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Mode of translational activation of the catalase (cat1) mRNA of rye leaves (Secale cereale L.) and its control through blue light and reactive oxygen.

The enzyme catalase (EC 1.11.1.6) is inactivated by light and must be continuously replaced by new synthesis in order to maintain a constant enzyme activity in leaves. In winter rye leaves (Secale cereale L.) posttranscriptional mechanisms determine the rate of new catalase synthesis, including a light-controlled reversible modification of the catalase cat1 mRNA by methylation which greatly enhanced its translation efficiency. The specificity and regulation of this mRNA activation were further investigated. The translation efficiency of the rye cat1 mRNA was much more enhanced by N-7 methylation of the cap than that of an lhcb transcript. Investigations with truncated rye cat1 mRNAs indicated that the translational enhancement resulting from N-7 cap methylation did not require the presence of specific sequences of cat1 5'- and 3'-untranslated regions. Translational activation of the cat1 mRNA in rye leaves was independent of photosynthesis and most effectively induced by blue light. Peroxides (H(2)O(2), tertiary butyl hydroperoxide) and conditions enforcing an H(2)O(2) accumulation in the leaves (aminotriazole, paraquat) also caused an activation of the cat1 mRNA. A search for further signalling systems controlling the replenishment of inactivated catalase in light suggested that an inositol-1,4,5-triphosphate-mediated liberation of Ca(2+) from internal stores and a protein phosphatase played some role. However, these signalling systems did not affect the activation of the cat1 mRNA. After removal of Ca(2+) by EGTA the cat1 mRNA was rapidly degraded.

Catalase↗

Tetrad-FISH analysis reveals recombination suppression by interstitial heterochromatin sequences in rye (Secale cereale).

Tetrad analysis is a genetic method that can locate genes and centromeres on a linkage map with a high degree of precision. Despite its effectiveness and accuracy, application of this method is generally limited to fungi, algae and mosses. Here we demonstrate a new method of tetrad analysis that is applicable to other organisms. This combines tetrad analysis with fluorescence in situ hybridization (FISH), and is thus referred to as tetrad-FISH analysis. We demonstrate the effectiveness of this method using tetrads of rye, Secale cereale. The rye strain JNK contains interstitial heterochromatin in a region of Chromosome 2R. We have previously cloned the tandemly repeated sequence forming this heterochromatin in the plasmid pScJNK. We performed FISH using pScJNK as the probe on tetrads obtained from heterozygotes for the heterochromatin region. The frequency of tetrads demonstrating positive signals in two cells that are diagonally opposite one another must correspond to the frequency of recombination in the interval between the heterochromatin and the centromere. Comparison between the results of tetrad-FISH analysis and linkage maps based on RFLP markers clearly indicated that heterochromatin strongly suppresses recombination of whole chromosomal regions. We discuss the effectiveness of tetrad-FISH analysis, particularly for the localization of functional centromeres in linkage maps.

Genetic Linkage↗

Distribution of 5-methylcytosine residues in 5S rRNA genes in Arabidopsis thaliana and Secale cereale.

Bisulfite genomic sequencing was used to localise 5-methylcytosine residues (mC) in 5S rRNA genes of Arabidopsis thaliana and Secale cereale. The maps of mC distribution were compared with the previously published map of the corresponding region in Nicotiana tabacum. In all three species, the level of methylation of 5S rRNA genes was generally higher than the average for the entire genome. The ratio of 5S rDNA methylation to average overall methylation was 44%/30-33% for N. tabacum, 27%/4-6% for A. thaliana and 24%/20-22% for S. cereale. With the exception of one clone from S. cereale, no methylation-free 5S rDNA was detected. The level of methylation at different sequence motifs in 5S rDNA was calculated for N. tabacum/A. thaliana/ S. cereale, and this analysis yielded the following values (expressed as a percentage of total C): mCG 90%/78%/85%, mCWG 89%/41%/53%, mCmCG 72%/32%/16%, mCCG 4%/2%/0%, mCHH 15%/6%/1%, where W=A or T, and H=A or C or T. Non-symmetrical methylation was almost negligible in the large genome of S. cereale but relatively frequent in N. tabacum and A. thaliana, suggesting that the strict correlation between genome size and cytosine methylation might be violated for this type of methylation. Among non-symmetrical motifs the mCWA triplets were significantly over-represented in Arabidopsis, while in tobacco this preference was not as pronounced. The differences in methylation levels in different sequence contexts might be of phylogenetic significance, but further species in related and different taxa need to be studied before firm conclusions can be drawn.

