Seeds represent a plant developmental stage of key agronomic value. Developing seeds undergo a series of contrasting physiological environments, some of which are accompanied with spontaneous and/or programmed DNA damage. Here, we review recent literature illustrating emerging evidence on the importance of maintaining genome stability during the complex life of a seed.
Chromosome and morphometric analyses of the croslet horseshoe bat (Rhinolophus coelophyllus) and least horseshoe bat (R. pusillus) from Northeast of Thailand were studied. Bat chromosome preparations were conducted by squash technique from bone marrow and testis. Conventional staining and Ag-NOR banding techniques were applied to stain the chromosomes. The results showed that the diploid chromosome number of R. coelophyllus and R. pusillus were 2n=62, and the fundamental number (NF) were 64 in both species. The types of autosomes observed were 26 large telocentric, 12 medium telocentric, and 22 small telocentric chromosomes in R. coelophyllus and R. pusillus. The X-chromosome was a largest acrocentric chromosome and the Y-chromosome was a small acrocentric chromosome in both species. NORs are located at the secondary constriction near the centromere on the long arm of the large acrocentric chromosome pair 13 in R. coelophyllus and R. pusillus. We found that during metaphase I the homologous chromosomes showed synapsis, which can be defined as 31 bivalents. Six external morphological characters were measured as well as 13 cranial and dental measurements. The karyotype formulae were as follows:
The first chromosome analysis of the whitecheek monocle bream (Scolopsis vosmeri Bloch, 1792) from the Gulf of Thailand, was studied. Kidney cell samples were taken from two male and two female fish. The mitotic chromosome preparations were done directly from kidney cells. Conventional and Ag-NOR staining techniques were applied to stain the chromosomes. The results showed that the diploid chromosome number of S. vosmeri was 2n=48, the fundamental numbers (NF) were 50 in both male and female. The types of chromosomes were 2 large acrocentric, 30 large telocentric, 14 medium telocentric, and 2 small telocentric chromosomes. The Ag-NOR banding indicated that a single pair of NORs was observed on the short arm subtelomeric region of the largest acrocentric chromosome pair 1. The karyotype formula could be deduced as:
In this study, we report the chromosome number on the eight Cousinia species belonging to six sections distributed in south east and north east parts of Iran. Seven of the counts are new to science and one provides confirmation of the previous report. The results of this study are the first reports of the basic chromosome number within sect. Spinuliferae and sect. haussknechtianae. The present study reports x=12 for C. lasiolepis from sect. Alpinae which is new for the material originated from flora of Iran. The result of this study also confirmed the previously reported basic chromosome number of x=13 which had been supposed to be erroneous for sect. Leiocaules.
Karyotype can be designated as representative of the species, and in some instances even of the genus. As karyotype is subjected to variation it can be used in the identification of the species or variety and to establish relationships amongst the species. Ipomoea L. the largest genus of the family Convolvulaceae has been subjected to modification many times and is constantly under debate. Taking this into consideration, the genus Ipomoea has been taken up for research. Over 500 species are distributed worldwide and in India just over 60 species could be recorded. Karyomorphologically, Ipomoea L. is a very inadequately investigated genus. To study the chromosome morphology, different parameters were considered such as arm ratio, centromeric index, presence or absence of satellites, total chromatin length, and total form percentage. Using the arm ratio of the long arm to short arm, two classes of chromosomes were obtained—metacentric and submetacentric. Thirteen specimens were investigated and it was established that their somatic chromosome counts varied from 2n=28 to 2n=32, indicating that the species of the genus fall under several basic series as x=14, 15, and 16 of which x=15 is the most frequent. In the investigation process, two new variants each of Ipomoea aquatica and Ipomoea cairica could also be recorded for the first time. Besides these, all the examined species possessed a variable number of satellite chromosomes ranging from two to 12, which could be aptly used as chromosomal markers for their proper taxonomical characterization.
Salvia przewalskii Maxim., which possesses high content of lipid-soluble tanshinones in roots, is a valuable medicinal plant in China. Its detailed meiotic analysis from pollen mother cells (PMCs) to tetrad was carried out for the first time. Most of the PMCs showed a regular meiotic behavior and regular chromosome segregation. Sixteen bivalents were observed in most PMCs at metaphase I, indicating that S. przewalskii was a species with chromosome number of 2n=32. However, a high-frequency of cytomixis, and transferring of chromatin or chromosome materials between adjacent pollen mother cells through cytomictic channels, were observed in PMCs at early prophase I, but rather rarely in meiosis II. Other meiotic abnormalities such as chromatin bridges, laggards, and micronucleus at low frequency were also detected in few PMCs at meiosis I and II.
The present study deals with the male meiosis of 20 species covered under 12 genera and two tribes. Four species shows new chromosome count from world as well as India level. Agrostis pilosula (2n=28), Polypogon monspeliensis (2n=56) and Eragrostis viscosa (2n=32) are the first chromosome reports in the world, whereas, Diplachne fusca (2n=20) is the first report from India. The meiotic course of all the investigated plant species is normal with high pollen fertility.
