Role of some growth regulators on cytogenetic activity of barley under salt stress

The effects of gibberellic acid (GA₃), kinetin (KIN), benzyladenine and ethylene (E) on mitotic activity and chromosomal aberrations in root tips of barley seeds (Hordeum vulgare L. cv. “Bülbül 89”) germinated under salt stress were investigated. It was determined that all of these plant growth regulators (PGRs) decreased mitotic index in root tips of barley seeds germinated at 20 °C and in distilled water. Furthermore, some of the PGRs studied increased significantly the frequency of chromosomal aberrations. The frequency of chromosomal aberrations in seeds treated with E and KIN was considerably higher than in the seeds germinated under nonstress conditions. The inhibitory effect of salt stress on mitotic index increased with increasing salt concentration (0.30, 0.35, 0.40 and 0.45 molal, m). GA₃ and KIN pretreatments showed a successful performance in ameliorating the negative effects of increasing salinity on mitotic activity. The number of chromosomal aberrations also increased with increasing NaCl concentration. However, most of the PGR pretreatments studied alleviated the detrimental effects of increasing salinity on chromosomal aberrations. KIN pretreatment at 0.30 and 0.35 m salinity could not rescued the cytogenetic activity of salt stress on this parameter.     

Induction of chromosomal disturbances other than tetraploidy in barley root tips by colchicine treatment

Barley embryos were treated by 0.1% colchicine for 30 min. Samples of root tips were fixed after 4 h, 8 h and 12 h. In the first sample,c-metaphases, normal metaphases and anaphases were present jointly. Inc-metaphases, chromosomes sometimes tended to make two groups with 7 chromosomes in each. In anaphases, lagging chromosomes, tripolar and multipolar anaphasos were found. No chromosomal aberrations were detected in anaphases and metaphases. No chromosome disturbances were found in root tips sampled 8 h and 12 h after colchicine treatment.     

Evaluation of cytological effects of Zn2+ in relation to germination and root growth of Nigella sativa L. and Triticum aestivum L

The effects of different treatments with zinc sulfate (Zn(2+)) on the cytology and growth of Nigella sativa and Triticum aestivum were investigated. Five concentrations of zinc sulfate ranging from 5 to 25mg/l were applied for 6, 12, 18, and 24h. The treatments reduced the germination percentages of N. sativa seeds and T. aestivum grains and inhibited the root growth of both plants. Concentrations higher than 25mg/l of Zn(2+) applied for 24h were toxic for both plants. The non-lethal concentrations of Zn(2+) showed an inhibitory effect on cell division in root tips of both plants and caused a decrease in their mitotic index values. The reduction in MI in root tips of T. aestivum was more evident than that of N. sativa. All treatments changed the frequency of mitotic phases as compared with the control values. The total percentage of abnormalities in N. saliva was more than that in T. aestivum. Zn(2+) treatments produced a number of mitotic abnormalities in dividing cells in root tips of both plants resulting from its action on the spindle apparatus such as C-metaphases, lagging chromosomes and multipolar anaphases and telophases. Also, Zn(2+) induced vacuolated nuclei and irregular prophases. The induction of chromosomal stickiness and chromosomal aberrations such as bridges and breaks indicates its action on the chromosome. These abnormalities (chromosome breaks and chromosomal bridges at ana-telophases) indicate true clastogenic potential of the ions tested.     

Vicia faba chromosome damage induced by low doses of gamma radiation

The rate of radiation damage to chromosomes by low doses of gamma rays (0.01-0.30 Gy) was studied in the root tips ofVicia faba. As criteria of the effect of ionizing radiation, the frequency of sister chromatid exchanges (SCEs), incidence of chromosomal aberrations and the number of micronuclei were evaluated and compared in irradiated cells. The results obtained confirmed that the analysis of SCEs did not represent an efficient indicator of radiation damage to chromosomes. On the contrary, the formation of chromosomal aberrations and micronuclei was effectively stimulated by low radiation doses, there being linear dose-effect relationships in the low doses region used.     

