Promoter analysis and immunolocalisation show that puroindoline genes are exclusively expressed in starchy endosperm cells of wheat grain

Over-Expression of a Wheat Late Maturity Alpha-Amylase Type 1 Impact on Starch Properties During Grain Development and Germination

The hydrolysis of starch is a complex process that requires synergistic action of multiple hydrolytic enzymes, including α-amylases. Wheat over-expression of TaAmy1, driven by seed specific promoter, resulted in a 20- to 230-fold total α-amylase activity in mature grains. Ectopic expression of TaAmy1 showed a significant elevated α-amylase activity in stem and leaf without consequences on transitory starch. In mature grain, overexpressed TaAMY1 was mainly located in the endosperm with high expression of TaAmy1. This is due to early developing grains having effect on starch granules from 18 days post-anthesis (DPA) and on soluble sugar accumulation from 30 DPA. While accumulation of TaAMY1 led to a high degree of damaged starch in grain, the dramatic alterations of starch visco-properties caused by the elevated levels of α-amylase essentially occurred during processing, thus suggesting a very small impact of related starch damage on grain properties. Abnormal accumulation of soluble sugar (α-gluco-oligosaccharide and sucrose) by TaAMY1 over-expression reduced the grain dormancy and enhanced abscisic acid (ABA) resistance. Germination study in the presence of α-amylase inhibitor suggested a very limited role of TaAMY1 in the early germination process and starch conversion into soluble sugars.

Dissecting the Role of Promoters of Pathogen-sensitive Genes in Plant Defense

Plants inherently show resistance to pathogen attack but are susceptible to multiple bacteria, viruses, fungi, and phytoplasmas. Diseases as a result of such infection leads to the deterioration of crop yield. Several pathogen-sensitive gene activities, promoters of such genes, associated transcription factors, and promoter elements responsible for crosstalk between the defense signaling pathways are involved in plant resistance towards a pathogen. Still, only a handful of genes and their promoters related to plant resistance have been identified to date. Such pathogen-sensitive promoters are accountable for elevating the transcriptional activity of certain genes in response to infection. Also, a suitable promoter is a key to devising successful crop improvement strategies as it ensures the optimum expression of the required transgene. The study of the promoters also helps in mining more details about the transcription factors controlling their activities and helps to unveil the involvement of new genes in the pathogen response. Therefore, the only way out to formulate new solutions is by analyzing the molecular aspects of these promoters in detail. In this review, we provided an overview of the promoter motifs and cis-regulatory elements having specific roles in pathogen attack response. To elaborate on the importance and get a vivid picture of the pathogen-sensitive promoter sequences, the key motifs and promoter elements were analyzed with the help of PlantCare and interpreted with available literature. This review intends to provide useful information for reconstructing the gene networks underlying the resistance of plants against pathogens.

Exploration of the functionality of sugars in cake-baking, and effects on cake quality

This review paper describes our exploratory experimental studies on the functionality of sucrose and other sugars in cake-baking, and effects on cake quality. We have used the American Association of Cereal Chemists Method 10-90.01 as a base cake-baking method, and have applied Differential Scanning Calorimetry, Rapid Visco-Analyzer, and time-lapse photography analyses in experimental design studies of the effects of the following ingredient and formulation variables on cake quality (e.g. texture, color, moisture content) and other finished-product properties (e.g. shape, dimensions): (a) cake formula levels of sucrose and water, in terms of %Sucrose and Total Solvent; (b) concentration of sucrose or other sugars (e.g. xylose, ribose, fructose, glucose, maltose, polydextrose) vs. wheat flour starch gelatinization temperature and starch pasting during baking and gluten development during mixing; (c) unchlorinated flour vs. chlorinated flours (of varying pH); (d) cake formula %Sucrose and TS vs. cake color, shape, and dimensions; (e) cakes formulated with sucrose or other sugars (i.e. xylose, fructose, glucose), and variable %S and TS, and unchlorinated or chlorinated flour (pH 4.6), vs. cake color, shape, and dimensions.

