Synteny is modernly used to describe the conservation of homologous genomic regions between chromosomes among different species, although the term was first introduced to mean the gene location on the same chromosomes. Using database of whole genome sequences and web-tools for computational comparative analyses, we can find synteny blocks at high resolution and analyze chromosomal rearrangement among different species. Our constructed synteny maps between Oryza sativa and Arabidopsis thaliana or Zea mays reflected the evolutionary lineages of the plants. These computational synteny analyses contribute to the understanding of chromosome evolution and the discovery of the quantitative trait locus between related species. Future synteny analysis will include information of epigenome and three-dimensional chromatin organization.
The present research work deals with the male meiotic study of 20 species belonging to 14 genera under the tribe Andropogoneae. Five species show meiotic abnormalities in the form of multivalents, laggards, bridges, unoriented bivalents, etc. and the other 15 species have normal meiotic behavior. All these abnormalities lead to heterogeneous sized pollen grains and low frequency of pollen fertility. Two species, Hemarthria compressa (2n=18+0-1B) and Imperata cylindrica (2n=20+0-2B), show the presence of accessory chromosomes along with the normal meiotic chromosome numbers. Chrysopogon serrulatus with 2n=60 is a first-time reported hexaploid cytotype.
The effect of royal jelly (RJ) on the seed germination, seedling growth (radicle length, radicle number and fresh weight), mitotic activity and chromosomal aberrations of Allium cepa L. germinated under both normal conditions and salt stress were investigated in this work. The radicle length and fresh weight of the seeds germinated in the medium with RJ alone increased in comparison with ones of the control seeds germinated in distilled water medium while their germination percentage and radicle number statistically exhibited the same values as the control seeds. Furthermore, the mitotic index and frequency of chromosomal aberrations in root tip meristems of A. cepa seeds germinated in the medium with RJ alone demonstrated a significant increase according to ones of the control seeds germinated in distilled water medium. On the other hand, salt stress considerably inhibited the seed germination and seedling growth of A. cepa. In addition, it markedly decreased the mitotic index in root tip meristems of the seeds and increased the number of chromosomal aberrations. The inhibitive effect of salt on the seed germination, seedling growth and mitotic activity was alleviated in dramatically varying degrees by RJ application. However, the detrimental effects of salt on the chromosomal aberrations greatly increased with this treatment.
The karyotype of six Iranian ecotypes of Nigella sativa, which is a member of the Ranunculaceae family, was studied. The results showed that all studied ecotypes contained 12 chromosomes (2n=2x=12). The karyotype formulas for the ecotypes are: G1: 5m+1T, G2: 4m+1sm+1st, G3: 5m+1st, G4: 5m+1T, G5: 4m+1sm+1T and G6: 3m+2st+1sm. The total form percentages (TF%) of the ecotypes observed were as follows: G1 40.64, G2 41.04, G3 43.83, G4 41.36, G5 39.60, G6 38.94. The largest total haploid length was detected in G6 (51.76 µm) while G4 demonstrated the least (32.56 µm). The first two principal component analysis (PCA) justified over 89% of the total variations of cytological characteristics. UPGMA cluster analysis was carried out for chromosomal parameters which classified the studied ecotypes into five classes.
