The regeneration and cytogenetic analysis of 7 cassava (Manihot esculenta Crantz) cultivars obtained by organogenesis and somatic embryogenesis were investigated. In the first phase, callus formation was induced in young leaves using MS medium supplemented with 1.0, 5.0, 10.0, 15.0 and 20.0 mg/l of 2, 4-D or without a growth regulator (control). In the second phase (development), the calli obtained in the above treatments were transferred to MS medium supplemented with factorial combinations of GA3 and BAP at 0, 0.5, 1.0, 1.5 and 2.0 mg/l. Results of the first phase showed that 2, 4-D induced the formation of both friable and compact calli. The compact calli displayed root and shoot formation, whilst somatic embryos were obtained only from friable calli in the medium with 1.0 mg/l GA3. Plants obtained from somatic embryos were regenerated in MS medium supplemented with 0.04 mg/l BAP, 0.02 mg/l NAA and 0.05 mg/l GA3. Cytogenetic analysis in 167 regenerated plants from somatic embryogenesis and 176 from organogenesis showed 2n=36 as a normal diploid chromosome number.
Thymus kotschyanus and Thymus pubescence are 2 vast spreaded species of Thyme, growing all around the country in Iran. This study has characterized karyotypes of 4 populations of T. kotschyanus and 3 populations of T. pubescence all collected from their natural habitats. In other words, 2 ploidy levels were observed within the species and their chromosomes were mainly of m and the rest of sm type. Therefore, 2 data groups were formed for the 2 ploidy levels. Factorial analysis of variance was carried out on the data groups in completely randomized design model, regarding the populations and chromosomes of each group as the 2 factors. Total form percentage (TF%), and several other parameters were estimated to compare the karyotypes of the populations and the species. Analysis of variance presented significant differences between the diploid and tetraploid populations and their chromosomes, based on the data recorded on the karyotypes of the populations. Size of the chromosomes among the diploid populations of T. kotschyanus species varied from 0.92 to 2.06 μm. Chromosome length of the only diploid population of T. pubescence species varied from 1.05 to 2.32 μm. Within the 2 tetraploid populations of T. pubescence species the size of the chromosomes varied from 0.83 to 1.88 μm. Chromosome length of the only tetraploid population of T. kotschyanus species varied from 0.91 to 1.66 μm. In fact all of the chromosomes of the 2 species are very small in size. In average the chromosomes of tetraploid populations are smaller than the chromosomes of diploid populations.
In this work we analyzed the in situ restriction endonucleases digestion on the nucleolar organizer region, NOR, localized in C chromosomes of Bradysia hygida. Neuroblast chromosomes in situ digestion with PstI revealed evident chromatin extraction at the NOR region on both homologous C chromosomes, while the digestion with EcoRI or HindIII removed only one of the C chromosomes NOR chromatin. The same results were observed when in situ digestion with HindIII+PstI and HindIII+EcoRI were processed. These data are correlated with the fragments size by hybridization of purified genomic DNA with Rhynchosciara americana rDNA. The cleavage with EcoRI or PstI produced fragments of high molecular weight, while the single digestion with HindIII and combined with EcoRI or PstI only showed fragments of low molecular weight. In conclusion, no correlation between the size of the fragment and the in situ digestion was observed. The accessibility of the enzyme at the NOR site can be facilitated when the chromatin is an open state and the region presents transcriptional activity, allowing the digestion and removal of the chromatin out of the chromosome.
Cytogenetic studies carried out on the tetraploid (2n=4x=36) accession of Brachiaria decumbens (BRA007722) revealed an unusual pattern of the nucleolar cycle during microsporogenesis. Nucleolus behavior was normal during prophase and disappeared at the end of diakinesis. After dissolution, it was fractioned into multiple micronucleoli of different sizes at metaphase which persisted during early anaphase. Some entered in a fusion process in late anaphase: they reduced their number and increased in size. Since fusion process continued throughout the cycle, in late telophase all were rejoined into a unique nucleolus in the sister nuclei. They persisted in this condition until the end of prophase II and then disappeared once more. Such nucleolar behavior was also reported in the second division, while at the end of the meiotic process tetrads had 4 microspores with a normal nucleolus. Pollen viability was not affected by this anomalous nucleolar cycle behavior. A mutation affecting some steps of the nucleolar cycle has been suggested.
