Participation of the intracellular enzymes in the control of the mutation process

Summary The influence of repair and replication on the frequency of spontaneous chromosome aberrations and of those induced by gamma-irradiation is reported.Using the technique of labelling DNA with radioactive ³H-thymidine and measuring the radioactivity of DNA isolated from embryos, the time of initiation and the duration of DNA synthesis in barley seeds was studied after the soaking of the seeds had begun. The average duration of each phase of the first DNA synthesis cycle in soaking barley seeds was found to be as follows: pre-DNA synthesis stage, 10–11 hrs; DNA synthesis stage, 8 hrs. After gamma-irradiation, the intensity of DNA synthesis decreased and the beginning of DNA synthesis was delayed.It was found that the inhibition of repair by caffeine led to an increase in the frequency of both spontaneous and induced chromosome aberrations. Caffeine enhanced several times the frequency of chromosome and chromatid aberrations at the time of the maximal activity of repair enzymes. During DNA replication, caffeine had a lower effect on the realization of premutational lesions.An inhibitor of DNA replication — hydroxyurea — had no influence on the frequency of spontaneous chromosome aberrations during the replication period, whereas after gamma-irradiation, hydroxyurea enhanced the frequency of aberrations mainly at the stage of DNA replication.The relatively small mutagenic action of both agents (caffeine and hydroxyurea) was observed during all stages of the cell cycle of germinating barley seeds.     

Genetic mapping of the gene affecting polyphenol oxidase activity in tetraploid durum wheat

The quality of durum wheat (Triticum turgidum ssp. durum) is influenced by polyphenol oxidase(PPO) activity and its corresponding substrates. A saturated molecular-marker linkage map was constructed previously by using a set of recombinant inbred (RI) lines, derived from a cross between durum wheat cultivars Jennah Khetifa and Cham 1. Quantitative trait loci (QTL) for PPO activity in seeds were mapped in this population. PPO activity in seeds of the parents and 110 RI lines was measured spectrophotometrically. The PPO activity of Cham 1 was significantly lower than that of Jennah Khetifa. QTL analysis of these data indicated that most of PPO activity was associated with major loci on the long arm of chromosome 2A. The trait was found to be strongly associated with the SSR marker Xgwm312@2A. With this knowledge, marker-assisted selection can be used to select genotypes with lower PPO activity in durum wheat populations.     

Modifying effect of dioxane on the cytogenetic activity of N-nitroso-N-methylurea

Dry seeds of Crepis capillaris L. were treated with N-nitroso-N-methyl urea (NMU) and with dioxane (DO) an organic solvent, at pH 7.0 and pH 5.7. The treatment with NMU only was used as a positive control. Three concentrations of NMU were applied. The cytogenetic activity of NMU was found to considerably decrease at two values of pH, while NMU was solved in DO. The relationship between different types of chromosome aberrations remained unchanged in this case.     

空间条件对几种粮食作物的同工酶和细胞学特性的影响

搭载１９８７年发射的两颗返地卫星（８月５—１０日和９月９—１７日）的几种小麦、大麦种子,经回收后初步研究表明：（１）对发芽率的影响：空间处理的种子,其发芽率与对照无差别;（２）对茎及生育期的影响：空间处理的种子长成的幼苗比对照强壮,植株高度有些品种明显的矮于对照。生育期有不同程度延长;（３）对染色体结构的影响：花粉母细胞减数分裂观察表明搭载卫星的种子当代可诱导出比地面更多的染色体桥、落后染色体及染色体数目异于正常体细胞数目的现象。小麦品种Ｃｏｃｏｒｉｔ—７１经空间处理后花粉母细胞的染色体数目异常可高达２０．５１％,而地面对照组其花粉母细胞基本正常（２ｎ＝２８）;（４）对同工酶的影响：经空间处理的小麦种子酯酶、过氧化物酶的同工酶谱带空间处理的比地面对照减少。由此可见,空间处理可诱导纯合植物种子发生变异,为农作物育种创造一个新途径。     

Comparative in vivo and in vitro study of the cytogenetic effects of 153Sm-EDTMP in lymphocytes of patients with bone metastases.