Karyological analysis in the Sumatra serow (Capricornis sumatraensis) from Thailand were conducted. Blood samples were taken from two male and two female serows. After standard whole blood lymphocytes had been cultured at 37°C for 72 h in the presence of colchicine, metaphase spreads were performed on microscopic slides and air-dried. Conventional, GTG-, high-resolution, Ag-NOR banding and fluorescence in situ hybridization (FISH) were applied to stain the chromosomes. The results showed that the diploid chromosome number of C. sumatraensis was 2n=48 and the fundamental number (NF) for both sexes were 60. The types of autosomes were 2 large metacentric, 4 large submetacentric, 2 large acrocentric, 2 medium telocentric, 4 small submetacentric and 32 small telocentric chromosomes. The X chromosome was a medium telocentric chromosome and the Y chromosome was a smallest telocentric chromosome. From the GTG-banding and high-resolution techniques, the numbers of bands in the C. sumatraensis were 147 and 207, respectively, and each chromosome pair could be clearly differentiated. In addition, the long arm near telomere (subtelomeric region) of chromosome pairs 2, 3 and 4 showed clearly observable heteromorphic nucleolar organization regions (NORs) (2a2b, 3a3b, 4a4b). This is the first report on natural polymorphism of NORs. The microsatellites d(AC)15 accumulated at the telomeres of several pairs and interstitial sites of some chromosomes. The microsatellites d(CGG)10 highly accumulated at the correspondence sites of NORs. FISH with the telomeric probe revealed hybridization signals on each telomere of all chromosomes and interstitial telomeric sites were not detected. The karyotype formula could be deduced as:
This paper aims to study the cytogenetic characterization of Cattleya nobilior species and C. bowringiana and hybrids of orchids C. violacea “type”×C. granulosa, C. violacea “type”×C. harrisoniae “perola,” and C. violacea “type”×C. nobilior “amaliae.” Cattleya nobilior has 2n=2x=30 metacentric chromosomes, with size ranging from 0.54 to 1.58 µm and an active NOR in the first chromosome pair, and C. bowringiana has 2n=2x=34 metacentric chromosomes, from 0.38 to 1.46 µm of size and an active NOR in the first chromosome pair. As for the hybrids, C. violacea “type”×C. harrisoniae “pérola” has 2n=2x=32 metacentric chromosomes, with size from 0.47 to 1.73 µm and an active NOR in the second chromosome pair, C. violacea “type”×C. nobilior “amaliae” has 2n=2x=66 metacentric chromosomes, with size between 0.22 to 1.48 µm and active NORs in chromosome pairs 1 and 3, and C. violacea “type”×C. granulosa with 2n=2x=86 metacentric chromosomes, with size from 0.26 to 1.56 µm and an active NOR in chromosome pairs 3 and 23.
In the present study, chromosome numbers in 13 wild and cultivated Curcuma species were investigated. Chromosome number of C. sylvatica is reported for the first time. Cytological analyses on 13 Curcuma species indicated the presence of 2n=42, 63 and 105 somatic chromosome number, which indicate the plausible occurrence of polyploidy in the genus.
Cytogenetic analysis of painted sweetlip (Plectorhinchus pictus) in Thailand was performed for the first time. The specimens were collected from Andaman Sea, Pluket Province, southern of Thailand. Chromosomes were prepared from kidney tissues followed by conventional staining and NOR banding techniques. The results showed that the diploid chromosome number of P. pictus is 2n=48, and the fundamental numbers (NF) are 48 in both sexes. The karyotype of this fish consisted of 30 large telocentric and 18 medium telocentric chromosomes. No differentiated sex chromosomes were observed. The region adjacent to the subcentromeric of the fifth telocentric chromosome pair presented clearly observable secondary constriction/NORs. The karyotype formula for P. pictus is as follows:
An accession-based study carried out on Anthoxanthum odoratum from Kullu district revealed a tetraploid chromosome count of n=10 and the presence of multiple chromosomal associations of up to 10 chromosomes due to structural heterozygosity for reciprocal translocations. Owing to the presence of multivalents, the individuals showed considerable amounts of non-viable male gametes. Structural heterozygosity in the species has also been detected to affect the chiasma frequency significantly, thereby increasing the variability. Similar effects of translocations in increasing chiasma frequency and affecting pollen fertility have been reported by workers in other species.
The morphology and mitotic karyotype of two species of Phyrgomorphidae, i.e., Chrotogonus trachypterus trachypterus and Colemania sphenarioides, collected from Chandoli National Park were studied. The mitotic karyotype of these species were prepared from testis and were stained with acetocarmine by conventional method. The result showed that the chromosome number of the two species are similar with 2n=19 (18+XO) in male and 2n=20 (18+XX) in female. The karyotype formula of Chrotogonus trachypterus trachypterus is Lt2+Mt5+St2 and that of Colemania sphenarioides is Lt3+Mt4+St2.
