Barley Mutant Research Articles

A Chlorophyll-Less Barley Mutant “NYB” Is Insensitive to Water Stress

"NYB" is a chlorophyll-less barley mutant, which grows relatively slow and unhealthily. The effects of water stress on photosystem II (PSII) of NYB and its wild type (WT) were investigated. Unexpected results indicated that the mutant was more resistant to water stress, because: PSII core proteins D1, D2 and LHCII declined more in WT than in NYB under water stress, and the corresponding psbA, psbD and cab mRNAs also decreased more dramatically in WT; CO2 assimilation, stomatal conductance, maximum efficiency of PSII photochemistry (Fv/Fm), efficiency of excitation energy capture by open PSII reaction centres (Fv'/Fm'), quantum yield of PSII electron transport (Phi(PSII)) and DCIP photoreduction in NYB were less sensitive to water stress than in WT, although the non-photochemical quenching coefficient (q(N)) and the photochemical quenching coefficient (q(P)) were almost the same in NYB and WT. Effective chlorophyll utilization and improved PSII protein formation in the mutant may be the reason for the enhanced stress resistance. Other possible mechanisms are also discussed.

Comparing two microarray platforms for identifying mutated genes in barley ( Hordeum vulgare L.)

We have previously described the evaluation of a cDNA microarray platform to identify and clone mutated barley ( Hordeum vulgare L.) genes, using their transcriptionally defective mutant alleles (S. Zakhrabekova, C.G. Kannangara, D. von Wettstein, M. Hansson, A microarray approach for identification of mutated genes, Plant Physiol. Biochem. 40 (2002) 189–197). It was concluded that competitive hybridization between phenotypically similar mutants could specifically highlight an arrayed clone, corresponding to the mutated gene. In this study we evaluate whether the Affymetrix microarray platform can be used for the same purpose. The Affymetrix barley microarray contains a large number of clones (22,792 probe sets). In this and the previous study we used two barley mutant strains, xantha-h.57 and xantha-f.27, with known mutations in different subunit genes of the chlorophyll biosynthetic enzyme magnesium chelatase (EC 6.6.1.1). Mutant xantha-h.57 produces no Xantha-h mRNA whereas in xantha-f.27 the nonsense mutation in the last exon of the gene, results in nonsense-mediated decay of Xantha-f mRNA. We conclude that the Affymetrix platform meets our requirements and that our approach successfully highlighted the arrayed Xantha-h clone and that Xantha-f was among the top fourteen candidates.

Molecular mapping of genes involved in root hair formation in barley

In the presented study, the existing AFLP and SSR maps of barley were used to find chromosomal position of four genes controlling different stages of root hair development. Four barley mutants were used in the analysis: the root hairless mutant rhl1.b, mutant rhp1.b with root hair development blocked at the initial bulge formation, mutant rhi1.a with irregular pattern of sparsely located root hairs and mutant rhs1.a with very short root hairs. Each mutant was crossed with parents of ‘Steptoe’/‘Morex’ mapping population and F2 progenies of crosses: mutant × ‘Steptoe’ and mutant × ‘Morex’ were analyzed for segregation of root hair phenotype and polymorphic AFLP and SSR markers. It was possible to map all the analyzed genes on barley chromosomes: rhl1 gene on the short arm of chromosome 7H, rhp1 gene on chromosome 1H, rhs1 locus in the pericentromeric region of chromosome 5H and rhi1 gene on the long arm of chromosome 6H. Subsequently, the Bulk Segregant Analysis and AFLP technique were used for saturation of the identified regions with new markers. The joint maps were constructed using as common points the SSR markers located in the target regions. Linkage maps of the regions around the four genes involved in the root hair formation in barley were composed of 8–11 markers and spanned over 16.1–49.0 cM. The distances between localized genes and the closest markers ranged from 1.0 to 3.8 cM. The identified chromosomal locations of genes can be used for their fine mapping and future map-based cloning.