153Sm-EDTMP is a radiopharmaceutical used in nuclear medicine for relief of metastatic bone pain with promising results, but there are few studies about the effects of 153Sm-EDTMP in human cells. This study was conducted for the evaluation of the cytogenetic effects of 153Sm-EDTMP in blood lymphocytes from patients with bone metastases (without previous radio or chemotherapy), using the chromosome aberration technique. The degree of cytological damage found in in vivo blood cells of patients was compared with those found in in vitro in an adjusted dose-response curve. Blood samples were collected before and 1 hr after the administration of 153Sm-EDTMP(about 42.31 MBq/kg). The frequency of structural chromosome aberration per cell observed in 1 hr samples (0.054+/-0.035 CA/cell) was higher than basal ones (0.031+/-0.026 CA/cell), although this difference was not statistically significant (p= 0.101). For in vitro assay, blood samples were exposed to different concentrations of 153Sm-EDTMP, during 1 hr (0.37-1.11 MBq/ml). An increase in the frequency of chromosome aberration per cell as a function of the radioactive concentration was found. The data were adjusted by linear regression model (Y= 3.52+/-2.24 x 10(-2) + 11.15+/-3.46 x 10(-2) X). The frequency of aberration/cell found in vivo was 0.054 and for the same activity in vitro was 0.098, this difference being statistically significant (p = 0.02). This result may be related to blood clearance, osteoblastic activity and individual variability. For a more accurate analysis, the study of more donors is necessary.     

Coordinated Regulation of the Genes Participating in Starch Biosynthesis by the Rice Floury-2 Locus

The recessive floury-2 (flo-2) locus of rice (Oryza sativa L.), which is located on chromosome 4, causes a strong reduction in expression of the gene encoding an isoform of branching enzyme RBE1 in immature seeds 10 d after flowering. Mapping of the RBE1 gene demonstrated the localization on rice chromosome 6, suggesting that the wild-type Floury-2 (Flo-2) gene regulates RBE1 gene expression in trans. However, reduced expression of the genes encoding some other starch-synthesizing enzymes, including another isoform of branching enzyme RBE3 and granule-bound starch synthase, was also found in the flo-2 seeds. In spite of the low level of RBE1 gene expression in the immature seeds of the flo-2 mutants, the RBE1 gene was equally expressed in the leaves of the wild type and flo-2 mutants. Thus, these results imply that the Flo-2 gene may co-regulate expression of some of the genes participating in starch synthesis possibly in a developing seed-specific manner.     

Effects of Temperature, Moisture, and Oxygen on the Induction of Chromosome Damage in Seeds of Barley, Broad Beans, and Peas during Storage

The effects of temperature, seed moisture content, and oxygenlevel on the production of chromosome aberrations during seedstorage have been investigated. It has been found that an increasein any of these factors increases the rate of loss of seed viabilityand that any treatment which leads to a loss of viability alsoleads to an accumulation of aberrant cells in the embryo. Undermost storage conditions, irrespective of the combination offactors which leads to loss of viability or the rate at whichviability is lost, the relationship between percentage viabilityand mean frequency of aberrant cells in the surviving seed populationis always the same. Under very severe storage conditions, whichresult in half-viability periods of about a week or less, however,the relationship is altered so that for any given percentageviability the mean frequency of aberrant cells in the survivingseeds is less than is typical of more normal storage conditions.In all treatments (except the most severe) the curve showingmean frequency of aberrant cells in surviving seeds againsttime eventually became asymptotic to a critical value peculiarto the species. It is suggested that these results are compatible with the hypothesisthat under most storage conditions death of the embryo is theresult of the accumulation of nuclear damage which is reflectedin chromosome breakage; it is emphasized, however, that thevisible chromosome breakage itself is probably not criticalto the seed's survival. When the nuclear damage has reacheda critical level, of which the frequency of aberrant cells isan index, the seed is no longer capable of germinating. Undervery severe storage conditions, additional factors appear tobe involved. An effort was made to test the frequently suggested hypothesisthat chromosome aberrations produced during the ageing of seedsare the result of the accumulation of automutagenic substances.Attempts to demonstrate the presence of mutagenic substancesin water-, ethanol-, and ether-extracts of fresh and aged seedsgave negative results. Aqueous extracts showed antimitotic andgermination inhibitory activity, but this was the same fromboth aged and fresh seeds.     

