Fluorescence in situ hybridization (FISH) with both of 5S and 18S rDNAs, and Arabidopsis-type telomere sequences was carried out in 3 species of the genus Artemisia (Asteraceae) with different basic chromosome numbers, x=8, 9 and 17, to understand their chromosomal organization and evolution. Chromosomal distribution of telomere sequences, which was restricted only to the ends of all chromosomes, was reported here for the first time in this genus. Although 5S rRNA gene loci are generally localized independently of 45S rRNA gene loci in eukaryotic chromosomes, all of the 5S rDNA sites are the same number and co-localized with the 18S rDNA sites in the species investigated. We also discussed the chromosomal evolution of A. feddei (x=8) and A. princeps (x=17) having a derivative basic chromosome number in this genus.
Cytogenetic study was carried out on willow aphids viz. Cavariella aegopodii and Tuberolachnus salignus in order to ascertain the karyotype and sex determination in these aphids from different localities of Himachal Pradesh, India. In Cavariella aegopodii, collected from Shimla, Mashobra and Shoghi localities, 2n is 10. There is 1 pair of long, 2 pairs of medium sized and 2 pairs of short chromosomes. However, karyotypic variation was observed in aphid populations collected from the Solan locality, where the variable diploid chromosome numbers such as 2n=8, 9 and 10 were also recorded. The male sexuals of Cavariella aegopodii are diploid having 2n=9 with 4 pairs of autosomes and a single X chromosome. The various stages of meiosis in the testes of the male mainly occur during the early developmental stages and can also be found in the first and second instar nymphs. The Cavariella aegopodii has XX-XO type of sex determination system. In Tuberolachnus salignus collected from the Shimla, Mashobra and Shoghi localities, 2n is 20. The idiogram of Tuberolachnus salignus reveals the gradual decrease in chromosome length. However, karyotypic variation was observed in aphids collected from the Solan locality where the diploid chromosome number (2n) ranged from 18 to 20.
Jatropha curcas L. belonging to the Euphorbiaceae is becoming a significant crop in tropical areas nowadays. The genetic diversity among 1 African and 5 Asian varieties were analyzed by multicolor fluorescence in situ hybridization (McFISH) using 5S and 45S ribosomal RNA genes (rDNAs). One locus of 5S rDNA and 2 loci for 45S rDNA were detected at specific regions of the chromosomes in all the materials. Also, telomeric repeats (TTTAGGG)n were localized on the terminal regions of all chromosomes. The present results confirm the stability of these major repeated sequences among Jatropha lines.
Chromosome numbers and meiotic behaviour of 10 native species of Hybanthus in South America were analyzed. 3 different chromosome numbers were found: 2n=16 for Hybanthus atropurpureus (A. St.-Hil.) Taub., H. bigibbosus (A. St.-Hil.) Hassl. and H. paraguariensis (Chodat) Schulze-Menz, 2n=32 for H. bicolor (A. St.-Hil.) Baill., H. calceolaria (L.) Oken, H. communis (A. St.-Hil.) Taub., H. hasslerianus (Chodat) Hassl., H. leucopogon Sparre and H. nanus (A. St.-Hil.) Paula-Souza, and 2n=48 for H. longistylus Schulze-Menz. This is one of the first reports for 8 analyzed species. Nowadays, the basic chromosome numbers in the South American Hybanthus species are under discussion. The presence of 1 tetravalent in H. atropurpureus, H. bigibbosus and H. paraguariensis (2n=16) would suggest the duplication of chromosome sets, and therefore would indicate that the basic chromosome number is x=4, at least, for this group of South American Hybanthus species. The studied species would be tetraploids (2n=4x=16), octoploids (2n=8x=32) and dodecaploids in H. longistylus (2n=12x=48). In light of these findings, such polyploidy would likely have played an important role during the speciation of this heterogenerous generic assembly.
