A γ-hordein gene

Association mapping of malting quality traits in UK spring and winter barley cultivar collections

Historical malting quality data was collated from UK national and recommended list trial data and used in a GWAS. 25 QTL were identified, with the majority from spring barley cultivar sets. In Europe, the most economically significant use of barley is the production of malt for use in the brewing and distilling industries. As such, selection for traits related to malting quality is of great commercial interest. In order to study the genetic basis of variation for malting quality traits in UK cultivars, a historical set of trial data was collated from national and recommended list trials from the period 1988 to 2016. This data was used to estimate variety means for 20 quality related traits in 451 spring barley cultivars, and 407 winter cultivars. Genotypes for these cultivars were generated using iSelect 9k and 50k genotyping platforms, and a genome wide association scan performed to identify malting quality quantitative trait loci (QTL). 24 QTL were identified in spring barley cultivars, and 2 from the winter set. A number of these correspond to known malting quality related genes but the remainder represents novel genetic variation that is accessible to breeders for the genetic improvement of new cultivars.

Overexpressing wheat low-molecular-weight glutenin subunits in rice (Oryza sativa L. japonica cv. Koami) seeds

Genes encoding wheat low-molecular-weight glutenin subunits (LMW-GSs) that confer dough strength and extensibility were previously identified from Korean wheat cultivars. To improve low viscoelasticity of rice (Oryza sativa L.) dough caused by the lack of seed storage proteins comparable to wheat gluten, two genes, LMW03 and LMW28, encoding LMW-GSs are cloned from Korean wheat cultivar Jokyoung. The LMW genes are inserted into binary vectors under the control of the rice endosperm-specific Glu-B1 promoter. Transgenic rice plants expressing LMW03 or LMW28 in their seeds are generated using Agrobacterium-mediated transformation. The expression of recombinant wheat LMW-GS in the transgenic rice seeds was confirmed by SDS-PAGE and immunoblot analysis. Their accumulation in the endosperm and aleurone layers of rice seeds was observed through in situ immuno-hybridization.

Cellular Localization of Wheat High Molecular Weight Glutenin Subunits in Transgenic Rice Grain

Rice (Oryza sativa L.) is a primary global food cereal. However, when compared to wheat, rice has poor food processing qualities. Dough that is made from rice flour has low viscoelasticity because rice seed lacks storage proteins that are comparable to gluten protein from wheat. Thus, current research efforts aim to improve rice flour processing qualities through the transgenic expression of viscoelastic proteins in rice seeds. In this study, we characterized the transgenic expression of wheat glutenin subunits in rice seeds. The two genes 1Dx5_KK and 1Dy10_JK, which both encode wheat high-molecular-weight glutenin subunits that confer high dough elasticity, were cloned from Korean wheat cultivars KeumKang and JoKyung, respectively. These genes were inserted into binary vectors under the control of the rice endosperm-specific Glu-B1 promoter and were expressed in the high-amylose Korean rice cultivar Koami (Oryza sativa L.). Individual expression of both glutenin subunits was confirmed by SDS-PAGE and immunoblot analyses performed using T₃ generation of transgenic rice seeds. The subcellular localization of 1Dx5_KK and 1Dy10_JK in the rice seed endosperm was confirmed by immunofluorescence analysis, indicating that the wheat glutenin subunits accumulate in protein body-II and novel protein body types in the rice seed. These results contribute to our understanding of engineered seed storage proteins in rice.

Comparing Multiple Reaction Monitoring and Sequential Window Acquisition of All Theoretical Mass Spectra for the Relative Quantification of Barley Gluten in Selectively Bred Barley Lines

Celiac disease (CD) is a disease of the small intestine that occurs in genetically susceptible subjects triggered by the ingestion of cereal gluten proteins for which the only treatment is strict adherence to a life-long gluten-free diet. Barley contains four gluten protein families, and the existence of barley genotypes that do not accumulate the B-, C-, and D-hordeins paved the way for the development of an ultralow gluten phenotype. Using conventional breeding strategies, three null mutations behaving as recessive alleles were combined to create a hordein triple-null barley variety. Proteomics has become an invaluable tool for characterization and quantification of the protein complement of cereal grains. In this study multiple reaction monitoring (MRM) mass spectrometry, viewed as the gold standard for peptide quantification, was compared to the data-independent acquisition strategy known as SWATH-MS (sequential window acquisition of all theoretical mass spectra). SWATH-MS was comparable (p < 0.001) to MRM-MS for 32/33 peptides assessed across the four families of hordeins (gluten) in eight barley lines. The results of SWATH-MS analysis further confirmed the absence of the B-, C-, and D-hordeins in the triple-null barley line and showed significantly reduced levels ranging from <1% to 16% relative to wild-type (WT) cv Sloop for the minor γ-hordein class. SWATH-MS represents a valuable tool for quantitative proteomics based on its ability to generate reproducible data comparable with MRM-MS, but has the added benefits of allowing reinterrogation of data to improve analytical performance, ask new questions, and in this case perform quantification of trypsin-resistant proteins (C-hordeins) through analysis of their semi- or nontryptic fragments.

