The freeze-thaw cycle exacerbates the ecotoxicity of polystyrene nanoplastics to Secale cereale L. seedlings

In the context of global climate change, recurrent freeze-thaw cycles (FTC) and concurrent exposure to polystyrene nanoplastics (PSNPs) directly impact crop growth and indirectly affect resilience to abiotic stress. In January 2023, experiments at the Environmental Biology Laboratory, Jilin University, Changchun, China, exposed rye seedlings to 100 nm PSNPs at concentrations of 0, 10, 50, and 100 mg/L for seven days, followed by three FTC. Scanning electron microscopy (SEM) demonstrated that PSNPs migrated from the roots to the leaves, with FTC significantly exacerbating their accumulation within plant tissues. Transmission electron microscopy (TEM) observations showed that FTC disrupted normal cell division, and combined stress from NPs damaged plant organs, particularly chloroplasts, thereby substantially inhibiting photosynthesis. FTC delayed plant phenological stages. Under combined stress, malondialdehyde (MDA) accumulation in plant tissues increased by 15.6%, while hydrogen peroxide (H2O2) content decreased. Simultaneously, the activities of peroxidase (POD) and catalase (CAT) increased by 34.2% and 38.6%, respectively. Molecular docking unveiled that PSNPs could bind to the active center of POD/CAT through hydrogen bonding or hydrophobic interactions. The Integrated Biomarker Response (IBR) index highlighted FTC as a crucial determinant for pronounced effects. Moreover, an apparent dose-dependent effect was observed, with antioxidant enzyme activities in rye seedlings induced by low pollutant concentrations and inhibited by high concentrations. These results indicate that FTC and PSNPs can disrupt plant membrane systems and cause severe oxidative damage. Overall, this study provides compelling scientific evidence of the risks associated with NPs exposure in plants subjected to abiotic stress.

Photosystems and antioxidative system of rye, wheat and triticale under Pb stress

Lead (Pb²⁺) pollution in the soil sub-ecosystem has been a continuously growing problem due to economic development and ever-increasing anthropogenic activities across the world. In this study, the photosynthetic performance and antioxidant capacity of Triticeae cereals (rye, wheat and triticale) were compared to assess the activities of antioxidants, the degree of oxidative damage, photochemical efficiency and the levels of photosynthetic proteins under Pb stress (0.5 mM, 1 mM and 2 mM Pb (NO₃)₂). Compared with triticale, Pb treatments imposed severe oxidative damage in rye and wheat. In addition, the highest activity of major antioxidant enzymes (SOD, POD, CAT, and GPX) was also found to be elevated. Triticale accumulated the highest Pb contents in roots. The concentration of mineral ions (Mg, Ca, and K) was also high in its leaves, compared with rye and wheat. Consistently, triticale showed higher photosynthetic activity under Pb stress. Immunoblotting of proteins revealed that rye and wheat have significantly lower levels of D1 (photosystem II subunit A, PsbA) and D2 (photosystem II subunit D, PsbD) proteins, while no obvious decrease was noticed in triticale. The amount of light-harvesting complex II b6 (Lhcb6; CP24) and light-harvesting complex II b5 (Lhcb5; CP26) was significantly increased in rye and wheat. However, the increase in PsbS (photosystem II subunit S) protein only occurred in wheat and triticale exposed to Pb treatment. Taken together, these findings demonstrate that triticale shows higher antioxidant capacity and photosynthetic efficiency than wheat and rye under Pb stress, suggesting that triticale has high tolerance to Pb and could be used as a heavy metal-tolerant plant.

The rye transcription factor ScSTOP1 regulates the tolerance to aluminum by activating the ALMT1 transporter

Plants have evolved different mechanisms to increase their tolerance to aluminum (Al) toxicity and low pH in the soil. The Zn finger transcription factor SENSITIVE TO PROTON RHIZOTOXICITY1 (STOP1) plays an essential role in the adaptation of plants to Al and low pH stresses. In this work, we isolated the ScSTOP1 gene from rye (Secale cereale L.), which is located on chromosome 3RS. The ectopic expression of ScSTOP1 complements the Arabidopsis stop1 mutation in terms of root growth inhibition due to Al and pH stress, as well as phosphate starvation tolerance, suggesting that rye ScSTOP1 is a functional ortholog of AtSTOP1. A putative STOP1 binding motif was identified in the promoter of a well-known STOP1 target from rye and Arabidopsis and was later corroborated by genomic DAP-seq analyses. Coexpression analyses verified that ScSTOP1 activated the promoter of ScALMT1. We have also identified a putative phosphorylatable serine in STOP1 that is phylogenetically conserved and critical for such activation. Our data indicated that ScSTOP1 also regulated Al and pH tolerance in rye.

Qualitative Study on the Production of the Allelochemicals Benzoxazinones by Inducing Polyploidy in Gramineae with Colchicine

The possibility of inducing polyploidy in grasses by treatment with colchicine and its effect on the production and root exudate content of 2,4-dihydroxy-7-methoxy-2 H-1,4-benzoxazin-3-one (DIMBOA) and 2,4-dihydroxy-2 H-benzoxazin-3-one (DIBOA) was studied in wheat, corn, and rye. Caryopses treated with colchicine at concentrations in the range of 0.1-10 mg/mL for 8 and 48 h and with inoculation of the growth medium are markedly affected in terms of both the distribution and concentration levels of allelochemicals in plants. A greater accumulation was observed in the root with respect to the stem, and this increased with an increasing concentration of colchicine and with treatment time. Analysis of the compounds released by root exudates showed that treatment with colchicine at a concentration higher than 1 mg/mL caused a significant increase in the concentrations of allelochemicals measured in the growth medium. It is proposed that treatment with colchicine of seedling caryopses mixoploids plant populations and that the overall effect is an increase in the levels of allelochemicals released. The ecological implications of this behavior are discussed along with the impact of plant-plant interactions (allelopathy).

Indaziflam: a new cellulose-biosynthesis-inhibiting herbicide provides long-term control of invasive winter annual grasses

BACKGROUND

Indaziflam is a cellulose-biosynthesis-inhibiting (CBI) herbicide that is a unique mode of action for resistance management and has broad spectrum activity at low application rates. This research further explores indaziflam's activity on monocotyledons and dicotyledons and evaluates indaziflam's potential for restoring non-crop sites infested with invasive winter annual grasses.

