ChAy/Bx, a novel chimeric high-molecular-weight glutenin subunit gene apparently created by homoeologous recombination in Triticum turgidum ssp. dicoccoides

High-molecular-weight glutenin subunits (HMW-GSs) are of considerable interest, because they play a crucial role in determining dough viscoelastic properties and end-use quality of wheat flour. In this paper, ChAy/Bx, a novel chimeric HMW-GS gene from Triticum turgidum ssp. dicoccoides (AABB, 2n = 4x = 28) accession D129, was isolated and characterized. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) analysis revealed that the electrophoretic mobility of the glutenin subunit encoded by ChAy/Bx was slightly faster than that of 1Dy12. The complete ORF of ChAy/Bx contained 1671 bp encoding a deduced polypeptide of 555 amino acid residues (or 534 amino acid residues for the mature protein), making it the smallest HMW-GS gene known from Triticum species. Sequence analysis showed that ChAy/Bx was neither a conventional x-type nor a conventional y-type subunit gene, but a novel chimeric gene. Its first 1305 nt sequence was highly homologous with the corresponding sequence of 1Ay type genes, while its final 366 nt sequence was highly homologous with the corresponding sequence of 1Bx type genes. The mature ChAy/Bx protein consisted of the N-terminus of 1Ay type subunit (the first 414 amino acid residues) and the C-terminus of 1Bx type subunit (the final 120 amino acid residues). Secondary structure prediction showed that ChAy/Bx contained some domains of 1Ay subunit and some domains of 1Bx subunit. The special structure of this HMW glutenin chimera ChAy/Bx subunit might have unique effects on the end-use quality of wheat flour. Here we propose that homoeologous recombination might be a novel pathway for allelic variation or molecular evolution of HMW-GSs.     

An approach for isolating high-molecular-weight glutenin subunit genes using monoclonal antibodies.

High-molecular-weight glutenin subunits (HMW-GSs) play an important role in the breadmaking quality of wheat flour. In China, cultivars such as Triticum aestivum 'Xiaoyan No. 6' carrying the 1Bx14 and 1By15 glutenin subunits usually have attributes that result in high-quality bread and noodles. HMW-GS 1Bx14 and 1By15 were isolated by preparative sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) and used as an antigen to immunize BALB/c mice. A resulting monoclonal antibody belonging to the IgG1 subclass was shown to bind to all HMW-GSs of Triticum aestivum cultivars, but did not bind to other storage proteins of wheat seeds in a Western blot analysis. After screening a complementary DNA expression library from immature seeds of 'Xiaoyan No. 6' using the monoclonal antibody, the HMW-GS 1By15 gene was isolated and fully sequenced. The deduced amino acid sequence showed an extra stretch of 15 amino acid repeats consisting of a hexapeptide and a nonapeptide in the repetitive domain of this y-type HMW subunit. Bacterial expression of a modified 1By15 gene, in which the coding sequence for the signal peptide was removed and a BamHI site eliminated, gave rise to a protein with mobility identical to that of HMW-GSs extracted from seeds of 'Xiaoyan No. 6' via SDS-PAGE. This approach for isolating genes using specific monoclonal antibody against HMW-GS genes is a good alternative to the extensively used polymerase chain reaction (PCR) technology based on sequence homology of HMW-GSs in wheat and its relatives.     

Molecular characterization of high molecular weight glutenin subunit allele 1Bx23 in common wheat introduced from hexaploid triticale

High molecular weight glutenin subunit (HMW-GS) 1Bx23, an x-type subset encoded by Glu-B1p, which is only distributed in Triticum turgidum, was successfully transferred from hexaploid triticale to common wheat line SY95-71. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) shows that subunit 1Bx23 has a faster mobility than subunit 1Bx7 and 1Bx20, but slower than 1Bx17. Primers designed from the conserved regions in wheat HMW-GS gene promoter and coding sequences were used to amplify the genomic DNA of SY95-71. Total nucleotide sequences of 3426 bp including an open reading frame of 2385 bp and upstream sequence of 1038 bp were obtained. Compared with the reported gene sequences of Glu-B1-1 alleles, including 1Bx7, 1Bx14, 1Bx20 and 1Bx17, the promoter region of the 1Bx23 was displayed close to 1Bx7 and 1Bx17. The deduced amino acid sequence of coding region of 1Bx23 exhibited 34, 30, 20 and 22 amino acid substitutions from that of 1Bx14, 1Bx20, 1Bx7 and 1Bx17, respectively. A phylogenetic tree based on the nucleotide sequence alignment of the Glu-1Bx alleles shows that the 1Bx23 are apparently clustered with 1Bx7 and 1Bx17, and more ancient than 1Bx14 and 1Bx20, suggesting that the evolution speeds are different among Glu-1Bx genes. Additionally, the potential use of wheat line SY95-71 to further screen the quality contribution of unique subunit 1Bx23 is also discussed.     

