cDNA encoding a wheat (Triticum aestivum cv. Chinese Spring) glycine-rich RNA-binding protein

A wheat cDNA encoding a glycine-rich RNA-binding protein, whGRP-1, was isolated. WhGRP-1 contains two conserved domains, the RNA-binding motif (RNP motif) combined with a series of glycine-rich imperfect repeats, characteristic of a conserved family of plant RNA-binding proteins. Northern analysis revealed that whGRP-1 mRNA accumulates to high levels in roots and to lower levels in leaves of wheat seedlings. whGRP-1 mRNA accumulation is not enhanced by exogenous abscisic acid in seedlings and accumulates to very high levels during wheat embryo development, showing a pattern different from that of the ABA-inducible wheat Em gene.     

Hybrid seed development and viability in crosses of T. aestivum (cv. Chinese Spring) monosomic lines with S. cereale

Summary The diploid and tetraploid wheats have a crossing barrier that inhibits development and viability of the F₁ hybrid seeds which result from their pollination with rye. This barrier is ineffective in synthetic or natural hexaploid wheat × rye crosses. From the results obtained by crossing the Chinese Spring monosomic series to a diploid rye composite, it was concluded that the breakdown of this barrier in hexaploid wheats is determined by polygenes, but may also involve genedosage effects. While more than half of the hexaploidwheat chromosomes may contribute to the breakdown of the barrier, chromosome 1D had the strongest effect. Its absence resulted in shrivelled and inviable hybrid kernels similar to those obtained when the T. durum cultivar Langdon was crossed with rye.     

Plant regeneration from protoplasts of wheat (Triticum aestivum cv. Hartog)

Morphologically normal green plants have reproducibly been regenerated from protoplasts of an Australian wheat (Triticum aestivum cv. Hartog). The protoplasts were isolated from fine embryogenic suspension cultures which were initiated from embryogenic callus. Protoplasts were incubated in a modified liquid MS medium containing half strength of the macroelements, 5 m 2,4-D and 0.6 M glucose. Colonies were formed at frequencies ranging from 0.1% to 5%. The frequency of colonies forming fully developed plants varied between 1% and 25%. More than eighty green plants with morphologically normal shoots and roots have been obtained and there was no difficulty in establishing these plants in soil. A cytological study of several randomly selected regenerated plants showed the normal chromosome complement for wheat (2n = 42).     

Characterization of a cysteine protease from wheat Triticum aestivum (cv. Giza 164)

Enzymes, especially proteases, have become an important and indispensable part of the processes used by the modern food and feed industry to produce a large and diversified range of products for human and animal consumption. A cysteine protease, used extensively in the food industry, was purified from germinated wheat Triticum aestivum (cv. Giza 164) grains through a simple reproducible method consisting of extraction, ion exchange chromatography and gel filtration. The molecular weight of the enzyme was estimated to be 61000+/-1200-62000+/-1500 by SDS-PAGE and gel filtration. The cysteine protease had an isoelectric point and pH optimum at 4.4 and 4.0, respectively. The enzyme exhibited more activity toward azocasein than the other examined substrates with K(m) 2.8+/-0.15 mg azocasein/ml. In addition, it had a temperature optimum of 50 degrees C and based on a heat stability study 55% of its initial activity remained after preincubation of the enzyme at 50 degrees C for 30 min prior to substrate addition. All the examined metal cations inhibited the enzyme except Co(2+), Mg(2+), Mn(2+) and Li(+). The proteolytic activity of the enzyme was inhibited by thiol-specific inhibitors, whereas iodoacetate and p-hydroxymercuribenzoate caused a competitive inhibition with Ki values 6+/-0.3 mM and 21+/-1.2 microM, respectively. Soybean trypsin inhibitor had no effect on the enzyme. The enzyme activity remained almost constant for 150 days of storage at -20 degrees C. The properties of this enzyme, temperature and pH optima, substrate specificity, stability and sensitivity to inhibitors or activators, meet the prerequisites needed for food industries.     