Creation of the first ultra-low gluten barley (Hordeum vulgare L.) for coeliac and gluten-intolerant populations

Coeliac disease is a well-defined condition that is estimated to affect approximately 1% of the population worldwide. Noncoeliac gluten sensitivity is a condition that is less well defined, but is estimated to affect up to 10% of the population, and is often self-diagnosed. At present, the only remedy for both conditions is a lifelong gluten-free diet. A gluten-free diet is often expensive, high in fat and low in fibre, which in themselves can lead to adverse health outcomes. Thus, there is an opportunity to use novel plant breeding strategies to develop alternative gluten-free grains. In this work, we describe the breeding and characterization of a novel ultra-low gluten (ULG) barley variety in which the hordein (gluten) content was reduced to below 5 ppm. This was achieved using traditional breeding strategies to combine three recessive alleles, which act independently of each other to lower the hordein content in the parental varieties. The grain of the initial variety was shrunken compared to wild-type barleys. We implemented a breeding strategy to improve the grain size to near wild-type levels and demonstrated that the grains can be malted and brewed successfully. The ULG barley has the potential to provide novel healthy foods and beverages for those who require a gluten-free diet.

The γ-gliadin-like γ-prolamin genes in the tribe Triticeae

The γ-prolamins are important components of seed storage proteins in wheat and other Triticeae species. Here, the γ-prolamin genes from the diploid Triticeae species were systemically characterized. Most of the γ-prolamins (except 75 K γ-secalins) characterized were defined as γ-gliadin-like γ-prolamins, since they shared same characteristic model structure with γ-gliadins. Over one-third of these putatively functional γ-prolamin peptides contained different number of cysteine residues as compared to the eight residues present in γ-gliadins. Sequence polymorphism and linkage disequilibrium analyses showed the conservation of γ-prolamin genes in Triticeae species under evolutionary selection. Phylogenetic analyses indicated that these γ-prolamin genes can not be clearly separated according to their genomic origins, reflecting the conservation of γ-gliadinlike γ-prolamin genes after the divergence of Triticeae species. A screening of coeliac disease (CD) toxic epitopes shows that the γ-prolamins from some other genomes contain much fewer epitopes than those from the A, S (B) and D genomes of wheat. These findings contribute to better understanding of γ-prolamin family in Triticeae and build a ground for breeding less CD-toxic wheat cultivars.

A new class of wheat gliadin genes and proteins

The utility of mining DNA sequence data to understand the structure and expression of cereal prolamin genes is demonstrated by the identification of a new class of wheat prolamins. This previously unrecognized wheat prolamin class, given the name δ-gliadins, is the most direct ortholog of barley γ3-hordeins. Phylogenetic analysis shows that the orthologous δ-gliadins and γ3-hordeins form a distinct prolamin branch that existed separate from the γ-gliadins and γ-hordeins in an ancestral Triticeae prior to the branching of wheat and barley. The expressed δ-gliadins are encoded by a single gene in each of the hexaploid wheat genomes. This single δ-gliadin/γ3-hordein ortholog may be a general feature of the Triticeae tribe since examination of ESTs from three barley cultivars also confirms a single γ3-hordein gene. Analysis of ESTs and cDNAs shows that the genes are expressed in at least five hexaploid wheat cultivars in addition to diploids Triticum monococcum and Aegilops tauschii. The latter two sequences also allow assignment of the δ-gliadin genes to the A and D genomes, respectively, with the third sequence type assumed to be from the B genome. Two wheat cultivars for which there are sufficient ESTs show different patterns of expression, i.e., with cv Chinese Spring expressing the genes from the A and B genomes, while cv Recital has ESTs from the A and D genomes. Genomic sequences of Chinese Spring show that the D genome gene is inactivated by tandem premature stop codons. A fourth δ-gliadin sequence occurs in the D genome of both Chinese Spring and Ae. tauschii, but no ESTs match this sequence and limited genomic sequences indicates a pseudogene containing frame shifts and premature stop codons. Sequencing of BACs covering a 3 Mb region from Ae. tauschii locates the δ-gliadin gene to the complex Gli-1 plus Glu-3 region on chromosome 1.