Marker-assisted transfer of PinaD1a gene to develop soft grain wheat cultivars

Grain softness has been a major trait of interest in wheat because of its role in producing flour suitable for making high-quality biscuits, cookies, cakes and some other products. In the present study, marker-assisted backcross breeding scheme was deployed to develop advanced wheat lines with soft grains. The Australian soft-grained variety Barham was used as the donor parent to transfer the puroindoline grain softness gene Pina-D1a to the Indian variety, DBW14, which is hard grained and has PinaD1bPinbD1a genes. Foreground selection with allele-specific PCR-based primer for Pina-D1a (positive selection) was used to identify heterozygous BC1F1 plants. Background selection with 173 polymorphic SSR primers covering all the 21 chromosomes was also carried out, in the foreground-selected BC1F1 plants. BC1F2 plants were selected by ascertaining the presence of Pina-D1a (positive selection) and absence of Pina-D1b (negative selection). Using the approach of positive, negative and background selection with molecular markers, 15 BC1F2 and 31 BC2F1 plants were finally selected. The 15 BC1F2 plants were selfed and the 31 BC2F1 plants were further backcrossed and selfed to raise BC3F1 and BC2F2 progenies, respectively. A part of the BC2F2 seed of each of the 31 plants was analyzed for grain hardness index (GHI) with single-kernel characterization system. The GHI varied from 12.1 to 37.1 in the seeds borne on the 31 BC2F1 plants. The reasons for this variation and further course of action are discussed.

Production of bioactive wheat puroindoline proteins in Nicotiana benthamiana using a virus-based transient expression system

The emergence of antibiotic resistant pathogenic strains of bacteria has necessitated the development of novel antimicrobial agents. The puroindoline A and B (PINA and PINB) proteins of wheat, well-known for their roles in determining the important phenotype of grain texture, are also antimicrobial, making them attractive as natural bio-control agents. However, the biochemical basis of PIN functionality remains unclear due to limitations in expressing them at the required yield and purity and lack of accurate tertiary structure. This study focussed on rapid transient expression of PINs targeted to different subcellular compartments (chloroplast, apoplast, endoplasmic reticulum and cytosol) of Nicotiana benthamiana leaf cells using the deconstructed tobacco mosaic virus-based 'magnICON®' system. The expressed recombinant PINs were characterised by Western blot using the Durotest anti-friabilin antibody, enzyme-linked immunosorbent assays (ELISA) and antimicrobial activity tests. Maximum yield of the His-tagged PINs occurred when targeted to the chloroplast. Both PINs exhibited oligomeric and monomeric forms on gels, but Western blots with the widely used Durotest anti-friabilin antibody identified only oligomeric forms. Only the PINs purified by a hydrophobic interaction method exhibited monomeric forms with the anti-His tag antibody, indicating correct folding. Interestingly, the Durotest antibody did not bind to monomers, suggesting their epitope may be obscured. PINs purified by His-tag affinity purification under native conditions or by the hydrophobic method exhibited antimicrobial activities. The successful in planta expression and optimisation of purification will enable future studies to examine the detailed structure of the PINs and explore novel bio-control applications in health, food and/or agriculture.

The trafficking pathway of a wheat storage protein in transgenic rice endosperm

BACKGROUND AND AIMS

The trafficking of proteins in the endoplasmic reticulum (ER) of plant cells is a topic of considerable interest since this organelle serves as an entry point for proteins destined for other organelles, as well as for the ER itself. In the current work, transgenic rice was used to study the pattern and pathway of deposition of the wheat high molecular weight (HMW) glutenin sub-unit (GS) 1Dx5 within the rice endosperm using specific antibodies to determine whether it is deposited in the same or different protein bodies from the rice storage proteins, and whether it is located in the same or separate phases within these.

METHODS

The protein distribution and the expression pattern of HMW sub-unit 1Dx5 in transgenic rice endosperm at different stages of development were determined using light and electron microscopy after labelling with antibodies.

KEY RESULTS

The use of HMW-GS-specific antibodies showed that sub-unit 1Dx5 was expressed mainly in the sub-aleurone cells of the endosperm and that it was deposited in both types of protein body present in the rice endosperm: derived from the ER and containing prolamins, and derived from the vacuole and containing glutelins. In addition, new types of protein bodies were also formed within the endosperm cells.