Effects of Low Phytate Barley (Hordeum vulgare L.) on Zinc Utilization in Young Broiler Chicks

Two 21-d experiments were conducted to evaluate the effects of low phytate barley (LPB) on Zn utilization by young broiler chicks and to determine the contribution of endogenous phytase, present in LPB. In the first experiment, ninety-six 1-d-old male chicks were assigned to a 2 x 3 factorial arrangement of treatments (4 pens of 4 chicks/treatment). Factors were barley type [wild-type barley (WTB) and LPB mutant M 955] and supplemental Zn (0, 10, or 20 mg of Zn/kg). In the second experiment, two hundred forty 1-d-old straight-run broiler chicks were assigned to a 2 x 2 x 3 factorial arrangement of treatments (4 pens of 5 chicks/treatment). Factors were barley type (WTB and LPB), autoclave treatment [nonautoclaved or autoclaved (121 degrees C, 20 kg/cm(2), 20 min)], and supplemental Zn (0, 10 or 20 mg of Zn/kg). Barley made up 60% of the diets and was the only source of phytate. On average, basal diets contained 26 mg of Zn/kg. Feed intake and body weight gain were greater (P < 0.05) in broilers fed LPB compared with WTB in experiment 2. Zinc concentration in toes and tibias were affected (P < 0.0001) by barley type (LPB > WTB) and supplemented Zn levels (20 > 10 > 0 mg of Zn/kg), and significant barley type x Zn interactions were also observed in both experiments. Substitution of LPB for WTB increased tibia and toe Zn by 46 and 25%, respectively, an increase comparable to that achieved with supplementing the diet with 20 mg of Zn/kg. No effect of autoclaving was observed for any variable in experiment 2. Retention of P and Zn was higher (P < 0.001) in chicks fed LPB compared with WTB in both experiments. Zinc retention was influenced (P < 0.0001) by dietary Zn, and barley type x Zn level interactions (P < 0.05) were observed in both experiments. Chicks fed LPB utilized more dietary Zn and P than those fed WTB, and this improved mineral utilization was not due to endogenous phytase present in barley.

Are Mutations in Genetically Modified Plants Dangerous?

Are Mutations in Genetically Modified Plants Dangerous?

Low-phytate barley cultivars improve the utilization of phosphorus, calcium, nitrogen, energy, and dry matter in diets fed to young swine1

A 28-d experiment was conducted using 45 crossbred barrows with an average initial BW of 9.5 kg and age of 35 d to evaluate low-phytate barley (LPB) mutants (M) M422, M635, and M955, which were hulled, near-isogenic progeny of the normal barley (NB) Harrington and had 47, 66, and 80% less phytic acid, respectively, than NB. A hull-less LPB, M422-H, which was not near-isogenic to the other cultivars, was also evaluated. Apparent nutrient balance, bone measurements, and growth performance were the response criteria evaluated. The barrows were fed the diets to appetite in meal form in individual metabolism crates. Barley and soybean meal were the only sources of phytic acid. Dietary protein supplementation and ME/kg were equalized in all diets. The treatments were diets containing NB, M422, M635, or M422-H without or with added inorganic P (iP), or M955 without added iP. Diets with added iP contained 0.30% available P (aP), the same concentration of aP provided by the diet containing M955 without added iP. There were linear increases (P < or = 0.02) in ADG, G:F, metacarpal and radius bone strength, and fat-free dry weight, and in the absorption and retention (g/d and % of intake) of P and Ca with increasing dietary concentration of aP from the near-isogenic cultivars NB, M422, M635, or M955 without added iP. There were linear decreases in the grams (P < or = 0.02) and percentages (P < 0.001) of P and Ca excreted per day with increasing dietary concentration of aP without added iP. There were no responses for N or energy balance. Growth performance and bone response criteria did not differ for barrows fed the diet containing M955 or the near-isogenic diets containing NB, M422, or M635 with added iP. However, barrows fed the diet containing M955 had greater (P < or = 0.02) percentages of P, N, and energy absorption and retention, Ca absorption, and DM digestibility and had less (P < or = 0.02, g/d and %) excretion of P, N, energy, and Ca (g) per day than barrows fed the diets containing the near-isogenic NB or LPB cultivars with added iP. When dietary aP was equalized with iP, the excretion of P in feces plus urine (g/d) was reduced by 20.2, 27.9, and 44.6%, respectively, in barrows fed the diets containing M422 + iP, M635 + iP, or M955 compared with barrows fed the diet containing NB + iP. Energy utilization did not differ for barrows fed the diets containing hulled or hull-less LPB when ME/kg was equalized with lard. In conclusion, the apparent utilization of P and Ca, the bone strength and fat-free dry weight, and growth performance increased with increasing dietary concentration of aP provided by LPB, in association with linear decreases in P and Ca excretion. Barrows fed the diet containing M955 also had greater utilization and less excretion of P, Ca, N, energy, and DM than barrows fed the diets containing the near-isogenic NB or LPB cultivars with added iP to equalize aP at 0.30%.

