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Independent Regulatory Aspects and Posttranslational Modifications of Two beta-Amylases of Rye : Use of a Mutant Inbred Line.

We have examined the occurrence/disappearance, tissue location, and posttranslational modification of beta-amylase proteins in rye (Secale cereale L.) kernels at three physiological stages (development, maturity, germination) with a normal inbred line and a mutant line exhibiting a high but incomplete beta-amylase deficiency. This deficiency corresponds to a lack of accumulation of beta-amylase activity in the endosperm and does not affect the level of activity in the outer pericarp and green tissues as compared to the normal line. Two antigenically related but distinct beta-amylases (I and II) were detected in the normal line (II being the major constituent) and only one (I) in the mutant line. I and II display very similar electrophoretic polymorphism. In both lines, I appears to be ubiquitous, although it disappears from the outer pericarp during ripening. Antigen II was present only in the normal line and appears to be specific for the endosperm and perhaps for the maternal green tissues of the seed. Posttranslational modifications occurring during germination, which are mimicked by the action of papain, affect II but not I. The two groups of beta-amylases are discussed in relation to recent reports indicating the presence of two types of beta-amylase with different functions and gene loci in barley and wheat.

Journal Article↗

Resistance to low temperature photoinhibition is not associated with isolated thylakoid membranes of winter rye.

In vivo measurements of chlorophyll a fluorescence indicate that cold-hardened winter rye (Secale cereale L. cv Musketeer) develops a resistance to low temperature-induced photoinhibition compared with nonhardened rye. After 7.2 hours at 5 degrees C and 1550 micromoles per square meter per second, the ratio of variable fluorescence/maximum fluorescence was depressed by only 23% in cold-hardened rye compared with 46% in nonhardened rye. We have tested the hypothesis that the principal site of this resistance to photoinhibition resides at the level of rye thylakoid membranes. Thylakoids were isolated from cold-hardened and nonhardened rye and exposed to high irradiance (1000-2600 micromoles per square meter per second) at either 5 or 20 degrees C. The photoinhibitory response measured by room temperature fluorescence induction, photosystem II electron transport, photoacoustic spectroscopy, or [(14)C]atrazine binding indicates that the differential resistance to low temperature-induced photoinhibition in vivo is not observed in isolated thylakoids. Similar results were obtained whether isolated rye thylakoids were photoinhibited or thylakoids were isolated from rye leaves preexposed to a photoinhibitory treatment. Thus, we conclude that increased resistance to low temperature-induced photoinhibition is not a property of thylakoid membranes but is associated with a higher level of cellular organization.

Journal Article↗

Solute Accumulation and Compartmentation during the Cold Acclimation of Puma Rye.

During cold acclimation of Puma rye (Secale cereale L. cv Puma), the intracellular osmotic potential nearly doubles. During this period, the accumulation of glycinebetaine, proline, and soluble sugars was monitored. The amount of glycinebetaine increased from 290 to 1300 micrograms per gram fresh weight during the 4-week acclimation period. Proline content did not change during the first 3 weeks of acclimation but then increased from 27 to 580 micrograms per gram fresh weight during the next 3 weeks. The total soluble sugar content more than doubled by the second week of cold acclimation, increasing from 11 to 26 milligrams per gram fresh weight. Most of this increase can be attributed to the accumulation of sucrose and raffinose, whose levels increased from 2.4 and 0 to 11 and 5 milligrams per gram fresh weight, respectively. The content of monosaccharides, predominantly glucose, remained at a constant 10 milligrams per gram fresh weight throughout the acclimation period. A comparison of the sugar content of protoplasts versus vacuoles isolated from cold-acclimated leaves revealed that the extravacuolar volume contained monosaccharides, sucrose, and raffinose. Thus, the increased amounts of sucrose and raffinose that occur during cold acclimation are present in compartments external to the vacuole and may contribute to cryoprotection.

Journal Article↗

Differential Detergent Stability of the Major Light-Harvesting Complex II in Thylakoids Isolated from Monocotyledonous and Dicotyledonous Plants.