The internal transcribed spacer (ITS) regions of nuclear ribosomal DNA in Iris ensata and I. germanica were sequenced to design the species-specific primers, which allowed us to identify their hybrids by PCR amplification. In 17 plants obtained through protoplast fusion between I. ensata and I. germanica, their hybridity was tested by this method, and 12 plants among these plants had 2 bands specific to parental species. Therefore, these plants were identified as somatic hybrids between I. ensata and I. germanica.
The present investigation has been conducted to study the mutagenic effect of the 2 biofertilizers Rhizobacterien and Phosphoren on mitotic division in root tips of Vicia faba, addition to the cell image was used to estimate and analyze the gray values of these cells. The 2 applied biofertilizers induced a significant and/or highly significant increase in mitotic activity. Proliferation activity was activated with the increase of the biofertilizers treatments. Moreover, the percentage of cells having 2C-DNA content (G0/G1) decreased than those of control, while the percentage of the cells 3C (S phase) and 4C (G2, M) increased than control at cell image analysis. On the other hand, the biofertilizers induced several chromosomal aberrations in mitotic cells.
The purpose of this microscopic histochemical study was to establish the developmental sequence leading to sterility in a cytoplasmic male sterile Helianthus petiolaris line. Histochemical studies showed that CMS anthers, in contrast to fertile anthers, lacked carbohydrate storage at sporogenous stage. CMS sporogenous cells were thick-walled and ascorbic acid-rich. Subsequent developmental pattern was not uniform in CMS anthers. The variations were found in different anthers and in different locules of the same anther. Two categories of CMS anthers lacked callose deposition and showed premature disintegration of tapetal cell layer, which lead to precocious formation of periplasmodium. In one type, CMS anthers contained naked microspores. In another type, coenocytic microspores were formed. The microspores lacked reserve metabolites. In the third category of CMS anthers normal callose deposition and tetrad formation were observed. In this category callose deposition and hypertrophied tapetal cell layer persisted until mature stage of the anther. Results in all 3 categories of CMS anthers link tapetal abnormality to male sterility.
The karyotype of Chymomyza rufithorax, a species belonging to the procnemis species group of the genus Cymomyza (Diptera, Drosophilidae), is the fundamental one of Cymomyza species, consisting of a pair of rods with a proximal constriction (X chromosome), 2 pairs of large metacentric chromosomes, and a pair of dots. In males of this species, the X chromosome does not have a synaptic mate, and the chromosome number is 7. Therefore the male of this species belongs to the “XO” type, which has been reported for only 3 species in the genus Chymomyza. Meiotic chromosome configurations of the “XO” type males from C. rufithorax and C. obscuroides and the XY males from C. pararufithorax and C. costata were described. XY pairing was found in the XY males, but an X chromosome univalent was observed in the “XO” type males. Meiotic pairing configurations of other autosomes in the “XO” males were found to be similar to those in XY males. These data suggest that the Y chromosome or its pairing site might have degenerated or been eliminated from the genome during the course of speciation.