5-Methylcytosine↗

Secale cereale inter-microsatellites (SCIMs): chromosomal location and genetic inheritance.

The polymerase chain reaction (PCR) was used to locate Sectale cereale (inter-simple sequence repeat ISSR) or Secale cereale inter-microsatellite (SCIM) markers using wheat-rye addition lines in order to develop a set of molecular markers distributed on the seven rye chromosomes. The number of SCIM markers located on 1R, 2R, 3R, 4R, 5R, 6R and 7R chromosomes were 4, 3, 12, 3, 2, 9 and 8, respectively. Therefore, a total of 41 new SCIMs were located on the seven rye chromosomes. The segregation of the 63 different SCIM markers in three different F2 was studied. The observed ISSR segregations were the 3:1 (50.7%), the 15:1 (12.7%) and the 1:1 (14.2%). The linkage analysis carried out indicated that seven of the segregating SCIMs were linked to chromosome 7R and two were linked to chromosome 4R. The use of the SCIM markers as a source of molecular markers that could be linked to interesting genes or other important agronomic traits is discussed.

Chromosome Mapping↗

Gas chromatographic method for the analysis of allelopathic natural products in rye (Secale cereale L.).

Accurate and reproducible methods for the analysis of plant allelochemicals are a requirement for the study of chemical interactions between plants. This paper describes a method for sample preparation and quantitative analysis of the allelopathic chemical content of rye (Secale cereale L.) using gas chromatography (GC). Sample preparation consists of extraction of freeze-dried rye vegetative tissue with aqueous ethanol followed by partitioning of the allelochemicals into ethyl acetate, evaporation, and derivatization using the trimethylsilylating reagent N-methyl-N-trimethylsilyltrifluoroacetamide. GC analysis of the silylated mixture was performed using flame ionization detection. This method permits analysis of all known rye allelopathic agents including 2,4-dihydroxy-1,4-benzoxazin-3-one, its corresponding glucoside, 2-benzoxazolinone, beta-hydroxybutyric acid, and beta-phenyllactic acid. Identities of all compounds were confirmed by GC/MS analysis.

3-Hydroxybutyric Acid↗

2,3-Epoxybrassinosteroids are intermediates in the biosynthesis of castasterone in seedlings of Secale cereale.

The involvement of the 2,3-epoxybrassinosteroids secasterone and 2,3-diepisecasterone in the biosynthesis of castasterone has been demonstrated in seedlings of Secale cereale by LC-ESI-MS. Deuterated secasterone, upon administration to rye seedlings, was incorporated into castasterone and its 2beta- and 3beta-epimers. Administration of deuterated 2,3-diepisecasterone resulted in castasterone and 2-epicastasterone. A biosynthetic subpathway from typhasterol/teasterone via 2,3-epoxybrassinosteroid intermediates to castasterone is discussed.

Cholestanols↗

Biosynthesis of 2,3-epoxybrassinosteroids in seedlings of Secale cereale.

Two new brassinosteroids, (22R,23R,24S)-22,23-dihydroxy-24-methyl-5alpha-cholest-2-en-6-one (secasterol) and (22R,23R,24S)-22,23-dihydroxy-2alpha,3alpha-epoxy-24-methyl-5alpha-cholest-6-one (2,3-diepisecasterone) have been identified together with a known 2,3-epoxybrassinosteroid, secasterone, in seedlings of Secale cereale. Deuterated secasterol, teasterone, and typhasterol, upon administration to rye seedlings, were incorporated into secasterone and 2,3-diepisecasterone, indicating a biosynthetic route via teasterone/typhasterol to secasterol to 2,3-epoxybrassinosteroids.

Hydroxycholesterols↗

Proteolytic activities in dormant rye (Secale cereale L.) grain.