RESULTS

Treated Arabidopsis, downy brome, feral rye and kochia were all susceptible to indaziflam in a dose-dependent manner. We confirmed that indaziflam has increased activity on monocots (average GR₅₀  = 231 pm and 0.38 g AI ha^-1 ) at reduced concentrations compared with dicots (average GR₅₀  = 512 pm and 0.87 g AI ha^-1 ). Fluorescence microscopy confirmed common CBI symptomologies following indaziflam treatments, as well as aberrant root and cell morphology. Across five application timings, indaziflam treatments resulted in superior invasive winter annual grass control 2 years after treatment (from 84 ± 5.1% to 99 ± 0.5%) compared with imazapic (36% ± 1.2%). Indaziflam treatments significantly increased biomass and species richness of co-occurring species 2 years after treatment.

CONCLUSION

Indaziflam's increased activity on monocots could provide a new alternative management strategy for long-term control of multiple invasive winter annual grasses that invade >23 million ha of US rangeland. Indaziflam could potentially be used to eliminate the soil seed bank of these invasive grasses, reduce fine fuel accumulation and ultimately increase the competitiveness of perennial co-occuring species. © 2017 Society of Chemical Industry.

Hybrid dwarfness in crosses between wheat (Triticum aestivum L.) and rye (Secale cereale L.): a new look at an old phenomenon

The existence of hybrid dwarfs from intraspecific crosses in wheat (Triticum aestivum) was described 100 years ago, and the genetics underlying hybrid dwarfness are well understood. In this study, we report a dwarf phenotype in interspecific hybrids between wheat and rye (Secale cereale). We identified two rye lines that produce hybrid dwarfs with wheat and have none of the hitherto known hybrid dwarfing genes. Genetic analyses revealed that both rye lines carry a single allelic gene responsible for the dwarf phenotype. This gene was designated Hdw-R1 (Hybrid dwarf-R1). Application of gibberellic acid (GA3 ) to both intraspecific (wheat-wheat) and interspecific (wheat-rye) hybrids showed that hybrid dwarfness cannot be overcome by treatment with this phytohormone. Histological analysis of shoot apices showed that wheat-rye hybrids with the dwarf phenotype at 21 and 45 days after germination failed to develop further. Shoot apices of dwarf plants did not elongate, did not form new primordia and had a dome-shaped appearance in the seed. The possible relationship between hybrid dwarfness and the genes responsible for the transition from vegetative to generative growth stage is discussed.

The effects of woodchip- and straw-derived biochars on the persistence of the herbicide 4-chloro-2-methylphenoxyacetic acid (MCPA) in soils

Sorption and degradation are the primary processes controlling the efficacy and runoff contamination risk of agrochemicals. This study assessed the influence of two biochars, made from woodchips and straw at a pyrolysis temperature of 725°C and applied to a loamy sand and a sandy soil in the concentration of 5.3 g 100 g(-1) sandy soil and 4.1 g 100 g(-1) loamy sand soil, or 53 t ha(-1) for both soil types, on degradation of the herbicide 4-chloro-2-methylphenoxyacetic acid (MCPA). Soils were spiked with 50 mg MCPA kg(-1) soil. In the sandy soil, significantly more MCPA remained after 100 days if amended with straw-derived biochar in comparison to wood-derived biochar. Both biochars types significantly increased urease activity (p<0.05) after 37 days in the loamy sand soil, but these differences disappeared after 100 days. A root and shoot elongation test demonstrated that the soils containing straw-derived biochar and spiked with MCPA, showed the highest phytotoxicity. Both biochars were found to retard MCPA degradation in loamy sand and sandy soils. This effect could not be explained only by sorption processes due to comparatively low developed micro/mesoporous structure of both biochars shown by BET surface analysis. However, an enhanced MCPA persistence and soil toxicity in sandy soil amended with straw biochar was observed and further studies are needed to reveal the responsible mechanisms.

Various effects of the photosystem II--inhibiting herbicides on 5-n-alkylresorcinol accumulation in rye seedlings

The effect of three PSII-inhibiting herbicides, lenacil, linuron, and pyrazon, on the accumulation of 5-n-alkylresorcinols in rye seedlings (Secale cereale L.) grown under various light and thermal conditions was studied. All used chemicals increased resorcinolic lipid content in both green and etiolated plants grown at 29 °C. At 22 °C pyrazon and lenacil decreased the content of alkylresorcinols in plants kept in the darkness and increased their amount in the light-grown seedlings. In turn, level of resorcinolic lipids was decreased by linuron in both etiolated and green plants. At the lowest tested temperature lenacil enhanced production of alkylresorcinols only in etiolated rye seedlings, whereas the light-independent stimulatory action of pyrazon on alkylresorcinol accumulation in rye grown at 15 °C was observed. Additionally, only the latter did not exert a negative effect on rye seedling growth under any of tested conditions. Compared with respective controls, the herbicides used also markedly modified the qualitative pattern of resorcinolic homologs. Interestingly, the observed changes generally favored the enhanced antifungal activity of these compounds. Our study provides novel information on the influence of PSII inhibitors on alkylresorcinol metabolism in rye seedlings. The unquestionable achievement of this work is the observation that low dose of pyrazon mainly stimulated both growth and alkylresorcinol synthesis in rye seedlings, a non-target plant. Moreover, our experimental work showed unambiguously that the observed pyrazon-driven accumulation and homolog pattern modification of alkylresorcinols dramatically improved the resistance of winter rye to infections caused by Rhizoctonia cerealis.

Effect of Norflurazon on Resorcinolic Lipid Metabolism in Rye Seedlings

Norflurazon is a selective pyridazinone herbicide excessively employed in the control of many annual grasses and broad-leaved weeds. This chemical causes plant bleaching due to the inhibition of the carotenoid pigment biogenesis as well as induces irreparable changes to chloroplasts, which are considered the organelles where the biosynthesis of resorcinolic lipids takes place. Resorcinolic lipids, a group of phenolic compounds, constitute not only an essential part of the plant antifungal defense system, but also are an important component of the human cereal diet. The aim of this study was to investigate the effect of norflurazon on the biosynthesis of resorcinolic lipids in 5-day-old rye plants (Secale cereale L.) that were grown at three different temperatures under light or dark conditions. At all tested temperatures, norflurazon decreased the fresh biomass of light-grown rye seedlings and increased the weight of plants grown in darkness. Compared with respective controls, this herbicide caused an increase in total content of alkylresorcinols in both green and etiolated plants with the exception of dark-grown norflurazon-treated rye at 29 °C. The general level of saturated homologues was markedly decreased by norflurazon in all etiolated plants and in light-grown seedlings at 15 °C. Independent of thermal and light conditions, in all norflurazon-treated samples two alkylresorcinol derivatives predominated: 1,3-dihydroxy-5-n-heptadecylbenzene and 1,3-dihydroxy-5-n-nonadecylbenzene. Thus, our results suggest that norflurazon affected the metabolism of alkylresorcinols in rye seedlings and its action was dependent on external stimuli.