中国春双端二体中端体的配对研究

21个中国春双端二体与中国春品种杂交,观察了杂种F_1减数分裂中期Ⅰ端体与相应染色体的配对。结果表明:14个组合的中期Ⅰ具有1个异形三价体的PMC的百分数超过90%;有3个组合(6A、5B和6D)分别为89.87%、83.56%和85.71%;2个组合(4A和1B)低于80%。在4A、1B和5B的3个组合中,具有1个异形二价体和1个单价端体的PMC超过15%。在4A、1B和4D的组合中,还有一定频率的PMC具有2个单价端体。用21个组合中端体配对频率计算的二价体频率与中国春品种中期Ⅰ构型频率基本一致。这些结果表明,染色体臂作为端体时和它作为双臂染色体的一部分时,是以同样的方便程度配对的。     

Developmental traits affecting low-temperature tolerance response in near-isogenic lines for the Vernalization locus Vrn-A1 in wheat (Triticum aestivum L. em Thell)

Investigation of low-temperature (LT) tolerance in cereals has commonly led to the region of the vyn-A1 vernalization gene or its homologue in related genomes. Two cultivars, one a non-hardy spring wheat and one a very cold-hardy winter wheat, whose growth habits are determined by the Vrn-A1 (spring habit) and vrn-A1 (winter habit) alleles, were chosen to produce reciprocal near-isogenic lines (NILs). These lines were then used to determine the relationship between rate of phenological development and the degree and duration of LT tolerance gene expression. Each allele was isolated in the genetic backgrounds of the non-hardy spring wheat 'Manitou' and the very cold-hardy winter wheat 'Norstar'. The effects of each allele on phenological development and low-temperature tolerance (LT50) were determined at regular intervals over a 4 degrees C acclimation period of 0-98 d. The vegetative/reproductive transition, as determined by final leaf number (FLN), was found to be a major developmental factor influencing LT tolerance. Possession of a vernalization requirement increased both the length of the vegetative growth phase and LT tolerance. Similarly, increased FLN in spring Norstar and winter Manitou NILs delayed their vegetative/reproductive transition and increased their LT tolerance relative to Manitou. Although the winter Manitou NILs had a lower FLN than the spring Norstar NILs, they were able to extend their vegetative stage to a similar length by increasing the phyllochron (interval between the appearance of successive leaves). Cereal plants have four ways of increasing the length of the vegetative phase, all of which extend the time that low-temperature tolerance genes are more highly expressed: (1) vernalization; (2) photoperiod responses; (3) increased leaf number; and (4) increased length of the phyllochron.     

Molecular and biochemical characterization of cytosolic phosphoglucomutase in wheat endosperm (Triticum aestivum L. cv. Axona)

Evidence from a number of plant tissues suggests that phosphoglucomutase (PGM) is present in both the cytosol and the plastid. The cytosolic and plastidic isoforms of PGM have been partially purified from wheat endosperm (Triticum aestivum L. cv. Axona). Both isoforms required glucose 1,6-bisphosphate for their activity with K(a) values of 4.5 micro M and 3.8 micro M for cytosolic and plastidic isoforms, respectively, and followed normal Michaelis-Menten kinetics with glucose 1-phosphate as the substrate with K(m) values of 0.1 mM and 0.12 mM for the cytosolic and plastidic isoforms, respectively. A cDNA clone was isolated from wheat endosperm that encodes the cytosolic isoform of PGM. The deduced amino acid sequence shows significant homology to PGMs from eukaryotic and prokaryotic sources. PGM activity was measured in whole cell extracts and in amyloplasts isolated during the development of wheat endosperm. Results indicate an approximate 80% reduction in measurable activity of plastidial and cytosolic PGM between 8 d and 30 d post-anthesis. Northern analysis showed a reduction in cytosolic PGM mRNA accumulation during the same period of development. The implications of the changes in PGM activity during the synthesis of starch in developing endosperm are discussed.     

Back-cross reciprocal monosomic analysis of Fusarium head blight resistance in wheat (Triticum aestivum L.)

 Fusarium head blight (FHB or scab) caused by Fusarium spp. is a widespread disease of cereals causing yield and quality losses and contaminating cereal products with mycotoxins. The breeding of resistant varieties is the method of choice for controlling the disease. Unfortunately, the genetic basis of scab resistance is still poorly understood. We present the results of a back-cross reciprocal monosomic analysis of FHB resistance using the highly resistant Hungarian winter wheat line ‘U-136.1’ and the highly susceptible cultivar ‘Hobbit-sib’. Resistance testing was performed in a field trial artificially inoculated with a Fusarium culmorum conidial suspension. Five hemizygous families containing ‘U-136.1’ chromosomes 6B, 5A, 6D, 1B, and 4B had a visually reduced spread of infection compared to lines having the ‘Hobbit-sib’ chromosome. Chromosome 2B from ‘U-136.1’ had an increased spread of infection. The critical chromosomes controlling seed weight were 6D, 3B, 5A, and 6B while those controlling deoxynivalenol (DON) content were homoeologous groups 2 and 6, although the latter effects were not significant due to a high coefficient of variation. Results from this and other studies show that chromosomes 6D, 6B, 5A, 4D, and 7A have frequently been associated with scab resistance in a number of wheat cultivars. Research groups now attempting to map scab resistance in wheat using markers should pay special attention to the above-mentioned chromosomes. Received: 31 March 1998 / Accepted: 14 July 1998     

