The potential induction of the chromosomic aberration of water samples from Santa Maria da Vitória River was evaluated by the Allium cepa test-system. This river supplies approximately 30% of the Grande Vitória region with water. The main environmental impact on this river are from domestic effluents from the municipal districts and agrotoxic contaminations. Water samples were collected in 5 sites in the rainy season (March—high temperatures) and in the dry season (August—low temperatures) of 2006, and 2 treatments—acute and chronic—were performed. The chromosomic aberration index was significantly higher in 2 sites of this river and also in the rainy season compared with the dry season. This genotoxic effect may be related to agricultural influence and to domestic effluents that occur close to these 2 sites and to the presence of fertilizers, pesticides and iron oxide from the basin soils that are leached out by the rain and reach the river.
The cytological study of several populations in 4 species of Cousinia tenuifolia, C. tabrisiana, C. urumiensis and C. microcephala showed the occurrence of 2n=2x=26 chromosome number in all the species studied, information which is new to science. The species formed mainly bivalents and univalents in the metaphase of meiosis I, but in some populations quadrivalents were also formed due to heterozygote translocations. A wide range of meiotic abnormalities were observed including laggard chromosome formation, chromosomes stickiness and tripolar cell formation, leading to the formation of unreduced pollen grains. The occurrence of 0–2 B-chromosomes was observed in most of the species and populations studied. Karyotype analysis showed that the chromosomes are metacentric (m) and submetacentric (sm), varying in size from 0.55 to 1.79 µm. The ANOVA test showed significant difference in total chromosome length, size of the long arm and short arm of the chromosomes as well as arm ratio of the chromosome pair numbers 1–4 and 8, indicating the role of both quantitative and structural changes of chromosome in cytological diversity of Cousinia species.
Rhoeo discolor (2n=12) exhibit a complete translocation heterozygote in which a ring of 12 chromosomes is often observed from diakinesis through metaphase-I. This was used to study the effect of colchicine on chromosome pairing during meiosis. Pachytene pairing appeared unaffected, but only 9.80% of the PMCs formed a ring of 12 chromosomes at metaphase-I of meiosis. While 16.60% of cells had a complete chain of 12, 66.20% had chain configurations of varying (2–11) number of chromosomes and 7.10% had complete univalence. Adjacent orientation was found in the majority of cells with chain complexes of 2–11 choromosomes. The result was highly disturbed post metaphase-I stages. 76% of anaphase-I and 64% of telophase-I stages were abnormal. Only 42% pollen grains were fertile and 26% pollen grains showed abnormal chromosome number at pollen mitosis. It is concluded that the presence of aberrant cells at metaphase-I is either due to colchicine induced ineffectiveness of pairing at the very small pairing region or to the failure of chiasma formation.
Every year, millions of people are added to the total number of mobile telephone users. The convenience of this device is indisputable but its safety remains inconclusive. Questions are still asked all around the world about mobile telephone safety and whether these phones pose a hazard to health. Electromagnetic waves (EMWs) are made up of linked electric and magnetic components moving together through space at the speed of light. The electric and magnetic components that form EMWs can be referred to as radiofrequency fields. The present work searched for the cytogenetic effect of EMWs emitted from mobile telephones and their relay stations. This was achieved using Micronucleated polychromatic erythrocytes (MNPCEs) and an examination of the sperm abnormality of rats. The data obtained revealed a marked increase in the frequency of micronucleated polychromatic erythrocyte cells that were taken from bone marrow cells and sperm abnormality from the testes of rats exposed for 2 weeks to electromagnetic waves emitted from global systems for mobile telephone communication base stations and mobile telephone systems. The obtained results were significant at the statistical level. In addition, the frequency of micronucleus formation was more affected in the group of rats exposed to mobile telephone systems than others and remained high in the recovery group. Also, the frequency of sperm abnormality was more sensitive in the day group of telephone base station rats than others. In the present work, the results indicated that prolonged exposure to the EMWs emitted from global systems for mobile communication base stations or cellular mobile telephone communication causes clastogenic effects at the level of MNPCEs as well as abnormally shaped sperm.