Molecular cloning, heterologous expression, and phylogenetic analysis of a novel y-type HMW glutenin subunit gene from the G genome of Triticum timopheevi.

A novel y-type high molecular weight (HMW) glutenin subunit gene from the G genome of Triticum timopheevi (2n=4x=28, AAGG) was isolated and characterized. Genomic DNA from accession CWI17006 was amplified and a 2200 bp fragment was obtained. Sequence analysis revealed a complete open reading frame including N- and C-terminal ends and a central repetitive domain encoding 565 amino acid residues. The molecular weight of the deduced subunit was 77,031, close to that of the x-type glutenin subunits. Its mature protein structure, however, demonstrated that it was a typical y-type HMW subunit. To our knowledge, this is the largest y-type subunit gene among Triticum genomes. The molecular structure and phylogenetic analysis assigned it to the G genome and it is the first characterized y-type HMW glutenin subunit gene from T. timopheevi. Comparative analysis and secondary structure prediction showed that the subunit possessed some unique characters, especially 2 large insertions of 45 (6 hexapeptides and a nonapeptide) and 12 (2 hexapeptides) amino acid residues that mainly contributed to its higher molecular weight and allowed more coils to be formed in its tertiary structure. Additionally, more alpha-helixes in the repeat domain of the subunit were found when compared with 3 other y-type subunits. We speculate that these structural characteristics improve the formation of gluten polymer. The novel subunit, expressed as a fusion protein in E. coli, moved more slowly in SDS-PAGE than the subunit Bx7, so it was designated Gy7*. As indicated in previous studies, increased size and more numerous coils and alpha-helixes of the repetitive domain might enhance the functional properties of HMW glutenins. Consequently, the novel Gy7* gene could have greater potential for improving wheat quality.     

Production of a monoclonal antibody specific for high molecular weight glutenin subunits (HMW-GS) in wheat and its antigenic determinant

Wheat high molecular weight glutenin subunits (HMW-GS) 1Bx14 and 1By15 isolated by preparative SDS-PAGE are used as antigen to immunize BALB/c mice. Subcutaneous inoculation of the antigen is performed. The intra-peritoneal injection is completed 3 days before fusion with myeloma cell (SP2/0) via PEG-1500. The fusion cells are selected by indirect enzyme-linked immuno-sorbent assay (ELISA). Positive hybrid cells are further verified three times by limit dilution of the culture cells. A hybridoma cell line is successfully obtained. The monoclonal antibody belongs to IgG1 subclass. In immunoblotting, the antibody binds to all HMW-GS of T.aestivum cultivars, but does not bind to other storage proteins in seeds of wheat. This result is consisting with the high homology in amino acid sequences among the HMW glutenin subunits in wheat. The antibody also binds to HMW-GS storage proteins in Aegilops squarrosa and T. durum (durum wheat). Furthermore, it also binds to HMW storage proteins in Secale cereale (rye),Hordeum vulgare (barley). However, it never binds seed storage proteins in other cereals such as maize, oat, rice, foxtail millet, sorghum etc. The antigen determinant recognized by the antibody has been located within hexapeptide [PGQGQQ] or / and nonapeptide [GYYPTSPQQ] in the central repetitive region of HMW-GS.     