Rye oxidative stress under long term Al exposure

Aluminium (Al) toxicity decreases plant growth. Secale cereale L. is among the most Al-tolerant crop species. In order to study the response to Al-long term exposure, two rye genotypes with different Al sensitivity ('D. Zlote' and 'Riodeva') were exposed to 1.11 and 1.85mM Al and the antioxidant responses were followed for 2 and 3 weeks in roots and leaves. Al toxicity signals, such as a severe decrease in root growth, occurred sooner in 'Riodeva.' The antioxidant response was dependent on the genotype, the organ, Al concentration and the exposure period. Al-exposed roots of 'D. Zlote' showed earlier enhancements of APX, SOD and G-POX activities than those of 'Riodeva.' 'D. Zlote' roots showed stimulation of the AsA-GSH cycle after the second week (when root growth inhibition was less severe), while later (when severe root growth inhibition was observed), oxidation of AsA and GSH pools was observed. In leaves of both genotypes, CAT, SOD and G-POX activities increased with Al exposure. In these leaves, the effect of AsA-GSH was time dependent, with maximum oxidation at the second week, followed by recovery. We confirmed that the oxidation state of AsA and GSH pools is involved in the detoxification of Al-induced oxidative stress. Moreover, our data demonstrate that the production of ROS does not correlate with the Al-induced root growth decrease. Finally, the differences observed over time indicate that long term exposure may provide additional information on rye sensitivity to Al, and contribute to a better understanding of this species' mechanisms of Al tolerance.

Rapid auxin-mediated changes in the proteome of the epidermal cells in rye coleoptiles: implications for the initiation of growth

In axial organs of juvenile plants, the phytohormone auxin (indole-3-acetic acid, IAA) rapidly mediates cell wall loosening and hence promotes turgor-driven elongation. In this study, we used rye (Secale cereale) coleoptile sections to investigate possible effects of IAA on the proteome of the cells. In a first set of experiments, we document that IAA causes organ elongation via promotion of expansion of the rigid outer wall of the outer epidermis. A quantitative comparison of the proteome (membrane-associated proteins), using two-dimensional difference gel electrophoresis (2-D DIGE), revealed that, within 2 h of auxin treatment, at least 16 protein spots were up- or down-regulated by IAA. These proteins were identified using reverse-phase liquid chromatography electrospray tandem mass spectrometry. Four of these proteins were detected in the growth-controlling outer epidermis and were further analysed. One epidermal polypeptide, a small Ras-related GTP-binding protein, was rapidly down-regulated by IAA (after 0.5 h of incubation) by -35% compared to the control. Concomitantly, a subunit of the 26S proteasome was up-regulated by IAA (+30% within 1 h). In addition, this protein displayed IAA-mediated post-translational modification. The implications of these rapid auxin effects with respect to signal transduction and IAA-mediated secretion of glycoproteins (osmiophilic nano-particles) into the growth-controlling outer epidermal wall are discussed.

Rapid auxin-mediated changes in the proteome of the epidermal cells in rye coleoptiles: implications for the initiation of growth

In axial organs of juvenile plants, the phytohormone auxin (indole-3-acetic acid, IAA) rapidly mediates cell wall loosening and hence promotes turgor-driven elongation. In this study, we used rye (Secale cereale) coleoptile sections to investigate possible effects of IAA on the proteome of the cells. In a first set of experiments, we document that IAA causes organ elongation via promotion of expansion of the rigid outer wall of the outer epidermis. A quantitative comparison of the proteome (membrane-associated proteins), using two-dimensional difference gel electrophoresis (2-D DIGE), revealed that, within 2 h of auxin treatment, at least 16 protein spots were up- or down-regulated by IAA. These proteins were identified using reverse-phase liquid chromatography electrospray tandem mass spectrometry. Four of these proteins were detected in the growth-controlling outer epidermis and were further analysed. One epidermal polypeptide, a small Ras-related GTP-binding protein, was rapidly down-regulated by IAA (after 0.5 h of incubation) by -35% compared to the control. Concomitantly, a subunit of the 26S proteasome was up-regulated by IAA (+30% within 1 h). In addition, this protein displayed IAA-mediated post-translational modification. The implications of these rapid auxin effects with respect to signal transduction and IAA-mediated secretion of glycoproteins (osmiophilic nano-particles) into the growth-controlling outer epidermal wall are discussed.

Nitric oxide improves aluminum tolerance by regulating hormonal equilibrium in the root apices of rye and wheat

Nitric oxide (NO) has emerged as a key molecule involved in many physiological processes in plants. Whether NO reduces aluminum (Al) toxicity by regulating the levels of endogenous hormones in plants is still unknown. In this study, the effects of NO on Al tolerance and hormonal changes in the root apices of rye and wheat were investigated. Rye was more tolerant to Al stress than wheat according to the results of root elongation and Al content determined. Root inhibition exposed to Al was in relation to Al accumulation in the root apices. Al treatment decreased GA content and increased the values of IAA/GA and ABA/GA. Supplementation of NO donor sodium nitroprusside (SNP) reduced the inhibition of root elongation by increasing GA content and decreasing the values of IAA/GA and IAA/ZR under Al stress. NO scavenger 2-(4-carboxy-2-phenyl)-4,4,5,5-tetramethylinidazoline-1-oxyl-3-oxide (cPTIO) can reversed SNP alleviating effect on Al toxicity. However, the regulating patterns of NO on the values of ABA/GA, GA/ZR and ABA/(IAA+GA+ZR) were different between rye and wheat. The values of ABA/GA and ABA/(IAA+GA+ZR) increased in rye, but decreased in wheat. The change of GA/ZR value was opposite. These results suggest that NO may reduce Al accumulation in the root apices by regulating hormonal equilibrium to enhance Al-tolerance in plants, which effect is more remarkable in Al-sensitive wheat.

Allelopathic effects of ragweed (Ambrosia artemisiifolia L.) on cultivated plants

During the past years ragweed has been coming to the forefront of interest in Hungary and in other European countries as well because its serious health risk. Results of the 5th National Weed Survey has proven that ragweed is the most important weed species on Hungarian field lands, its coverage shows a rising tendency in cereals moreover it not only occurs in cultivated plants. Allelopathic effects of aqueous extracts derived from different parts of ragweed plants (air dried leafy stems, seeds) on the germination and growth of other cultivated plants [maize (Zea mays L.), winter wheat (Triticum aestivum L.), rye (Secale cereale L.), oat (Avena sativa L.)] were studied. The extracts made for the trials were prepared with distilled water. Petri dishes were used for the germination experiments and distilled water was used as a control treatment. The seven days long experiment was carried out within a Binder-type thermostat under dark conditions. The germination percentage was checked in every two days and the growth of sprouts was evaluated after a week counting the germinated seeds and measuring the length of the radicle and plumule. The measured data were statistically analysed and the effect of extracts on germinating and length of sprouts were assessed.