Recessiveness and Dominance in Barley Mutants Deficient in Mg-Chelatase Subunit D, an AAA Protein Involved in Chlorophyll Biosynthesis

Mg-chelatase catalyzes the insertion of Mg2+ into protoporphyrin IX at the first committed step of the chlorophyll biosynthetic pathway. It consists of three subunits: I, D, and H. The I subunit belongs to the AAA protein superfamily (ATPases associated with various cellular activities) that is known to form hexameric ring structures in an ATP-dependant fashion. Dominant mutations in the I subunit revealed that it functions in a cooperative manner. We demonstrated that the D subunit forms ATP-independent oligomeric structures and should also be classified as an AAA protein. Furthermore, we addressed the question of cooperativity of the D subunit with barley (Hordeum vulgare) mutant analyses. The recessive behavior in vivo was explained by the absence of mutant proteins in the barley cell. Analogous mutations in Rhodobacter capsulatus and the resulting D proteins were studied in vitro. Mixtures of wild-type and mutant R. capsulatus D subunits showed a lower activity compared with wild-type subunits alone. Thus, the mutant D subunits displayed dominant behavior in vitro, revealing cooperativity between the D subunits in the oligomeric state. We propose a model where the D oligomer forms a platform for the stepwise assembly of the I subunits. The cooperative behavior suggests that the D oligomer takes an active part in the conformational dynamics between the subunits of the enzyme.

The barley mutant emr1 exhibits restored resistance against Magnaporthe oryzae in the hypersusceptible mlo-genetic background

Barley plants having wild-type or mutant alleles at the MLO locus show opposite responses to infection with different pathogens, i.e. plants homozygous for mutant alleles (mlo) are resistant to powdery mildew but hypersusceptible to the rice blast fungus Magnaporthe oryzae and vice versa for plants with at least one wild-type MLO-allele. A mutational analysis was performed in the mlo-genetic background aimed at identifying of individuals with restored resistance against M. oryzae. Here, we describe the barley enhanced Magnaporthe resistance (emr1) mutant which showed restored resistance against blast in the absence of wild-type MLO. The emr1 mutant could be classified as a loss of function mutant. It could be excluded that resistance of emr1 is a back-mutation at the mlo-locus, because emr1 retained resistance against Bgh. The mutant did not display generally increased resistance as was evidenced by infection with either brown rust or net blotch pathogens. Additionally, resistance in emr1 was not associated with constitutively activated defence as confirmed by monitoring PR-gene transcript accumulation. Microscopic analysis showed that resistance of the emr1 mutant against M. oryzae was correlated with blocked penetration in epidermal cells and a concomitantly reduced progression into the mesophyll. These findings are reminiscent of the defence phenotypes against M. oryzae previously described for wild-type barley MLO genotypes. Therefore, it is tempting to speculate that resistance in the emr1 mutant was regained by the knockdown of putative suppressor element(s) acting in the defence scenario against M. oryzae, which diminish resistance only in mlo but not in MLO genotypes.

Dietary low-phytate mutant-M 955 barley grain alters phytate degradation and mineral digestion in sheep fed high-grain diets