Barley γ3-hordein: glycosylation at an atypical site, disulfide bridge analysis, and reactivity with IgE from patients allergic to wheat

Post translational modifications of a seed storage protein, barley γ3-hordein, were determined using immunochemical and mass spectrometry methods. IgE reactivity towards this protein was measured using sera from patients diagnosed with allergies to wheat. N-glycosylation was found at an atypical Asn-Leu-Cys site. The observed glycan contains xylose. This indicates that at least some γ3-hordein molecules trafficked through the Golgi apparatus. Disulfide bridges in native γ3-hordein were almost the same as those found in wheat γ46-gliadin, except the bridge involving the cysteine included in the glycosylation site. IgE reacted more strongly towards the recombinant than the natural γ3-hordein protein. IgE binding to γ3-hordein increased when the protein sample was reduced. Glycosylation and disulfide bridges therefore decrease epitope accessibility. Thus the IgE from patients sensitized to wheat cross-react with γ3-hordein due to sequence homology with wheat allergens rather than through shared carbohydrate determinants.

Analysis of a rare recombination event within the multigenic Hor 2 locus of barley (Hordeum vulgare L.)

A rare recombinant within the multigenic Hor 2 locus of barley was detected by SD-PAGE of hordein fractions from F2 grain from the cross Bomi × P12/3. Analysis of a homozygous F4 line by 2-D IEF/SDS-PAGE showed that recombination between the class I/II and class III subfamilies of genes had occurred, indicating that they are spatially separate within the Hor 2 locus. RFLP analysis using a B hordein-related cDNA clone confirmed that recombination had occurred, while similar analysis using a genomic clone related to γ-type hordein (encoded by the Hor 5/HrdF locus) indicated the order of the two subfamilies of genes on the short arm of chromosome 5, the class I/II genes being closer to the centromere. The results are consistent with the origin of the B hordein gene family from initial duplication of a single ancestral gene to give two genes which diverged to become the ancestors of the class I/II and class III subfamilies. Subsequent cycles of duplication and divergence have resulted in the present high degree of polymorphism.

From analysis of mutants to genetic engineering

This chapter describes the research of developing transgenic barley for synthesis of recombinant proteins with practical significance and of metabolic engineering of proanthocyanidin-free barley. The results were obtained by graduate students, postdoctoral researchers, and visiting scientists at the Carlsberg Laboratory from 1972-1996 and during the past ten years at Washington State University. It is written in appreciation of their enthusiasm, skill, and perseverance.

Real-time polymerase chain reaction based assays for quantitative detection of barley, rice, sunflower, and wheat

Quality assurance is a major issue in the food industry. The authenticity of food ingredients and their traceability are required by consumers and authorities. Plant species such as barley (Hordeum vulgare), rice (Oryza sativa), sunflower (Helianthus annuus), and wheat (Triticum aestivum) are very common among the ingredients of many processed food products; therefore the development of specific assays for their specific detection and quantification are needed. Furthermore, the production and trade of genetically modified lines from an increasing number of plant species brings about the need for control within research, environmental risk assessment, labeling/legal, and consumers' information purposes. We report here the development of four independent real-time polymerase chain reaction (PCR) assays suitable for identification and quantification of four plant species (barley, rice, sunflower, and wheat). These assays target gamma-hordein, gos9, helianthinin, and acetyl-CoA carboxylase sequences, respectively, and were able to specifically detect and quantify DNA from the target plant species. In addition, the simultaneous amplification of RALyase allowed bread from durum wheat to be distinguished. Limits of detection were 1 genome copy for barley, sunflower, and wheat and 3.3 copies for rice real-time PCR systems, whereas limits of quantification were 10 genome copies for barley, sunflower, or wheat and approximately 100 haploid genomes for rice real-time PCR systems. Real-time PCR cycling conditions of the four assays were stated as standard to facilitate their use in routine laboratory analyses. The assays were finally adapted to conventional PCR for detection purposes, with the exception of the wheat assay, which detects rye simultaneously with similar sensitivity in an agarose gel.

Cloning and molecular characterization of B-hordeins from Hordeum chilense (Roem. et Schult.)