Plants of Pteris cretica L. were collected from four different forests of Himachal Pradesh, India to know the chromosome variability and reproductive status of the species. In the study area, two cytologic forms, diploid (2n=58) and triploid (2n=87), of P. cretica are met with. The triploid cytotype is uncommon in distribution. Both the cytotypes are apogamous in nature. Meiotic analysis of different accessions of P. cretica revealed that meiotic course was highly irregular with reduced spore fertility. High incidence of micronuclei in triploid cytotype is a conspicuous phenomenon among other meiotic abnormalities. Variations in spore size and shape have been observed during spore studies. The present count of one B-chromosome (3n=87+1B) in triploid apogamous form is the first report of B-chromosome in the species.
The objective of this study was to characterize the Brazilian green Dwarf coconut (Cocos nucifera L.) by meiotic analysis and by conventional and differential karyotyping (CMA/DAPI and telomeric FISH). Sixteen pairs of bivalent were observed in the meiosis, indicating that the species is diploid and has 2n=2x=32 chromosomes. Some abnormalities were observed, such as asynchronous division and anaphase with converging fibers. The estimated recombination rate for this species was 17.04, equivalent to an average of 1.06 chiasmata per bivalent. The meiotic index was 79% and the pollen viability was 89.5%, both values considered satisfactory. The conventional karyotyping validated the observed number of chromosomes in the meiosis, i.e., 2n=32 chromosomes. The length of chromosomes ranged from 5.57 µm to 2.13 µm. The karyotype was considered asymmetric, with 11 metacentric and five submetacentric chromosomes pairs. The CMA/DAPI banding revealed terminal blocks in two chromosome pairs (one metacentric and one submetacentric), which was coincident with the nucleolus organizing region (NOR), and allowed the satellite characterization, which had 1.36 µm (chromosome 4) and 0.85 µm (chromosome 7). The telomeric FISH revealed signs only in the terminal region in all chromosomes, suggesting that this species has undergone no structural rearrangement of chromosomes during its evolution and that the telomeres of the coconut chromosomes are Arabidopsis type (TTTAGGG).
This study aimed to investigate chlorpyrifos contamination and chromosome aberrations in H. rugulosus in an affected agricultural area compared to an unaffected area. Five H. rugulosus were collected. Chlorpyrifos concentrations were analyzed with a gas chromatograph equipped with dual capillary columns and a flame photometric detector (GC-FPD). Chromosome aberrations were studied in bone marrow. The average chlorpyrifos concentrations in H. rugulosus samples from the agricultural and unaffected areas were 11.43±7.91 and 0.31±0.31 mg kg−1, respectively. The difference in chlorpyrifos concentrations in H. rugulosus samples between the areas was significant (p＜0.05). The diploid chromosome number in H. rugulosus from both areas was 2n=26, and the numbers of chromosome aberrations in H. rugulosus in the agricultural area were higher than those in the unaffected area. There are five types of chromosome aberrations, including single chromatid gap (SCG), single chromatid break (SCB), deletion (D), centric gap (CG), and centric fragmentation (CF). The most common chromosome aberrations in the samples from the affected area were CG. The difference in chromosomal aberrations in H. rugulosus between the areas was significant (p＜0.05).
The effects on genotoxicity of AgNO3 (10 µM, 20 µM and 50 µM) in Allium cepa L. were studied under 6 h of treatment followed by recovery experiments. The oxidative damage caused by AgNO3 reduced the root length, catalase (CAT) activity and mitotic index. Enhanced antioxidant enzyme activities were noticed in ascorbate peroxidase (APX), guaiacol peroxidase (GPX) and superoxide dismutase (SOD) activity to scavenge the oxidative stress. The effect of toxicity was found to be dose dependent in antioxidative enzyme level and more pronounced in root systems than shoot. Evan’s blue uptake was more in the treated root cells over control as a cell death parameter that indicates cytotoxicity. Recovery experiments of 48 h showed significant changes of antioxidative enzymes towards normalization of cell. AgNO3 treated tissues produced H2O2 and O2− that damaged the somatic chromosomes, leading to formation of spindle abnormalities (multipolarity, sticky bridge in anaphase, early separation, clumping of chromosomes, late separation, laggard chromosome) and direct chromosomal damage, i.e., chromosome break and chromosome erosion. Recovery experiments revealed reduction of abnormalities from ca. 48% of the dividing cell to ca. 3.5% in metaphase and ca. 36.5% to ca. 5.5% in anaphase cells that was near to control. Our results indicate that short exposure of low doses of Ag-induced oxidative damage can be reversible in antioxidant enzyme and chromosomal level by repairing the cell damage. This experiment elucidates the role of reactive oxygen intermediates in silver (Ag)-induced DNA damage, cell death and oxidative cell damage.
