2A self-cleaving peptides (2A peptides), originally identified in a short oligopeptide sequence of foot and mouth disease RNA virus, consist of short amino acids that specify ribosome skipping. They enable the expression of multiple proteins within a single open reading frame through a co-translational cleavage event. The 2A-mediated co-expression system can overcome the problem of uneven expression of different proteins, and contributes to the development of leading technology for imaging and genome editing. It may also enable the evaluation of the expression levels of proteins through comparison of the intensity of their fluorescence. This review provides a recent overview of the 2A-mediated co-expression system and introduces several optimizations to improve cleavage efficiency for practical use.
The toxic effects of methiocarb insecticide were investigated using bulbs of Allium cepa as test material. Physiological effects were investigated with rooting percentage, root length, and weight gain; Cytogenetic effects were analyzed with micronucleus (MN), chromosomal damage and mitotic index (MI) and anatomical effects were investigated on root tip cell. Biochemical effects were investigated by measuring the malondialdehyde (MDA) levels, catalase (CAT) and superoxide dismutase (SOD) activities. For this aim, A. cepa bulbs were divided into four groups, one control, and three applications; the bulbs in the control group were treated with tap water; the bulbs in the application group were treated with 2.5 mg L−1, 5.0 mg L−1 and 7.5 mg L−1 doses of methiocarb for 72 h. Methiocarb administration caused a decrease in physiological parameters compared to the control group. Methiocarb administration caused an increase in the number of MN and chromosomal damage, and a decrease in MI, besides methiocarb application caused some anatomical damages on cells of root tips. Methiocarb administration caused a dose-dependent increase in CAT and SOD activities and MDA levels compared to the control group. As a result, methiocarb caused toxic effects, and the Allium test material was found to be a useful bioindicator for monitoring these effects.
Random amplified polymorphic DNA (RAPD) and inter-simple sequence repeat (ISSR) variation among 24 cultivars of four Brassica species (B. rapa, B. juncea, B. napus, and B. oleracea) was examined using individual- and bulked-samples-based approaches. In both the approaches, eight plants were sampled for each cultivar, and were amplified individually and as bulked DNA, respectively. In total, 305 and 422 bands were scored in the individual- and bulked-samples-based approaches, respectively, and almost all the bands (99.8–100%) were polymorphic. Based on the individual-samples dataset, the within cultivar variation was smaller than the among cultivars variation, leading to a distribution reflecting genome compositions of each cultivar with principal coordinates analysis (PCoA) and unweighted pair-group method with arithmetic average (UPGMA) analysis. Although PCoA and UPGMA analysis based on bulked-samples data clustered the cultivars into groups with more emphasized variance among species than the results obtained by the individual-based approach, both PCoA plots and dendrograms of the individual- and bulked-samples-based approaches, respectively, were highly correlated with each other. These findings indicate that the number of individuals used to profile each cultivar can be reduced to eight per cultivar for analysis of the genetic variability in Brassica using RAPD and ISSR polymorphism, and the bulked-samples-based approach can be used to describe the genetic relationship among Brassica cultivars.
Sesbania cannabina commonly known as Dhaincha in India is adaptable to different adverse climatic conditions such as waterlogging, drought, soil salinity etc. and is widely used as green manure crop and may have potential as forage for cattle. Heavy metal toxicity in soil possesses a major threat to plant growth and development. Effect of zinc chloride on germination, survival percentage and meiotic divisions of S. cannabina were studied. For this purpose, the soaked seeds of S. cannabina were treated with different concentrations zinc chloride solution i.e., 25, 50, 100 and 200 ppm for 3 h and sown to rise M1 generation. Seed germination percentage was highest in control as compared to treated sets and it tends to decrease with increasing doses of treatment. Plants grown from treated seeds of all doses showed diversity among themselves regarding survival percentages. The result showed varied chromosomal anomalies, scattering, stickiness, unorientaion, disturbed metaphase, precocious movement, lagging chromosome, bridge formation etc. Meiotic aberrations were also found to be increased with the increase in treatment doses.