Cessation of coleoptile elongation and loss of auxin sensitivity in developing rye seedlings: a quantitative proteomic analysis

The use of the grass coleoptile for the elucidation of the mechanism of cell elongation is a legacy of the classic experiments of Charles Darwin, who described this organ in 1880 as a "reddish sheath". In this study we quantified the growth of intact, etiolated rye (Secale cereale L.) seedlings and selected 3-day-old (growing) vs. 4-day-old (pierced) coleoptiles for a comparative analysis. Upon emergence of the reddish primary leaf on day 4 after sowing, growth slowed down by 70% and the sensitivity of the coleoptile to auxin (Indole-3-acetic acid) was lost, but turgor pressure was maintained. A quantitative comparison of the proteome (microsomal- and cytoplasmic protein fractions, respectively), using the two-dimensional difference gel electrophoresis (2-D DIGE)-technique, revealed that at least 28 proteins (spots) were differentially up- or down-regulated more than 1.5-fold. Eight of these proteins were identified by reverse-phase liquid chromatography-electrospray tandem mass spectrometry. Cessation of coleoptile growth was associated with the down-regulation (- 81 %) of subunit E of the vacuolar H(+)-ATPase (V-ATPase) and the up-regulation of enzymes involved in lignification (phenylalanine ammonia lyase) and wounding responses (xylanase inhibitor; two lipoxygenases). We conclude that the degradation of the V-ATPases, electrogenic proton pumps on the tonoplast and the membranes of the Golgi- dependent secretory pathway, may be the cause for the cessation of growth in turgid coleoptiles and the associated loss of auxin sensitivity. However, the intracellular signals that cause these proteomic changes have not yet been identified.

Cycloate, an inhibitor of fatty acid elongase, modulates the metabolism of very-long-side-chain alkylresorcinols in rye seedlings

BACKGROUND

Cycloate inhibits the biosynthesis of very-long-chain fatty acids, the essential constituents of plant waxes and suberin. Fatty acids also serve as precursors of aliphatic carbon chains in resorcinolic lipids, which play a fundamental role in the plant defence system against fungal pathogens. In this study, the effect of cycloate on the biosynthesis of 5-n-alkylresorcinols in rye seedlings (Secale cereale L.) grown under various light and thermal conditions was examined.

RESULTS

The content of alkylresorcinols biosynthesised in rye was generally increased by the herbicide in both green and etiolated plants. The presence of cycloate also affected patterns of alkylresorcinol homologues in plants grown at 15 and 22 degrees C; very-long-side-chain compounds were less abundant, whereas both short-chain saturated and unsaturated homologues were generally accumulated. No cycloate-related effects caused by homologue pattern modifications were observed at elevated temperature.

CONCLUSION

This study extends present understanding of the mode of action of thiocarbamate herbicides. Cycloate markedly affected the biosynthesis of very-long-side-chain resorcinolic lipids in rye seedlings, confirming the existence of parallels in both fatty acid and alkylresorcinol biosynthetic pathways. The observed cycloate-driven accumulation of 5-n-alkylresorcinols may improve the resistance of cereals to infections caused by microbial pathogens.

Physical analysis of the complex rye (Secale cereale L.) Alt4 aluminium (aluminum) tolerance locus using a whole-genome BAC library of rye cv. Blanco

Rye is a diploid crop species with many outstanding qualities, and is important as a source of new traits for wheat and triticale improvement. Rye is highly tolerant of aluminum (Al) toxicity, and possesses a complex structure at the Alt4 Al tolerance locus not found at the corresponding locus in wheat. Here we describe a BAC library of rye cv. Blanco, representing a valuable resource for rye molecular genetic studies, and assess the library's suitability for investigating Al tolerance genes. The library provides 6 x genome coverage of the 8.1 Gb rye genome, has an average insert size of 131 kb, and contains only ~2% of empty or organelle-derived clones. Genetic analysis attributed the Al tolerance of Blanco to the Alt4 locus on the short arm of chromosome 7R, and revealed the presence of multiple allelic variants (haplotypes) of the Alt4 locus in the BAC library. BAC clones containing ALMT1 gene clusters from several Alt4 haplotypes were identified, and will provide useful starting points for exploring the basis for the structural variability and functional specialization of ALMT1 genes at this locus.

Effect of ozonolysis pretreatment on enzymatic digestibility of wheat and rye straw

Wheat and rye straws were pretreated with ozone to increase the enzymatic hydrolysis extent of potentially fermentable sugars. Through a 2(5-1) factorial design, this work studies the influence of five operating parameters (moisture content, particle size, ozone concentration, type of biomass and air/ozone flow rate) on ozonization pretreatment of straw in a fixed bed reactor under room conditions. The acid insoluble lignin content of the biomass was reduced in all experiments involving hemicellulose degradation. Near negligible losses of cellulose were observed. Enzymatic hydrolysis yields of up to 88.6% and 57% were obtained compared to 29% and 16% in non-ozonated wheat and rye straw respectively. Moisture content and type of biomass showed the most significant effects on ozonolysis. Additionally, ozonolysis experiments in basic medium with sodium hydroxide evidenced a reduction in solubilization and/or degradation of lignin and reliable cellulose and hemicellulose degradation.

Relationships between transcription, silver staining, and chromatin organization of nucleolar organizers in Secale cereale

The nucleolar organizer regions (NORs) are composed of hundreds of rRNA genes, typically spanning several megabases. Cytologically, NORs include regions that are highly condensed and regions that are decondensed, the latter corresponding to regions at which associated proteins stain intensively with silver (Ag-NORs) and where active rRNA gene transcription is thought to occur. To test the relationship between rRNA gene activity, NOR silver staining, and rDNA (genes coding for rRNA) chromatin condensation, we used the DNA methyl-transferase inhibitor 5-azacytidine to evaluate the correlation between the epigenetic regulation of rRNA genes and NOR silver staining in the plant Secale cereale. Following 5-azacytidine treatment, we observed an increase in rRNA gene transcription as well as a reduction in the number of cells showing a significant difference in the size of the silver-stained domains in the two NORs. These transcriptional changes occurred concomitantly with an increase in nuclear and nucleolar size and were associated with the reallocation of most of the rDNA from perinucleolar heterochromatin into the nucleolus. Collectively, these results suggest that rRNA gene transcription, silver staining, and NOR decondensation are interrelated in S. cereale.

