Image cytometric measurements demonstrated a dose-dependent effect of aflatoxin B2 (AFB2) treatments on the components of mitotic cell cycle in Vicia faba L. root meristematic cells. The most evident effect appears to be the accumulation of cells in the G0/G1 phase at the expense of other phases of the cycle (S phase, G2 phase, M phase). These results indicate that this toxin acts as an inhibitor of cell cycle progression at the G1 transition point. In addition, a dose-dependent increase in a fraction of cells having <2C DNA and >4C DNA results from the AFB2 treatments. The inhibition of mitotic activity induced by AFB2 treatments is associated with a reduction in seedling growth. Cytological examination of dividing cells revealed an abundance of dose-dependent chromosome abnormalities produced by the applied treatments of AFB2. Chromosomal abnormalities associated with stickiness of chromosomes or due to an action on the mitotic apparatus are the dominant abnormalities induced by this toxin. Some of these abnormalities, particularly chromosome lagging and multipolar ana-telophase configurations, may account for the formation of cells with <the 2C DNA value or more >4C DNA value. However, true clastogenic chromosomal aberrations including chromosome breaks and ring chromosomes at metaphase and chromosomal bridges at ana-telophase were scored in substantial proportion of cells. The induction of whole chromosome breaks at metaphase is congruent with the indication by the cytometric measurements that AFB2 acts on the G, transition point. The capacity of this toxin to induce clastogenic aberrations may be regarded as an indication of its genotoxic potential. This is also indicated by the formation of micronuclei in interphase cells.
A comparison of cytological characters of the selected species of Calyceraceae (Acicarpha) and Dipsacaceae (Dipsacus, Scabiosa) is given, including chromosome numbers, condensing behavior at prophase and description of interphase nuclei. The results corroborate the isolation of Calyceraceae from the Dipsacales s.str. The cytological data are discussed with respect to previous morphological and molecular results. Karyotype description and banding patterns (C-banding and fiuorochromes) are described here for the first time for the genus Acicarpha.
Seeds of Capsicum annuum L. var. G-4 Bhagyalakshmi were subjected to 15, 25, 35 kR doses of gamma ray, and 0.8% and 1% ethyl methane sulphonate (EMS). Effects of mutagenic treatments of meiosis viz. chromosomal anamolies, pollen sterility, seed sterility and survival percentage in M2 generation have been reported. EMS was found more effective in inducing meiotic irregularities than gamma ray treatment. A dose dependent increase in meiotic anomalies was obtained with all the mutagenic treatments.
The somatic chromosome number and karyomorphological details were investigated in two tree legumes : Albizzia procera and A. chinensis. Somatic chromosome number was 26 in both the species with common symmetric karyotype formula A2 B14 C10. Karyological similarities indicate a close relationship between these two taxa. Significant biochemical difference of soluble seed protein content was recorded. Analysis of the soluble seed protein profile through SDS-PAGE (12%) technique clearly exhibited differences in their protein bands between the two species. The characteristic common protein banding pattern both in number (6) and their molecular weights (kDa) also reflected homology between the taxa. The present study on seed protein analysis was found to be useful in demarcation of genetic diversity between the two species of Albizzia which otherwise showed very close in their karyomorphological detail.
Karyotype analysis including determination of somatic chromosome number, chromosome length and volume, 4C DNA content and Interphase Chromosome Volume (INV) were carried out in Astrophytum asterias, A. capricorne, A. myriostigma var. nudum and A. ornatum of the family Cactaceae. Somatic chromosome number was 2n=22 in each of the studied species. Karyotype analysis showed minute structural alterations in the chromosomes. Total chromosome length varied from 56.65 μM in A. myriostigma cv. nudum to 60.76 μM in A. ornatum and the chromosome volume ranged from 48.12 pM3 in A. ornatum to 66.95 μM3 in A. myriostigma var. nudum. Significant changes on the TF% suggested the formation of the median chromosomes from the sub-median types in A. asterias and A. myriostigma var. nudum that might be due to translocation of chromosomes during evolution. Significant variations in the 4C DNA content were noticed among the species which ranged from 9.23 pg in A. capricorne to 10.12 pg in A. myriostigma var. nudum. Total chromosome volume and INV showed high degree of correlation with the nuclear DNA content of the species. Interspecific variability of the nuclear DNA content might be due to the variations in the repetitive DNA sequences of the genome. The structural alterations in the chromosomes as well as loss or addition of highly repetitive sequences in the genome caused variations in the nuclear DNA at interspecific level indicating a micro-change of nuclear material during evolution.