A survey of isolated thylakoids from 11 different higher plant species (Spinacia oleracea L., Pisum sativum L., Vicia faba L., Brassica napus L., Vigna sinensis L., Vinca minor L., Secale cereale L., Triticum aestivum L., Triticosecale Wittn., Hordeum vulgare L., Zea mays L.) indicated that the ratio of the oligomeric:monomeric form of the light-harvesting complex II was twofold higher for the dicots (3.16 +/- 0.35) than the monocots (1.64 +/- 0.25) examined under identical separation procedures. Under conditions specifically designed to stabilize the oligomeric form in vitro, we show that the oligomeric form of dicot light-harvesting complex II is twice as stable to solubilization in the presence of sodium dodecyl sulfate (SDS) than that observed for monocots. This decreased stability of monocot light-harvesting complex II is associated with a twofold increase in the trienoic fatty acid level of thylakoid phosphatidylglycerol but with no significant changes in the trienoic fatty acid levels in the major galactolipids. In addition, SDS polyacrylamide gel electrophoresis and western blot analyses with monoclonal antibodies indicated that monocots exhibited greater heterogeneity in the polypeptide complements associated with subfractions of light-harvesting complex II than the dicots examined. The data indicate that the oligomeric form of the light-harvesting complex II is not the result of a simple oligomerization of a common monomeric unit. We suggest that the difference in stability of the oligomeric form of light-harvesting complex II in isolated thylakoids of monocots and dicots is probably due to a differential accessibility to SDS. The differential SDS accessibility may be due to differences in thylakoid protein-protein and/or protein-lipid interactions.

Journal Article↗

Comparison of skin-prick test assay and reverse enzyme immunoassay competition (REINA-C) for biological activity of allergens.

An in vitro technique for measuring the relative potency of allergenic extracts has been developed and compared with the dose-response skin-prick test. The in vitro technique is a modification of an ELISA based on the method of antigen capture using polystyrene microtitre wells as solid phase (REINA-competition) and is also based on a dose-response. Both methods have been applied to allergen extracts of Dermatophagoides pteronyssinus, Phleum pratense, Secale cereale, Lolium perenne, Plantago lanceolata, Artemisia vulgaris, Salsola kali and Parietaria judaica. For each allergen, the slope of the regression log-log dose-response lines displayed by skin-prick test and REINA-C does not show a statistically significant difference, being parallel (P < 0.001), and indicating that the allergen-ligand binding kinetics are identical in both methods.

Adult↗

Pollen allergen homologues in barley and other crop species.

Pollen from 10 agricultural plant species was surveyed for the presence of proteins crossreactive with group I, group IV and group IX allergens. Barley (Hordeum vulgare), maize (Zea mays), rye (Secale cerale), triticale (xTriticosecale cereale), oats (Avena sativa), Canola (Brassica napus) and sunflower (Helianthus annus) pollens contained numerous allergen cognate proteins. Northern blot analysis of barley pollen RNA revealed the presence of group I and group IX allergen transcripts. The barley pollen cDNA hvp9742, and three other cloned allergens: phlenum protense (Phl p) V, Phl p Va and Lolium perenne (Lol p) 1b, were demonstrated to have extensive nucleotide and amino acid sequence similarity to the Poa p IX isoallergens. It was concluded that hvp9742 represents a Poa p IX isoallergen homologue expressed by barley pollen, and was therefore designated Hor v IX. It is further shown that the most highly conserved domains of all seven proteins, including Hor v IX, map to previously defined Poa p IX antibody binding epitopes.

Allergens↗

Grass pollen hyposensitization versus placebo therapy. I. Clinical effectiveness and methodological aspects of a pre-seasonal course of desensitization with a four-grass pollen extract.