The xanthophyll cycle pigments in Secale cereale leaves under combined Cd and high light stress conditions

Leaves of Secale cereale seedlings were exposed to high light illumination (1200micromolm(-2)s(-1)) and Cd ions at 5 or 50microM concentrations. Influence of these stress factors on violaxanthin cycle pigments content was analysed chromatographically. Chlorophyll a fluorescence induction was used to analyse response of PSII to stress conditions and contribution of light-harvesting complex (LHCII) in non-photochemical quenching of excitation energy. The Cd-induced all-trans violaxanthin isomerization was analysed by HPLC technique in acetonitrile:methanol:water (72:8:3, v/v) solvent mixture. Interestingly, in the control and Cd-treated leaves subjected to high light, photochemical utilization of absorbed energy increased. This indicates plant adaptation to high light stress. In control plants high light caused zeaxanthin formation, however, the presence of Cd in the nutrient solution resulted in reduction of the second step of violaxanthin de-epoxidation process and anteraxanthin accumulation. In this study we have also shown, that non-photochemical quenching can be independent of anteraxanthin and zeaxanthin content. The particular increase in the cis isomers fraction in Cd-treated leaves has been explained in terms of a direct metal-pigment interaction as confirmed by Cd-induced all-trans violaxanthin isomerization in organic solvent, leading to formation of 13-cis, 9-cis and 15-cis isomers.

Effect of colchicine and telocentric chromosome conformation on centromere and telomere dynamics at meiotic prophase I in wheat-rye additions

Association of telomeres in a bouquet and clustering of centromere regions have been proposed to be involved in the search and recognition of homologous partners. We have analysed the role of these structures in meiotic chromosome pairing in wheat-rye addition lines by applying colchicine for disturbing presynaptic telomere movements and by modifying the centromere position from submetacentric to telocentric for studying centromere effects. Rye chromosomes, wheat and rye centromeres, and telomeres were identified by fluorescence in-situ hybridization. Presynaptic association of centromeres in pairs or in more complex structures involved mainly non-homologous chromosomes as deduced from the behaviour of rye centromeres. While centromere association was not affected by colchicine, colchicine inhibited bouquet formation, which caused failure of homologous synapsis. Homologous centromeres of rye telocentrics associated earlier than those of rye submetacentric chromosomes, indicating that migration of the telocentrics' centromeres to the telomere pole during bouquet formation facilitated their association. Homologous chromosomes associated in premeiotic interphase can recognize each other and initiate synapsis at zygotene. However, telomere convergence is needed for bringing together the majority of homologous pairs that normally occupy separate territories in premeiotic nuclei.

Gravitropic plant growth regulation and ethylene: an unsought cardinal coordinate for a disused model

According to the Cholodny-Went hypothesis, gravitropic differential growth is brought about by the redistribution of auxin (indolyl-3-acetic acid, IAA). We reinvestigated the relevance of different auxins and studied the role of ethylene in hypocotyls of sunflower and shoots and roots of rye and maize seedlings. Incubation of coleoptiles and of sunflower hypocotyls in solutions of IAA and dichlorophenoxyacetic acid as well as naphthylacetic acid resulted in a two- to threefold length increase compared to water controls. In spite of this pronounced general effect on elongation growth, gravi-curvature was similar to water controls. In contrast to this, inhibition of ethylene synthesis by aminoethoxyvinylglycine prevented differential growth of both hypocotyls and coleoptiles and of roots of maize. In horizontally stimulated maize roots growing on surfaces, inhibition of ethylene perception by methylcyclopropene inhibited roots to adapt growth to the surface, resulting in a lasting vertical orientation of the root tips. This effect is accompanied by up- and down-regulation of a number of proteins as detected by two-dimensional matrix-assisted laser desorption-ionization time-of-flight mass spectrometry. Together the data query the regulatory relevance of IAA redistribution for gravitropic differential growth. They corroborate the crucial regulatory role of ethylene for gravitropic differential growth, both in roots and coleoptiles of maize as well as in hypocotyls.

Colchicine-induced polyploidization depends on tubulin polymerization in c-metaphase cells

The microtubule cytoskeleton plays a crucial role in the cell cycle and in mitosis. Colchicine is a microtubule-depolymerizing agent that has long been used to induce chromosome individualization in cells arrested at metaphase and also in the induction of polyploid plants. Although attempts have been made to explain the processes and mechanisms underlying polyploidy induction, the role of the cytoskeleton still remains largely unknown. Through immunodetection of alpha-tubulin, different concentrations (0.5 or 5 mM) of colchicine were found to produce opposite effects in the organization of the cytoskeleton in rye (Secale cereale L.). A low concentration (0.5 mM) induced depolymerization of the microtubular cytoskeleton in all phases of the cell cycle. In contrast, a high concentration (5 mM) was found to induce the polymerization of new tubulin-containing structures in c-metaphase cells. Furthermore, both treatments also showed contrasting effects in the induction of polyploid cells. Flow cytometric analysis and quantitative assessments of nucleolus-organizing regions revealed that only the high-concentration colchicine treatment was effective in the formation of polyploid cells. Our studies indicate that spindle disruption alone is insufficient for the induction of polyploid cells. The absence of any tubulin structures in plants treated with colchicine at the low concentration induced cell anomalies, such as the occurrence of nuclei with irregular shape and/or (additional) micronuclei, 12 h after recovery, pointing to a direct effect on cell viability. In contrast, the almost insignificant level of cell anomalies in the high-concentration treatment suggests that the presence of new tubulin-containing structures allows the reconstitution of 4C nuclei and their progression into the cell cycle.

[Effects of sodium nitroprusside on mitochondrial function of rye and wheat root tip under aluminum stress]

Sodium nitroprusside (SNP) could ameliorate the inhibition effect of Al on root growth of rye (Secale cereale L. cv. King) and wheat (Triticum aestivum L. cv. Jinmai47). Respiratory rate, P/O, OPR (oxygenated phosphate rate), R(3) (oxygen consumption rate with ADP and substrate present), R(4) (oxygen consumption rate with substrate) and RCR (respiratory control ratio, R(3)/R(4)) of root tips from rye and wheat decreased, as well as the activities of H(+)-ATPase, H(+)-PPase, Na(+)-K(+)-ATPase, Ca(2+)-ATPase and Mg(2+)-ATPase, but they increased with SNP treatment. It showed that mitochondrial respiratory functions of root tips from rye and wheat were damaged, phosphorylation was un-coupled by Al, but that of rye was less than that of wheat. Rye has high Al-resistance ability than wheat. SNP is one of donor of NO, it is suggested that NO can ameliorate remarkably respiratory dysfunction resulted from Al stress, so that NO can ameliorate the inhibition effect of Al on plant growth.