137Cs uptake in spring wheat (Triticum aestivum L.cv. Tonic) at varying K supply

Spring wheat (Triticum aestivum L. cv. Tonic) was grown for 16 days in a sandy loam soil which was contaminated with ¹³⁷Cs. The soil was fertilised with K at three rates (0,1 and 2 mmol K per 950 g dry soil) and with NO₃ ^--N at two rates (0 and 2 mmol per 950 g dry soil) in a factorial design. The ¹³⁷Cs Activity Concentration (AC) in the shoot tissue significantly reduced 8.2-fold (nil N treatment, p<0.001) and 9.3-fold (highest N dose, p<0.001) with increasing K supply. In contrast, the K application increased the ¹³⁷Cs AC in soil solution 1.7 fold (nil N treatment) or had no significant effect (highest N dose). At similar K application, the application of N increased the ¹³⁷Cs AC in the shoot compared to the control. This effect is most probably due to the increased NH₄ ⁺ concentration in soil solution which increased the ¹³⁷Cs AC in soil solution. The soil solution composition (¹³⁷Cs and K concentration) in the rhizosphere was estimated from the average soil solution composition at day 16 and solute transport calculations. The ¹³⁷Cs AC in the shoot tissue was predicted from the estimated soil solution composition in the rhizosphere and the relationship between K concentration and ¹³⁷Cs uptake derived from a nutrient solution experiment. The predictions of ¹³⁷Cs AC's in the shoot are qualitatively correct for the fertiliser effects but underestimate the observations between 1.4 and 9.9 fold.     

F1 hybrid versus 32 selected F7 lines performance of common winter wheat (Triticum aestivum ssp. vulgare)

Summary One F₁ common wheat hybrid (Zlatna Dolina x Primépi) which had exhibited significant heterosis in a previous study was compared with 32 F₇ lines selected from the same cross. The yield test was planted in the 1976–1977 season at two locations: Zagreb, Yugoslavia (optimal environment) and Hutchinson, Kansas, USA (stress environment). The purpose of this experiment was to determine if a homozygous segregant superior to the F₁ hybrid could be obtained from the same cross combination.Heading date, plant height, disease incidence, grain yield and its components, protein content, and sedimentation value were examined at Zagreb. Germination, winterhardiness and grain yield were determined at Hutchinson.At Zagreb, the F₁ hybrid exhibited significant heterosis in grain yield, even though two of the three yield components were intermediate to parent values. Heterotic effects were greater in the stress environment (Hutchinson), mainly due to the poor winterhardiness and lower yield of one parent variety. At Zagreb, grain yield of the f₁ hybrid was significantly better than the best F₇ line. However at Hutchinson, the two leading F₇ Unes outyielded the f₁ hybrid, but differences were not significant.It can be concluded that genes involved in heterosis in the hybrid, Zlatna Dolina x Primépi, were not fixed in the homozygous lines selected from the same cross.     

Comparative changes in the antioxidant system in the flag leaf of early and normally senescing near-isogenic lines of wheat (Triticum aestivum L.)

Key message

The antioxidant system was significantly inhibited in the early aging line than the near-isogenic normal aging line during senescence.

Abstract

The antioxidant system plays pivotal roles in removal of reactive oxygen species (ROS) produced during leaf senescence. To explore its roles in leaf senescence of wheat (Triticum aestivum L.), the concentrations of antioxidants, activities, and gene expression of antioxidant enzymes were evaluated in flag leaves of the early aging line (EAL) and the near-isogenic normal aging line (NL) during senescence. The results showed that the total chlorophyll and soluble protein in the EAL declined earlier and faster, while more malondialdehyde and ROS accumulated compared with the NL. The activities of superoxide dismutase, catalase, ascorbate peroxidase, dehydroascorbate reductase, and glutathione reductase were lower in the EAL than in the NL across multiple measuring dates. Additionally, the EAL had less amounts of reduced ascorbate and glutathione as well as lower reduction state with the progression of senescence. Concomitantly, the gene expression of antioxidant enzymes in the EAL was also significantly repressed relative to those in the NL during natural senescence. Taken together, the earlier onset and faster rate of senescence in the EAL could be a result of an imbalance of ROS production and ROS-scavenging antioxidant system, which provided valuable hints toward understanding leaf senescence of wheat.     