山楂种子体眠和萌发与营养物质植物生长物质关系的研究

对低温层积不同时期的山楂种仁中的氨基酸、植物生长物质等几项生理生化指标进行了定量分析的结果表明层积１５至１８个月时因缺水出现二次休眠,在种子内部发生一系列生理变化,从中得知脱落酸,吲哚乙酸为生长抑制剂,玉米素核苷,赤霉素为促进剂。脯氨酸对干旱比较明感,随着层积时间的延长营养物质趋于升高,酶的活性提高,为种子发芽提供了能量。     

Radiation-population monitoring of Pinus sylvestris L. in the zone of the Chernobyl power plant

Cytogenetic and genetic effects in populations of Pinus sylvestris L. suffered wiak, average, strong and sublethal radiation damage after the Chernobyl accident in 1986 were studied. The absorbed dozes for trees in these plantings were from 0.1 up to 20 Gy. It was shown that the amount of cells with chromosome aberrations in sprouts of seeds of a crop of 1993, are comparable with effects marked at once after accident in 1986. In 1997 and in 1998 the amount of cells with chromosome aberrations in sprouts of seeds in majority inspected plantings decreased to control values. The effect of adaptation was detected, when seeds of Pinus sylvestris L., gathered in 1997 from inspected trees, were exposed to additional 4 Gy gamma-radiation.     

Effect of laser light treatment on some biochemical and physiological processes in seeds and seedlings of white lupine and faba bean

The aim of present study was to determine the changes of some biochemical and physiological processes, which occurred in seeds and seedlings of white lupine and faba bean after pre-sowing treatment with laser beams. It was found this treatment of seeds considerably increased the activity of amylolytic enzymes in seeds of both plants. The greatest differentiation of the enzymatic activity was noticed after 120?h from the time of sowing but the activity of these enzymes in the seeds of both tested plants was similar and it had the same course in time. The irradiated seeds of white lupine and faba bean had higher fresh weight at the time of imbibition than the seeds which were not treated with laser beams. It resulted in earlier and more uniform germination. The concentration of free radicals increased considerably in the seeds pre-treated with laser beams and the largest increase in seeds of both plant species was noticed after five exposures to laser beams. Treating seeds with laser beams considerably increased the amount of indole-3-acetic acid (IAA) in the germinating seeds. Three exposures of seeds caused the largest increase of this plant hormone content in the seeds. The activity of IAA in faba bean was slightly higher than in white lupine seeds. Pre-sowing stimulation with laser had a positive influence on the growth and development of seedlings, which had longer hypocotyl and roots in comparison to seedlings which grew from non irradiated seeds.     

Genoprotective human blood activity and its mechanisms

Anticlastogenic properties of plasma and proteins (albumin and gamma-globulin) of the human blood were studied using seeds of Crepis capillaris (chromosome aberration assay). Antimutagen p-amino-benzoic acid was used as a comparative reagent. Anticlastogenic activity dependent of processing conditions of the biosubstrate used; for the pre-processing and combined processing anticlastogenic effect was higher than for post-processing, the processing properties of the blood being higher than those of the blood proteins. Anticlastogenic potential of biosubstrates did not depend on mutation inductor. Complex-formimg properties of plasma and blood albumen have been revealed using spectrop-hotometry through the substantial spectral displacement--relative to the expected spectrum--for the mixture of biosubstrata and mutagens. Using chemoluminescence, all plasma, albumin and gamma-globulin concentrations have been shown to enhance generation of hydroxyl radical of the Fenton reagent, especially for albumin in 1.0 g/l concentration. The general trend for all experiments was that the said substances diminished the stimulating effect as their concentrations grew. Peroxidation of yolk lipoproteids showed that only high concentrations of blood's plasma and albumen have antioxidizing properties. gamma-Globulin did not reveal any ability to inhibit lipid peroxidation of yolk lipoproteids. Complex-forming mechanisms of blood's albumen and antioxidizing property of human plasma and proteins have been proved to form the blood's anticlastogenic potential.     

航天诱变凤仙花小孢子母细胞减数分裂的研究

对卫星搭载凤仙花与对照组的小孢子母细胞减数分裂以及四分孢子期内的小孢子数目、形状进行了对比研究,发现经过航天搭载的凤仙花种子在第一代(SP1)植物的小孢子母细胞减数分裂中出现了染色体桥、落后染色体和分散染色体;四分孢子时期易出现多分孢子及四分孢子不分离等现象。而对照组则很难发现染色体畸变和小孢子的异常现象。     

Lectins in Immature Pods of Winged Bean,Psophocarpus tetragonolobus (L.) DC.