The positioning of rye homologous chromosomes added to wheat through the cell cycle in somatic cells untreated and treated with colchicine

The arrangement of chromosome pairs 5RL and 7R added to the wild type and the ph1b mutant line of hexaploid wheat are analyzed in 2N somatic root tip cells during the cell cycle relative to the arrangement that chromosomes 5RL show in 4N tapetal cells produced after colchicine treatment. Both homologous chromosome pairs are identified at interphase and mitosis by fluorescence in situ hybridization. In nuclei at interphase, chromosomes appear as discrete domains that show the Rabl orientation. Homologous chromosomes are predominantly non-associated and their positioning seems not to be influenced by the Ph1 gene that suppresses homoeologous meiotic pairing. This pattern of arrangement contrasts with the high level of somatic pairing that sister chromosomes show in the interphase that follows chromosome duplication induced by colchicine. Disruption of pairing observed in some 4N nuclei is produced at c-anaphase which suggests no topological redistribution of homologues during conformation of the new nucleus. Homologous chromosomes show no predominant arrangement in ellipsoidal metaphase plates, which contrasts with the preferential opposite location of homologues in human prometaphase rosettes. Differences between chromosomes in the variation of the length through the cell cycle and in the chromatin morphology when the Ph1 is absent suggest different patterns of chromatin condensation in both chromosomes.

Development of PCR-based codominant markers flanking the Alt3 gene in rye

Aluminum (Al) toxicity is considered to be a major problem for crop growth and production on acid soils. The ability of crops to overcome Al toxicity varies among crop species and cultivars. Rye (Secale cereale L.) is the most Al-tolerant species among the Triticeae. Our previous study showed that Al tolerance in a rye F6 recombinant inbred line (RIL) population was controlled by a single gene designated as the aluminum tolerance (Alt3) gene on chromosome 4RL. Based on the DNA sequence of a rice (Oryza sativa L.) BAC clone suspected to be syntenic to the Alt3 gene region, we developed two PCR-based codominant markers flanking the gene. These two markers, a sequence-tagged site (STS) marker and a cleaved amplified polymorphic sequence (CAPS) marker, each flanked the Alt3 gene at an approximate distance of 0.4 cM and can be used to facilitate high-resolution mapping of the gene. The markers might also be used for marker-assisted selection in rye or wheat (Triticum aestivum L.) breeding programs to obtain Al-tolerant lines and (or) cultivars.

Generation of rye (Secale cereale L.) plants with low transgene copy number after biolistic gene transfer and production of instantly marker-free transgenic rye

Rye is extremely recalcitrant to tissue culture and genetic transformation. We describe the efficient and reproducible production of stably expressing transgenic rye plants after biolistic gene transfer to callus tissue derived from immature embryos. Key factors in the production of transgenic rye plants include the identification of biolistic gene transfer parameters and a selection protocol, which does not affect its regeneration ability. The bar gene was used as a selectable marker and selection was performed by spraying the regenerated shoots with 0.05% Basta solution without any previous selection of tissue cultures. Based on Southern blot analysis, a total of 21 transgenic rye plants with independent transgene integration patterns were produced. A low transgene copy number was observed in most transgenic plants and 40% of the plants had a single transgene copy insert. The high frequency of single transgene copy inserts might be a consequence of the selection system, which is based on the identification of stably expressing transgenic plantlets rather than stably expressing tissue cultures. All transgenic rye lines with single transgene inserts showed stable transgene expression in sexual progenies, but indications of transcriptional and post-transcriptional gene silencing were observed in few transgenic lines with multiple transgene inserts. Tissue culture-based selection was not necessary for the generation of transgenic rye. The identification of 17 transgenic rye plants without using any selectable marker gene by PCR amplification of transgene sequences is also demonstrated. Instant generation of selectable marker-free transgenic rye avoids a negative impact of selective agents on the transgenic tissue cultures, responds to public concerns on the safety of selectable markers and will support multiple transformation cycles for transgene pyramiding.

Calcium interacts with antifreeze proteins and chitinase from cold-acclimated winter rye

During cold acclimation, winter rye (Secale cereale) plants accumulate pathogenesis-related proteins that are also antifreeze proteins (AFPs) because they adsorb onto ice and inhibit its growth. Although they promote winter survival in planta, these dual-function AFPs proteins lose activity when stored at subzero temperatures in vitro, so we examined their stability in solutions containing CaCl2, MgCl2, or NaCl. Antifreeze activity was unaffected by salts before freezing, but decreased after freezing and thawing in CaCl2 and was recovered by adding a chelator. Ca2+ enhanced chitinase activity 3- to 5-fold in unfrozen samples, although hydrolytic activity also decreased after freezing and thawing in CaCl2. Native PAGE, circular dichroism, and Trp fluorescence experiments showed that the AFPs partially unfold after freezing and thawing, but they fold more compactly or aggregate in CaCl2. Ruthenium red, which binds to Ca(2+)-binding sites, readily stained AFPs in the absence of Ca2+, but less stain was visible after freezing and thawing AFPs in CaCl2. We conclude that the structure of AFPs changes during freezing and thawing, creating new Ca(2+)-binding sites. Once Ca2+ binds to those sites, antifreeze activity, chitinase activity and ruthenium red binding are all inhibited. Because free Ca2+ concentrations are typically low in the apoplast, antifreeze activity is probably stable to freezing and thawing in planta. Ca2+ may regulate chitinase activity if concentrations are increased locally by release from pectin or interaction with Ca(2+)-binding proteins. Furthermore, antifreeze activity can be easily maintained in vitro by including a chelator during frozen storage.

Physiological and biochemical characterization of ethylene-generated gravicompetence in primary shoots of coleoptile-less gravi-incompetent rye seedlings

A recent study demonstrated that gravi-incompetent coleoptile-less seedlings of rye exhibit gravi-competence after exogenous application of ethylene. Treatments and conditions which induce and interfere with this phenomenon were analysed in more detail. Aminocyclopropane-1-carboxylic acid (ACC) as a precursor of ethylene has similar gravicompetence-inducing effects and also appropriate conditions of light, which strongly enhances ethylene synthesis. Both effects can be inhibited by the ethylene-perception blocking agent methylcyclopropene (MCP) or inhibitors of ethylene synthesis such as aminovinylglycine (AVG), indicating that light exerts its gravicompetence-generating effect via induced/enhanced ethylene synthesis. Gain in gravicompetence is accompanied by the induced/enhanced occurrence of calreticulin and lipoxygenase as detected by 2D-gels and Q-TOFF-analyses. Previously gravicompetent, light-grown coleoptile-less seedlings are characterized by gravi-incompetent growth during subsequent horizontal gravistimulation when perception of ethylene is inhibited by MCP. The results demonstrate that continuous perception of ethylene is an indispensable step, permanently required for the regulation of gravitropic growth in germinating primary shoots of rye, either within the process of graviperception and/or of the transduction of the gravi-signal.