CONCLUSIONS

The results suggest that the HMW 1Dx5 protein could be trafficked by either the ER or vacuolar pathway, possibly depending on the stage of development, and that its accumulation in the rice endosperm could compromise the structural integrity of protein bodies and their segregation into two distinct populations in the mature endosperm.

Wheat (Triticum aestivum L. and T. turgidum L. ssp. durum) Kernel Hardness: I. Current View on the Role of Puroindolines and Polar Lipids

Wheat hardness has major consequences for the entire wheat supply chain from breeders and millers over manufacturers to, finally, consumers of wheat-based products. Indeed, differences in hardness among Triticum aestivum L. or between T. aestivum L. and T. turgidum L. ssp. durum wheat cultivars determine not only their milling properties, but also the properties of flour or semolina endosperm particles, their preferential use in cereal-based applications, and the quality of the latter. Although the mechanism causing differences in wheat hardness has been subject of research more than once, it is still not completely understood. It is widely accepted that differences in wheat hardness originate from differences in the interaction between the starch granules and the endosperm protein matrix in the kernel. This interaction seems impacted by the presence of either puroindoline a and/or b, polar lipids on the starch granule surface, or by a combination of both. We focus here on wheat hardness and its relation to the presence of puroindolines and polar lipids. More in particular, the structure, properties, and genetics of puroindolines and their interactions with polar lipids are critically discussed as is their possible role in wheat hardness. We also address future research needs as well as the presence of puroindoline-type proteins in other cereals.

Expression pattern of the alpha-kafirin promoter coupled with a signal peptide from Sorghum bicolor L. Moench

Regulatory sequences with endosperm specificity are essential for foreign gene expression in the desired tissue for both grain quality improvement and molecular pharming. In this study, promoters of seed storage α-kafirin genes coupled with signal sequence (ss) were isolated from Sorghum bicolor L. Moench genomic DNA by PCR. The α-kafirin promoter (α-kaf) contains endosperm specificity-determining motifs, prolamin-box, the O2-box 1, CATC, and TATA boxes required for α-kafirin gene expression in sorghum seeds. The constructs pMB-Ubi-gfp and pMB-kaf-gfp were microprojectile bombarded into various sorghum and sweet corn explants. GFP expression was detected on all explants using the Ubi promoter but only in seeds for the α-kaf promoter. This shows that the α-kaf promoter isolated was functional and demonstrated seed-specific GFP expression. The constructs pMB-Ubi-ss-gfp and pMB-kaf-ss-gfp were also bombarded into the same explants. Detection of GFP expression showed that the signal peptide (SP)::GFP fusion can assemble and fold properly, preserving the fluorescent properties of GFP.

Biolistic- and Agrobacterium-mediated transformation protocols for wheat

After rice, wheat is considered to be the most important world food crop, and the demand for high-quality wheat flour is increasing. Although there are no GM varieties currently grown, wheat is an important target for biotechnology, and we anticipate that GM wheat will be commercially available in 10-15 years. In this chapter, we summarize the main features and challenges of wheat transformation and then describe detailed protocols for the production of transgenic wheat plants both by biolistic and Agrobacterium-mediated DNA-delivery. Although these methods are used mainly for bread wheat (Triticum aestivum L.), they can also be successfully applied, with slight modifications, to tetraploid durum wheat (T. turgidum L. var. durum). The appropriate size and developmental stage of explants (immature embryo-derived scutella), the conditions to produce embryogenic callus tissues, and the methods to regenerate transgenic plants under increasing selection pressure are provided in the protocol. To illustrate the application of herbicide selection system, we have chosen to describe the use of the plasmid pAHC25 for biolistic transformation, while for Agrobacterium-mediated transformation the binary vector pAL156 (incorporating both the bar gene and the uidA gene) has been chosen. Beside the step-by-step methodology for obtaining stably transformed and normal fertile plants, procedures for screening and testing transgenic wheat plants are also discussed.