One of the main limitations of cereal breeding is the lack of genetic variability within cultivated crops. Hordeum chilense is a wild relative of Hordeum vulgare, which has been successfully used in the synthesis of amphiploids by crossing with Triticum spp. Among the agronomic traits of these new amphiploids, the allelic variation in the endosperm storage proteins and their influence on breadmaking and malting quality are of special interest. B-hordeins are sulfur rich prolamins, which account for 70-80% of the total hordein fraction in barley. In this work, rapid amplification of cDNA ends by PCR (RACE-PCR) has been used for the cloning of the full-length open reading frame (ORF) of six sequences of B3-hordeins from two lines of H. chilense. Two consensus sequences of 813 and 822 bp for the H1 and H7 lines, respectively, were determined by alignment of all the sequences generated. Between both lines, differences involving single base changes, which could correspond to single nucleotide polymorphisms (SNP), insertions and deletions were observed. Of these differences, only six out of the 13 within the ORF caused a change of amino acid. Two insertions/deletions of 9 and 12 bp were also observed between both lines. The derived amino acid sequences showed a similar structure to the B-hordeins from cultivated barley and other prolamins. The repetitive region is based on the repetition of the motif PQQPFPQQ. The copy number of the B3-hordeins was estimated as a minimum of nine and five copies for the H1 and H7 lines, respectively. The expression profile of the B-hordeins through the developing endosperm is also described in this work. This study of the storage proteins of H. chilense is a useful contribution to the knowledge of the genetic diversity available in wild relatives of cultivated barley. In addition, the origin of the different prolamins can be better understood with an in-depth knowledge of its wild equivalent.

Cloning and characterization of a gamma-3 hordein mRNA (cDNA) from Hordeum chilense (Roem. et Schult.)

Hordeum chilense is a wild relative of H. vulgare, cultivated barley, that has been successfully used in the synthesis of amphiploids by crossing with Triticum spp. These amphiploids-named generically x Tritordeum-have been tested under field conditions, and one of them, the hexaploid tritordeum obtained following chromosome doubling of the hybrid H. chilense x T. turgidum, shows traits of interest inherited from the barley parent. Of great interest is the allelic variation observed in the endosperm storage proteins and their influence on the breadmaking and malting quality of tritordeum. We report here two mRNA (cDNA) sequences for a gamma-3 hordein from two accession lines of H. chilense, H1 and H7, and their characterization by quantitative real time (QRT)-PCR in the developing endosperm. Sequences were obtained by rapid amplification of cDNA ends and "edge-to-edge" amplification of open reading frames from cDNA of H. chilense. Eight putative single nucleotide polymorphisms and one codon insertion were identified in the sequences of the H1 and H7 gamma-3 hordeins. The deduced amino acid sequences showed similar features to that of the gamma-3 hordein and gamma-gliadins from barley and wheat, respectively. While the repetitive motif (PQQQPF) is similar to that of the gamma-3 hordein from H. vulgare, there are 19 motif repeats in H. vulgare, whereas H. chilense shows 15 tandem repeats. The transcription of the genes encoding for the gamma-3 hordein were monitored by QRT-PCR: in both lines maximum transcription occurred 12 days after flowering.

The promoter of the gene Itr1 from barley confers a different tissue specificity in transgenic tobacco

Tissue-specific expression of the gene coding for trypsin inhibitor BTI-CMe in barley (Itr1) occurs during the first half of endosperm development. In transgenic tobacco, the Itr1 promoter drives expression of the beta-glucuronidase reporter gene not only in developing endosperm but also in embryo, cotyledons and the meristematic intercotyledonary zone of germinating seedlings. A promoter fragment extending 343 bp upstream of the translation initiation ATG codon was sufficient for full transgene expression, whereas, the proximal 83 bp segment of the promoter was inactive. Possible reasons for the differences in expression patterns are discussed.

Separation of acidic barley endosperm proteins by two-dimensional electrophoresis

Proteins in barley aleurone and starchy endosperm from developing seeds were separated by two-dimensional (2-D) electrophoresis according to O'Farrell's method. The effect of different extraction methods on the separation was compared. The two best extraction methods were compared by amino acid analysis of extracts and residues. Some tissue-specific proteins in both tissues are described. Different methods for transfer of separated proteins onto membranes were compared. Amino terminal and internal sequences were determined after transfer of separated proteins or their proteolytic products onto membranes. Amino acid sequence data allowed the identification of 12 different proteins, while 6 remain unidentified and 8 appeared to have a blocked amino terminal.