The mapping of QTLS for chlorophyll content and responsiveness to gibberellic (GA3) and abscisic (ABA) acids in rye

Genetic maps containing molecular markers are useful tools for the identification of genes underlying quantitative traits (QTLs). Three traits important for plant physiology, i.e. chlorophyll content, sensitivity to GA and sensitivity to ABA, were evaluated for 99 F2 families of the DS2 x RXL10 rye mapping population. The observed variation in the chlorophyll content in rye leaves was shown to be under the genetic control of four independent QTLs. They were located on the following chromosome arms: 1RL (QChc-1R.1), 3RS (QChc-3R.1), 4RL (QChc-4R.1) and 5RL (QChc-5R.1) The marker-assisted selection of recombinants comprising positively-acting alleles at these loci may significantly increase the chlorophyll content in rye leaves, which should result in a higher efficiency of photosynthesis. A decreasing of plant height in rye is one of the major aims of breeders selecting for lodging resistance. The polymorphism of genes controlling sensitivity to gibberellic acid may be the basis for a potential selection strategy. Three QTLs underlying the sensitivity of rye seedlings to GA were located on chromosomes 5RL (QGar-5R.1), 1RL (QGar-1R.1) and on 7RL (QGar-7R.1). The dwarfing allele of a Dw1 locus present in line RXL10 was mapped in the same position as the QGar-5R.1 gene. Sensitivity to ABA plays an important role in imposing dormancy in rye grain. Three QTLs affecting sensitivity to ABA were found. They were mapped on chromosomes 1RS (QAbr-1R.1), 2R in the centromeric region (QAbr-2R.1) and on 5RL (QAbr-5R.1). QAbr-5R.1, Dw1 and QGar-5R.1 are located in the same position on the distal part of the 5RL chromosome arm, which suggests that they belong to a single locus for a major regulatory gene controlling the development of rye plants.

Expressed sequence tag-based gene expression analysis under aluminum stress in rye

To understand the mechanisms responsible for aluminum (Al) toxicity and tolerance in plants, an expressed sequence tag (EST) approach was used to analyze changes in gene expression in roots of rye (Secale cereale L. cv Blanco) under Al stress. Two cDNA libraries were constructed (Al stressed and unstressed), and a total of 1,194 and 774 ESTs were generated, respectively. The putative proteins encoded by these cDNAs were uncovered by Basic Local Alignment Search Tool searches, and those ESTs showing similarity to proteins of known function were classified according to 13 different functional categories. A total of 671 known function genes were used to analyze the gene expression patterns in rye cv Blanco root tips under Al stress. Many of the previously identified Al-responsive genes showed expression differences between the libraries within 6 h of Al stress. Certain genes were selected, and their expression profiles were studied during a 48-h period using northern analysis. A total of 13 novel genes involved in cell elongation and division (tonoplast aquaporin and ubiquitin-like protein SMT3), oxidative stress (glutathione peroxidase, glucose-6-phosphate-dehydrogenase, and ascorbate peroxidase), iron metabolism (iron deficiency-specific proteins IDS3a, IDS3b, and IDS1; S-adenosyl methionine synthase; and methionine synthase), and other cellular mechanisms (pathogenesis-related protein 1.2, heme oxygenase, and epoxide hydrolase) were demonstrated to be regulated by Al stress. These genes provide new insights about the response of Al-tolerant plants to toxic levels of Al.

Ethylene perception generates gravicompetence in gravi-incompetent leaves of rye seedlings

The elongating leaves of young rye seedlings do not show a gravitropic response when placed horizontally. However, after treatment with ethylene, either supplied exogenously via ethephon or by application of its precursor 1-aminocyclopropane-1-carboxylic acid (ACC), gravicompetence is seen. The inhibition of ethylene perception by 1-methylcyclopropene (MCP) prevents gravicompetence. Young rye leaves provide a useful model system in which to identify the components of the gravity sensing or response systems, the presence of which govern gravicompetence.

The gravitropic setpoint angle of dark-grown rye seedlings and the role of ethylene

The orientation growth of coleoptiles of dark-grown seedlings of rye (Secale cereale L. cv. Marder II), when grown under various conditions, was analysed with respect to the gravivector ('gravitropic setpoint angle', GSA). Coleoptiles growing through moist vermiculite attain and maintain a GSA with an average of about 180 degrees, i.e. a vertical orientation. Seedlings growing uncovered either on the surface of vermiculite or positionally fixed on filter paper attain and maintain a GSA of 140-150 degrees (i.e. deviating from the vertical by an average of 30-40 degrees ). Changing the position of the embryo relative to the horizontally fixed seed kernel or of the angle of the seed with respect to gravity during germination (+/-40 degrees relative to the horizontal) had no significant effect on the subsequent GSA of both covered and uncovered seedlings. The GSA of uncovered coleoptiles could be restored close to 180 degrees by treatment of the seedlings with ethylene, either applied via ethephon or 1-aminocyclopropane-1-carboxylic acid (ACC) as well as by fruit-released ethylene. The results are discussed with respect to the mechanism of the regulation of gravitropic growth of grass seedlings.

Accumulation of dehydrin-like proteins in the mitochondria of cereals in response to cold, freezing, drought and ABA treatment

BACKGROUND

Dehydrins are known as Group II late embryogenesis abundant proteins. Their high hydrophilicity and thermostability suggest that they may be structure stabilizers with detergent and chaperone-like properties. They are localised in the nucleus, cytoplasm, and plasma membrane. We have recently found putative dehydrins in the mitochondria of some cereals in response to cold. It is not known whether dehydrin-like proteins accumulate in plant mitochondria in response to stimuli other than cold stress.

RESULTS

We have found five putative dehydrins in the mitochondria of winter wheat, rye and maize seedlings. Two of these polypeptides had the same molecular masses in all three species (63 and 52 kD) and were thermostable. Drought, freezing, cold, and exogenous ABA treatment led to higher accumulation of dehydrin-like protein (dlp) 63 kD in the rye and wheat mitochondria. Protein 52 kD was induced by cold adaptation and ABA. Some accumulation of these proteins in the maize mitochondria was found after cold exposition only. The other three proteins appeared to be heat-sensitive and were either slightly induced or not induced at all by all treatments used.