Transgenic rice plants harboring the grain hardness-locus region of Aegilops tauschii

Grain hardness of wheat is determined by the hardness (Ha)-locus region, which contains three friabilin-related genes: puroindoline-a (Pina), puroindoline-b (Pinb) and GSP-1. In our previous study, we produced the transgenic rice plants harboring the large genomic fragment of the Ha-locus region of Aegilops tauschii containing Pina and GSP-1 genes by Agrobacterium-mediated transformation. To examine the effects of the transgenes in the rice endosperms, we firstly confirmed the homozygosity of the T-DNAs in four independent T2 lines by using fluorescence in situ hybridization (FISH) and DNA gel blot analyses. The transgenes, Pina and GSP-1, were stably expressed in endosperms of the T3 and T4 seeds at RNA and protein levels, indicating that the promoters and other regulatory elements on the wheat Ha-locus region function in rice, and that multigene transformation using a large genomic fragment is a useful strategy. The functional contribution of the transgene-derived friabilins to the rice endosperm structure was considered as an increase of spaces between compound starch granules, resulting in a high proportion of white turbidity seeds.

The RNA-mediated silencing of one of the Pin genes in allohexaploid wheat simultaneously decreases the expression of the other, and increases grain hardness

The RNAi-mediated silencing of Pina and Pinb, the two genes responsible for the grain texture of allohexaploid wheat, was induced and analysed in two wheat cultivars, Kontesa and Torka. A characterization of the two genes in non-transgenic plants revealed that Pinb carries a point mutation, designated Pinb-D1c in both cultivars. This mutation does not influence transcript abundance or protein content. Two silencing cassettes of the hpRNA type were constructed and used for stable transformation via Agrobacterium. In total, 43 transgenic lines representing the two cultivars were obtained, transformed with the silencing cassettes for Pina or for Pinb or co-transformed with both cassettes. The relative transcript levels of the two genes in the same progeny plant were found to be similar, independent of the silencing cassette used. The reduction in the Pina and Pinb transcript levels in the segregating T(1) progeny of Kontesa and Torka transformed with one of the silencing cassettes exceeded 80%. Co-transformation with the silencing cassettes for both genes resulted in a reduction of over 91% of Pina and Pinb transcripts in some segregating T(1) progeny of Kontesa. The silencing was transmitted to the T(4) kernel generation of the T(3) lines. A significant reduction or lack of both puroindoline proteins in the silenced lines correlated with an essential increase in grain hardness. The discussion covers some new insights into the function of the Pin genes, including the simultaneous silencing of both, independent of the siRNA signal.

Transgene expression systems in the Triticeae cereals

The control of transgene expression is vital both for the elucidation of gene function and for the engineering of transgenic crops. Given the dominance of the Triticeae cereals in the agricultural economy of the temperate world, the development of well-performing transgene expression systems of known functionality is of primary importance. Transgenes can be expressed either transiently or stably. Transient expression systems based on direct or virus-mediated gene transfer are particularly useful in situations where the need is to rapidly screen large numbers of genes. However, an unequivocal understanding of gene function generally requires that a transgene functions throughout the plant's life and is transmitted through the sexual cycle, since this alone allows its effect to be decoupled from the plant's response to the generally stressful gene transfer event. Temporal, spatial and quantitative control of a transgene's expression depends on its regulatory environment, which includes both its promoter and certain associated untranslated region sequences. While many transgenic approaches aim to manipulate plant phenotype via ectopic gene expression, a transgene sequence can be also configured to down-regulate the expression of its endogenous counterpart, a strategy which exploits the natural gene silencing machinery of plants. In this review, current technical opportunities for controlling transgene expression in the Triticeae species are described. Apart from protocols for transient and stable gene transfer, the choice of promoters and other untranslated regulatory elements, we also consider signal peptides, as they too govern the abundance and particularly the sub-cellular localization of transgene products.

Authentication of food allergen quality by physicochemical and immunological methods

Purified allergens are required to detect cross-contamination with other allergenic foods and to understand allergen interaction with other components of the food matrix. Pure allergens are also used for the diagnosis and treatment of food allergies. For example, serological methods are being developed to improve the quality of diagnosis, and to reduce the need for food challenge tests. In addition, recombinant allergens are being evaluated as candidate vaccines for safe and efficacious specific immunotherapy. Pure allergens are indispensable as reference materials for the calibration and standardization of methods between different laboratories and operators for risk assessment in the food industry. Therefore, there is a need for well-defined purified food allergens. In this context, a panel of 46 food allergens from plant and animal sources has been purified, from either the food sources or as recombinant forms, within the EU-funded EuroPrevall project. These allergens have been characterized by a battery of diagnostic tests demonstrating that they constitute an authentic, well-defined library of comparable quality. The review summarizes the applications, potentials and limitations of key techniques used for the characterization and authentication of these allergen preparations, with a special emphasis on protein purity and identity, folding, post-translational modifications and immunochemical properties. One key area identified is the development of powerful analytical techniques, such as mass spectrometry and nuclear magnetic resonance, to improve the authentication of allergens for routine applications in allergy management.