Lectin activity in immature pods from 30 strains of winged bean was investigated. Most of the lectin activity occurred in green shells and a small portion in immature seeds. Hemagglutinating activity of green shells was classified into four groups, according to the agglutination of trypsinized human type A, B, and O erythrocytes. Extracts from green shells of four representative strains which showed different hemagglutination patterns gave different elution profiles of lectin activity from ion exchange columns. Four types of lectin activity with different blood group specificities were apparently found in green shells.     

Antioxidant potential of Coriandrum sativum L. seed extract

The seeds of C. sativum are used as a traditional drug for the treatment of diabetes. The antioxidant and free-radical-scavenging property of seeds in vitro was studied and also investigated whether the administration of seeds curtails oxidative stress in the kidney of streptozotocin-induced diabetic rats. Incorporation of seed powder in the diet led to marked lowering of blood glucose and a rise in the levels of insulin in diabetic rats. A parallel beneficial effect was observed on oxidant -antioxidant balance in the kidney. Addition of coriander seed powder not only inhibited the process of peroxidative damage but also significantly reactivated the antioxidant enzymes and antioxidant levels in diabetic rats. The total polyphenolic content of the seeds was found to be 12.2 gallic acid equivalents (GAE)/g while total flavanoid content was found to be 12.6 quercetin equivalents/g. The seeds also showed scavenging activity against superoxides and hydroxyl radicals in a concentration-dependent manner. Maximum free radical-scavenging action and free radical reducing power of coriander seed extract was observed at a concentration of 50 microg GAE. Islet histology structures showed degeneration of pancreatic islets in diabetic rats which was also reduced in diabetic rats treated with seed powder. These results show that C. sativum seeds not only possess antihyperglycemic properties but antioxidative properties also. Increased dietary intake of coriander seeds decrease the oxidative burden in diabetes mellitus.     

Asparaginyl endopeptidase during maturation and germination of durum wheat

Asparaginyl-endopeptidase activity was detected in endosperms of maturing and germinating wheat seeds. The highest activity was found during maturation before the maximal accumulation of storage proteins. The enzyme activity then decreased in the dry seeds and increased again during germination. The increase of activity during germination required the presence of the embryo. In fact, the activity found in detached endosperms was lower than that found in attached ones. The localization at tissue level of the enzyme reveals differences between maturation and germination: the enzyme was about equally located in the aleurone layer and starchy endosperm during maturation, but solely in the aleurone layer during germination. The asparaginyl enzymes from maturing and germinating seeds had many similar properties, such as pH optimum, pH stability, thermal stability and sensitivity to thiol reagents and to thiol compounds. The results suggest that asparaginyl endopeptidases may be involved in the modification of proproteins of storage proteins during seed maturation and in the degradation of storage proteins deposited in the aleurone layer during germination.     

Cloning and sequence analysis of genes involved in erythromycin biosynthesis in Saccharopolyspora erythraea: sequence similarities between EryG and a family of S-adenosylmethionine-dependent methyltransferases.

Summary Treatment of tomato seeds with ethyl methanesulphonate (EMS) followed by allyl alcohol selection of M₂ seeds has led to the identification of one plant (B15-1) heterozygous for an alcohol dehydrogenase (Adh) null mutation. Genetic analysis and expression studies indicated that the mutation corresponded to the structural gene of the Adh-1 locus on chromosome 4. Homozygous Adh-1 null mutants lacked ADH-1 activity in both pollen and seeds. Using an antiserum directed against ADH from Arabidopsis thaliana, which crossreacts with ADH-1 and ADH-2 proteins from tomato, no ADH-1 protein was detected in seeds of the null mutant. Northern blot analysis showed that Adh-1 mRNA was synthesized at wild-type levels in immature seeds of the null mutant, but dropped to 25% in mature seeds. Expression of the Adh-2 gene on chromosome 6 was unaffected. The potential use of the Adh-1 null mutant in selecting rare transposon insertion mutations in a cross with mutable Adh-1 ⁺ tomato lines is discussed.     

Tissue and subcellular distribution of the lectin from Datura stramonium (thorn apple).