小麦高分子量谷蛋白亚基Glu-B1位点沉默基因的克隆与序列分析

二粒小麦（Triticum turgidum L．var．dicoccoides）具有极其丰富的遗传多样性,是栽培小麦品种改良的巨大基因库。在高分子量谷蛋白基因的组成上,它具有许多栽培小麦不存在的变异类型,在Glu—B1位点上的变异更大。我们利用种子贮藏蛋白的SDS—PAGE方法从原产于伊朗的二粒小麦材料PI94640中观察到缺失Glu—B1区的高分子量谷蛋白亚基。利用Glu-1Bx基因保守序列设计PCR引物,对该材料的总DNA扩增,获得了X型亚基编码基因（Glu-1Bxm）的全序列,其全长为3442bp含1070bp的启动子区。序列比较发现,Glu-1Bxm在启动子区序列与Glu—1Bx7的最为相似。而在基因编码区,我们发现Glu—1Bxm仅编码212个氨基酸,由于开放阅读框中起始密码子后第637位核苷酸发生了点突变,即编码谷酰胺的CAA突变为终止密码TAA,可能直接导致了该高分子量谷蛋白亚基的失活,这是我们在小麦Glu—B1位点基因沉默分子证据的首次报道。将Glu—1Bxm全序列与Glu—B1位点其他等位基因进行了系统树分析,发现Glu—1Bxm是较为古老的类型。本文还对该特异高分子量谷蛋白亚基变异类型对品质遗传改良研究的意义进行了讨论。     

Two quality-associated HMW glutenin subunits in a somatic hybrid line between <Emphasis Type="Italic">Triticum aestivum</Emphasis> and <Emphasis Type="Italic">Agropyron elongatum</Emphasis>

High-molecular-weight glutenin subunits (HMW-GSs) from hybrid line II-12 between wheat (Triticum aestivum L.) and Agropyron elongatum (Host) Nivski were characterized with SDS-PAGE. Out of these HMW-GSs, two subunits, h1Bx and h1By, had mobilities similar to the subunits 1Bx13 and 1By16 from common wheat 4072, which was used as control. Polyclonal antibodies (pAbs) of h1Bx and h1By were prepared, and Western blotting showed that the pAbs had strong affinities for h1Bx and h1By, separately. The specificity of h1Bx-pAb was further checked; it preferentially recognized subunits h1Bx and 1Bx13. HMW-GS gene coding sequences were amplified by genomic polymerase chain reaction from hybrid II-12. Two of the five amplicons, marked II2a and II31b, were sequenced. Their coding sequences are clustered to Glu-1Bx7 and Glu-1By9 of common wheat. Three discrepant regions in deduced amino acid sequences of II2a and 31b repeated one time more than Glu-1Bx7 and Glu-1By9. N-terminal sequences of h1Bx and h1By were determined, which were identical to the published sequences of 1Bx13 and 1By16 and in agreement with that deduced from II2a and II31b, respectively. These results indicated that the two novel genes separated from the hybrid wheat derived from the allelic variation of 1Bx7 and 1By9 of the parent wheat. There is an additional cysteine residue positioned at 271st amino acid of the mature peptide of II2a, which may be related to the high quality of the flour.     

Production of a monoclonal antibody specific for high molecular weight glutenin subunits (HMW-GS) in wheat and its antigenic determinant

Wheat high molecular weight glutenin subunits (HMW-GS) 1Bx14 and 1By15 isolated by preparative SDS-PAGE are used as antigen to immunize BALB/c mice. Subcutaneous inoculation of the antigen is performed. The intra-peritoneal injection is completed 3 days before fusion with myeloma cell (SP2/0) via PEG-1500. The fusion cells are selected by indirect enzyme-linked immuno-sorbent assay (ELISA). Positive hybrid cells are further verified three times by limit dilution of the culture cells. A hybridoma cell line is successfully obtained. The monoclonal antibody belongs to lgG1 subclass. In immunoblotting, the antibody binds to all HMW-GS of T. aestivum cultivars, but does not bind to other storage proteins in seeds of wheat. This result is consisting with the high homology in amino acid sequences among the HMW glutenin subunits in wheat. The antibody also binds to HMW-GS storage proteins in Aegilops squarrosa and T. durum (durum wheat). Furthermore, it also binds to HMW storage proteins in Secale cereale (rye), Hordeum vulgare (barley). However, it never binds seed storage proteins in other cereals such as maize, oat, rice, foxtail millet, sorghum etc. The antigen determinant recognized by the antibody has been located within hexapeptide [PGQGQQ] or / and nonapeptide [GYYPTSPQQ] in the central repetitive region of HMW-GS.     

The characterization and comparative analysis of high-molecular-weight glutenin genes from genomes A and B of a hexaploid bread wheat

Summary Two high-molecular-weight subunit (HMWS) glutenin genes from the A and B genomes of the hexaploid bread wheat Triticum aestivum L. cv Cheyenne have been isolated and sequenced. Both of these genes are of the high M_r class (x-type) of HMW glutenins, and have not been previously reported. The entire set of six HMW genes from cultivar Cheyenne have now been isolated and characterized. An analysis of the Ax and Bx sequences shows that the Ax sequence is similar to the homoeologous gene from the D genome, while the Bx repeat structure is significantly different. The repetitive region of these proteins can be modelled as a series of interspersed copies of repeat modifs of 6, 9, and 15 amino acid residues. The evolution of these genes includes single-base substitutions over the entire coding region, plus insertion/deletions of single or blocks of repeats in the central repetitive domain.     