Greater production demands for ruminants require increased dietary inclusion of high-energy feeds. Grains and oil seeds are most commonly used to enhance diet energy density. However, use of such feeds proportionally increases the amount of dietary phytate phosphorus (P), which the ruminant may not be able to fully utilise. Our objectives for this study were to determine the extent of phytate degradation and mineral digestion in wethers fed high-grain diets consisting of either a non-mutant or low-phytate mutant barley grain. In two separate experiments, mature Columbia wethers ( n = 7) fitted with rumen and duodenal cannulas and Columbia × Polypay wether lambs ( n = 8) were individually fed one of two finishing diets formulated with either non-mutant Harrington (HARR) variety or low-phytate mutant-M 955 (M955) barley grains. Total-P intake was similar (P=0.46–0.70) between the M955 and HARR treatments for mature (5756 and 5550 mg/day, respectively) and lamb (5207 and 4894 mg/day, respectively) wethers. Dietary water-soluble P was 3.6 times greater in M955 versus HARR diets and phytate P was 11 times greater in HARR versus M955 treatment diets. Apparent total-P digestion was similar between M955 and HARR treatments (P=0.52–0.69). More monoester P was identified in the duodenal chyme of mature wethers fed HARR treatment diet, presumably due to incomplete hydrolysis of phytate P in the rumen. Feeding M955, compared to HARR, treatment diet resulted in greater (P<0.05) apparent partial-tract digestion of calcium (Ca) and total-tract digestion of iron (Fe), magnesium (Mg), and zinc in mature wethers and apparent total-tract digestion of Mg and Fe and retention of Ca, Fe, and Mg in wether lambs. These results indicate that phytate in diets formulated with Harrington variety barley grain may not be fully digested in the rumen. Subsequent passage of partially digested phytate from the rumen may interfere with mineral digestion in wethers fed high-grain diets.

Water mobility in the endosperm of high beta-glucan barley mutants as studied by nuclear magnetic resonance imaging

(1)H NMR imaging (MRI) was used as a noninvasive technique to study water distribution and mobility in hydrated barley (Hordeum vulgare L.) seeds of accessions with varying content of beta glucan (BG), a highly hygroscopic cell wall component. High contents of BG in barley are unfavorable in malting where it leads to clotting of filters and hazing of beer as well as in animal feed where it hinders the rapid uptake of energy. However, a high content of BG has a positive nutritional effect, as it lowers the cholesterol and the glycaemic index. It was studied whether water distribution and mobility were related to content and location of BG. Water mobility was investigated by following the rate and mode of desiccation in hydrated single seeds. In order to determine the different water components, a multispin echo experiment was set up to reveal the T(2) transverse relaxation rates of water within the seeds. A principal component analysis (PCA) discriminated control seeds from the high-BG mutant seeds. MRI proved efficient in tracing the differences in water-holding capacity of contrasting barley seeds. All accessions showed nonuniform distribution of water at full hydration as well as during desiccation. The embryo retained water even after 36 h of drying, whereas the endosperm showed low and heterogeneous mobility of the water after drying. The relaxation time constants indicated that the BG mutants had regions of much higher water mobility around the ventral crease compared to the control. It is concluded that MRI can be applied to investigate temporal and spatial differences in the location of specific chemical compounds in single seeds.

Protein Polyubiquitination Plays a Role in Basal Host Resistance of Barley

To study protein ubiquitination pathways in the interaction of barley (Hordeum vulgare) with the powdery mildew fungus (Blumeria graminis), we measured protein turnover and performed transient-induced gene silencing (TIGS) of ubiquitin and 26S proteasome subunit encoding genes in epidermal cells. Attack by B. graminis hyperdestabilized a novel unstable green fluorescent protein fusion that contains a destabilization domain of a putative barley 1-aminocyclopropane-1-carboxylate synthase, suggesting enhanced protein turnover. Partial depletion of cellular ubiquitin levels by TIGS induced extreme susceptibility of transformed cells toward the appropriate host pathogen B. graminis f. sp hordei, whereas papilla-based resistance to the nonhost pathogen B. graminis f. sp tritici and host resistance mediated by the mlo gene (for mildew resistance locus O) remained unaffected. Cells were rescued from TIGS-induced ubiquitin depletion by synthetic genes encoding wild-type or mutant barley monoubiquitin proteins. The strongest rescue was from a gene encoding a K63R mutant form of ubiquitin blocked in several ubiquitination pathways while still allowing Lys-48-dependent polyubiquitination required for proteasomal protein degradation. Systematic RNA interference of 40 genes encoding all 17 subunits of the proteasome 19S regulatory particle failed to induce hypersusceptibility against B. graminis f. sp hordei. This suggests a role for Lys-48-linked protein polyubiquitination, which is independent from the proteasome pathway, in basal host defense of barley.