The present work reports the results of a double-blind clinical trial, comparing the effects of hyposensitization treatment versus placebo in 33 patients with allergic rhinitis, sensitive to a crude extract of the pollen of four different grasses (Dactylis glomerata, Lolium perenne, Secale cereale, and Phleum pratense). The distribution of these patients in the two groups was done randomly and gave two comparable groups, as far as clinical and biological features are concerned. The treatment course included five low doses of the aqueous extract followed by 12 injections of Al(OH)3-adsorbed aliquots of the same extract. Evaluation of the clinical scores was based on diary cards on which symptoms and medications were recorded. A reevaluation of the significance of the symptom and medication scores is presented and the link between both scores is studied. Particular attention is given to the methodological and statistical problems raised during this study. The non-parametric tests reveal a significant difference (P less or equal to than 0.03) in the total clinical score between the treated and the placebo groups for the second half of the observation period, when the pathology was most intense.

Adolescent↗

Grass pollen immunotherapy induces highly cross-reactive IgG antibodies to group V allergen from different grass species.

Sera from two groups of patients receiving grass pollen immunotherapy were tested on IgG reactivity with group V allergen from six different grass species. One group of patients was treated with a mixture of 10 grass species, and the other with a mixture of five. Only Lolium perenne, Dactylis glomerata, and Phleum pratense were present in both mixtures. Although Anthoxanthum odoratum and Secale cereale were absent from the mixture of five, IgG responses to Ant o V and Sec c V were comparable in both patient groups. This reactivity was inhibited for 92-99% with L. perenne extract, illustrating the cross-reactive nature of the IgG antibodies. The presence of A. odoratum and S. cereale in the mixture resulted in only minor amounts of species-specific anti-group V IgG. These results indicate that application of just one grass species in immunotherapy might be sufficient to induce an IgG response that covers other relevant Gramineae species as well.

Allergens↗

The Triticeae genetic resources of central Italy: collection, evaluation and conservation.

One hundred and six landraces belonging to 7 species of the Triticeae tribe were collected in central Italy by DBVBA (Perugia University), DIBIAGA (Ancona University) and ARSSA (Abruzzo Region Agricultural Development Agency) in different individual and joint missions. A few accessions were supplied by private and other public organisations. Triticum dicoccum Schubler is the most widespread species, followed by T. aestivum L., T. monococcum L., T. spelta L., T. turgidum var. durum Desf., Secale cereale L. and Hordeum vulgare L. Besides the presence of landraces reproduced by farmers over generations, information related to on-farm management and to qualitative/organoleptic traits as well as information related to their local names, uses, traditions and social context was gathered during the missions. The majority of the accessions was characterised by morphological and phenological traits and molecular markers. This work shows the presence of morpho-phenologic and genetic differences among landraces and the importance of some species in the agricultural systems and food customs of the investigated area. Particularly for emmer three well distinct landraces are present, "Farro Italia Centrale", "Farro della Garfagnana" and "Farro Italia Meridionale". Other interesting and traditional landraces are the "Solina" common wheat in Abruzzo and the "Orzo mondo" naked barley in Marche. Most of the populations are still cultivated in marginal lands and under low input or organic agronomic conditions; nevertheless, in many cases, they are found near modern varieties in conventional agriculture systems. Moreover, the in situ (on-farm) conservation of Triticeae landraces in central Italy is strictly linked to elderly farmers.

Conservation of Natural Resources↗

Polyploidization-induced genome variation in triticale.

Polyploidization-induced genome variation in triticale (x Triticosecale Wittmack) was investigated using both AFLP and RFLP analyses. The AFLP analyses were implemented with both EcoRI-MseI (E-M) and PstI-MseI (P-M) primer combinations, which, because of their relative differences in sensitivity to cytosine methylation, primarily amplify repetitive and low-copy sequences, respectively. The results showed that the genomic sequences in triticale involved a great degree of variation including both repetitive and low-copy sequences. The frequency of losing parental bands was much higher than the frequency of gaining novel bands, suggesting that sequence elimination might be a major force causing genome variation in triticale. In all cases, variation in E-M primer-amplified parental bands was more frequent in triticale than that using P-M primers, suggesting that repetitive sequences were more involved in variation than low-copy sequences. The data also showed that the wheat (Triticum spp.) genomes were relatively highly conserved in triticales, especially in octoploid triticales, whereas the rye (Secale cereale L.) genome consistently demonstrated a very high level of genomic sequence variation (68%-72%) regardless of the triticale ploidy levels or primers used. In addition, when a parental AFLP band was present in both wheat and rye, the tendency of the AFLP band to be present in triticale was much higher than when it was present in only one of the progenitors. Furthermore, the cDNA-probed RFLP analyses showed that over 97% of the wheat coding sequences were maintained in triticale, whereas only about 61.6% of the rye coding sequences were maintained, suggesting that the rye genome variation in triticale also involved a high degree of rye coding sequence changes. The data also suggested that concerted evolution might occur in the genomic sequences of triticale. In addition, the observed genome variation in wheat-rye addition lines was similar to that in triticale, suggesting that wheat-rye addition lines can be used to thoroughly study the genome evolution of polyploid triticale.