Reduviids comprise the largest family of predaceous land Heteropterans and are characterized by a modal autosomal diploid number of 20 with both simple and multiple sex chromosome systems. Multiple systems are more frequent in Harpactorinae and Stenopodainae. Microchromosomes are invariably absent in this family. Stenopodainae have a diploid autosomal number of 20/22 (n=10A/11A) plus different multiple sex chromosome systems (XnY/XnXn). In the present work the chromosome complement and course of meiosis of two species viz. Oncocephalus notatus (2n=23=20A+X1X2Y) and Sastrapada baerensprungi (2n=23=20A+X1X2Y) (Stenopodainae) collected from the Punjab region of India and new to the cytogenetic world, are described.
Chromosme numbers in 22 germplasm collections and 28 open-pollinated seedling progenies of turmeric (Curcuma longa L.) were determined by counting the chromosomes of somatic metaphase plates. Among the germplasm collections analyzed 20 have 2n=63, the accepted chromosome number of turmeric, 1 collection was 2n=61 and another 1 was 2n=84. The seedling progenies showed various chromosome numbers ranging from 2n=63 to 2n=86, of which 2n=84 was the most frequent. The role of abnormalities during triploid chromosomes segregation in generating chromosome number variation among open pollinated seedling progenies is discussed.
The active, selective digestion of mitochondrial DNA (mtDNA) from 1 parent in the zygote is a possible molecular mechanism for the uniparental inheritance of mitochondria, but direct evidence has been observed in few species. In this study, we observed the behavior of mitochondria and mtDNA during mating of the myxamoeba of the true slime mold Didymium iridis. To show the selective digestion of mtDNA in the zygote, 2 myxamoebal strains of D. iridis were crossed, and the changes of mitochondria and mtDNA were observed over time by phase-contrast observation using alkaline fixation method and DAPI staining. Each myxamoeba of D. iridis contained about 30 mitochondria, and the zygote had about 60. Each mitochondrion contains rod-shaped mtDNA. About 4.5 h after mating, the fluorescence of mtDNA in about 30 mitochondria decreased simultaneously to give small spots, and then disappeared completely by 5 h after mating. In contrast, the mtDNA in the other 30 mitochondria and all of the mitochondrial sheaths remained unchanged. This is the fourth microscopic report that shows selective mtDNA disappearance. The rapid, selective disappearance of mtDNA observed in D. iridis is likely the result of selective digestion of mtDNA from 1 parent, as in other known cases of mtDNA disappearance.
RAPD analysis of 5 morphologically identical Lycaenid butterflies was carried out using 7 decamer primers. Total 114 bands produced of which 110 were polymorphic with 96.49% of similarity. Dendrograms based on similarity coefficient grouped 5 species in to two distinct clusters. Cluster-I comprised of Psuedozizeeria maha and Zizeeria karsandra while, cluster-II formed of 3 species. Cluster-II was again subdivided into two sub clusters. Sub cluster-I composed of Zizina otis and Zizula hylax, subcluster-II composed of Chilades trochylus. Similarities between these species was discussed on the basis of morphological and RAPD data.
The present research work was undertaken to assess the effect of gibberellic acid (GA3) applied exogenously to the Safflower plant for the study of pollen behavior. A cytological characterization in safflower from meiosis to pollen formation revealed that whereas meiosis was recorded to be normal in control plants with normal microsporogenesis, GA3-treated plants possessed disturbed tetrad configurations of pollen. GA3 caused deductions in pollen yield and increased the formation of abnormal meiotic products. Our study elucidates that the microspore sacs, instead of having normal four microspores, possessed 1 (monad), 2 (dyads), 3 (triads) and even up to 5 (polyads) microspores, which may produce unreduced gametes at later stages. A significant variation in the degree of pollen mortality was also displayed amongst these pollens. Another interesting feature noticed during the study was the fusion among tetrads due to wall dissolution.
Chromosomal responses to thiourea, caffeine, sodium azide and colchicine were studied in pupal foot pad polytene chromosomes of Sarcophaga ruficornis. The stress was given at different concentrations for different time intervals and in each case only a single large puff in chromosome arm II L at the region 12A was induced. The same puff was induced in several sarcophagid species by heat shock and chemical agents. These findings suggest that a single prominent puff is a hallmark of the stress response in sarcophagids and thus can be used as a biomarker in environmental toxicology.