The Potential of Common Cereals to form Retrograded Resistant Starch

Resistant starch (RS) has been recognised as a functional fibre with many health-promoting effects. RS exists in four forms &amp;ndash; RS&lt;sub&gt;1&lt;/sub&gt;, RS&lt;sub&gt;2&lt;/sub&gt;, RS&lt;sub&gt;3&lt;/sub&gt;, and RS&lt;sub&gt;4&lt;/sub&gt;. The RS&lt;sub&gt;3 &lt;/sub&gt;type is generated by amylose retrogradation typically resulting from food processing procedures. The aim of this study was to demonstrate the potential ability of six agriculturally important cereals to generate type RS&lt;sub&gt;3 &lt;/sub&gt;resistant starch after retrogradation of their amylose. In comparison with all tested cereals, the statistically significant highest level of RS&lt;sub&gt;3&lt;/sub&gt; (5.28% &amp;plusmn; 0.68) was detected in triticale, mainly in the Pinokio, Presto, Tricolor, and Kendo cultivars. Significant highly content was also found in rye (4.93% &amp;plusmn; 0.73), especially in Selgo, Esprit, Dankowskie Nowe, and Apart cultivars, in comparison with wheat, spring and winter barley, tritordeum and oat. There were unsignificant differences between triticale and rye in RS&lt;sub&gt;3&lt;/sub&gt; levels. Wheat contained less RS&lt;sub&gt;3&lt;/sub&gt; (3.87% &amp;plusmn; 0.55) in comparison to triticale and rye. The best wheats with this trait were the Athlet, Boka, Trane, Versailles, and Torysa cultivars. The content of RS&lt;sub&gt;3&lt;/sub&gt; in barley was not high (2.35% &amp;plusmn; 0.45 in winter barley, 2.51% &amp;plusmn; 0.25 in spring barley), similar to tritordeum (2.26% &amp;plusmn; 0.36). The RS&lt;sub&gt;3&lt;/sub&gt; content in high amylose barley mutant Glacier was two-fold higher than in other tested barley cultivars (P&amp;nbsp;&amp;lt;&amp;nbsp;0.01). Only minimal level of RS&lt;sub&gt;3&lt;/sub&gt; can be generated from oat seed starch (0.41% &amp;plusmn; 0.09). These results indicate that plant species as well as crop cultivar screening are important for the identification of suitable natural sources of resistant starch. Concerning the production of functional foods, it is important to recognize that valuable bread cereals such as wheat and rye are superior sources of this type of dietary fibre and are highly beneficial to the human health. However, it is advisable to continue for other years in these annual results and localities too. &amp;nbsp;

Biochemical and structural analyses of a higher plant photosystem II supercomplex of a photosystem I‐less mutant of barley

Photosystem II of higher plants is a multisubunit transmembrane complex composed of a core moiety and an extensive peripheral antenna system. The number of antenna polypeptides per core complex is modulated following environmental conditions in order to optimize photosynthetic performance. In this study, we used a barley (Hordeum vulgare) mutant, viridis zb63, which lacks photosystem I, to mimic extreme and chronic overexcitation of photosystem II. The mutation was shown to reduce the photosystem II antenna to a minimal size of about 100 chlorophylls per photosystem II reaction centre, which was not further reducible. The minimal photosystem II unit was analysed by biochemical methods and by electron microscopy, and found to consist of a dimeric photosystem II reaction centre core surrounded by monomeric Lhcb4 (chlorophyll protein 29), Lhcb5 (chlorophyll protein 26) and trimeric light-harvesting complex II antenna proteins. This minimal photosystem II unit forms arrays in vivo, possibly to increase the efficiency of energy distribution and provide photoprotection. In wild-type plants, an additional antenna protein, chlorophyll protein 24 (Lhcb6), which is not expressed in viridis zb63, is proposed to associate to this minimal unit and stabilize larger antenna systems when needed. The analysis of the mutant also revealed the presence of two distinct signalling pathways activated by excess light absorbed by photosystem II: one, dependent on the redox state of the electron transport chain, is involved in the regulation of antenna size, and the second, more directly linked to the level of photoinhibitory stress perceived by the cell, participates in regulating carotenoid biosynthesis.