One plant of translocation heterozygote has been isolated from ethyl methane sulphonate (EMS) treated population sets on a morphological basis in cumin, Cuminum cyminum L. The meiotic analysis in the plant showed the preponderance of ring quadrivalents along with five bivalents in pollen mother cells (PMCs) at metaphase I. Various multiple chromosomal associations along with rings and chains were also observed with some univalents and bivalents. Pollen fertility of the plant reduced efficaciously to 34.18% against 98.28% in control plants. At anaphase I, 38.13% frequency of unequal segregation (6 : 8) and laggards were observed in 28.81% of PMCs along with 33.05% of regular segregation (7 : 7). The present investigation explains the cytological assessment and consequences in translocation heterozygote induced by EMS treatment.
We analyzed molecular phylogenetically using two low-copy nuclear markers (AK1 and Esterase) and plastid ndhF DNA sequence in the Dryopteris atrata complex. According to nuclear allele constitution and plastid ndhF sequence, apogamous species of the D. atrata complex seemed to be of hybrid origin. The genome constitution of the D. atrata complex showed that apogamous fern species which produce regularly shaped spores can maintain genome constitution if it is of hybrid origin between apogamous species and sexual species. Otherwise, sterile hybrids will be going to hybrid collapse because they cannot prevent genetic segregation.
Three species of Rauvolfia L. viz. R. serpentina L. Benth. ex Kurz, R. vomitoria Afz. and R. tetraphylla L. were studied with differential banding for cytogenetic characterization. R. serpentina and R. vomitoria were found to possess 2n=22 chromosomes, whereas 2n=66 in R. tetraphylla. The three species have distinct chromomycin A3 (CMA)- and 4′, 6-diamidino-2-phenylindole (DAPI)-banding patterns in respect of the number, location, and relative size to complement. No satellite was observed in the three species after orcein and DAPI-banding. However, a pair of satellites was found in R. vomitoria and R. tetraphylla after CMA-staining. In addition, R. vomitoria and R. tetraphylla showed similarities in some karyomorphological features which suggested that these species might share some common genome.
Comparative chromosome analysis by conventional staining with orcein and differential staining with CMA and DAPI was carried out in three Amaranthus species viz. A. viridis, A. tricolor, and A. lividus. Although, the three species were found to possess 2n=34 chromosomes, differed in respect of total length of chromosome complement. Each Amaranthus species showed a characteristic fluorescent banding pattern based on distribution and amount of CMA- and DAPI-bands. In the three species, out of 22 CMA-banded and 27 DAPI-banded chromosomes, seven and eight were entirely fluoresced with CMA and DAPI, respectively. The compiled data gathered from comparative chromosome analysis on orcein, CMA-and DAPI-banding will be useful for cytogenetical characterization of Amaranthus species.
Two species of Plumbago from Bangladesh viz. P. zeylanica L. and P. indica L. were studied cytogenetically for authentic characterization. P. zeylanica and P. indica possessed 2n=28 and 2n=14 somatic chromosomes, respectively. These species differed in respect of total length of chromosomes in the complement, range of chromosome length and number of satellites. The two species showed distinct chromomycin A3 (CMA)- and 4′,6-diamidino-2-phenylindole (DAPI)-banding patterns. P. zeylanica and P. indica showed 11 and four CMA-bands, and six and two DAPI-bands, respectively. Several entirely fluoresced chromosomes were observed in both species after CMA- and DAPI-bandings. The difference in number, location and amount of CMA- and DAPI-bands suggested chromosomal diversification between the two species.
We report on the occurrence of karyotypes of two species and one variety of dandelion, Taraxacum denudatum var. denudatum, var. arakii, and T. pectinatum, in western Japan. The two varieties of T. denudatum had two polyploid numbers of 2n=32 (4x) and 40 (5x). In T. denudatum var. denudatum, the tetraploid plants had a karyotype form expressed as 2n=32=3M+25m+2mcs+1sm+1smcs, and the pentaploid plants comprised two karyotype forms of 2n=40=2M+32m+2mcs+3sm+1smcs and 2n=40=5M+32m+3mcs. In T. denudatum var. arakii, the tetraploids had a karyotype form expressed as 2n=32=27m+5mcs and the pentaploids had a karyotype form of 2n=40=3M+33m+3mcs. Taraxacum pectinatum was a tetraploid dandelion with a karyotype expressed as 2n=32=23m+5mcs+2sm+2smcs. The present study by their karyotype analyses suggests that T. denudatum var. denudatum, T. denudatum var. arakii, and T. pectinatum are all allopolyploid dandelions.