Adiantum lunulatum Burm. of family Adiantaceae locally known as Hansraj is commonly found only in district Kangra rather than other parts of Himachal Pradesh. The entire plant is utilized for medicinal purposes. The focus of the current study was to elucidate the cytological status of this fern but its occurrence was not as common compared to its other family members such as Adiantum capillus-veneris L. or Adiantum caudatum L. from Himachal Pradesh. Specimens from 16 different populations of the species from Kangra valley were investigated for detailed meiosis. The apogamous mode of reproduction is an established phenomenon in fern. Two types of sporangia were found one with normal meiotic course (32 spores) and other one with abnormal (64 spores). Meiotic analysis revealed that some accessions with 32 well developed spores showed n=90 bivalents while others showed meiotic abnormalities such as stickiness, unoriented bivalents, laggards, bridges, micronuclei, and polyads with 64 spores per sporangia. Presence of univalents and trivalents at M-I were reported. Thus, failure of the species to produce viable spores due to meiotic abnormalities is an obvious consequence. Heterogenous, empty, and shriveled spores of different shapes and sizes were also present.
Chromosomal attributes of the critically endangered medicinal plant Swertia chirayita along with its allied species S. nervosa and S. bimaculata are precisely essential to assess phylogenetic relationships. The present study deals with karyomorphometric analysis based on patterns of fluorescence chromosome banding and nuclear genome size estimation by flow cytometry reported for the first time in S. chirayita (2n=26), S. nervosa (2n=26) and S. bimaculata (2n=26). Fluorescent banding revealed the distinct differences in chromosomal CMA+ve/DAPI−ve heterochromatic sites among the species. There were six chromosomes with CMA+ve signals in S. chirayita and two chromosomes with CMA+ve signals in S. bimaculata whereas all chromosomes of S. nervosa displayed CMA+ve signals. Due to a difference in CMA banding pattern, proportion of GC rich regions differed among the chromosomes of S. chirayita (3.32%), S. nervosa (18.76%), and S. bimaculata (0.64%). S. bimaculata had the highest 2C DNA content (9.82 pg/2C) compared to S. nervosa (1.95 pg/2C) and S. chirayita (1.09 pg/2C). Lowest amount of GC-rich CMA sites along with highest DNA content distinguished S. bimaculata from the other two species. A nearly nine-fold difference in nuclear genome size among the homoploid species of Swertia (2n=26) and particular chromosomal discrimination by localized CMA bands allowed interpretation of karyotypic affiliations in the three species of Swertia.
Analyses of pachytene karyotype were conducted in 18 different accessions of Eleusine indica (L.) Gaertn., Panicum antidotale Retz. and Setaria italica (L.) Beauv. However, these accessions showed the presence of chromomeric patterns at or around the centromeric regions. The pachytene chromosome complements of different accessions of these genera differed in the length of the long arm, short arm, and total chromomeres of their constituent chromosomes. The accessions exhibited significant variability in their pachytene chromosome characteristics.
Four Oxalis L. species namely O. corymbosa, O. corniculata, O. latifolia, and O. triangularis were investigated cytogenetically and at the molecular level for proper characterization. Different 2n chromosome numbers were found in four species, such as 2n=44 in O. corniculata, 2n=28 in O. latifolia, 2n=30 in O. corymbosa, and 2n=30 in O. triangularis. The diploid chromosome number 2n=30 is the first report for O. triangularis. The four species differed with respect to centromeric formulae, such as 30m in O. corymbosa, 44m in O. corniculata, 24m+4sm in O. latifolia, 26m+4sm in O. triangularis. The four species of Oxalis have distinct CMA- and DAPI banding patterns based on the number, location, intensity, and percentage of GC- and AT-rich repeats. With the help of CMA and DAPI staining, it was possible to mark certain chromosomes specific for each species. Moreover, the four species possess distinct RAPD fingerprinting patterns with species-specific unique marker fragments. RAPD fingerprinting analysis placed O. corymbosa in a different cluster whereas the rest three in another cluster. Therefore, the compilation of the cytological and molecular information will be useful for authentic identification and characterization of the four Oxalis species found in Bangladesh.