Conceptual validation of self-organisation studied by spectroscopy in an endosperm gene model as a data-driven logistic strategy in chemometrics

Chemometric models including data pre-treatment and inspection software are able to evaluate the coarsely grained “top down” observational data from biological tissues through spectroscopic sensors in a dialogue with fine-grained analytical “bottom up” data in a sequential exploratory selection strategy. It facilitates interpretation and development of new theoretical concepts. This is demonstrated by a data set of 11 barley mutant endosperm genes and crosses focusing on the extremely high mutant gene discrimination capability by Near Infrared Reflection Spectroscopy (NIRS). It represents patterns of intact chemical bonds from self-organised endosperm tissues, which are validated to prior spectroscopic, chemical and genetic knowledge. Principal Component Analysis (PCA) of spectra could classify different endosperm mutant genes and changed gene backgrounds. A new carbohydrate pathway regulation from starch to β-glucan was identified. Specific mutant genes were defined visually by directly inspecting and validating spectral patterns from genetically defined barleys. Genetic concepts such as “the phenome” and “pleiotropy” were given new definitions, phenomenologically expressed as log1/ R MSC (Multiple Scatter Corrected) NIRS fingerprints comparing mutants in an iso-genic background. Chemometric models are efficient in over-viewing genetic and environmental spectral differences but are not able to reproduce and predict in detail the finely tuned spectra from the “natural computer” of the self-organising tissue. Thus it is always necessary to return to spectral data for a final visual evaluation. In statistics and chemometrics mathematical formalism in data modelling should be integrated with the chemical and biological meaning of data-patterns. Ideas for problem solution may be combined from both sides.

In vitro culture response of barley (Hordeum vulgare) ethylene synthesis mutant MC 169

Although it is generally accepted that plant in vitro culture response is influenced by the donor genotype, the genetic and molecular bases of this phenomenon are barely known. As a consequence, the optimization of tissue culture protocols is mainly empirically done. Researchers of the IGEAF studied the genetic basis of the in vitro regeneration of various plant species, including the tissue culture response of artificially induced barley mutants. One barley mutant, MC 169, carries a nuclear gene, recently described controlling the root growth in hydroponic cultivation. Under this condition, the roots of MC 169 mutant plants were longer than those of the original wild type line MC 182, a fact that was associated with a reduced ethylene biosynthesis. On the other hand, it is known that ethylene accumulation is inhibitory for in vitro regeneration of several plant species. In this study, we compared the in vitro culture response of mutant MC 169 with that of its mother line MC 182. The data about induction and regeneration of calli as well as those of habituated calli formation demonstrated that mutant MC 169 and its mother line MC 182 show a similar in vitro behaviour.

Acclimation to temperature and irradiance modulates PSII charge recombination

Acclimation of wild type and the chlorina F2 mutant of barley to either high light or low temperature results in a 2- to 3-fold increase in non-photochemical quenching which occurred independently of either energy-dependent quenching (qE), xanthophyll cycle-mediated antenna quenching or state transitions. Results of in vivo thermoluminescence measurements used to address this conundrum indicated that excitation pressure regulates the temperature gap for S 2 Q B - and S 2 Q A - charge recombinations within photosystem II reaction centers. This is discussed in terms of photoprotection through non-radiative charge recombination.

Candidate genes for barley mutants involved in plant architecture: an in silico approach

To individuate candidate genes (CGs) for a set of barley developmental mutants, a synteny approach comparing the genomes of barley and rice has been introduced. Based on map positions of mutants, sequenced RFLP markers linked to the target loci were selected. The markers were mapped in silico by BLAST searches against the rice genome sequence and chromosomal regions syntenous to barley target intervals were identified. Rice syntenous regions were defined for 15 barley chromosomal intervals hosting 23 mutant loci affecting plant height (brh1; brh2; sld4), shoot and inflorescence branching (als; brc1; cul-2, -3, -5, -15, -16; dub1; mnd6; vrs1), development of leaves (lig) and leaf-like organs (cal-b19, -C15, -d4; lks5; suKD-25; suKE-74; suKF-76; trd; trp). Annotation of 110 Mb of rice genomic sequence made it possible to screen for putative CGs which are listed together with the reasons supporting mutant-gene associations. For two loci, CGs were identified with a clear probability to represent the locus considered. These include FRIZZY PANICLE, a candidate for the brc1 barley mutant, and the rice ortholog of maize Liguleless1 (Lg1), a candidate for the barley lig locus on chromosome 2H. For this locus, the validity of the approach was supported by the PCR-amplification of a genomic fragment of the orthologous barley sequence. SNP mapping located this fragment on chromosome 2H in the region hosting the lig genetic locus.