Biological Evolution↗

Use of a large-scale Triticeae expressed sequence tag resource to reveal gene expression profiles in hexaploid wheat (Triticum aestivum L.).

The US Wheat Genome Project, funded by the National Science Foundation, developed the first large public Triticeae expressed sequence tag (EST) resource. Altogether, 116,272 ESTs were produced, comprising 100,674 5' ESTs and 15 598 3' ESTs. These ESTs were derived from 42 cDNA libraries, which were created from hexaploid bread wheat (Triticum aestivum L.) and its close relatives, including diploid wheat (T. monococcum L. and Aegilops speltoides L.), tetraploid wheat (T. turgidum L.), and rye (Secale cereale L.), using tissues collected from various stages of plant growth and development and under diverse regimes of abiotic and biotic stress treatments. ESTs were assembled into 18,876 contigs and 23,034 singletons, or 41,910 wheat unigenes. Over 90% of the contigs contained fewer than 10 EST members, implying that the ESTs represented a diverse selection of genes and that genes expressed at low and moderate to high levels were well sampled. Statistical methods were used to study the correlation of gene expression patterns, based on the ESTs clustered in the 1536 contigs that contained at least 10 5' EST members and thus representing the most abundant genes expressed in wheat. Analysis further identified genes in wheat that were significantly upregulated (p < 0.05) in tissues under various abiotic stresses when compared with control tissues. Though the function annotation cannot be assigned for many of these genes, it is likely that they play a role associated with the stress response. This study predicted the possible functionality for 4% of total wheat unigenes, which leaves the remaining 96% with their functional roles and expression patterns largely unknown. Nonetheless, the EST data generated in this project provide a diverse and rich source for gene discovery in wheat.

Cluster Analysis↗

Characterization and distribution of an interspersed repeated nucleotide sequence from Lophopyrum elongatum and mapping of a segregation-distortion factor with it.

Repeated nucleotide sequence pLeUCD2 cloned from Lophopyrum elongatum is highly abundant in the genomes of diploid and polyploid wheatgrass species of genera Lophopyrum, Thinopyrum, Pseudoroegneria, Agropyron, Elymus, Elytrigia, and Pascopyrum but undetectable by Southern blot hybridization in Triticum and representative species of Dasypyrum, Hordeum, Psathyrostachys, Secale, Taeniatherum, Heteranthelium, and Leymus in the tribe Triticeae. The DNA fragment inserted in pLeUCD2 is 277 bp long and AT rich (65%), and contains numerous inverted and palindromic repeats. In situ DNA hybridization substantiated a previous hypothesis that the sequence is interspersed in the wheatgrass genomes. Heterogeneity and clustering of like repeats of the pLeUCD2 family along wheatgrass chromosomes was used to map a segregation-distortion factor, designated Sd-1, proximal to the Lr19 locus in recombinant chromosomes of L. ponticum chromosome 7Ag and wheat chromosome 7D.

Base Sequence↗

Phylogenetic relationships of 10 grass species: an assessment of phylogenetic utility of the internal transcribed spacer region in nuclear ribosomal DNA in monocots.