Chromosome damage induced by artificial seed aging in barley

Summary Barley (Hordeum vulgare L. Himalaya) seeds were artificially aged under two storage conditions (32 °C/12% moisture content (m.c.) and 38 °C/18% m.c.) to study the behavior of induced chromosomal aberrations during plant growth. The frequencies of aberrant anaphases at first mitosis in root tips were correlated with loss of germinability. However, after 3 and 5 weeks' growth, aberration frequency declined. In plants grown from artificially aged seeds, the frequency of aberrant anaphases appeared to be stabilized at about 1% after 5 weeks' growth, in spite of the large differences in the frequencies at first mitosis. This suggests that because of their genetic imbalance, cells with chromosomal aberrations induced by seed aging were being excluded during plant growth. Meiotic chromosome configurations at MI were normal (7 II) in all plants studied, although a few precocious separations were found. Meiotic aberrations were found at AI-TI, AII-TII and the tetrad stages in the pollen mother cells of plants grown from the control and artificially aged seeds. However, there were no clear differences among the control and the two aging treatments. It was obvious that some cells with meiotic chromosomal aberrations were lost between the AI-TI and AII-TII stages, and still more between the AII-TII and tetrad stages. The frequency of tetrads with micronuclei in plants produced from artificially aged seeds was the same as in the control. The plants grown from artificially aged seeds showed high pollen fertility (95.2 to 97.0%) and seed fertility (90.1 to 97.2%) which was comparable to the control values (97.4 and 97.9%) respectively, indicating no special effects of seed aging. Anaphase cells of the first mitosis in the next (A₂) generation were analyzed to study the transmission of chromosomal aberrations through mitotic and meiotic cell divisions in the A₁ generation. Aberrant anaphases in the progeny from the artificially aged seeds were not higher than those of the control progeny. This indicates that the chromosomal aberrations induced by seed aging are not transmitted to the next generation.Published with the approval of the Director of the Colorado state Experiment Station as Scientific Series No. 2776     

Protoplasmic Incompatibility and Cell Lysis in PODOSPORA ANSERINA. I. Genetic Investigations on Mutations of a Novel Modifier Gene That Suppresses Cell Destruction

The distribution of chromosomal aberrations between and within chromosomes of male D, melanogaster somatic cells after treatment with UV has been analyzed. -- Distribution of the breaks between chromosomes was largely nonrandom since we found a higher aberration frequency than that expected on the Y chromosome. Moreover, within the chromosomes the aberrations are clustered in the pericentromeric heterochromatic regions. The above distribution is compared with that of the breaks induced by X rays and methyl-methane-sulphonate (MMS) which were distributed in a different pattern.     

LSD induced genetic damage in barley

LSD has been found to induce extensive chromosomal aberrations in barley. The drug also stimulated mitotic activity in cells of the root tips within a few hours of the treatment. The chromosomal aberrations induced by LSD appeared to be qualitatively different from those produced by ionizing radiation and various other chemicals. Most of the broken ends failed to reunite and there was a disproportionately large number of breaks in the region of the centromere. The seedling height was found to be reduced as a result of treatment, presumably because of the induced genetic damage.     

LSD induced genetic damage in barley

LSD has been found to induce extensive chromosomal aberrations in barley. The drug also stimulated mitotic activity in cells of the root tips within a few hours of the treatment. The chromosomal aberrations induced by LSD appeared to be qualitatively different from those produced by ionizing radiation and various other chemicals. Most of the broken ends failed to reunite and there was a disproportionately large number of breaks in the region of the centromere. The seedling height was found to be reduced as a result of treatment, presumably because of the induced genetic damage.     