Isolation of the endosperm-specific LPAAT gene promoter from coconut (Cocos nucifera L.) and its functional analysis in transgenic rice plants

As one of the key tropical crops, coconut (Cocos nucifera L.) is a member of the monocotyledonous family Aracaceae (Palmaceae). In this study, we amplified the upstream region of an endosperm-specific expression gene, Lysophosphatidyl acyltransferase (LPAAT), from the coconut genomic DNA by chromosome walking. In this sequence, we found several types of promoter-related elements including TATA-box, CAAT-box and Skn1-motif. In order to further examine its function, three different 5'-deletion fragments were inserted into pBI101.3, a plant expression vector harboring the LPAAT upstream sequence, leading to pBI101.3-L1, pBI101.3-L2 and pBI101.3-L3, respectively. We obtained transgenic plants of rice by Agrobacterium-mediated callus transformation and plant regeneration and detected the expression of gus gene by histochemical staining and fluorometric determination. We found that gus gene driven by the three deletion fragments was specifically expressed in the endosperm of rice seeds, but not in the empty vector of pBI101.3 and other tissues. The highest expression level of GUS was at 15 DAF in pBI101.3-L3 and pBI101.3-L2 transgenic lines, while the same level was detected at 10 DAF in pBI101.3-L1. The expression driven by the whole fragment was up to 1.76- and 2.8-fold higher than those driven by the -817 bp and -453 bp upstream fragments, and 10.7-fold higher than that driven by the vector without the promoter. Taken together, our results strongly suggest that these promoter fragments from coconut have a significant potential in genetically improving endosperm in main crops.

Agrobacterium-mediated transformation of durum wheat (Triticum turgidum L. var. durum cv Stewart) with improved efficiency

An efficient Agrobacterium-mediated durum wheat transformation system has been developed for the production of 121 independent transgenic lines. This improved system used Agrobacterium strain AGL1 containing the superbinary pGreen/pSoup vector system and durum wheat cv Stewart as the recipient plant. Acetosyringone at 400 microM was added to both the inoculation and cultivation medium, and picloram at 10 mg l(-1) and 2 mg l(-1) was used in the cultivation and induction medium, respectively. Compared with 200 microM in the inoculation and cultivation media, the increased acetosyringone concentration led to significantly higher GUS (beta-glucuronidase) transient expression and T-DNA delivery efficiency. However, no evident effects of acetosyringone concentration on regeneration frequency were observed. The higher acetosyringone concentration led to an improvement in average final transformation efficiency from 4.7% to 6.3%. Furthermore, the concentration of picloram in the co-cultivation medium had significant effects on callus induction and regeneration. Compared with 2 mg l(-1) picloram in the co-cultivation medium, increasing the concentration to 10 mg l(-1) picloram resulted in improved final transformation frequency from 2.8% to 6.3%, with the highest frequency of 12.3% reached in one particular experiment, although statistical analysis showed that this difference in final transformation efficiency had a low level of significance. Stable integration of foreign genes, their expression, and inheritance were confirmed by Southern blot analyses, GUS assay, and genetic analysis. Analysis of T(1) progeny showed that, of the 31 transgenic lines randomly selected, nearly one-third had a segregation ratio of 3:1, while the remainder had ratios typical of two or three independently segregating loci.