A discovery of nucleolar organizer regions (NORs) polymorphism and karyological analysis in the Smith's barb, Puntioplites proctozysron (Bleeker, 1865) from Nong Khai province, in the northeast of Thailand, were studied. Blood samples were taken from 4 male and 4 female fish. After standard whole blood lymphocytes had been cultured at 27°C for 96 hours in the presence of colchicine, metaphase spreads were performed on microscopic slides and air-dried. Conventional and Ag-NOR staining techniques were applied to stain the chromosome. The results showed that the diploid chromosomes number of P. proctozysron was 2n=50 and the fundamental numbers (NF) of both sexes were 82. The types of autosomes were 4 large metacentric, 8 large submetacentric, 2 large acrocentric, 2 large telocentric, 2 medium metacentric, 6 medium submetacentric, 10 medium acrocentric, 14 medium telocentric and 2 small telocentric chromosomes. No strange size chromosomes related to sex were observed. In addition, the short arm near telomere of chromosome pair 4 showed clearly observable nucleolar organizer regions (NORs). This is the first report on polymorphism of NORs in P. proctozysron. The result showed that a heteromorphism in 1 female had a different size of NORs of chromosome pair 4 (4a4b), while 3 females and 4 males had an equal size of both chromosome pair 4 with a homomorphism (4a4a). The karyotype formula for P. proctozysron is as follows: 2n (diploid) 50=L4m+L8sm+L2a+L2t+M2m+M6sm+M10a+M14t+S2t
Availability of basic genetic information on a plant species is the first pre-requisite in designing any genetic improvement programme for the species. This study was therefore carried out to determine the karyotype of Gongronema latifolium to obtain basic knowledge on ploidy level and karyotype as a first step in understanding the genetics of this spice plant. Karyotype and flow cytometry (FCM) studies were carried out on 4 accessions of G. latifolium collected from the humid forest vegetation in Abia, Akwa Ibom, Cross River and Imo States of Nigeria. Chromosome number of Abia accessions were 2n=20 and 22 with karyotype formulae, 3m+4sm+2a+1t and 2m+4sm+2a+3t, respectively; Akwa Ibom accessions, 2n=18 with formula: 3m+5sm+1a; Cross River accessions, 2n=18 and 22 with formulae: 2m+4sm+2a+1t and 3m+4sm+3a+1t, respectively; Imo accessions, 2x=22 and 24 with formulae: 1m+5sm+3a+2t and 2m+7sm+2a+1t, respectively. Results obtained revealed cytotype variation and the occurrence of 4 cytotypes, 2n=18, 20, 22 and 24. We therefore conclude that G. latifolium is a diploid species with variable basic numbers. Four basic numbers, n=9, 10, 11 and 12, were therefore proposed for G. latifolium. FCM showed the presence of 2C and 4C DNA content and provided evidence for endoreduplication, a likely evolutionary survival mechanism in this climbing vegetable plant species. This is the first report of karyotype analysis in Gongronema latifolium, an important indigenous African vegetable spice plant with huge medicinal value.
A first karyotype analysis and chromosomal characteristic of nucleolar organizer regions (NORs) of the common sheathfish, Micronema apogon (Bleeker 1985), from the Chao Praya, Chi, and Song karm basins (3 populations), Thailand, were studied. Kidney cell samples were taken from 10 male and 10 female fish. The mitotic chromosome preparations were conducted by taken directly from kidney, spleen and/or gill cells. Conventional and Ag-NOR staining techniques were applied to stain the chromosomes. The results showed that diploid chromosomes number of M. apogon was 2n=64, and the fundamental numbers (NF) were 108 in both sexes. The chromosome types consist of 10 large metacentric, 12 large submetacentric, 4 large acrocentric, 2 large telocentric, 8 medium metacentric, 8 medium submetacentric, 2 medium acrocentric, 8 medium telocentric and 10 small telocentric chromosomes. No strange size chromosomes related to sex were observed. In chromosome pair 3, the region adjacent to the telomere of the short arm showed clearly observable secondary constriction/NORs. The karyotype formula for M. apogon could be deduced as: 2n (diploid) 64=L10m+L12sm+L4a+L2t+M8m+M8sm+M2a+M8t+S10t
In plants, the prokaryote-derived chloroplast division protein FtsZ is divided into the FtsZ1 and FtsZ2 families. To clarify the relationship between FtsZ1 and FtsZ2 expression and chloroplast division in the unicellular green alga Nannochloris bacillaris, we compared FtsZ1 and FtsZ2 expression in alga cultured in 2 nutritionally different media. Cells grown in a rich medium had 1 FtsZ ring throughout the cell division cycle, whereas cells in an inorganic medium showed only 1 FtsZ ring during the chloroplast division phase. Both FtsZ1 and FtsZ2 mRNA levels in the rich medium were higher than those in the inorganic medium. However, a much larger difference in the amount of transcripts between cells cultured in the rich and in the inorganic media was observed in FtsZ2 than that in FtsZ1, suggesting different gene regulatory mechanisms between the FtsZ genes. N. bacillaris cells cultured in inorganic medium showed cell division photoperiodicity, whereas cells cultured in organic media proliferated continuously under a light/dark cycle. Although FtsZ1 was expressed constantly throughout the chloroplast division cycle in the rich medium, the increase in FtsZ1 mRNA level was simultaneous with chloroplast division under a light/dark cycle in the inorganic medium. FtsZ2 was expressed constantly in both media. The control of chloroplast division by regulating FtsZ ring formation is discussed.