Plants of Datura stramonium (thorn-apple) were dissected into their component tissues and examined for the presence of the Datura lectin. This lectin was easily detected in seeds and in various parts of the flowers of adult plants. Traces were also found in green (emerged) cotyledons and roots of seedlings. The specific lectin activity in seeds contained within the fruits increased as the seeds matured. Mature seeds were homogenized in sucrose and separated by differential centrifugation into four fractions, three of which were clearly of distinct composition. Most of the lectin activity sedimented with the low-speed (cell-wall/protein-body) pellet, but a similar specific activity was recovered from the other fractions. However, if EDTA was included in the homogenization medium, three or four times more lectin activity was recovered in the soluble fraction. Immunofluorescent staining of formaldehyde-fixed sections showed that the lectin was localized in the cytoplasm, with little associated with cell walls. The possible relevance of these results to the function of the lectin in plant cells is discussed.     

Genetic and in silico comparative mapping of the polyphenol oxidase gene in bread wheat (Triticum aestivum L.)

Polyphenol oxidases (PPOs) are involved in the time-dependent darkening and discolouration of Asian noodles and other wheat end products. In this study, a doubled haploid (DH) population derived from Chara (moderately high PPO activity)/WW2449 (low PPO activity) was screened for PPO activity based on l-DOPA and l-tyrosine assays using whole seeds. Both these assays were significantly genetically correlated (r=0.91) in measuring the PPO activity in this DH population. Quantitative trait loci (QTLs) analysis utilising a skeleton map enabled us to identify a major QTL controlling PPO activity based on l-DOPA and l-tyrosine on the long arm of chromosome 2A. The simple sequence repeat (SSR) marker GWM294b explained over 82% of the line mean phenotypic variation from samples collected in both 2000 and 2003. Four SSR markers were validated for PPO linkage in genetically diverse backgrounds and proven to correctly predict the PPO activity in more than 92% of wheat lines. Physical mapping using deletion lines of Chinese Spring has confirmed the location of the GWM294b, GWM312 and WMC170 on chromosome 2AL, between deletion breakpoints 2AL-C to 0.85. In order to identify functional gene markers, data searches for alignments between rice BAC/PAC clones assembled on chromosome 1 and 4, chromosome 7, and (1) the wheat expressed sequence tags mapped in deletion bin (2AL-C to 0.85) and (2) the coding sequence of a previously cloned wheat PPO gene were made and found significant sequence similarities with the PPO gene or common central domain of tyrosinase. Available PPO gene sequences in the National Centre for Biotechnology Information (NCBI) database have revealed that there is a significant molecular diversity at the nucleotide and amino acid level in the wheat PPO genes.Electronic Supplementary Material Supplementary material is available for this article at .     

Environmental impact on age-related dynamics of karyotypical instability in plants

The dynamics of karyotypical instability of Allium fistulosum L. (Welsh onion) during aging of genetically homogenous seeds from plants grown in three different areas was studied. We analyzed the frequency of anaphase cells with chromosomal aberrations "damage", as a number of chromosomal aberrations per cell with aberrations, and germinating capacity, as an indicator of the 'toxic' influence of age. The seeds' aging was accompanied by an increase in karyotypical instability (increasing frequency of anaphases with aberrations) and with certain changes in the spectrum of chromosome aberrations. The clearest distinctions between old and young seeds were found for the frequency of anaphase cells with chromosome aberrations. The general level of karyotypical instability positively correlates with the age of the seeds. The regression coefficient (b) corresponds to the general tendency of karyotypical instability during seeds' senescence under storage. For 'good' (A), 'normal' (B) and 'bad' (C) conditions, the coefficients (b's) are b(A)=0.22, b(B)=0.46 and b(C)=0.84 (p<0.05 for C, and p<0.001 for A and B). It was found that different ecological conditions of plant vegetation strongly influence age-related dynamics of chromosomal instability in the seeds obtained from these plants. Possible mechanisms of the transgenerational impact of this effect are discussed.     

A Comparison of the Quantitative Effects of Seed Moisture Content and Temperature on the Accumulation of Chromosome Damage and Loss of Seed Viability in Lettuce

The rate of accumulation of cells containing chromosome aberrationsin lettuce (Lactuca sativa L.) seeds is a positive functionof temperature and moisture content. It may be described byan equation similar to that for loss of seed viability. Therelative effect of temperature on the rates of loss of viabilityand accumulation of chromosome aberrations is the same. In contrast,the relative effect of moisture on the rate of loss of viabilityis greater than that for the rate of accumulation of aberrations.Hence considerably more chromosome damage accumulates beforedeath in drier lettuce seeds. Lactuca sativa, lettuce, seed storage, seed viability, seed longevity, chromosomal aberrations temperature, moisture content