带芒草属低分子量谷蛋白基因的克隆及序列分析

在普通小麦中获得了大量的低分子量谷蛋白基因序列, 而在小麦近缘属物种中获得的同源基因则比较少, 导致对麦类低分子量谷蛋白基因家族成员间的关系还不清楚。因此, 进行近缘属物种低分子量谷蛋白基因的研究是非常必要的。此研究通过特殊设计的1对引物, 以小麦近缘属带芒草物种的基因组DNA为模板, 经过PCR和克隆, 从中得到了一条核苷酸序列长度为1 035 bp, 推测的氨基酸序列为343个氨基酸残基的低分子量谷蛋白基因, 该基因序列具有小麦低分子量谷蛋白基因的典型特征, 包括21个氨基酸残基的信号肽、13个氨基酸的N-端和由可重复的短肽单元组成的重复区以及1个C末端。序列比对结果揭示了来自带芒草的低分子量谷蛋白基因与小麦同源基因的差异及相互关系。此研究结果对从带芒草属以及其他小麦近缘属物种中分离未知低分子量谷蛋白基因有参考价值和借鉴意义。     

Characterization of two HMW glutenin subunit genes from Taenitherum Nevski

The compositions of high molecular weight (HMW) glutenin subunits from three species of Taenitherum Nevski (TaTa, 2n = 2x = 14), Ta. caput-medusae, Ta. crinitum and Ta. asperum, were investigated by SDS-PAGE analysis. The electrophoresis mobility of the x-type HMW glutenin subunits were slower or equal to that of wheat HMW glutenin subunit Dx2, and the electrophoresis mobility of the y-type subunits were faster than that of wheat HMW glutenin subunit Dy12. Two HMW glutenin genes, designated as Tax and Tay, were isolated from Ta. crinitum, and their complete nucleotide coding sequences were determined. Sequencing and multiple sequences alignment suggested that the HMW glutenin subunits derived from Ta. crinitum had the similar structures to the HMW glutenin subunits from wheat and related species with a signal peptide, and N- and C-conservative domains flanking by a repetitive domain consisted of the repeated short peptide motifs. However, the encoding sequences of Tax and Tay had some novel modification compared with the HMW glutenin genes reported so far: (1) A short peptide with the consensus sequences of KGGSFYP, which was observed in the N-terminal of all known HMW glutenin genes, was absent in Tax; (2) There is a specified short peptide tandem of tripeptide, hexapeptide and nonapeptide and three tandem of tripeptide in the repetitive domain of Tax; (3) The amino acid residues number is 105 (an extra Q presented) but not 104 in the N-terminal of Tay, which was similar to most of y-type HMW glutenin genes from Elytrigia elongata and Crithopsis delileana. Phylogenetic analysis indicated that Tax subunit was mostly related to Ax1, Cx, Ux and Dx5, and Tay was more related to Ay, Cy and Ry.     

Structure,variation and expression analysis of glutenin gene promoters from Triticum aestivum cultivar Chinese Spring shows the distal region of promoter 1Bx7 is key regulatory sequence

In this study, ten glutenin gene promoters were isolated from model wheat (Triticum aestivum L. cv. Chinese Spring) using a genomic PCR strategy with gene-specific primers. Six belonged to high-molecular-weight glutenin subunit (HMW-GS) gene promoters, and four to low-molecular-weight glutenin subunit (LMW-GS). Sequence lengths varied from 1361 to 2554 bp. We show that the glutenin gene promoter motifs are conserved in diverse sequences in this study, with HMW-GS and LMW-GS gene promoters characterized by distinct conserved motif combinations. Our findings show that HMW-GS promoters contain more functional motifs in the distal region of the glutenin gene promoter (> − 700 bp) compared with LMW-GS. The y-type HMW-GS gene promoters possess unique motifs including RY repeat and as-2 box compared to the x-type. We also identified important motifs in the distal region of HMW-GS gene promoters including the 5′-UTR Py-rich stretch motif and the as-2 box motif. We found that cis-acting elements in the distal region of promoter 1Bx7 enhanced the expression of HMW-GS gene 1Bx7. Taken together, these data support efforts in designing molecular breeding strategies aiming to improve wheat quality. Our results offer insight into the regulatory mechanisms of glutenin gene expression.     