Erinocarpus Nimmo ex J. Graham a monotypic endemic genus from Western Ghats represented by E. nimmonii J. Graham is distributed in central and northern Western Ghats. The present paper describes the distribution, meiotic count, mitotic count and karyotype analysis of the genus. The somatic chromosome number (2n)=48 and meiotic chromosome number (n)=24 are reported for the first time. The karyotype is of 2A Stebbins category of asymmetry and the karyotype formula is categorised as 2n=48=20m+28sm (2 SAT).
Cells of land plants contain several kinds of plastids such as chloroplasts, etioplasts, proplastids, leucoplasts, and amyloplasts. Among them, the chloroplast, the most well characterized type of plastid, relies on expression of plastid-encoded photosynthetic genes. The genome of plastids encodes many photosynthetic genes that are mainly transcribed by the plastid-encoded plastid RNA polymerase (PEP). Transcriptional activity of PEP is controlled by nuclear-encoded sigma factors that are important for transcription initiation and promoter selectivity. Arabidopsis thaliana possesses 6 sigma factor genes, SIG1 to 6. Here, we analyzed the function of SIG6, a gene related to chloroplast differentiation. The null mutant (sig6-1) of the SIG6 gene exhibited a pale green phenotype in the cotyledons and in the basal part of emerging true leaves at early stages of development. Interestingly, as leaves matured, the color of cotyledons and true leaves changed to green. In the wild-type and sig6-1 mutant, plastids visualized by green fluorescent protein (GFP) were observed under the epifluorescence microscope. In cotyledons of 3-day-old seedlings, chloroplasts of the sig6-1 mutant showed small and irregular morphology compared with that of the wild-type chloroplasts. However, amyloplasts and leucoplasts in root tissues showed no obvious differences between the wild-type and the sig6-1 mutant. These results suggest that SIG6 plays a key role during the early stages of chloroplast differentiation, but not in differentiation into other types of plastids such as leucoplasts and amyloplasts.
2B chromosomes are reported here in Papaver somniferum L., cultivar Vivek, which had previously not been reported. The present piece of work investigates the influence of B-chromosomes on the genetic system of the plant and it proposes that variations are present not only between carrier and non-carrier plants but also between carrier and non-carrier pollen mother cells (PMCs) of the carrier plants. Morphologically B and non B carrier plants were indistinguishable but they showed a significant effect on the endophenotype of the plant without depriving it of its vigor. The study deals with a brief investigation on the genomic behavior of B-chromosomes and their influence on A-chromosome's chiasma frequency and pollen fertility. In comparison to non-carrier plants, an increase in chiasma frequency with mild reduction in fertility has also been observed in B-carrier plants. With regard to earlier investigations, the possible mechanism of action of B-chromosomes has been discussed. Owing to their particular properties, B-chromosomes might be used to elucidate wider issues of genome organization and evolution in plants and make sense of them.