Genetics of yellow berry in wheat (Triticum aestivum)

Summary The inheritance of yellow berry, a grain disorder in durum and bread wheats, was studied in six intervarietal crosses in bread wheat. The trait was found to be controlled by either two or three dominant genes. Monosomic analysis using Chinese Spring monosomic series showed the presence of two major dominant genes on chromosomes 1A and 7A, and four modifiers on 4A, 4B, 6A and 6D, which influence the expression of yellow berry in bread wheat.     

Flow sorting of mitotic chromosomes in common wheat (Triticum aestivum L.)

The aim of this study was to develop an improved procedure for preparation of chromosome suspensions, and to evaluate the potential of flow cytometry for chromosome sorting in wheat. Suspensions of intact chromosomes were prepared by mechanical homogenization of synchronized root tips after mild fixation with formaldehyde. Histograms of relative fluorescence intensity (flow karyotypes) obtained after the analysis of DAPI-stained chromosomes were characterized and the chromosome content of all peaks on wheat flow karyotype was determined for the first time. Only chromosome 3B could be discriminated on flow karyotypes of wheat lines with standard karyotype. Remaining chromosomes formed three composite peaks and could be sorted only as groups. Chromosome 3B could be sorted at purity >95% as determined by microscopic evaluation of sorted fractions that were labeled using C-PRINS with primers for GAA microsatellites and for Afa repeats, respectively. Chromosome 5BL/7BL could be sorted in two wheat cultivars at similar purity, indicating a potential of various wheat stocks for sorting of other chromosome types. PCR with chromosome-specific primers confirmed the identity of sorted fractions and suitability of flow-sorted chromosomes for physical mapping and for construction of small-insert DNA libraries. Sorted chromosomes were also found suitable for the preparation of high-molecular-weight DNA. On the basis of these results, it seems realistic to propose construction of large-insert chromosome-specific DNA libraries in wheat. The availability of such libraries would greatly simplify the analysis of the complex wheat genome.     

Translocation and utilization of carbon in wheat (Triticum aestivum)

Wheat ( Triticum aestivum L. cv. SUN 9E) was grown in a growth chamber under conditions of low soil nitrogen. Translocation of carbon to the roots and the subsequent utilization of these carbohydrates was determined. In vegetative plants (22 days old), 21.5 mg C day⁻¹ were translocated to the roots. 29% of this was incorporated into dry matter, 32% was respired (28% via the cytochrome and 4% via a SHAM-sensitive, presumably the alternative nonphosphorylating, pathway) and 39% was translocated back to the shoots, mainly in the form of amino acids. – The rote of root maintenance respiration during the vegetative phase was estimated to be 0.7 mg O₂ h⁻¹ (g dry weight of roots)⁻¹ and the root growth respiration to be 0.41 g O₂ (g dry weight of roots)⁻¹. Total carbohydrate utilization due to root respiration via the alternative, nonphosphorylating pathway during the major part of the growth period was calculated to be only ca 6% of carbohydrate utilization for grain growth. The rate of specific mass transfer (SMT) of sugars in the sieve tubes was estimated from the data on C-translocation and data on the total area occupied by sieve tubes in a cross section of the root system. SMT was calculated to be 0.8 mg sucrose s⁻¹ cm⁻², which is very similar to the published value on SMT for other organs, except roots.     

A complete mitochondrial genome of wheat (Triticum aestivum cv. Chinese Yumai), and fast evolving mitochondrial genes in higher plants

Plant mitochondrial genomes, encoding necessary proteins involved in the system of energy production, play an important role in the development and reproduction of the plant. They occupy a specific evolutionary pattern relative to their nuclear counterparts. Here, we determined the winter wheat (Triticum aestivum cv. Chinese Yumai) mitochondrial genome in a length of 452 and 526 bp by shotgun sequencing its BAC library. It contains 202 genes, including 35 known protein-coding genes, three rRNA and 17 tRNA genes, as well as 149 open reading frames (ORFs; greater than 300 bp in length). The sequence is almost identical to the previously reported sequence of the spring wheat (T. aestivum cv. Chinese Spring); we only identified seven SNPs (three transitions and four transversions) and 10 indels (insertions and deletions) between the two independently acquired sequences, and all variations were found in non-coding regions. This result confirmed the accuracy of the previously reported mitochondrial sequence of the Chinese Spring wheat. The nucleotide frequency and codon usage of wheat are common among the lineage of higher plant with a high AT-content of 58%. Molecular evolutionary analysis demonstrated that plant mitochondrial genomes evolved at different rates, which may correlate with substantial variations in metabolic rate and generation time among plant lineages. In addition, through the estimation of the ratio of non-synonymous to synonymous substitution rates between orthologous mitochondrion-encoded genes of higher plants, we found an accelerated evolutionary rate that seems to be the result of relaxed selection.