,Two genes with odd number cysteine residues,one is from Elymus sibiricus,and the other fromâ…¡-12, were conducted prokaryotic expression and then constructed the eukaryotic expression vectors pCAMBIA3301-E42,pCAMBIA3301-â…¡-93 controlled by the promoter ubiquitin.After that these two genes were transformed into the wheat strain respectively by using Agrobacterium-mediated transformation method.Nineteen positive transgenic plants were obtained by PCR screening.It can greatly promote the further study of these genes concerning molecular characteristics,genetic analysis, functional detection and the application for wheat breeding.H1Dx5,which is cloned from the somatic hybrid wheat introgression lineâ…¡-12, is a potential quality-associated HWM-GS subunit according to its primary structure of deduced amino acid.We have constructed the eukaryotic expression vector pBIN20-H1Dx5 successfully as to pave a way for studying its function and potential utility,in plant breeding.