Endoproteolytic, exoproteolytic, carboxypeptidase, aminopeptidase, and N-alpha-benzoyl-arginine-p-nitroanilide hydrolyzing activities were detected in 0.05 M sodium acetate buffer (pH 5.0) extracts of whole meal of the rye (Secale cereale L.) varieties Amando, Halo, and Humbolt. The proteolytic enzymes of Humbolt, the variety with the highest proteolytic activity, optimally hydrolyzed hemoglobin around pH 3.5 and 40-45 degrees C. In the different milling fractions of Humbolt, azocasein and hemoglobin hydrolytic activities were especially found in the bran and shorts. Proteolytic enzymes in the bran extract were concentrated in the 35-60% ammonium sulfate precipitate. Pepstatin A, an inhibitor of aspartic proteases, reduced approximately 88 and approximately 75% of the hemoglobin and azocasein hydrolyzing activities of this precipitate, respectively. Phenylmethanesulfonyl fluoride, an inhibitor of serine proteases, inhibited approximately 33% of both cited activities. Both rye and wheat storage proteins were degraded by Humbolt rye whole meal enzyme extract and the above-mentioned ammonium sulfate rye bran fraction in vitro. With the latter fraction digestion was more pronounced.

Aminopeptidases↗

Content of phenolic acids and ferulic acid dehydrodimers in 17 rye (Secale cereale L.) varieties.

The contents of pnenolic acids and ferulic acid dehydrodimers were quantified by HPLC analysis after alkaline hydrolysis in kernels of 17 rye (Secale cereale L.) varieties grown in one location in Denmark during 1997 and 1998. Significant variations (P < 0.05) with regard to the concentration of the analyzed components were observed among the different rye varieties and also between different harvest years. However, the content of phenolic acids in the analyzed rye varieties was narrow compared to cereals such as wheat and barley. The concentration of ferulic acid, the most abundant phenolic acid ranged from 900 to 1170 microgram g(-1) dry matter. The content in sinapic acid ranged from 70 to 140 microgram g(-1) dry matter, p-coumaric acid ranged from 40 to 70 microgram g(-1) dry matter, and caffeic, p-hydroxybenzoic, protocatechuic, and vanillic acids were all detected in concentrations less than 20 microgram g(-1) dry matter. The most abundant ferulic acid dehydrodimer 8-O-4 -DiFA was quantified in concentrations from 130 to 200 microgram g(-1) dry matter followed by 8,5 -DiFA benzofuran form (50-100 microgram g(-1) dry matter), 5,5 -DiFA (40-70 microgram g(-1) dry matter), and 8,5 -DiFA (20-40 microgram g(-1) dry matter).

Bread↗

Genetic diversity amongst landraces of rye (Secale cereale L.) from northern Europe.

Genetic variation and diversity were estimated for three improved varieties and 18 landraces of Secale cereale, originating from the northern Europe. This material was compared with eight improved varieties and 16 landraces from Sweden, which were analysed before. The analysis used starch gel electrophoresis with the enzymes ACO, GPI, MDH, PGD and PGM and resulted in one fixed locus and seven polymorphic loci. Most of the genetic diversity was found within the accessions and it was very small between accessions. The results show that the landraces from Germany and Norway have a low genetic variation compared to the other landraces in this study. This can possibly be explained with a small original sample size of some accessions. However, in the dendrogram these accessions are well separated. The landraces from Sweden and Finland showed a high genetic variation, which is almost the same for all these accessions. In the dendrogram all of the Finnish landraces and 11 of the Swedish ones were grouped together with a very small diversity index; they can almost be considered as part of the same accession. This is probably due to the fact that a high number of Finnish immigrants arrived in Sweden during the 17th century bringing their own rye material. The early Finnish rye landraces may have the same original source. The data also show that landraces as well as improved varieties have a high heterozygosity but they are separated in the dendrogram into different clusters. The currently used varieties show a large genetic distance variation, different from that in the landraces.

Chi-Square Distribution↗

Decline in ribonucleic acid and protein synthesis with loss of viability during the early hours of imbibition of rye (Secale cereale L.) embryos.

A decline in protein synthesis and slow germination accompanies loss of viability in embryos of rye (Secale cereale L.) grains. Associated with this, incorporation of precursors into all the major classes of RNA is decreased and the processing of precursor rRNA to 25S and 18S RNA is retarded. Embryos that just reach 0% viability still synthesize some low-molecular-weight non-nucleolar material, although they do not synthesize protein. It is suggested that early-synthesized RNA could play a major part in determining the extent of protein synthesis at early germination, and thereby regulate the rate at which germination can proceed.