Gamma irradiations (5, 10, 20 kR) to Nigella sativa L. (black cumin) seeds (moisture content 7.5%) induced 5 translocation heterozygotes (P-14 and P-26 from 5 kR and P-32, P-36 and P-37 from 10 kR). P-14, P-32 and P-36 were viable translocations; while, P-26 and P-37 yielded only abortive seeds at R1 following selfing and on open or controlled pollination. The translocation heterozygotes exhibited the formation of either a ring or a chain of 4 chromosomes in 38.71% to 77.72% meiocytes. Predominance of rings occurred in all translocation heterozygotes excepting P-26 where rings and chains were nearly equal. P-14 and P-26 had more adjacent orientation of quadrivalents than alternate; while, P-32, P-36 and P-37 demonstrated random orientations. The quadrivalent behaviour was found to be persistent in all generations of P-14, P-32 and P-36. The rings showed preponderance of adjacent orientation and the chains demonstrated frequent alternate orientation. Though normal 6/6 separation of chromosomes at AI was observed in 85.8, 83.3, 69.4, 82.3 and 86.4% cells of P-14, P-26, P-32, P-36 and P-37 respectively, pollen fertility was reduced in the heterozygotes (8.2 to 37.5%). F1’s raised from intercrossing of P-14, P-32 and P-36 were meiotically assessed and the results indicated that same 2 non-homologous chromosomes were involved in translocation and the 2 longest chromosome pairs AA and BB (nucleolar pair) were suggested to be associated. P-14, P-32 and P-36 had marker phenotypic traits and characteristically P-36 possessed non-shattering capsule trait.
Fifteen specimens of Bryconamericus aff. exodon collected from Três Bocas stream, basin of the Tibagi river (PR, Brazil), were analysed cytogenetically. The diploid number of 52 chromosomes was observed and the presence of 2 cytotypes, with variations in the karyotypic formulae. Cytotype I presented 16M+12SM+6ST+18A and fundamental number (FN) of 86 and cytotype II 10M+24SM+6ST+12A and fundamental number (FN) of 92. A size heteromorphism was detected in cytotype II in the first pair of metacentric chromosomes in some individuals. These variations may be related to chromosomal rearrangements, such as pericentric inversions, that played an important role in the karyotypic evolution of this group of fish.
Genome relations among 3 octaploid species of Sesamum namely S. radiatum, S. occidentale and S. schinzianum were analyzed. These 3 African wild species exhibited normal 32 bivalents at diakinesis and metaphase-I and showed high degree of pollen fertility and seed set. In S. radiatum×S. occidentale F1 hybrids, mean chromosome pairing of 0.81I+31.6II per cell was found. About 86% of the pollen mother cells revealed 32 bivalents formation. This suggests that genomes of S. radiatum and S. occidentale are similar and homologous. Both these parental species are morphologically similar. F1 and F2 progenies are highly fertile. Based on these evidences it is proposed that S. occidentale be treated as a variety of S. radiatum. Mean chromosome pairing of 0.154I+31.79II+0.11IV per cell was found in S. radiatum×S. schinzianum hybrid. About 92% of the PMCs revealed 32 bivalents. This pairing behaviour indicates that genomes of S. radiatum and S. schinzianum are similar and homologous. These 2 species have diverged and differentiated by 2 translocations as evident from 2 quadrivalent formation in the hybrid. It is proposed that S. radiatum and S. schinzianum have descended from a common ancestral octaploid species. Isolating barriers preventing gene flow between species in nature is discussed.
Chromotoxic effects of artificial yellow dye, used by grocer for colouring yellow pulses has been studied on root mitosis of Allium cepa. Root tips were treated with 3 concentrations (100, 200, 400 ppm) for 1, 2, 4 h. The dye inhibited cell division and there was decline in the mitotic index with the increase in dye concentration and duration of treatment. Dye induced a wide range of mitotic abnormalities like changed nuclear morphology, nuclear death, perforation, micronuclei, fragment, bridges, nuclear bursting, giant cell, polyploidy etc. Use of such artificial dye for colouring the consumables warrants serious consideration.