Heracleum lanatum Michx. also known as Cow parsnip, is an important medicinal plant belonging to the family Apiaceae. At present, chromosome number and meiotic behavior analysis has been carried out in 6 wild populations of Heracleum lanatum from different study areas such as Keylong, Udaipur, Trilokinath, Batal, Losar and Kaza of Lahaul & Spiti (Cold Desert) region of the North Indian higher altitude Himalayas. Morphologically, all these populations do not show any noticeable differences. All the presently worked out populations are diploid (2n=22) showing a base number of x=11. The meiotic course in all the populations is found to be abnormal, beside with normal bivalents, stickiness of bivalents, presence of bridges and laggards during anaphases and telophases, cytomixis involving more than 2 PMCs at A-I, A-II, T-I and T-II. The chromatin transfer phenomenon among the pollen mother cells (PMCs) in 6 populations caused various meiotic abnormalities. Hence this phenomenon of cytomixis seems to be directly under genetic control and it affects the meiotic course and is directly responsible for abnormal meiotic behavior. Besides abnormal meiotic course the microsporogenesis was found to be normal. No significant correlation was found between cytomixis and pollen fertility, however some cytomictic plants showed low values with 79.56–89.40% of pollen fertility.
To infer genome structures and chromosome differentiations with karyomorphological changing among these 3 Drosera species, we applied base-specific fluorescent staining with GC-rich specific chromomycin A3 (CMA) and AT-rich specific 4′,6-diamidino-2-phenylindole (DAPI), fluorescent in situ hybridization (FISH) with 45S rDNA, and genomic in situ hybridization (GISH) with 2 parental genomic probes of D. rotundifolia (2n=20) and D. spatulata (2n=40) to somatic metaphase chromosomes of D. tokaiensis (2n=60). The chromosome ploidies in somatic cells were diploid in D. rotundifolia, tetraploid in D. spatulata, and hexaploid in D. tokaiensis. All 20 chromosomes of D. rotundifolia were middle size, while all 40 chromosomes of D. spatulata were small size. Drosera tokaiensis showed a bimodal karyotype which had 20 middle-sized chromosomes and 40 small-sized chromosomes. In base-specific fluorescent staining, satellites stained with CMA positive and DAPI negative were observed at one end of 1 pair of small sized chromosomes in D. spatulata and D. tokaiensis, but not in D. rotundifolia. The FISH results showed that the 45S rDNA signals of all species were located at chromosome ends or satellites. Two major signals for the 45S rDNAs were observed in D. rotundifolia, while 2 major signals and 2 minor signals were detected in both D. spatulata and D. tokaiensis. Dual simultaneous GISH showed the sufficient demonstration to discriminate parental genomes in D. tokaiensis.
Cotton is cultivated in Iran with diploid and tetraploid forms and hybridization is a means to increase the genetic diversity and obtain new elite cultivars in this crop. The present study considers cytogenetic study of the Mehr (Gossypium hirsutum) cotton cultivar and its crossing progenies. The cultivars showed bivalents, univalents and quadrivalents in metaphase of meiosis I. They differed significantly in mean values of chiasmata formation and chromosome pairing due to genetic difference. Different types of meiotic abnormalities like chromosome stickiness, laggard formation, micronucleus, tripolar and multipolar cell formation, cytomixis and unreduced pollen grain formation occurred in the parental genotypes and their hybrids. Grouping of the cultivars based on cytogenetic features showed the effect of parental genotypes on the meiotic behavior of their crossing progenies.
Delphinium malabaricum (Huth) Munz. and its variety D. malabaricum var. ghaticum Billore (Ranunculaceae) were cytologically examined. Both taxa were found to possess 2n=16 diploid chromosome number. The 8 pairs of homologous chromosomes were characterized into 1 metacentric, 1 submetacentric and 6 subtelocentric chromosomes. The total length of diploid complements and range of chromosome length were more or less the same in the species and its variety. The length of metaphase chromosomes ranged from 1.42 to 5.35 μm in D. malabaricum var. malabaricum and from 1.77 to 5.30 μm in D. malabaricum var. ghaticum with an average length of 2.88 μm and 2.92 μm, respectively. The total chromosome length (TCL) of the former was 23.05 μm and that of the latter was 23.38 μm. The prevalence of chromosomes with subtelocentric centromeres indicated a tendency towards asymmetric karyotype, which revealed an advanced feature. Hence both the taxa belong to Stebbins's 2B type karyotypic symmetry class. The results revealed that D. malabaricum var. malabaricum and D. malabaricum var. ghaticum have a similar karyotype pattern, despite differing morphologically. Thus, it may be concluded that the external morphological variation occurred independently of the chromosomal variation, which may have played a prominent role in the intraspecific differentiation of D. malabaricum.