Plant Proteins↗

Isolation and partial characterization of wheat-germ-agglutinin-like lectins from rye (Secale cereale) and barley (Hordeum vulgare) embryos.

Lectins have been isolated from embryos of Secale cereale (rye) and Hordeum vulgare (barley) by affinity chromatography on immobilized N-acetylglucosamine. Both lectins are dimeric proteins of two identical subunits of mol.wt. 18000. They resemble strongly wheat-germ agglutinin with respect to their chemical, physical, biological and immunological properties.

Amino Acids↗

The regulation of phosphatidylcholine biosynthesis in rye (Secale cereale) roots. Stimulation of the nucleotide pathway by low temperature.

The incorporation of [14C]choline chloride and [14C]glycerol into segments taken from rye (Secale cereale L., cv. Rheidal) roots was greater in segments from roots grown at 5 degrees C than in segments taken from roots growing at 20 degrees C. The incorporation was measured at the temperature at which the root had been growing. Measurements in vitro of the enzymes of the nucleotide pathway showed activity of choline kinase (EC 2.7.1.32), choline-phosphate cytidylyltransferase (EC 2.7.7.15) and cholinephosphotransferase (EC 2.7.8.2) to be higher in homogenates from the cooler roots when assayed at 5 degrees C than the activities assayed at 20 degrees C in the 20 degrees C-root homogenates. Changes in vivo in the pool sizes of the CDP-base intermediates with temperature, relative differences in nucleotide-pathway-enzyme activities and a pulse-chase experiment with [14C]choline indicated that the rate-limiting step for phosphatidylcholine biosynthesis in this tissue, at both temperatures, was the reaction catalysed by cytidylyltransferase.

Choline↗

Physical mapping of a low-copy DNA sequence in rye (Secale cereale L.).

A 900-base-pair (bp) sequence from a cDNA clone of the rye endosperm-storage-protein gene Sec-1 was labeled with biotin and hybridized to Secale cereale 'Blanco' chromosomes. Hybridization was seen on the satellite part of the short arm of chromosome 1R, where the Sec-1 gene has been genetically mapped, in approximately 8.5% of the cells analyzed. The clone cross-hybridized at a lower frequency to rye chromosome arms 1R (long) (4.4%) and 2R (short) (2.6%), where two additional rye storage-protein loci, Sec-3 and Sec-2, respectively, have been mapped. A fourth hybridization site was observed on the short arm of chromosome 6R at a frequency of 3.0%. The cross-hybridization is attributed to a combination of residual sequence homology between the protein loci and the low-stringency conditions used in in situ hybridization. In situ hybridization mapping, in combination with chromosome walking by using molecular techniques, is suggested as an excellent approach to physical mapping of chromosomes.

Base Sequence↗

Differential uptake of tritiated thymidine into hetero- and euchromatin in Melanoplus and Secale.

Grasshoppers of the species Melanoplus differentialis were injected with tritium-labelled thymidine. At intervals thereafter autoradiographic stripping film was applied over Feulgen squashes and sections. In this species during early prophase of meiosis the sex chromosome forms a heterochromatic block large enough to be resolved in tritium autoradiographs. A study of the squash preparations reveals that the sex chromosome is synthesizing DNA at a different period of time from the euchromatic autosomes. Since there is a developmental sequence of spermatocyte cysts along the testicular tubes it is possible from the sections to show that the heterochromatin synthesizes DNA later than does the euchromatin. To find out whether the results obtained in Melanoplus were characteristic of heterochromatin in general, young seedlings of rye were grown in a tritiated thymidine solution and Feulgen squashes were made as for Melanoplus. In rye leaf nuclei there is a large block of heterochromatin constituted by the proximal regions of the chromosomes and a euchromatic one formed by the median and distal regions of the same chromosomes. Here also the heterochromatin synthesizes DNA at a different period of time from the euchromatin. It is concluded that in rye the asynchrony of synthesis occurs within each chromosome. Counts of silver grains over the two types of chromatin in nuclei of Melanoplus and Secale disclosed that the number of grains per unit area was two to three times higher over the heterochromatin. To check the DNA content, Feulgen photometric measurements were made of Melanoplus nuclei at the same stage. The Feulgen and grain counts agree in showing that the heterochromatin contains two to three times more DNA per unit area than the euchromatin.