The determinants of grain texture in cereals

Kernel hardness is an important agronomic trait that influences end-product properties. In wheat cultivars, this trait is determined by the Puroindoline a (Pina) and Puroindoline b (Pinb) genes, located in the Hardness locus (Ha) on chromosome 5DS of the D genome. Wild type alleles code puroindoline a (PINA) and puroindoline b (PINB) proteins, which form a 15-kDa friabilin present on the surface of water-washed starch granules. Both the proteins are accumulated in the starch endosperm cells and aleurone of the mature kernels. Puroindoline-like genes coding puroindoline-like proteins in the starch endosperm occur in some of the genomes of Triticeae and Aveneae cereals. Orthologs are present in barley, rye and oats. However, some genomes of these diploid and polyploid cereals, like that of Triticum turgidum var. durum (AABB) lack the puroindoline genes, having a very hard kernel texture. The two wild type alleles in opposition (dominant loci) control the soft phenotype. Mutation either in Pina or Pinb or in both leads to a medium-hard or hard kernel texture. The most frequent types of Pin mutations are point mutations within the coding sequence resulting in the substitution of a single amino acid or a null allele. The latter is the result of a frame shift determined by base deletion or insertion or a one-point mutation to the stop codon. The lipid-binding properties of the puroindolines affect not only the dough quality but also the plants' resistance to pathogens. Genetic modification of cereals with Puroindoline genes and/or their promoters enable more detailed functional analyses and the production of plants with the desired characteristics.

Seed-specific expression of the wheat puroindoline genes improves maize wet milling yields

The texture of maize (Zea mays L.) seeds is important to seed processing properties, and soft dent maize is preferred for both wet-milling and livestock feed applications. The puroindoline genes (Pina and Pinb) are the functional components of the wheat (Triticum aestivum L.) Hardness locus and together function to create soft grain texture in wheat. The PINs (PINA and PINB) are believed to act by binding to lipids on the surface of starch granules, preventing tight adhesion between starch granules and the surrounding protein matrix during seed maturation. Here, maize kernel structure and wet milling properties were successfully modified by the endosperm-specific expression of wheat Pins (Pina and Pinb). Pins were introduced into maize under the control of a maize gamma-Zein promoter. Three Pina/Pinb expression positive transgenic lines were evaluated over two growing seasons. Textural analysis of the maize seeds indicated that the expression of PINs decreased adhesion between starch and protein matrix and reduced maize grain hardness significantly. Reduction in pressure required to fracture kernels ranged from 15.65% to 36.86% compared with control seeds. Further, the PINs transgenic maize seeds had increased levels of extractable starch as characterized by a small scale wet milling method. Starch yield was increased by 4.86% on average without negatively impacting starch purity. The development of softer maize hybrids with higher starch extractability would be of value to maize processors.

Trafficking of storage proteins in developing grain of wheat

The processing properties of the wheat flour are largely determined by the structures and interactions of the grain storage proteins (also called gluten proteins) which form a continuous visco-elastic network in dough. Wheat gluten proteins are classically divided into two groups, the monomeric gliadins and the polymeric glutenins, with the latter being further classified into low molecular weight (LMW) and high molecular weight (HMW) subunits. The synthesis, folding and deposition of the gluten proteins take place within the endomembrane system of the plant cell. However, determination of the precise routes of trafficking and deposition of individual gluten proteins in developing wheat grain has been limited in the past by the difficulty of developing monospecific antibodies. To overcome this limitation, a single gluten protein (a LMW subunit) was expressed in transgenic wheat with a C-terminal epitope tag, allowing the protein to be located in the cells of the developing grain using highly specific antibodies. This approach was also combined with the use of wider specificity antibodies to compare the trafficking and deposition of different gluten protein groups within the same endosperm cells. These studies are in agreement with previous suggestions that two trafficking pathways occur in wheat, with the proteins either being transported via the Golgi apparatus into the vacuole or accumulating directly within the lumen of the ER. They also suggest that the same individual protein could be trafficked by either pathway, possibly depending on the stage of development, and that segregation of gluten proteins both between and within protein bodies may occur.

Promoter sequences for defining transgene expression

The design of reverse genetic experiments that utilize transgenic approaches often requires transgenes to be expressed in a predefined pattern and there is limited information regarding the gene expression profile for specific promoters. It is important that expression patterns are predetermined in the specific genotype targeted for transformation because the same promoter-transgene construct can produce different expression patterns in different host species. This chapter compares constitutive, targeted, or inducible promoters that have been characterized in specific cereal species.