Mitotic chromosomal abnormalities and DNA polymorphism in the Nile tilapia (Oreochromis niloticus,Linnaeus, 1758) as a biomarker for water pollution by heavy metals

Mitotic chromosomal aberrations and DNA polymorphism (RAPD marker) were carried out on the Nile tilapia Oreochromis niloticus collected from five sites in Minia governorate, Egypt to test their applicability as biomonitors for heavy metal contaminants of water. The diploid chromosome number of O. niloticus population was 2 n = 44. Different types of chromosomal aberrations were recorded (e.g., deletion, ring, centromeric attenuation, end-to-end association, dicentric chromosome, stickiness chromosomes, endomitosis, fragments and chromatid gap). The chromosomal aberrations varied between O. niloticus population collected from five sites, and the most common type was ring (R) chromosomes. Samples obtained from Bahr Yousef and Irrigation drain exhibited the highest aberration frequency. The frequency of chromosomal aberration was positively correlated with the concentration of heavy metals where their concentration in the surface water of Irrigation drain and Bahr Yousef exceeded the limits defined by WHO as well as the concentration of Pb in muscles. The RAPD marker was also used to identify genetic variation among Nile tilapia samples collected from five different water sources. It created polymorphic and unique bands that can be used as genetic markers to track DNA variations. The dendrogram also revealed that exposure to heavy metal pollution causes gradual accumulation of variance, whereas areas subjected to environmental stress showed higher genetic variation and clustered together.     

Induction of chromosome aberrations in cultured human lymphocytes treated with ethoxyquin

The chromosomal aberration test was employed to investigate the effect in vitro of a known antioxidant and food preservative, ethoxyquin (EQ, 1,2-dihydro-6-ethoxy-2,2,4-trimethylquinoline) on human chromosomes. The studies were undertaken because there are no published in vitro data on genotoxicity of EQ in mammalian cells and there are many reports pointing out that it may be harmful to animals and human beings. Lymphocytes obtained from three healthy donors were incubated with EQ (0.01–0.5 mM) both with and without metabolic activation. Stability studies performed by HPLC analysis showed that EQ was stable under the conditions of the lymphocyte cultures. The results of the chromosome aberration assay showed that EQ induces chromosome aberrations: gaps and breaks as well as dicentrics and atypical translocation chromosomes.     

Radiobiological effects of a low-energy ion beam on wheat

The radiobiological effects of a low-energy nitrogen ion (N⁺) beam on wheat were studied, particularly with regard to the induction of chromosome aberrations. The results demonstrated that the three test varieties showed different sensitivities to ion implantation, and a higher dose of ion implantation had a marked effect on the germination and survival rate of the seeds exposed. The germination rate and survival rate curve basically followed a similar trend in the same variety. Cytological analysis indicated that ion beams were effective in producing chromosome aberrations. The frequencies of mitotic or meiotic cells with chromosome aberrations increased linearly with increasing doses. The aberration types included, for example, acentric fragments, chromosome deletions, lagging chromosomes, chromosome bridges and micronuclei. In the root tip cells, aberrations chiefly consisted of acentric fragments and deletions. Chromosome bridges and lagging chromosomes were the main aberration phenomena observed in the pollen mother cells. The highest frequencies of root tip cells and pollen mother cells with chromosome aberrations were 15.2% and 39.8%, respectively. Changes in morphology and mutant were also observed in the plants derived from exposed seeds. Received: 10 April 2000 / Accepted: 10 October 2000     

Induction of chromosome aberrations in cultured human lymphocytes treated with ethoxyquin

The chromosomal aberration test was employed to investigate the effect in vitro of a known antioxidant and food preservative, ethoxyquin (EQ, 1,2-dihydro-6-ethoxy-2,2,4-trimethylquinoline) on human chromosomes. The studies were undertaken because there are no published in vitro data on genotoxicity of EQ in mammalian cells and there are many reports pointing out that it may be harmful to animals and human beings. Lymphocytes obtained from three healthy donors were incubated with EQ (0.01-0.5mM) both with and without metabolic activation. Stability studies performed by HPLC analysis showed that EQ was stable under the conditions of the lymphocyte cultures. The results of the chromosome aberration assay showed that EQ induces chromosome aberrations: gaps and breaks as well as dicentrics and atypical translocation chromosomes.     