Analysis of nuclear proteins interacting with a wheat alpha/beta-gliadin seed storage protein gene

The promoter region (-524 to -46) of the wheat alpha/beta-gliadin seed storage protein gene was analyzed for interactions with nuclear proteins from developing wheat seeds. Six complexes were detected within the first 165 bp upstream of the transcriptional start site. One of the proteins was a non-sequence specific AT-binding protein. The remaining five proteins bound in a sequence specific manner. One (CABP) mapped to a conserved CA-rich element at -134 to -112 while another (PalBP) mapped to an adjacent, palindromic sequence at -112 to -106. Three proteins (CTBPs 1-3) formed complexes at two, independent homologous sites. The activities of four of the binding proteins, CTBPs 1-3 and CABP, exhibited similar patterns of expression during seed development: they first appeared at early to mid stages, reached a maximum at mid stage and subsequently decreased, paralleling the pattern of gliadin mRNA accumulation. The non-specific AT-binding protein was detected at relatively high levels only at mid development. PalBP activity, on the other hand, first appeared at mid stage and was present at a constant level throughout later stages of development. The results suggest that the binding proteins may regulate gliadin expression in an antagonistic manner.

Evolutionary relationship of the members of the sulphur-rich hordein family revealed by common antigenic determinants

Five monoclonal antibodies raised against an enriched C hordein fraction have been characterized in detail and were found to be specific for the members of the sulphur-rich hordein family. Two antibodies specific for B hordein polypeptides were identified, one of which reacted predominantly with CNBr cleavage class III polypeptides. γ1 hordein was recognized by two antibodies, of which one also reacted with γ2 hordein and several members of the CNBr cleavage class II B hordein polypeptides. One antibody recognized γ3 hordein but cross-reacted at higher antibody concentration with almost all of the B and C hordein polypeptides. The specificity of the monoclonal antibodies was confirmed by Western blotting of one- or two-dimensionally separated hordein from the B hordein-deficient mutant hor2ca and its wild-type Carlsberg II and the γ3 hordein-deficient genotype Nevsky. The identification of the γ hordein-specific monoclonal antibodies was further supported by immune precipitation of in-vitro transcribed and translated γ2 hordein, and hor2ca and Carlsberg II mRNA translation products. The monoclonal antibodies were used to screen for mutants in γ hordein synthesis. Two mutants, one deficient in γ 1 hordein synthesis and a second in γ 2 or closely related B hordein polypeptides were identified. A model is proposed for the evolution of the sulphur-rich hordein loci Hor5 and Hor2.

Molecular images of cereal proteins by STM

Scanning tunnelling microscopy (STM) has been used to study a seed storage protein of wheat known as gamma-gliadin. The protein was deposited onto highly oriented pyrolytic graphite (HOPG) from solutions of trifluoroethanol (TFE) and 1% acetic acid. Samples were dried down and then scanned in air. Transmission electron microscopy (TEM) was also used to visualise the distribution of protein on the substrate. Small-angle X-ray scattering (SAXS) was used to compare the molecular size and shape obtained with those from the STM images.

Structural and functional analysis of promoter from gliadin, an endosperm-specific storage protein gene of Triticum aestivum L

To identify cis-regulatory elements of the gliadin gene, a study of the gliadin gene promoter was conducted by transient expression analysis of plasmid DNAs which were introduced into plant protoplasts by electroporation. The promoter region (-592 bp to +18 bp from the translational start) of this developmentally regulated gene, when fused upstream to the chloramphenicol acetyl transferase (CAT) reporter cassette was unable to direct significant CAT expression in wheat or tobacco suspension cells. Because this monocot gene promoter appeared to be under stringent tissue-specific control, a hybrid promoter approach using a nopaline synthase (nos) promoter was employed. A series of 3' deletions of the gliadin promoter were placed upstream of either a nonfunctional -101 nos or a nearly wild-type -155 nos promoter fused in turn to a CAT reporter gene cassette. Transient expression analysis of these plasmid DNAs in tobacco cells showed that the gliadin fragment could either restore the activity of the non-functional nos promoter (series I) or enhance the activity of the functional nos promoter (series II). The degree of restoration of the promoter function conferred by gliadin fragments of the first series was proportional to the enhancing effect of the same fragments in the second series of constructs. The transcriptional activity of the gliadin (-592 bp to -77 bp) -nos hybrid promoter was reduced by 26% upon 3' deletion of sequences in the region -141 bp to -77 bp, which contains both the TATA and CCAAT boxes.(ABSTRACT TRUNCATED AT 250 WORDS)