Karyomorphology and somatic chromosomic numbers of 4 species of Lupinus were examined. The chromosome studies reveal for the first time the presence of 2n=36 chromosomes in 3 South American species (L. albescens Hook. et Am., L. paraguariensis Chodat et Hassl., L. multiflorus Desr.). For the introduced species L. arboreus Sims., 2n=48 was confirmed. The karyotype of L. albescens shows 15 m+3 sm with the satellites in the short arms of the m pair 1 and, in the long arms of the sm chromosome pair 16. L. multiflorus shows 15 m+3 sm.
Although many chromosome studies have been conduced in Anostomidae, the data are still concentrated in some genera. Other Characiformes families, such as Chilodontidae, are still cytogenetically unknown. In order to contribute to the cytogenetical knowledge on Anostomidae and Chilodontidae, the mitotic chromosomes of 3 anostomid species, Abramites solarii, Anostomus ternetzi and Pseudanos trimaculatus, and 2 chilodontids, Caenotropus labirynthicus and Chilodus punctatus, were analyzed using Giemsa staining, C-banding and nucleolus organizer region distribution detected by silver nitrate (Ag-NOR) and mithramycin (MM) staining. Although 54 biarmed chromosomes and 1 chromosome pair bearing NOR sites represent a general trait, heterochromatin distribution and NOR chromosome pair position are variable among Anostomidae and Chilodontidae species. This trend suggests that cryptic changes along the chromosome complement of these fishes have occurred, even thought the gross karyotype structure has been strongly conserved during their chromosome evolution. Furthermore, it appears to have a parallelism between morphological/ecological diversity and chromosomal evolution rate among anostomids and chilodontids.
Meiotic chromosome pairing configurations were studied in 24 accessions representing all of the 9 annual Cicer species. The diploid chromosome number was confirmed to be 2n=16 in all the studied species. Meiosis in Cicer species was characterized by a rather diffused prophase, but nonetheless it progressed normally. Precocious as well as late disjunction of the longest chromosome pair was occasionally observed giving rise to false univalents and anaphase bridge, respectively. Regular 8 bivalents were characteristically observed in all the species. Only one chromosome pair was found to be associated with the nucleous at pachynema and/or diakinesis stage in all the accessions and species, including C. reticulatum which has been reported to have 2 pairs of satellited chromosomes containing rRNA gene cluster. There was little variaiton in chiasma frequency per PMC among accessions within a species, but considerable variation among species. The mean number of rod bivalents per PMC ranged from 2.62 in C. cuneatum to 6.12 in C. echinospermum, while the number of ring bivalents per PMC ranged from 1.89 in C. echinospermum to 5.38 in C. cuneatum. Chiasma frequency per unit genome length was primarily a function of the diploid genome length and showed a negative relationship (Y =0.780-0.016X, r2 = 0.86). The role of proportion of repetitive DNA sequences, in the form of heterochromatin, present in the genome and its distribution among chromosomes of the various Cicer species genome have been speculated to explain this negative relationship.
In cultures of the sciarid Bradysia hygida Sauaia et Alves (Diptera : Sciaridae) the oviposition is asynchronous which hinders the grouping of individually collected embryo samples to be used in biochemical analysis and to correlate the data obtained with the predominant embryonic stage of this sciarid. Here we describe a Feulgen staining method that allows the staging of embryo collections of B. hygida. The analysis of Feulgen stained egg samples collected at different time intervals after oviposition (48-72, 72-96, 96-144 h) also led to preliminary information about the B. hygida embryogenesis. The blastula phase is attained 48 h after oviposition and the duration of the B. hygida embryogenesis is estimated to last between 8-10 days.
In a L. multiflorum plant regenerated from culture, the centromere of one chromosome had mis-divided to produce two telocentric chromosomes. PRINS detected telomeric repeat sequences at the 'new' chromosome ends. The two telocentric chromosomes were closely associated in some mitotic cells and at metaphase I of meiosis they formed a Robertsonian trivalent with a standard bi-brachial chromosome. There was a preference for non-convergent orientation of the trivalent but the middle (standard) chromosome of the trivalent still migrated to one of the poles in most cases. There was selection against male transmission of aneuploid gametes but the two telocentric chromosomes together were transmitted normally.