Chromosomal aberrations and deoxyribonucleic acid single-strand breaks in adipose-derived stem cells during long-term expansion in vitro

Background aimsAdipose-derived stem cells (ASCs) are a promising mesenchymal cell source for tissue engineering approaches. To obtain an adequate cell amount, in vitro expansion of the cells may be required in some cases. To monitor potential contraindications for therapeutic applications in humans, DNA strand breaks and chromosomal aberrations in ASCs during in vitro expansion were examined.MethodsAfter isolation of ASC from human lipoaspirates of seven patients, in vitro expansion over 10 passages was performed. Cells from passages 1, 2, 3, 5 and 10 were used for the alkaline single-cell microgel electrophoresis (comet) assay to detect DNA single-strand breaks and alkali labile as well as incomplete excision repair sites. Chromosomal changes were examined by means of the chromosomal aberration test.ResultsDuring in vitro expansion, ASC showed no DNA single-strand breaks in the comet assay. With the chromosomal aberration test, however, a significant increase in chromosomal aberrations were detected.ConclusionsThe study showed that although no DNA fragmentation could be determined, the safety of ASC cannot be ensured with respect to chromosome stability during in vitro expansion. Thus, reliable analyses for detecting ASC populations, which accumulate chromosomal aberrations or even undergo malignant transformation during extensive in vitro expansion, must be implemented as part of the safety evaluation of these cells for stem cell–based therapy.     

入侵植物香丝草水浸提液对蚕豆和玉米根尖染色体行为的影响

以采自农田中自然生长的植物群落中的香丝草为供体,以典型的双子叶植物蚕豆和典型的单子叶植物玉米的幼苗为受体,运用根尖微核试验和染色体畸变试验,研究了香丝草的根、茎、叶和幼果4种器官水浸提液对受体的遗传毒性。结果表明:(1)在香丝草不同器官水浸提液作用下,蚕豆和玉米根尖细胞的有丝分裂各时期均受到明显影响,细胞中出现了微核、染色体桥、染色体断片、染色体环、染色体粘连及染色体滞后等多种染色体畸变。(2)香丝草各器官水浸提液对蚕豆幼苗根尖细胞分裂的抑制作用明显大于玉米。(3)香丝草各器官水浸提液对蚕豆和玉米幼苗根尖的染色体畸变诱导存在显著的浓度效应,即水浸提液浓度越高,受体的微核率和畸变率越高,相应的有丝分裂指数越低,水浸提液的诱导作用与浓度呈正相关关系,但不是简单的加和作用。(4)香丝草各器官水浸提液均具有较强的遗传毒性,但整体化感效应表现为叶＞幼果＞茎＞根,即叶片产生的化感作用最强。因此,香丝草分泌的化感物质可能通过对受体植物生长点的细胞有丝分裂和细胞形态产生影响,造成受体植物染色体的多种畸变和不可逆的遗传损伤,从而成功入侵新的栖息地。     

Artificial ageing of Vicia faba L. seeds caused by prolongation of G-1 phase

Broad bean (Vicia faba L. “Inovec”) seeds were artificially aged by means of storage at 30 %, resp. 25 % water content at 25 °C for 7-days to study the consequences on germination, root length and frequency of chromosomal aberrations. Under these conditions, significant changes in all parameters were observed. An increase of frequency of chromosomal aberrations in ana-telophase cells was confirmed by evaluation of c-metaphase cells. Synergic effect of artificial seed ageing was studied on different harvests of old seeds. Possible principles of this effect on cell level are discussed.     

Nonhomologous DNA end rejoining in chromosomal aberration formation

The role of recombination of nonhomologous DNA ends in chromosomal aberration formation was investigated in Chinese hamster ovary cells. Restriction enzymes that produce blunt, 3′ overhanging, or 5′ overhanging DNA double-strand breaks were electroporated into cells in various combinations, and chromosomal aberrations were analyzed at metaphase. For all enzyme combinations tested, there was a significant increase in the frequency of aberrations whose formation requires two breaks in the DNA over the sum obtained when each of the enzymes was tested separately and the aberration frequencies were totaled. No such pattern existed for terminal deletions, which presumably require only one DNA break. The extent of interaction did not depend on the homology in the overhanging sequences or on the combination of ends used, although the largest effect was seen with a combination of two blunt ends. This study shows that nonhomologous DNA double-strand breaks can interact to increase chromosomal aberration formation significantly.     