The genus Cyperus in family Cyperaceae shows large morphological and cytological diversity. Chromosome numbers and male meiosis were studied in six Cyperus species (C. digitatus Roxb., C. exaltatus Retz., C. fuscus Linn., C. globosus All., C. laevigatus Linn. and C. pygmaeus Rottb.) from various localities in North India. New chromosome numbers were recorded in C. digitatus (n=27), C. exaltatus (n=24), C. fuscus (n=13), C. globosus (n=20), C. laevigatus (n=21) and C. pygmaeus (n=27). Meiosis is normal in all the six species. Presently studied species show diploid to hexaploid levels (x=8, 9, 10, 11 and 12) with four species having euploid and two having aneuploid cytotypes. Pollen fertility is high ranging from 81.34 to 93.75% in these species.
Meiotic studies have been carried out on six accessions of Artemisia roxburghiana from four regions of Western Himalayas. The accessions collected from Chamba, Kinnaur and Kullu districts of Himachal Pradesh and Kargil district of Jammu and Kashmir showed a normal meiotic course leading to high pollen fertility. However, the accession collected from Drass region of cold deserts of Ladakh, Jammu, and Kashmir showed abnormal meiosis caused by structural heterozygosity for reciprocal translocations. The present study adds the first report of structural heterozygosity in the species. Chiasma frequency was also calculated in the accessions to see the effect of reciprocal translocations. Besides, reciprocal translocation, the accession also showed various meiotic abnormalities in the form of the early disjunction of bivalents, chromatin bridges and laggards leading to abnormal microsporogenesis. Structural heterozygosity and other meiotic abnormalities in the accession seem to be responsible for a reduction in pollen fertility.
The somatic chromosome numbers and karyotypes were examined in five Bellevalia taxa including two endemic species of B. chrisii and B. gracilis distributed in Turkey. The chromosome numbers were determined as 2n=2x=8 in all studied taxa [B. chrisii Yıldırım & B. Şahin sp. nov., B. glauca (Lindl.) Kunth., B. gracilis Feinbrun, B. longipes Post, B. sarmatica (Pallas ex Georgi) Woronow]. The karyotype formula was determined as 2m+sm+st in B. chrisii and B. longipes, 3m+st in B. glauca, B. gracilis and B. sarmatica. The findings for each of the analyzed taxa are compared with the results of previous studies.
Cytogenetical studies in three Thailand species of genus Colocasia Schott, C. fallex, C. gigantea and C. lihengiae, were reported. The species had the same chromosomes number of 2n=28 and their karyotypes were formulated as 24m+4sm, 20m+6sm+2st (2 sat) and 18m+2sm+8st, respectively. Differences among three species appeared in the number of m, sm and st chromosomes as well as satellite. These karyological data were discussed intra- and inter-specific variation in the Colocasia species.
Present study on male meiotic analysis of wild grass species from Uttarkashi district hills, Uttarakhand, India provides chromosome numbers for 10 species belonging to tribe Aveneae, family Poaceae. The study reports chromosome numbers firstly for Helictotrichon uniyalii (2n=4x=28, Rarhi Valley), Trisetum aeneum (2n=2x=14, Assi Ganga Valley) and Tr. clarkei (2n=4x=28, Assi Ganga Valley), and confirmed in the Indian species, Avena fatua (2n=6x=42, Purola Valley), Koeleria macrantha (2n=2x=14, Bhagirathi Valley), Phleum alpinum (2n=4x=28, Har Ki Dun Valley), P. pratense (2n=4x=28, Assi Ganga Valley), Trisetopsis aspera (2n=6x=42,; Assi Ganga Valley), T. virescens (2n=4x=28, Assi Ganga Valley and Bhagirathi Valley) and Tr. spicatum (2n=4x=28, Assi Ganga Valley, Bhagirathi Valley, and Har Ki Dun Valley). The meiotic course was normal in most of the species, although suggested a paracentric inversion in a plant of Tr. spicatum.