Entire sequences of the internal transcribed spacers (ITSs) and 5.8S subunit of nuclear ribosomal DNA (nrDNA) were obtained from nine grass species by direct double-stranded sequencing of polymerase chain reaction (PCR) amplified DNA fragments. These sequences from subfamily Pooideae (Triticum aestivum, Crithodium monococcum, Sitopsis speltoides, Hordeum vulgare, Secale montanum, Avena longiglumis, Bromus inermis, Brachypodium distachyon) and subfamily Panicoideae (Sorghum bicolor) together with published ITS sequence of rice (Oryza sativa, Bambusoideae) were analyzed using Wagner parsimony (PAUP) and the neighbor-joining distance method to assess the phylogenetic utility of ITS sequences at various taxonomic levels. Among the aligned sequences that ranged from 588 to 603 nucleotides in length, 118 of 269 variable sites contained potential phylogenetic information. A member of Bromus, B. inermis, was the sister taxon to the Triticeae species. Brachypodium was more distantly related to Triticeae than was Bromus or Avena. These data, with Oryza sativa as the outgroup, indicate monophyly of the Pooideae species and of the members of the tribe Triticeae within Pooideae. Phylogenetic trees of the 10 grass species generated from the ITS sequence data were in general agreement with phylogenies based on molecular data from ribosomal RNA (rRNA) and chloroplast DNA (cpDNA) of similar grass taxa. This study reaffirms that sequences of the ITS region are useful for phylogenetic inference among closely related monocot species.

Base Sequence↗

Phylogenetic relationships of the monogenomic species of the wheat tribe, Triticeae (Poaceae), inferred from nuclear rDNA (internal transcribed spacer) sequences.

Phylogenetic relationships of 30 diploid species of Triticeae (Poaceae) representing 19 genomes were estimated from the sequences of the internal transcribed spacer (ITS) region of nuclear ribosomal DNA. The ITS sequence phylogeny indicated that: (i) each genome group of species is monophyletic, concordant with cytogenetic evidence; (ii) Hordeum (I) and Critesion (H) are basal; (iii) Australopyrum (W) is closely related to Agropyron (P); (iv) Peridictyon (G), Heteranthelium (Q), and Dasypyrum (V) are closely related to Pseudoroegneria (S); (v) most of the annuals, Triticum s.l. (A, B, D), Crithopsis (K), Taeniatherum (T), Eremopyrum (F), Henrardia (O), Secale (R), and two perennials, Thinopyrum (J) and Lophopyrum (E), all of Mediterranean origin, are a monophyletic group. However, phylogenetic trees based on morphology group these Mediteranean species with various perennial lineages of the Arctic-temperate region. The molecular data and biogeography of the tribe suggest that the Mediterranean lineage is derived from the Arctic-temperate lineage and that the two lineages have evolved in parallel. Extensive morphological parallelism apparently obscures the true genealogical history of the tribe when only morphology is considered.

Africa, Northern↗

Repeated DNA sequences isolated by microdissection. I. Karyotyping of barley (Hordeum vulgare L.).

We report on microdissection, cloning and sequence, and Southern and fluorescence in situ hybridization (FISH) analysis of one moderately and one highly amplified repetitive DNA element, pHvMWG2314 and pHvMWG2315, respectively, isolated from barley (Hordeum vulgare L.) chromosome arm 3HL. The pHvMWG2315 sequence hybridizes to all 14 telomeric or subtelomeric regions of the barley chromosomes as determined by FISH. The 50 different hybridization sites that include intercalary signals allow the discrimination of all 14 chromosome arms and the construction of a kariotype of barley. The tandemly repeated subtelomeric element of 331 bp exists in all Triticeae species tested (H. vulgare, Agropyron elongatum, Secale cereale, Triticum tauschii, T. turgidum, and T. aestivum). It is AT rich (66%), exibits 84% sequence homology to subfragments of the D genome ¿specific¿ 1-kb element pAs1 of T. tauscii and 75% homology to interspersed genome-specific DNA sequence pHcKB6 from H. chilence. The repetitive sequence pHvMWG2314 is moderately amplified in barley and highly amplified in hexaploid wheat. The in situ experiments revealed no distinct signals on barley chromosomes, indicating a dispersed character for the sequence. The significance of the results for the identification of chromosomes and chromosome aberrations in FISH experiments are discussed.