A plant serpin gene. Structure, organization and expression of the gene encoding barley protein Z4

A 3133-bp nucleotide sequence of the gene Paz1 on chromosome 4 of barley, encoding endosperm protein Z4, has been determined. The sequence includes 1079 bp 5' upstream and 523 bp 3' downstream of the coding region. The 1079-bp 5' upstream region of the gene shows little similarity to 5' regions of other sequences genes expressed in the developing cereal endosperm. The coding sequence is interrupted by one 334-bp-long intron (bases 1497-1830). The deduced amino acid sequence, which was corroborated by peptide sequences, consists of 399 amino acids and has a molecular mass of 43,128 Da. This sequence confirms protein Z4 to be a member of the serpin superfamily of proteins. The similarity with other members of the family expressed as amino acids in identical positions is in the order of 25-30% and pronounced in the carboxy-terminal half of the molecule. Sequence residues assumed to form clusters stabilizing the tertiary structure are highly conserved. Protein Z4 is synthesized in the developing endosperm without a signal peptide and protein Z4 mRNA was evenly distributed among the free and membrane-bound polyribosomes of the endosperm cell. An internal hydrophobic region of 21 amino acids (residues 36-56) may serve as a signal for targeting the polypeptide into the lumen of the endoplasmic reticulum. The gene for protein Z4 could not be detected in the barley variety Maskin and some of its descendants. The 'high-lysine' allees, lys1 (Hiproly barley) and lys3a (Bomi mutant 1508) on chromosome 7, enhance and repress, respectively, the expression of the protein Z4 gene. Also, 1554 bp of another 8-kbp fragment of the barley genome Paz psi, similar to the protein-Z4-coding region, have been determined. Small insertions and deletions and the presence of an internal stop codon identify this fragment as part of a pseudogene related to the protein Z4 gene.

Cloning and characterization of a cDNA encoding a rice 13 kDa prolamin

A cDNA library constructed from mRNAs obtained from developing rice endosperm was screened with a cDNA clone (lambda RM7) of highest frequency of occurrence (1.8%). The translation product directed by the mRNA which was hybrid-released from lambda RM7 cDNA in a wheat germ cell-free system showed a molecular size of 13 kDa when coexisting with the protein body fraction of developing maize endosperm. A polypeptide sequence composed of 156 amino acids was deduced from the nucleotide sequence. By comparison with the 19 N-terminal amino acids obtained from Edman degradation of the isolated rice 13 kDa prolamin fraction, the signal sequence was determined as consisting of 19 amino acids. The deduced polypeptide is rich in hydrophobic amino acids such as Leu and Val, and also in Gln, but lacks Lys. Hence, the amino acid composition is consistent with that of rice 13 kDa prolamin. By homology with previously reported cereal prolamins, only a single octapeptide sequence, Gln-Gln-Gln-Cys-Cys-Gln-Gln-Leu, which was observed in 15 kDa and 27 kDa zein, B- and gamma-hordein, alpha/beta- and gamma-gliadin, and gamma-secalin was conserved in the rice 10 kDa and 13 kDa prolamin. No repetitive sequences and/or sequences homologous to other cereal prolamins, except the above octapeptide, were observed for the mature 13 kDa prolamin polypeptide. The signal sequence region of the 13 kDa prolamin, however, shows homology of more than 65% in both the nucleotide sequence and the amino acid sequence with rice 10 kDa prolamin and maize zein.

Mapping of the Hor2 locus in barley by pulsed field gel electrophoresis

High molecular weight DNA released from isolated protoplasts was digested with rare-cutting restriction enzymes and separated by pulsed field gel electrophoresis. The average size of undigested DNA was above 1500 kbp. Digests made with NotI, SfiL, Mlul and SalI was hybridized to a probe, common to all genes of the Hor2 locus encoding B-hordein polypeptides, and this revealed the maximum size of the locus to be 360 kbp. Two probes, specific for individual B-hordein genes, enabled the identification of two fragment classes in the locus, each containing an equal number of B-hordein genes. Double digests allowed ordering of sites and construction of a map covering 650 kbp around the Hor2 locus. No evidence for physical linkage of the two fragment classes was obtained. The possible assignment of the two classes of hybridizing fragments to the B1- and B3-hordein subgroups is discussed.