By selfing a desynaptic-SDR mutant of Rhoeo spathacea (GAVA 1.1) 123 plants were obtained, 90 of those exhibited a diploid chromosomes number, 29 resulted in diplandrogynous autotetraploids and 4 presented an hyperploid condition (2n=13, 2n=25). A sample of 10 diploid and 10 tetraploid plants was studied. In diploids, desynapsis reverts to ring-forming and 56.76% of 2884 PMC analyzed presented a ring of 12 chromosomes while the remaining PMC presented one or two chains. No more than one univalent/PMC was observed. At AI 61.95% PMC presented a 6 : 6 disjunction. Pollen fertility ranged from 0% (in a male sterile plant) to 62.90%. The male sterile mutant is the first recorded in R. spathacea and it is here identified as ms1. In diplandrogynous autotetraploid plants desynapsis was observed in 100% of 942 PMC, with 8 to 24 univalent/PMC. Twenty four univalents were observed in 37.09% of PMC analyzed and 59.9% PMC exhibited a range of 14-22 univalents/cell. At AI a 12 : 12 disjunction was observed in 37.89% of PMC. Pollen stainability of 48.02% was the observed average in tetraploid plants. These results confirm the hypothesis that in the rings observed at TI pairing occurs and therefore interchange of chromosome segments affecting the desynaptic gene is possible. As a result of this pairing at TI only diploid parts of the progeny revert desynapsis to ring-forming. Otherwise only one allele should be present.
A karyological analysis on Italian populations of 3 species, belonging to the genera Cephalanthera and Listera (Orchidaceae : Neottieae tribe) and characterized by asymmetrical karyotypes, was undertaken. Karyomorphological and C-banding data strongly suggest that in 2 species, namely C. damasonium and L. cordata, chromosomal rearrangements involving the large and medium-large chromosomes constituted the principal mechanism of chromosome evolution. This processis particularly evident in L. cordata, where karyotype evolution occurred by means of centric fission along with an increase in chromosome number and in the overall chromosomal heterochromatin content. Altogether the present observation on Italian specimens of the Neottieae corroborate previous proposals of a central role of Robertsonian rearrangements and quantitative heterochromatin varia-tion in karyotype reorganization.
The karyotype of the Persian sturgeon that occurs in the southern part of the CaspianSea (Iranian shoreline) was studied for the first time. Metaphase plates prepared in this study indicate that the chromosome number of this species in 2n=258±4. Owing to the presence of a greatnumber of microchromosomes (about half the number of the whole set) it was not possible to determine the exact number of chromosomes. The morphology of all the chromosomes was not clear due to the small size of the microchromosomes. The karyotype prepared of this species consisted of 67 pairs of meta-and submetacentric, 64 pairs of acrocentric and microchromosomes.
The polyploidization of K562 cells was examined by flowcytometry (FCM). M562 cells were polyploidized by demecolcine (colcemid) at a concentration of 81 nM. At this concentration, apoptosis was induced, as identified by a sub G1 peak in DNA histograms and by a DNA ladder in gel-electrophoresis. Staurosporine and K-252a polyploidized K562 cells without causing apoptosis, and altered the morphology from spherical to fibroblast-like. The adherency of K562 cells to dishes increased on exposure to staurosporine and K-252a, but not demecolcine. The rate of polyploidization by these drugs was almost the same. It was suggested that the mechanism of polyploidization of K562 cells was independent of the drug-induced change in adherency.
All 4 peony plants examined, Paeonia japonica Miyabe and Takeda, P. obovata Maxim., P. lactiflora Pall. cv. kumoinotsuru (Higo-peony), and P. lectiflora Pall. medical peony, had a diploid chromosome number of 2n=2x=10. Their karyotypes, also, were very similar or the sameand were constituted from 2 sets of chromosomes A to E. Nevertheless, the SAT-chromosome, hybridization signal of rRNA genes in interphase nuclei, and number of nucleolus per cell variedamong individuals and plants. The signals of rRNA genes in metaphase localized at the distal ends of homologous chromosomes A, B, D and E (8 signals) in P japonica and 2 kinds of P. lactiflora, and at the distal ends of homologous chromosomes B, D and E (6 signals) in P obovata. In conclusion, it is considered that variations in the number of satellites, signals of rRNA genes in interphase nuclei and nucleoli per cell can be attributed to the grade of interaction of rRNA genes.
Eleven species of Cyperaceae collected from central Nepal were karyomorphologically studied. Chromosome counts are reported for the first time to be 2n=42 for Carex cruciata, 2n=44 for C. cruenta, 2n=44 for C. fusiformis, 2n=44 for C. longipes var. nepalensis, 2n=44 for C. myosurus, n=14 for Isolepis setacea, and 2n=ca. 122 for Kobresia nepalensis. The chromosome counts of 2n=46 for C. remota and 2n=44 for Eleocharis kamtschatica are different from those presented in previous reports. The karyotypes of E. palustris (2n=16) and E. tetraquetra (2n=20) were the same as those presented in previous reports. One individual of E. palustris collected from Titigaon, Mustang District, showed 2n=15 chromosomes, which is considered to have been derived by fusion of 2 small chromosomes of the 2n=16 individual, forming one large chromosome.