Sequence and properties of HMW subunit 1Bx20 from pasta wheat (<Emphasis Type="Italic">Triticum durum</Emphasis>) which is associated with poor end use properties

The gene encoding high-molecular-weight (HMW) subunit 1Bx20 was isolated from durum wheat cv. Lira. It encodes a mature protein of 774 amino acid residues with an M(r) of 83,913. Comparison with the sequence of subunit 1Bx7 showed over 96% identity, the main difference being the substitution of two cysteine residues in the N-terminal domain of subunit 1Bx7 with tyrosine residues in 1Bx20. Comparison of the structures and stabilities of the two subunits purified from wheat using Fourier-transform infra-red and circular dichroism spectroscopy showed no significant differences. However, incorporation of subunit 1Bx7 into a base flour gave increased dough strength and stability measured by Mixograph analysis, while incorporation of subunit 1Bx20 resulted in small positive or negative effects on the parameters measured. It is concluded that the different effects of the two subunits could relate to the differences in their cysteine contents, thereby affecting the cross-linking and hence properties of the glutenin polymers.     

类大麦材料y型高分子量谷蛋白基因不表达的鉴定

利用SDS-PAGE检测了2份类大麦属植物的高分子量谷蛋白亚基组成,在小麦的高分子量区域仅检测到1条蛋白带,因此怀疑其y型亚基没有表达.根据其它高分子量谷蛋白提取方法的结果以及基因编码区部分序列测定,确认其y型高分子量谷蛋白基因是沉默的.     

Identification and characterization of high-molecular-weight glutenin genes in Polish triticale cultivars by PCR-based DNA markers

Molecular markers were used to identify the allele/gene composition of complex loci Glu-A1 and Glu-B1 of high-molecular-weight (HMW) glutenin subunits in triticale cultivars. Forty-six Polish cultivars of both winter and spring triticale were analysed with 7 PCR-based markers. Amplified DNA fragments of HMW glutenin Glu-1 genes were separated by agarose slab-gel electrophoresis. Differences between all 3 alleles at the locus Glu-A1 [Glu-A1a (encoding Ax1), 1b (Ax2*), and 1c (AxNull)], 4 alleles at Glu-B1-1 [Glu-B1-1a (Bx7), 1b (Bx7*), 1d (Bx6), 1ac (Bx6.8)], and 5 alleles at Glu-B1-2 [Glu-B1-2a (By8), 2b (By9), 2o (By8*), 2s (By18*), and 2z (By20*)] were revealed. In total, 16 allele combinations were observed. Molecular markers are particularly helpful in distinguishing the wheat Glu-A1a and Glu-A1b alleles from the rye Glu-R1a and Glu-R1b alleles in triticale genotypes, respectively, as well as subunits Bx7 from Bx7* and By8 from By8*, which could not be distinguished by SDS-PAGE. Novel glutenin subunits By18* and By20* (unique to triticale) were identified. HMW glutenin subunit combinations of Polish triticale cultivars, earlier identified by SDS-PAGE analyses, were verified by PCR-based DNA markers. Rapid identification of wheat Glu-1 alleles by molecular markers can be an efficient alternative to the standard separation procedure for early selection of useful triticale genotypes with good bread-making quality.     

Molecular cloning and comparative analysis of a y-type inactive HMW glutenin subunit gene from cultivated emmer wheat (Triticum dicoccum L.)

Cultivated emmer (Triticum dicoccum, 2n = 4x = 28, AABB) is closely related to bread wheat and possesses extensive allelic variations in high molecular weight glutenin subunit (HMW-GS) composition. These alleles may be an important genetic resource for wheat quality improvement. To isolate and clone HMW-GS genes from cultivated emmer, two pairs of allele-specific (AS) PCR primers were designed to amplify the coding sequence of y-type HMW-GS genes and their upstream sequences, respectively. The results showed that single bands of strong amplification were obtained through AS-PCR of genomic DNA from emmer. After cloning and sequencing the complete sequence of coding and 5'-flanking regions of a y-type subunit gene at Glu-A1 locus was obtained. Nucleotide and deduced amino acid sequences analysis showed that this gene possessed a similar structure as the previously reported Ay gene from common wheat, and is hence designated as Ay1d. The distinct feature of the Ay1d gene is that its coding region contains four stop codons and its upstream region has a 85-bp deletion in the same position of the Ay gene, which are probably responsible for the silencing of y-type subunit genes at Glu-A1 locus. Phylogenetic analysis of HMW glutenin subunit genes from different Triticum species and genomes were also carried out.     