Since extracts of the fruits of Solanum melongena are rich in flavonoids with a hypolipidemic effect, and because this fruit is widely consumed in Brazil and several others countries, we evaluated the possible genotoxic and cytotoxic activities of a S. melongena extract as well as its possible antigenotoxic effect on peripheral blood reticulocytes and bone marrow cells of Wistar rats. The animals were treated by gavage with 3 concentrations of the extract (25%, 50%, 80% of the LD50 (3 g/kg)) for genotoxic evaluation, and with 50% of the LD50 of the extract+cyclophosphamide for an evaluation of the antigenotoxic potential, for 5 consecutive days. Peripheral blood was collected at 0 h, 48 h, 120 h. The animals were submitted to euthanasia 24 h after the last treatment for chromosome preparations. There was no statistically significant difference in mean micronucleated reticulocytes (MNRETs) or mean number of chromosomal aberrations obtained at the 3 concentrations tested compared with negative control. The same was observed when the antigenotoxic was compared with positive control alone. No significant decrease in mitotic index (MI) was observed for all concentrations of the extract. These findings suggest that the extract of S. melongena, has no genotoxic and cytotoxic effect, and does not protect against cyclophosphamide clastogenicity in Wistar rat cells.
Mitochondrial nucleoids (mt-nucleoids) were isolated from 6 species of yeasts that belong to Saccharomyces cerevisiae, S. dairenensis, S. kluyveri, S. servazzii, S. exiguus, and Arxiozyma telluris. Each fraction during the mt-nucleoid isolation was analyzed for the detection of Abf2p-like DNA-binding protein and mitochondrial nuclease by SDS-DNA PAGE. This method revealed that the unique Abf2p-like protein, which ranges in molecular mass from 18—21 kDa, is associated with each mt-nucleoid fraction isolated from 6 yeasts. The appearance of nuclease activity on SDS-DNA gels significantly differed depending on the yeasts tested, and the nuclease activity in the mitochondrial fraction was detected in only 2 species of yeasts, S. kluyveri and A. telluris. In contrast, the nuclease activity was detected in the mt-nucleoid fraction, but not the mitochondrial fraction, of S. cerevisiae and S. exiguus. The zymographic assay on SDS-DNA gels showed that the mitochondrial nuclease from S. kluyveri and A. telluris was activated by Mn2+, Mg2+, Ca2+, but not by Zn2+. The effects of Co2+ on the mitochondrial nuclease activity differed between the 2 yeasts.
We studied the effects of the β-lactam antibiotic ampicillin on the morphology and number per cell of chloroplasts using cells of the liverwort Marchantia polymorpha in suspension culture. Cells in suspension culture without ampicillin contained a mean±SD of 20.6±9.5 chloroplasts. Those in culture with ampicillin showed a decrease in chloroplast number, reaching 7.5±6.5 after 14 d of treatment. Ampicillin-treated cells contained very large chloroplasts. Following removal of ampicillin on day 6, the chloroplast number recovered to that in untreated controls 8 d after removal. These results demonstrated inhibition of chloroplast division by this β-lactam antibiotic, suggesting that the bacterial peptidoglycan-related system has been conserved in the chloroplasts of liverwort.
Spalangia endius, a pupal parasitoid of tephritid flies, has a karyotype of n=4, the lowest haploid chromosome number ever recorded for a pteromalid. This was determined by examining mitotic cells of the neuroganglia of male pupae. A diploid chromosome number (2n)=8 was also determined from the neuroganglia of female pupae. The diploid mitotic karyotype is comprised of 4 metacentric chromosome pairs.
Ten-day-old Pelargonium zonale embryos were fixed in formaldehyde and embedded in Technovit 7100 resin. Sections were cut to a thickness of 0.6 μm and stained with 1 μg/ml DAPI. The samples were observed by epifluorescence microscopy using 365-nm excitation and by confocal laser scanning (CLS) microscopy using 405-nm excitation. The mitochondrial and plastid nuclei (nucleoids, DNA and protein complex) were visualized more clearly by CLS microscopy than by traditional fluorescence microscopy.
In order to study of intraspecific karyotype divergence in Ae. triuncialis, 13 populations of this species that were collected from Northwest regions of Iran were studied using squash technique. Chromosome number in all populations was 2n=28, but karyological characters such as total length of chromosomes, chromosome arm ratio, number and length of satellites, karyotype formulae and symmetrical indexes showed high variation. All results indicate presence of high genetic variation among the populations of Ae. triuncialis species. This variation can be useful in breeding programs of polyploid wheats and to broaden the genetic variability of the gene pool.