Detailed analysis of the expression of an alpha-gliadin promoter and the deposition of alpha-gliadin protein during wheat grain development

BACKGROUND AND AIMS

Alpha-gliadin proteins are important for the industrial quality of bread wheat flour, but they also contain many epitopes that can trigger celiac (coeliac) disease (CD). The B-genome-encoded alpha-gliadin genes, however, contain very few epitopes. Controlling alpha-gliadin gene expression in wheat requires knowledge on the processes of expression and deposition of alpha-gliadin protein during wheat grain development.

METHODS

A 592-bp fragment of the promotor of a B-genome-encoded alpha-gliadin gene driving the expression of a GUS reporter gene was transformed into wheat. A large number of transgenic lines were used for data collection. GUS staining was used to determine GUS expression during wheat kernel development, and immunogold labelling and tissue printing followed by staining with an alpha-gliadin-specific antibody was used to detect alpha-gliadin protein deposited in developing wheat kernels. The promoter sequence was screened for regulatory motifs and compared to other available alpha-gliadin promoter sequences.

KEY RESULTS

GUS expression was detected primarily in the cells of the starchy endosperm, notably in the subaleurone layer but also in the aleurone layer. The alpha-gliadin promoter was active from 11 days after anthesis (DAA) until maturity, with an expression similar to that of a 326-bp low molecular weight (LMW) subunit gene promoter reported previously. An alpha-gliadin-specific antibody detected alpha-gliadin protein in protein bodies in the starchy endosperm and in the subaleurone layer but, in contrast to the promoter activity, no alpha-gliadin was detected in the aleurone cell layer. Sequence comparison showed differences in regulatory elements between the promoters of alpha-gliadin genes originating from different genomes (A and B) of bread wheat both in the region used here and upstream.

CONCLUSIONS

The results suggest that additional regulator elements upstream of the promoter region used may specifically repress expression in the aleurone cell layer. Observed differences in expression regulator motifs between the alpha-gliadin genes on the different genomes (A and B) of bread wheat leads to a better understanding how alpha-gliadin expression can be controlled.

Effect of environmental stress during grain filling on the soluble proteome of wheat (Triticum aestivum) dough liquor

The influence of genotype and environment on a soluble wheat dough liquor proteome was studied for four cultivars grown under field conditions and under hot/dry and cool/wet regimes by two-dimensional electrophoresis followed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry or quadrupole time-of-flight mass spectrometry. Although the four cultivars had similar patterns, differences in the relative abundances of some components were observed. Similarly, some differences were observed between the control samples and the samples grown under cool/wet and hot/dry conditions. These included differences in the abundances of storage proteins belonging to the 7S globulin (vicilin-like) and alpha-globulin families and of protective proteins including members of the serpin, described as allergens, and chitinase families. A number of novel annotations were made as compared to previous work on the dough liquor of cv. Hereward, including two 19 kDa alpha-globulins, precursors of endochitinases A and C, and several polypeptides belonging to the 7S globulin (vicilin-like) family.

Efficient and rapid Agrobacterium-mediated genetic transformation of durum wheat (Triticum turgidum L. var. durum) using additional virulence genes

Genetic transformation of wheat, using biolistics or Agrobacterium, underpins a range of specific research methods for identifying genes and studying their function in planta. Transgenic approaches to study and modify traits in durum wheat have lagged behind those for bread wheat. Here we report the use of Agrobacterium strain AGL1, with additional vir genes housed in a helper plasmid, to transform and regenerate the durum wheat variety Ofanto. The use of the basic pSoup helper plasmid with no additional vir genes failed to generate transformants, whereas the presence of either virG542 or the 15 kb Komari fragment containing virB, virC and virG542 produced transformation efficiencies of between 0.6 and 9.7%. Of the 42 transgenic plants made, all but one (which set very few seeds) appeared morphologically normal and produced between 100 and 300 viable seeds. The transgene copy number and the segregation ratios were found to be very similar to those previously reported for bread wheat. We believe that this is the first report describing successful genetic transformation of tetraploid durum wheat (Triticum turgidum L. var. durum) mediated by Agrobacterium tumefaciens using immature embryos as the explant.