Relationship between the organization of the PSII supercomplex and the functions of the photosynthetic apparatus

The chlorophyll fluorescence and the photosynthetic oxygen evolution (flash-induced oxygen yield patterns and oxygen bursts under continuous irradiation) were investigated in the thylakoid membranes with different stoichiometry and organization of the chlorophyll-protein complexes. Data show that the alteration in the organization of the photosystem II (PSII) supercomplex, i.e. the amount and the organization of the light-harvesting chlorophyll a/ b protein complex (LHCII), which strongly modifies the electric properties of the membranes, influences both the energy redistribution between the two photosystems and the oxygen production reaction. The decrease of surface electric parameters (charge density and dipole moments), associated with increased degree of LHCII oligomerization, correlates with the strong reduction of the energy transfer from PSII to PSI. In the studied pea thylakoid membranes (wild types Borec, Auralia and their mutants Coeruleovireus 2/ 16, Costata2/ 133, Chlorotica XV/1422) with enhanced degree of oligomerization of LHCII was observed: (i) an increase of the S 0 populations of PSII in darkness; (ii) an increase of the misses; (iii) an alteration of the decay kinetics of the oxygen bursts under continuous irradiation. There is a strict correlation between the degree of LHCII oligomerization in the investigated pea mutants and the ratio of functionally active PSIIα to PSIIβ centers, while in thylakoid membranes without oligomeric structure of LHCII ( Chlorina f2 barley mutant) the PSIIα centers are not registered.

Effects of a Novel Barley, Himalaya 292, on Rheological and Breadmaking Properties of Wheat and Barley Doughs

ABSTRACTA barley mutant with high‐amylose starch, Himalaya 292, combines the potential cholesterol reducing effects of barley with the gastrointestinal benefits of high‐amylose resistant starches. Himalaya 292 has alterations in the content and composition of a range of grain constituents, thus conditions for successful addition to foods need to be defined. In this study, the rheological and breadmaking properties of doughs prepared by combining wheat flours (with various gluten protein compositions) with various barley genotypes (Himalaya 292 and the control cultivars Himalaya and Torrens) have been determined. The effects of barley addition on the rheological properties of the admixtures differed. While addition of Himalaya 292 increased the strength and reduced the extensibility of admixture doughs, addition of the Himalaya and Torrens barley flours to the wheat flours reduced both strength and extensibility. The addition of Himalaya and Torrens barley flour reduced water absorption levels. However, addition of Himalaya 292 whole grain flour increased the water absorption of the admixtures significantly (P &lt; 0.01). The baking data showed that selection of an appropriate wheat flour with a combination of strength and extensibility allows higher levels of incorporation of barley, facilitating an increased delivery per serving of constituents with positive health attributes in β‐glucan and resistant starch.

Characterization and Molecular Mapping of Genes Determining Semidwarfism in Barley

The semidwarf trait is desired in cereal breeding programs for increased lodging resistance. We characterized 27 brachytic (brh) semidwarf mutants in barley (Hordeum vulgare L.) and located the genes on barley chromosome linkage maps. All brachytic genes were transferred into the two-rowed cultivar Bowman by backcrossing four to seven times and selecting for semidwarf plants. The brachytic lines were evaluated for 10 phenotypic traits: plant height, awn, peduncle, and rachis internode length, leaf length and width, lodging, grain yield, number of kernels per spike, and kernel weight. We intercrossed the lines to determine which mutants were at independent loci and which were alleles at the same locus. F2 populations from 18 brh semidwarfs were constructed for genetic mapping using simple sequence repeat (SSR) markers. The brachytic semidwarf near-isogenic lines were significantly shorter than their normal counterparts and most had lower yields (16/27); shorter awns (26/27), peduncles (26/27), and rachis internodes (24/27); and reduced kernel weight (22/27). Twelve of the lines had shorter penultimate leaves and 15 had reduced lodging. Four lines had increased kernels per spike, while one had fewer kernels per spike. Allelism tests and mapping comparisons indicated that the 27 semidwarfs comprise 18 independent genetic loci. SSR mapping placed these loci in five of the seven barley chromosomes. Knowledge of the effects and locations of these brachytic semidwarf genes will help barley breeders select appropriate lines for barley improvement.