Base Composition↗

Cloning and characterization of a highly repeated DNA sequence in Hordeum vulgare L.

A novel repetitive DNA sequence, R10hvcop, has been identified in the barley (Hordeum vulgare L.) genome. This 830 base pair (bp) DNA sequence has a 606-bp open reading frame and is present as approximately 1.96 x 10(5) copies per haploid barley genome. Southern blot analysis revealed that repetitive DNA elements containing R10hvcop and related sequences were dispersed within the barley chromosomes. Sequences similar to R10hvcop were also found in wheat (Triticum aestivum L.), rye (Secale cereale L.), and oat (Avena sativa L.) with copy numbers of 8 x 10(4), 1.39 x 10(5), and 7.9 x 10(4) per haploid genome, respectively. Sequences similar to R10hvcop were also present in the corn (Zea mays L. ssp. mays) genome, but they were not highly repeated. Barley, wheat, rye, oat, and corn showed species-specific restriction fragment length polymorphisms of R10hvcop and related sequences. Computer-based similarity searches revealed that R10hvcop is closely related to reverse transcriptase genes in retrotransposon-like elements of several plant species and of Drosophila. The highly repetitive nature, interspersed distribution, and high degree of similarity to reverse transcriptase genes suggests that R10hvcop contains the sequence of a diverged reverse transcriptase gene.

Base Sequence↗

Chromosomal location and genetic mapping of the mismatch repair gene homologs MSH2, MSH3, and MSH6 in rye and wheat

The efficiency of homeologous recombination is influenced by mismatch repair genes in bacteria, yeast, and mammals. To elucidate a possible role of these genes in homeologous pairing and cross-compatibility in plants, gene probes of wheat (Triticum aestivum) specific for the mismatch repair gene homologues MSH2, MSH3, and MSH6 were used to map them to their genomic positions in rye (Secale cereale). Whereas MSH2 was mapped to the short arm of chromosome 1R, MSH3 was mapped to the long arm of chromosome 2R and MSH6 to the long arm of chromosome 5R. Southern blots with nullisomic-tetrasomic (NT) lines of wheat indicated the presence of the sequences on the respective homeologous group of wheat chromosomes. Additionally, an MSH6-specific homologue could also be detected on homoeologous group 3 of wheat. However, in the well-known, highly homoeologous pairing wheat mutant ph1b the MSH6-specific sequence is not within the deleted part of chromosome 5BL, indicating that the pairing phenotype is not due to a loss of one of the mismatch repair genes tested.

Journal Article↗

Understanding the cytological diploidization mechanism of polyploid wild wheats.

The allohexaploid Aegilops species (2n = 6x = 42), Ae. neglecta 6x (UUXtXtNN), Ae. juvenalis (DcDcXcXcUU), and Ae. vavilovii (DcDcXcXcSsSs) regularly form bivalents at metaphase I. However, in Ae. crassa 6x (DcDcXcXcDD) 0.27 quadrivalents per cell were observed probably as a consequence of the partial homology displayed by the D and Dc genomes. Likewise, the synthetic amphiploid Ae. ventricosa-Secale cereale (DDNNRR) is fertile and displays a diploid-like behavior at metaphase I, despite its recent origin. The pattern of synapsis at late zygotene and pachytene in the natural and artificial allohexaploids was analyzed by whole-mount surface-spreading of synaptonemal complexes under an electron microscope. It revealed that chromosomes were mostly associated as bivalents in all cases, the mean of multivalents per nucleus ranging from 0.17 (Ae. neglecta 6x) to 1.03 (Ae. crassa 6x) in the natural species and 1.05 in the Ae. ventricosa-S. cereale amphiploid. It can be concluded that the mechanism controlling bivalent formation in these species and also in the synthetic amphiploid acts mainly at zygotene by restricting synapsis to homologous chromosomes, but also acts at pachytene by preventing chiasma formation in the homoeologous associations. These observations are discussed in relation to the origin and evolution of the mechanism of diploidization in the allopolyploid species of the Poaceae family.

Chromosome Pairing↗