Cytogenetical studies were performed on 15 populations of 7 species and subspecies of the genus Melica as well as 4 populations of 2 species of the genus Milium growing wild in Iran. The meiotic analysis of Melica and Milium species studied showed the occurrence of a post pachytene diffuse stage possibly due to adaptation to adverse environmental conditions. Melica species studied possess 2n=2x=18 chromosome number. The chromosome numbers of M. persica subsp. persica and M. persica subsp. inaequiglumis have been reported for the first time. The ANOVA test performed among Melica species and populations studied, revealed a significant difference in the amount of total, terminal and intercalary chiasmata as well as amount of rod bivalents (p<0.01), indicating partly their genetic differences. Two populations of Milium vernale showed the presence of 2n=2x=14 and 2n=2x=18, while two populations of M. schmidtianum possessed 2n=2x=14 chromosome number, which is new for M. chmidtianum.
Diploid Lathyrus boissier showed the 7 bivalents in most of pollen mother cells at prophase and metaphase of meiosis. The disturbances in the meiotic stage appeared to have been caused by reciprocal translocation. Meiotic analyses of 232 pollen mother cells indicates occurrence of heterozygotic reciprocal translocation in 94 cells. When the crossing-over and chiasma formation take place in all 4 pairing segments, a ring of 4 chromosomes results, and when the chiasma was absent in one of the 4 pairing segments, a chain of 4 chromosomes results. Of the 94 transtocated MI cells examined, 24 had ring quaderivalents, 55 had open chain quaderivalents and 15 had alternate (zigzag) ring quaderivalents. From the present investigation it appears L. boissier has not acquired stability as yet and translocation has played an important role in its evolution. In this study chromosome count and meiotic behaviour of L. boissieri is presented here for the first time.
The present study was carried out in order to evaluate the mutagenic effect of 3 nitrogenous fertilizers; urea, ammonium nitrate and calcium nitrate; on Drosophila melanogaster. Newly hatched larvae were treated with the LC25 and LC50 of the 3 tested nitrogenous fertilizers. The classic sex-linked recessive lethal (SLRL) test was used to detect the differential mutagenic effect of the fertilizers on the 3 germ stages. The results showed that all fertilizers exhibited variable mutation frequencies in the different broods of spermatogenesis after a single treatment. Urea exhibited a direct mutagenic effect on post-meiotic stages whereas ammonium nitrate and calcium nitrate revealed an indirect mutagenic effect on meiotic and pre-meiotic stages. The electrophoretic separation of proteins (SDS-PAGE) showed that treatment with these fertilizers resulted in polymorphetic changes in different low and high molecular weight protein bands, causing alteration in the electrophoretic patterns and densities of proteins. This study showed that the tested nitrogenous fertilizers possess mutagenic potentialities which are related to their nitrogen content.
The 3 forms of Colocasia fallax Schott. complex, namely green petiole form, light purple petiole form and deep purple petiole form, available in Bangladesh were studied cytogenetically to confirm their taxonomic status after staining with orcein and CMA. The green petiole form and the deep purple petiole form were found to possess 2n=28 chromosomes whereas 2n=30 chromosomes were observed in the light purple petiole form. The centromeric formula was determined as 20 m+8 sm in the green petiole form, 26 m+2 sm+2 ac in the light purple petiole form and 24 m+4 sm in the deep purple petiole form. Acrocentric chromosomes were found only in the light purple petiole form. 4 satellites were found in the green petiole form after orcein staining while only 1 satellite observed in CMA staining of the same form. These satellites showed stain specific nature in this form. 8 and 11 CMA positive bands were found in the green petiole form and the deep purple petiole form, respectively. Only 2 centromeric CMA positive bands were found in the light purple petiole form. Different CMA banding pattern and percentage of GC-rich repeats were found in these 3 forms. CMA banding was able to identify some chromosomes in the green petiole form and the deep purple petiole form. The diploid chromosome numbers and overall karyotypic features indicated that the light purple petiole form possessed quite different genomes than the other 2 forms and thus may be placed in a different taxonomic rank. Except a minute difference in the karyotypic features, the green petiole form and the deep purple petiole form possessed almost entirely similar genomes and therefore could be considered as different varieties of Colocasia fallax.