Four recently released varieties of Gossypium hirsutum L. by Bangladesh Cotton Development Board (CDB) viz. CB-12, CB-13, CB-14, and Rupali-1 were studied cytogenetically and at the molecular level to elucidate the genomic diversity among the varieties. Although the four varieties were found to possess 2n=52 chromosomes, they differed in respect of karyotype formulae such as 48m+4sm in CB-12, 52m in CB-13, and 50m+2sm in CB-14 and in Rupali-1. Moreover, these varieties differed with respect to other karyotypic features such as total length of 2n chromosome complements, number of satellites, range of relative length, centromeric index, etc. Different number of satellites viz. two in CB-12 and Rupali-1 and four in CB-13 and CB-14, were found after only CMA-staining. CMA-fluoresced satellites of four cotton varieties suggest stain specificity. A wide range of CMA-positive bands were found in these four varieties. Out of four varieties no DAPI-positive band was found in CB-13 and Rupali-1. Fluorescence banding revealed genomic alteration and karyotype diversification within the four varieties. The five RAPD primers generated 53 bands with 90.56% polymorphism indacting diverse genomic nature. Two unique RAPD bands were found in Rupali-1 which could be used as markers. Therefore, each variety could be characterized by diverse karyotypes and molecular data.
The genus Eleiotis DC. (Fabaceae) is distributed from Burma to Sri Lanka and represented by only two species. The genus has not been screened for its cytological characters. In the present investigation, the mitotic chromosome counts (2n=20+2b) and basic karyomorphology in Eleiotis rottleri are reported for the first time and chromosome counts (2n=20+2b) in E. monophyllos are reported as a new cytotype. Generic cytotaxonomical characters of the genus Eleiotis viz. mitotic chromosome counts 2n=20+2b, two B-chromosomes and 1B category as per Stebbin asymmetry classes are also reported.
Moenkhausia sanctaefilomenae is a small freshwater characid fish that shows a conserved karyotype with respect to the standard genome, but also carries B microchromosomes. In the present study, one population of M. sanctaefilomenae from the Upper Paraná River basin was cytogenetically characterized, with emphasis on the analysis of B chromosomes. The M. sanctaefilomenae individuals showed a karyotype consisting of 2n=50 chromosomes with eight metacentrics, 36 submetacentrics, and six subtelocentrics, and a FN value of 100 in both sexes. In addition to the basic karyotype, all male and female individuals presented a variation from zero to eight B microchromosomes in mitotic metaphases. A secondary constriction was evident in the terminal region of the short arm of the subtelocentric pair 24, which corresponds to the Ag-NORs location. Analysis of the constitutive heterochromatin patterns by C-banding showed heterochromatic blocks in the centromeric and pericentromeric regions in most of the chromosomes. However, the B chromosomes were faintly stained with C-banding, similar to euchromatin in the A chromosomes. Aspects regarding the differences in the number and C-banding pattern of B chromosomes are discussed.
Three Asparagus species viz. A. racemosus Willd., A. officinalis L., and A. setaceus (Kunth) Jessop were investigated by cytogenetical and molecular analysis for authentic characterization. The diploid chromosome number 2n=20 was found in A. racemosus and A. setaceus, while, A. officinalis possesses 2n=22 chromosomes. Diploid chromosome number 2n=22 is the first report for A. officinalis. These three species differed in respect of other karyotypic features such as total length of 2n chromosome complements, number of satellites, range of relative lengths, centromeric indices, etc. Some unique CMA- and DAPI-banded chromosomes were found in three species which could be used as marker chromosomes for the respective species. A pair of satellites was observed in A. racemosus after CMA- and DAPI-staining but absent in orcein staining indicating the stain-specific nature of satellites. The chromosomes of three Asparagus species possessed different structural abnormalities such as deletions, tandem duplications, and dispersed distribution of GC- and AT-rich repetitive sequences. This organizational variation of chromosomes was one of the major reasons for karyotype diversification. Four primer combinations were applied for RAPD analysis in three species of Asparagus to find out their genomic relationship. The three species showed several unique bands useful as markers for each species. Therefore, the three Asparagus species could authentically be characterized by conventional and fluorescent karyotype together with RAPD fingerprinting.
Labeling of specific DNA sequences in living organisms is important for understanding the mechanism of gene regulation during development, differentiation, and environmental adaptation. Here we describe a CRISPR/Cas9-based chromatin visualization system in plants. We adapted the mammalian nuclease-dead Cas9-fluorescent protein (dCas9-FP) system to a plant expression vector. Transient expression of dCas9-FP and single guide RNA (sgRNA) for telomeric sequences efficiently labeled telomere repeats in tobacco.
The chromosome numbers and karyotypes belonging to populations of Psephellus aucherianus complex were discussed by this paper. The chromosome numbers of all populations were determined as 2n=30. Karyomorphological results indicated that the populations of Ps. aucherianus complex display a broad variation and differ from each other in some aspects. Mainly, the karyotype formula could be evaluated as very specific and discriminative for each taxa, even their populations. Otherwise, the chromosomal indices indicated that all populations had largely symmetrical karyotypes and low chromosomal heterogeneity as a common chromosomal pattern within this complex. As a general result, we can infer that the species of these complex can be clearly characterized and separated according to karyomorphologic features and more importantly, chromosome pattern and rearrangements are very useful and informative to explain theirs evolutionary interactions as well changes.