The family Cichlidae is considered a non-Ostariophysi freshwater fish family with diverse and geographical distribution wide in the world; nevertheless there is scarce cytogenetic information for the group. Accordingly, we aim to characterize Cichla kelberi and Cichla piquiti specimens by conventional cytogenetic (Giemsa, Ag-NOR, Banding C) and cyto-molecular (FISH with 5S, 18S, Rag1, Rex3, Rex6 and telomeric probes) markers. In both species, cytogenetic analyses showed 2n=48 chromosomes (all of the subtelocentric/acrocentric type), NORs located terminally on the second chromosome pair and heterochromatic blocks in the centromeres of some chromosomes. The location of the 18S ribosomal gene confirms what was previously observed with impregnation with silver nitrate, while the 5S rDNA is in interstitial position on the third chromosome pair. The telomeric probe, as expected, was present only in telomeric regions of all chromosomes. The Rag1, transposable elements, Rex3 and Rex6 present dispersed sites throughout most of the chromosomes, not characterizing a definite pattern of distribution. Thus, the present study adds relevant information about the cytogenetics and behavior of different repetitive DNA families in C. kelberi and C. piquiti, which require future studies to understand the gene behavior and evolution in Neotropical fish, especially in the genus Cichla.
The Astyanax scabripinis population from the São Francisco River, analyzed in the present study, had two different diploid numbers: 2n=50 chromosomes (cytotype I) with the karyotypic formula of 10m+20sm+8st+12a and NF=88, and 2n=48 chromosomes (cytotype II) with the karyotypic formula of 11m +18sm+9st+10a and NF=86. Individuals with cytotype II also had a heteromorphic pair in male and female karyotype (24 pair), and in some cells, a supernumerary acrocentric chromosome, which was similar in size to the last acrocentric. C-banding and Ag-NOR staining patterns also differed between the two cytotypes, reinforcing the hypothesis that there are two different species and that A. scabripinnis is a species complex.
A molecular cytogenetic analysis was conducted on the scleractinian coral Platygyra contorta, which is commonly found along temperate coasts in Japan. P. contorta was karyotyped (2n=28) by conventional G- and C-bandings, and the karyogram revealed that about 50% of the metaphase spreads had a homogenously staining region (hsr) in the terminal portion of the long arm of chromosome 12. Fluorescence in situ hybridization (FISH) showed that this hsr consisted of rRNA genes (rDNA) stained by C-banding. The presence of an hsr, which is a highly amplified rDNA, may explain the molecular diversity of coral rDNA. FISH visualized and demonstrated the presence of a telomere motif (TTA GGG)n in this coral using a human telomere probe. Furthermore, we isolated a specific FISH marker (312 bp) designated PC-T1, which was located near the centromere of chromosome 11. A sequence analysis revealed that the terminal part of PC-T1 (51 bp from the 3′ end) was 90% homologous with a Montipora capitate microsatellite and the Actinia equine 5S rRNA gene. Isolating FISH markers will assist the classification of scleractinian corals with the progression on describing their genome. The data obtained in this study will be valuable for discriminating species among scleractinian corals and understanding their genetics, including chromosomal evolution.
To analyze the genetic relationship between Torenia baillonii (2n=2x=16) and Torenia fournieri (2n=2x=18), an interspecific diploid hybrid (2n=2x=17) and a triploid hybrid (2n=3x=26) were produced. The behavior of meiotic chromosomes in the hybrids was examined by fluorescence in situ hybridization (FISH) with species-specific repeats. The mean pairing configuration of the diploid hybrid was 1.95 I+6.75 II+0.48 III and that of the triploid hybrid was 5.6 I+6.74 II+2.44 III. Genome analysis in the triploid hybrid using FISH revealed that the affinity between the genomes was x=0.79. The relatively low value indicates considerable conservation between homoeologous chromosomes of T. baillonii and T. fournieri, even though the two species have different chromosome numbers.
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