CONCLUSIONS

We have found that, not only cold, but also drought, freezing and exogenous ABA treatment result in accumulation of the thermostable dehydrins in plant mitochondria. Most cryotolerant species such as wheat and rye accumulate more heat-stable dehydrins than cryosensitive species such as maize. It has been supposed that their function is to stabilize proteins in the membrane or in the matrix. Heat-sensitive putative dehydrins probably are not involved in the stress reaction and adaptation of plants.

Stress-induced protein CSP 310: a third uncoupling system in plants

Addition of the cold-stress-related protein CSP 310 to mitochondria isolated from winter wheat ( Triticum aestivum L. cv. Zalarinka), winter rye ( Secale cereale L. cv. Dymka), maize ( Zea mays L. cv. VIR 36) and pea ( Pisum sativum L. cv. Marat) caused an increase in non-phosphorylative respiration. This increase was inhibited by KCN, indicating that the protein is not a CN-resistant alternative oxidase. Unlike plant mitochondrial uncoupling proteins such as PUMP, the uncoupling action of CSP 310 did not depend on the presence of free fatty acids in the incubation medium. We propose that the mechanism of the uncoupling action of CSP 310 differs from that of other known plant uncoupling systems and that the CSP 310 uncoupling system is a third uncoupling system in cereals.

Phytotoxic sesterterpene, 11-epiterpestacin, from Bipolaris sorokiniana NSDR-011

The structure of siccanol, a phytotoxic sesterterpene of fungal origin, was analyzed after chemical conversion by NMR spectroscopy. Siccanol was found to be an epimer of terpestacin that has been isolated from Arthrinium sp., and was thus renamed 11-epiterpestacin. Its stereochemistry was also identical with that of fusaproliferin, a structurally related mycotoxin from Fusarium proliferatum. Therefore, this sesterterpene may also be referred to as 24-deacetyl fusaproliferin. The phytotoxicity of 11-epiterpestacin was almost equal to that of terpestacin, but significantly higher than that of fusaproliferin.

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.

Thermal effect of CO(2) on apoplastic ice in rye and oat during freezing

Meristematic tissues from rye (Secale cereale) and oat (Avena sativa) were studied in an isothermal calorimeter at -3 degrees C. When the frozen tissue was placed in the calorimeter, the pressure increased within 4 d to 25 and 9 kPa above ambient pressure in the sample vessels containing crowns of rye and oat, respectively. Concurrently, the thermal output went down to -194 microW in rye over the 4-d period; this negative thermal activity could be accounted for by ice melting in the plants. When the pressure was released, the output from the calorimeter went from -194 to 229 microW within 1 h, suggesting that water had frozen in the plants. We propose that CO(2) from respiration had dissolved in the water in the plants and caused melting of ice (heat absorption) due to the colligative properties of solutions. When the pressure was released, the CO(2) came out of solution and the water froze (heat evolution). These thermal observations were duplicated in a simplified, non-biological system using a glycol/water mixture that was partially frozen at -3 degrees C.

5-Methylcytosine distribution and genome organization in triticale before and after treatment with 5-azacytidine

Triticale (2n=6x=42) is a hybrid plant including rye (R) and wheat (A and B) genomes. Using genomic in situ hybridization with rye DNA as a probe, we found the chromosomes of the R genome were not intermixed with the wheat chromosomes in 85% of nuclei. After treatment of seedlings with low doses of the drug 5-azacytidine (5-AC), leading to hypomethylation of the DNA, the chromosomes became intermixed in 60% of nuclei; the next generation showed intermediate organization. These results correlate with previous data showing that expression of R-genome rRNA genes, normally suppressed, is activated by 5-AC treatment and remains partially activated in the next generation. The distribution of 5-methylcytosine (5-mC) was studied using an antibody to 5-mC. Methylation was detected along the lengths of all chromosomes; there were some chromosome regions with enhanced and reduced methylation, but these were not located at consistent positions, nor were there differences between R and wheat genome chromosomes. After 5-AC treatment, lower levels of methylation were detected. After 5-AC treatment, in situ hybridization with rye genomic DNA sometimes showed micronuclei of rye origin and multiple translocations between wheat and rye chromosomes. Genomic DNA was analysed using methylation-sensitive restriction enzymes and, as probes, two rDNA sequences, two tandemly organised DNA sequences from rye (pSc200 and pSc250), and copia and the gypsy group retrotransposon fragments from rye and wheat. DNA extracted immediately after 5-AC treatment was cut more by methylation-sensitive restriction enzymes than DNA from untreated seedlings. Each probe gave a characteristic restriction fragment pattern, but rye- and wheat-origin probes behaved similarly, indicating that hypomethylation was induced in both genomes. In DNA samples from leaves taken 13–41 days after treatment, RFLP (Restriction Fragment Length Polymorphism) patterns were indistinguishable from controls and 5-AC treatments with all probes. Surprising differences in hybridization patterns were seen between DNA from root tips and leaves with the copia-fragment probes.

The kinetics of quinine blockade of the maxi cation channel in the plasma membrane of rye roots

The maxi cation channel from the plasma membrane of rye (Secale cereale L.) roots was studied following its incorporation into planar phosphatidylethanolamine bilayers. Current recordings were made in the presence of 100-mm KCl containing quinine on both sides of the bilayer. Quinine produced voltage- and concentration-dependent blockade of the channel, reducing its apparent unitary current and open probability. The voltage-dependence suggested that blockade was effected from the cytoplasmic side by cationic quinine. Blockade was modelled using a kinetic scheme with two independent blocked states termed B1 and B2 (B1 <==> O <==> B2). Rate constants promoting fast kinetics (k1 and k-1) were found to be several orders of magnitude greater than those promoting slow kinetics (k2 and k-2). Analysis of the fast kinetics indicated that the rate constants for blockade of the open channel at the first site (k1) and its clearance (k-1) had voltage-dependencies (zdelta(p)) of 0.41 and -0.71, respectively, and that the equilibrium dissociation constant for the binding site (Kd(0)) was about 1 mm. Analysis of the slow kinetics indicated that the rate constants for blockade of the open channel at the second site (k2) and its clearance (k-2) had zdelta(p) values of 0.12 and -1. 27, respectively. The Kd(0) value for the second binding site was about 10 mm.

[Thiamine allowance of animals receiving rye and wheat grains grown with the use of herbicides from the phenoxy acid chlorine derivative group]

Investigations carried out for several years have shown that the treatment of rye and wheat crops with an amine salt of 2,4-dichlorophenoxyacetic acid and dialene produces sometimes a decrease in the grain thiamine content of these cereals. Feeding of rye and wheat grains grown with the use of the amine salt of 2,4-dichlorophenoxyacetic acid to growing ratlings has demonstrated that the thiamine content in the liver of ratlings is directly proportional to thiamine supply to their body with food.