Characterization of a novel variant HMW-glutenin gene from Elymus canadensis

High molecular weight (HMW) glutenin subunits (GS) play a key role in the determination of end-use quality of wheat and other cereal crops. In this study, we report the isolation and characterization of both promoter region and ORF of novel HMW-GS allele 1St1.3 from a perennial Triticeae species, Elymus canadensis. The amino acid (AA) sequences of E. canadensis 1St1.3 were deduced as 434 aa. Its protein primary structure comprises a signal peptide with a conserved N-terminal domain, a central repetitive domain and a C-terminal domain. E. canadensis 1St 1.3 possesses several distinct characteristics which are different from those of wheat HMW-GSs. The N-terminal domains of E. canadensis 1St 1.3 resemble that of y-type subunits, while their C-terminal domains are more similar to x-type subunits. The deletion of 85 bp fragment has been observed in promoter region of 1St 1.3, however which has not interrupted the expression of this gene. Our results indicate that 1St 1.3 is novel HMW-GS variants which will be valuable for enhancing our understanding of structural differentiation and the evolutionary relationship among HMW-GSs in Triticeae species.     

Identification and molecular characterization of a large insertion within the repetitive domain of a high-molecular-weight glutenin subunit gene from hexaploid wheat

High-molecular-weight (HMW) glutenin subunits are a particular class of wheat endosperm proteins containing a large repetitive domain flanked by two short N- and C-terminal non-repetitive regions. Deletions and insertions within the central repetitive domain has been suggested to be mainly responsible for the length variations observed for this class of proteins. Nucleotide sequence comparison of a number of HMW glutenin genes allowed the identification of small insertions or deletions within the repetitive domain. However, only indirect evidence has been produced which suggests the occurrence of substantial insertions or deletions within this region when a large variation in molecular size is present between different HMW glutenin subunits. This paper represents the first report on the molecular characterization of an unusually large insertion within the repetitive domain of a functional HMW glutenin gene. This gene is located at the Glu-D1 locus of a hexaploid wheat genotype and contains an insertion of 561 base pairs that codes for 187 amino acids corresponding to the repetitive domain of a HMW glutenin subunit encoded at the same locus. The precise location of the insertion has been identified and the molecular processes underlying such mutational events are discussed.     

高冰草中一种新型高分子量麦谷蛋白亚基编码序列的研究

高冰草(Agropyron elongatun)是普通小麦(Triticum aestivum)的近缘禾草,SDS-PAGE显示其所编码的麦谷蛋白亚基的类型较普通小麦更加丰富,是普通小麦品质改良的重要亲本之一。利用基因组PCR的方法从高冰草中克隆到一个新的高分子量麦谷蛋白亚基(HMW-GS)基因(AgeloG2)全编码序列,同源性分析表明：与普通小麦的1Dy12基因比较在少数位点发生了碱基替换和一处6碱基序列的缺失,同源性为99％;与普通小麦的1Dy10基因比较,该基因亦只有少数碱基的替换和两处18碱基序列的增加及一处6碱基序列的缺失,同源性为98％。从推导的编码序列分析,AgeloG2编码y型HMW—GS。综上分析,AgeloG2是一个新的高分子量麦谷蛋白y-型亚基基因。聚类分析结果显示,无论在基因序列还是推导的氨基酸序列上,小麦1Dy亚基与AgeloG2的同源性都高于与粗山羊来源的y型亚基的同源性。     

小麦高分子量麦谷蛋白亚基1Dx5启动子驱动外源基因的表达

将小麦高分子量麦谷蛋白亚基(HMW-GS)基因的胚乳组织特异性表达启动子驱动的外源突变型1Dx5基因和gus基因导入小麦中.对其转基因植株连续3代的跟踪研究表明,突变型1Dx5基因的重复序列导致其表达蛋白分子量增大,并影响其它1Bx17 1By18亚基基因的表达.组织化学分析观察到gus基因在1Dx5基因启动子驱动下的表达表现出胚乳组织特异性,在开花2周后开始表达,表达量呈持续上升,至腊熟期达到最高,其次为籽粒成熟期.