Animals↗

Aluminium toxicity in rye (Secale cereale): root growth and dynamics of cytoplasmic Ca2+ in intact root tips.

Aluminium (Al) toxicity in rye (Secale cereale L.), an Al-resistant crop, was examined by measuring root elongation and cytoplasmic free activity of calcium ([Ca2+]cyt) in intact root apical cells. Measurement of [Ca2+]cyt, was achieved by loading a Ca2+-sensitive fluorescent probe. Fluo-3/AM ester, into root apical cells followed by detection of intracellular fluorescence using a confocal laser scanning microscope. After 20 min of exposure to 50 microM Al (pH 4-2) a slight increase in [Ca2+]cyt of root apical cells was observed, while the response of [Ca2+]cyt to 100 microM Al (pH 4.2) was faster and larger ([Ca2+]cyt increased by 46% in 10 min). Increases in [Ca2+]cyt were correlated with inhibition of root growth, generally measurable after 2 h. Addition of 400 microM malic acid (pH 4.2) largely ameliorated the effect of 100 microM Al on [Ca2+]cyt in root apical cells and protected root growth from Al toxicity. These results suggest that an increase in [Ca2+]cyt in root apical cells in rye is an early effect of Al toxicity and is followed by the secondary effect on root elongation.

Aluminum↗

Malate metabolism and reactions of oxidoreduction in cold-hardened winter rye (Secale cereale L.) leaves.

In cold-hardened leaves (CHL) of winter rye (Secale cereale L.) much higher levels of malate were detected by (13)C-NMR than in non-hardened leaves (NHL). As this was not observed previously, malate metabolism of CHL was studied in more detail by biochemical assays. The activities of several enzymes of malate metabolism, NADP-malate dehydrogenase, NAD-malate dehydrogenase, phosphoenolpyruvate carboxylase, and NADP-malic enzyme, were also increased in CHL. Short exposures to low temperature of 1-3 d did not induce increases in the malate content or in the activities of enzymes of malate metabolism in mature NHL. The malate content and the enzyme activities declined within 1-2 d after a transfer of CHL from their growing temperature of 4 degrees C to 22 degrees C. The malate content was further increased when CHL were exposed to a higher light intensity at 4 degrees C. In CO(2)-free air the malate content of CHL strongly declined at 4 degrees C. Malate may thus serve as an additional carbon sink and as a CO(2)-store in CHL. It may further function as a vacuolar osmolyte balancing increased concentrations of soluble sugars previously observed in the cytosol of CHL. Malate was not used as a source of reductants when CHL were exposed to photo-oxidative stress by treatment with paraquat. However, the activities of enzymes of the oxidative pentose phosphate pathway were markedly increased in CHL and may serve as non-photosynthetic sources of NADPH and thus contribute to the previously observed superior capacity of CHL of winter rye to maintain their antioxidants in a reduced state in the presence of paraquat.

Acclimatization↗

Analysis and sorting of rye (Secale cereale L.) chromosomes using flow cytometry.

Procedures for chromosome analysis and sorting using flow cytometry (flow cytogenetics) were developed for rye (Secale cereale L.). Suspensions of intact chromosomes were prepared by mechanical homogenization of synchronized root tips after mild fixation with formaldehyde. Histograms of relative fluorescence intensity obtained after the analysis of DAPI-stained chromosomes (flow karyotypes) were characterized and the chromosome content of the DNA peaks was determined. Chromosome 1R could be discriminated on a flow karyotype of S. cereale 'Imperial'. The remaining rye chromosomes (2R-7R) could be discriminated and sorted from individual wheat-rye addition lines. The analysis of lines with reconstructed karyotypes demonstrated a possibility of sorting translocation chromosomes. Supernumerary B chromosomes could be sorted from an experimental rye population and from S. cereale 'Adams'. Flow-sorted chromosomes were identified by fluorescence in situ hybridization (FISH) with probes for various DNA repeats. Large numbers of chromosomes of a single type sorted onto microscopic slides facilitated detection of rarely occurring chromosome variants by FISH with specific probes. PCR with chromosome-specific primers confirmed the identity of sorted fractions and indicated suitability of sorted chromosomes for physical mapping. The possibility to sort large numbers of chromosomes opens a way for the construction of large-insert chromosome-specific DNA libraries in rye.

Cell Separation↗