Characterization of Some Chromosomal Aberrations in Regenerated Rice Plants (<Emphasis Type="Italic">Oryza sativa</Emphasis>)

Somaclonal variation was studied in two Iranian land races of O. sativa spp. japonica var Hassani and O. sativa spp. indica var Sadridomsiah and 2000 plants of each cultivar were cytogenetically examined in two steps. In the first step, chromosome counts of root tips was used to detect ploidy levels and aneuploids of regenerated plants. In the second step, chromosomal aberrations were characterized by pachytene analysis of PMC’s. Ploidy levels were seen between n and 4n (haploids to tetraploids) in both cultivars with diploid resource (2n = 2x = 24). The total rate of variation for Hassani (japonica) was 13.7% including 10.8% for changes in chromosome number (ploidy levels and aneuploids) and 2.9% for chromosomal aberrations such as deficiency. A total rate of variation for Sadridomsiah (indica) was 15.6% including 12.4% for change in numbers and 3.2% for aberrations in construction. Most of important cytological mutations were observed in various chromosomes among regenerated plants of cultivars. Neither nullisomics nor inversions were distinguished in any samples.     

Chromosomal instability in an oxygen-tolerant variant of Chinese hamster ovary cells

Background levels of chromosomal aberrations and sister-chromatid exchanges (SCEs) were determined in CHO-99 cells, an oxygen-tolerant variant substrain of Chinese hamster ovary (CHO-20) cells capable of stable proliferation under an atmosphere of 99% O2/1% CO2, a level of hyperoxia at which cultured mammalian cells normally cannot survive. The mean chromosomal aberration frequency in CHO-99 cells was as high as 1 aberration per cell (mainly chromatid and chromosome gaps and breaks) versus 0.05 aberration/cell in CHO-20 cells, while the SCE frequency was 1.7- to 2.1-fold increased. While most aberrations were apparently distributed at random over the chromosomes, up to 31% of the aberrations appeared to be involved in site-specific fragility at a homologous site in chromosomes Z3 and Z4. Immediately upon shifting CHO-99 cells to air-equilibrated conditions their SCE frequency decreased to the control level, whereas the aberration rate persisted at a still elevated level of 0.16-0.31 aberration per cell, even after a culture period of 14 weeks under normoxia. This indicates that at least part of the chromosomal instability is a constitutional property of the variant cells, i.e., not directly dependent upon hyperoxic stress. In CHO-99 X CHO-20 hybrids the occurrence of chromatid-type aberrations and fragile site but not that of chromosome-type aberrations was suppressed under normoxic conditions, suggesting that chromatid-type aberrations and fragile site expression on the one hand and chromosome-type aberrations on the other hand are mediated by different constitutional defects in CHO-99 cells. No gross alterations in (deoxy)ribonucleoside triphosphate pools were detected in CHO-99 cells that could be held responsible for their chromosomal instability. In addition, no increased level of DNA damage was detected by the technique of alkaline elution. The excessive chromosomal instability in CHO-99 cells, as observed under hyperoxic conditions, may originate from reactive intermediates giving rise to DNA double-strand breaks and/or a type of DNA lesion that is resistant to the conditions of the alkaline elution technique. However, alternative mechanisms based upon reactive species interfering with DNA replication/repair processes cannot be excluded.     

Effect of LSD on mitotic and meiotic plant chromosomes

LSD was found to induce chromosomal aberrations in root tip cells of Allium cepa, Hordeum vulgare and Secale cereale. Aberrations occurred in the form of chromatid and isochromatid breaks with most of these breaks failing to rejoin. The distribution of chromosome breaks was not uniform over the length of chromosomes, and a majority of the breaks were localized at the centromeric regions. For a given dose of LSD (30 g/ml), onion appeared to be more susceptible than barley or rye. The diploid and tetraploid rye used in the study showed no appreciable difference in sensitivity to LSD treatment. — A preliminary study on meiotic chromosomes in LSD-treated diploid rye revealed the presence of univalents, chromosome breaks and fragments, suggesting that LSD can induce meiotic abnormalities in plant material.Contribution from the Department of Agronomy, University of Kentucky. The investigation reported in this paper (73-3-75) is in connection with a project of the Kentucky Agricultural Experiment Station and is published with the approval of the Director.