The human Rhesus (Rh) blood group is determined by 2 highly homologous RH genes, RHD and RHCE. These genes are located on chromosome 1p36.1, a genomic region representing copy number variation. In Rh-positive individuals, both RHD and RHCE genes are present, while in most Rh-negative individuals RHD genes are missing and are homozygous for a single RHCE gene. Some individuals with a serologically Rh-negative phenotype were diagnosed to be RHD-gene positive by a locus-specific DNA assay using polymerase chain reactions with sequence-specific primers (PCR-SSP). Therefore, the current PCR-based assay, examining the presence or absence of partial sequences of RHD genes, does not necessarily produce correct typing results. Alterations in the genomic structure of RHD that cause negative gene expressions are difficult to detect by the PCR-based assay because of highly homologous sequences of the 2 RH genes. In the present study, we examined, by extended chromatin fiber fluorescence in situ hybridization (fiber-FISH) with 2 DNA probes for introns 3 and 7 of the RH genes, the genomic structure of the RH gene region in 6 Rh-negative Japanese donors whose genotype was diagnosed as RHD-gene positive by the PCR-SSP assay. We demonstrated that varied sizes of deletion and/or insertion in the RH loci caused the Rh-negative phenotype.
Genomic in situ hybridization (GISH), using genomic DNA probe from O. australiensis, was used to study chromosome pairing among AA, EE and AE genomes, in the hybrid O. sativa×O. australiensis. In the conventional cytogenetic analysis, 0–4 bivalents and 20–24 univalents were recorded. GISH, however, revealed 1–5 bivalents and 19–23 univalents. 3 types of pairing were detected: pairing between A and E genome chromosomes, within AA genome chromosomes and within EE genome chromosomes. The frequency of association between O. sativa (AA) and O. australiensis (EE) chromosomes (0.98II/cell) greatly exceeded the level of pairing, within sativa chromosomes (0.15II/cell) or within australiensis chromosomes (0.05II/cell). Results indicated that conventional cytogenetic analysis either underestimates or overestimates the pairing behavior and that GISH is a powerful tool for detecting the nature of pairing in O. sativa×O. australiensis.
Presently, detailed cytological investigations have been carried out in 4 accessions of Anemone rivularis Buch.-Ham. ex DC, collected from the cold deserts of Lahaul-Spiti, Kinnaur, and Kullu districts of Himachal Pradesh (India). The phenomenon of cytomixis involving chromatin transfer among proximate pollen mother cells (PMCs) during male meiosis is recorded for the first time in the species. The effects of cytomixis on meiosis and pollen grains have also been discussed. In spite of the existence of intraspecific aneuploid and polyploid cytotypes (2n=14, 16, 24, 28, 48), all the accessions of the species unequivocally share the same diploid chromosome number, 2n=16. The accession studied from Kothi (Kullu) shows perfectly normal meiotic behaviour, cent per cent pollen fertility and uniform sized pollen grains. However, the accessions analyzed from Keylong and Kishori (Lahaul-Spiti) and Sangla (Kinnaur) show the phenomenon of cytomixis involving chromatin transfer among proximate PMCs, and associated meiotic abnormalities like chromosome stickiness, laggards and bridges at anaphase/telophase, micronuclei, some pollen malformation and pollen grains of heterogeneous sizes.
Seeds of Vicia faba L. var. PRT-12 were subjected to different doses/concentrations of gamma rays and methyl methane sulphonate (MMS) individually as well as in combination. The effect of different mutagenic treatments on meiosis and pollen fertility has been studied in M1 generation. Various types of meiotic aberrations and reduction in pollen fertility were observed in all the treatments. However, the combination treatments proved to be more effective in inducing meiotic aberrations and reduction in pollen fertility as compared to individual ones. Moreover, the frequency of meiotic aberrations was at its maximum at metaphase followed by anaphase and telophase stages.