Chromosome Clumping Research Articles

An account of chromosomal damage in PMCs of stripe rust infected barley

A study, on the effects of natural mild fungal infection on meiosis of Barley Pollen Mother Cells (PMCs), was done in order to analyze the chromosomal damage elicited by the pathogenic conditions. A pattern similar to common mutagens, of reduction in mitotic index and chiasma frequency, as well as, production of various aberrations that demonstrate chromosomal damage, was observed. The most common abnormalities were un-orientation and other spindle related aberrations, as well as stickiness and clumping of chromosomes. The disease induced a reduction in pollen viability as compared to the control plants. The results were compared with those of a high dose of a known mutagen ie gamma rays in order to draw commonalities between the two conditions.

Gamma Irradiation Induced Chromosome Aberrations in Meiotic Cells of Bread Wheat (Triticum aestivum L.)

Background and Objectives: Due to the ever-increasing human population and rapid urbanization, the available agricultural land becomes limited for the production of food grains. As a result, there is an urgent need for creating genetic variability upon which improved varieties could be made. The technology of induced mutagenesis plays an essential role in inducing genetic variations among crop species where hybridization is very challenging. Therefore, the present study has been designed to assess the mutagenic impact of gamma irradiation on the cytological behaviour of T. aestivum L in M1 and M2 generation.
 Materials and Methods: Bread wheat seeds of selected cultivar were irradiated at BARC, Mumbai with five doses. The irradiated and non-irradiated seeds were sown under field condition with three replicates for each dose according to randomized block design to raise the M1 and M2 generations for morphological and meiotic analysis. For meiosis, immature panicles were collected in early morning and immediately fixed in carnoy’s solution for at least 24 hours. Thereafter, anthers from buds were excised and squashed in acetocarmine followed by photomicrography of suitable PMCs to estimate chromosome aberrations.
 Results: The results displayed a progressive elevation in the chromosomal aberrations along with a significant influence on seedling emergence, plant survival and pollen fertility. The most frequent meiotic aberrations detected include chromatin clumping, univalents and early chromosome segregations at metaphase and lagging chromosomes, chromatin bridges and chromosome clumping at anaphase/telophase while unorientation, scattering, polarity disturbances and micronuclei were also noticed. In addition, the frequency of these chromosome aberrations significantly decreased in M2 generation depicting the reclamation in genomic structure.
 Conclusion: The present investigation supports the discovery that gamma irradiations are very effective in creating rapid genetic variability in crop plants including Triticum aestivum which could be essentially exploited for future mutation breeding programmes. The results revealed that the higher treatment doses are toxic whereas lower doses of gamma irradiations seem quite beneficial in generating promising traits with less toxicity. In this study, the cytotoxicity has increased along with gamma irradiation doses and therefore, the genetic structure of the selected bread wheat cultivar is highly affected, which will possibly create new favorable genetic changes in the following generations that would be useful for plant breeders for its improvement.

A comparative study of the oral epithelia of inflammatory hyperplasias and the dysplastic epithelia of oral squamous cell carcinoma by transmission electron microscopy

ObjectiveThis study aims to compare the atypical epithelial changes of oral inflammatory lesions with the dysplastic epithelial changes of oral squamous cell carcinomas and to examine the underlying pathogenetic mechanisms that cause the changes by transmission electron microscopy (TEM). MethodsEight cases of parulides (oral inflammatory lesions) and 10 cases of oral squamous cell carcinomas were studied. Each specimen was cut into two pieces: one piece was fixed in a neutral buffered 10 % formaldehyde solution and prepared for light microscopy, and the other was fixed in a cold, 2.5 % glutaraldehyde solution and prepared for TEM. ResultsBased on the six histopathologic criteria in this study, both types of epithelia showed similar ultrastructural features, but some significant differences are observed as follows: In parulides, the epithelial cells with features similar to abnormal mitoses showed nuclear fragments with chromatin condensation (karyorrhexis), and no discernible organelles in the cytoplasm, indicating that these are necrotic cells. In contrast, in oral squamous cell carcinomas, the epithelial cells with abnormal mitotic figures showed clumping of chromosomes with abnormal mitotic spindles, indicating that these are abnormally dividing cells. Abnormal keratinization was also seen. The nuclei of the abnormally keratinized cells were irregular with coarse and clumped chromatin. ConclusionsThe atypical epithelial changes in oral inflammatory lesions are a result of necrotic changes in the epithelia due to underlying inflammatory processes and are not true epithelial dysplasia. In contrast, the dysplastic epithelial changes in oral squamous cell carcinomas are dysplastic changes due to premalignant neoplastic processes.

Cytogenetic, chromosome count optimization and automation of Neolamarckia cadamba (Rubiaceae) root tips derived from in vitro mutagenesis

Chromosome count is the only direct way to determine the number of chromosomes of a species. This study is often considered trivial that seldom described and discussed in detail. Therefore, it is inevitable that the chromosome count protocol should be revised and revisited before it becomes obliterated. In the present study, we encountered challenges in obtaining a clear micrograph for the chromosome count of active mitotic cells of Neolamarckia cadamba (Roxb.) Bosser (Rubiaceae) root tips. Several obstacles were determined through micrograph observation, such as existing unwanted particles in cells, poor chromosome staining and chromosome clumping. To overcome these, root tip types, staining methodologies, squashing methods were among the factors assessed to obtain clear micrographs. The chromosome counts of N. cadamba under optimized procedure showed 2n = 44 chromosomes. We also apply digital technology in chromosome counts, such as online databases and graphic software that are open source and freely accessible to the public. Only basic laboratory equipment and chemicals were used throughout the study, thus making this study economical and applicable in a basic laboratory. The availability of online digital software and databases provide open-source platforms that will ease the efforts in chromosome count.

The Cyto-morphological Studies in Physalis minima Linn.

Cyto-morphological studies in a diploid natural population of Physalis minima Linn were done. It was a diploid natural population recorded behind Jal Mandir on Parasnath hills. Qualitative and quantitative parameters were investigated. Ten morphological characters like height of the plant, number of branches per plant, number of branches from main stem, number of nodes, length of internodes, number of heads per plant, length of leaf, breadth of leaf, length/breadth ratio of leaf andlength of petiole were recorded and statistically analyzed. Cytologically, the population showed, gametic number as n= 12. Most of the pollen mother cells were found to be normal; however, some abnormalities were also recorded. Clumping of chromosomes recorded in both meiotic phases i,e. metaphase-I and anaphase-I. Along with it, at metaphase-I, the anomalies recorded as formation of univalents, multivalents and precocious separation of chromosomes. Anaphase-I showed chromosomal laggards, simple chromosomal bridges and unequal separation of chromosomes as anomalies. The half chiasma per chromosome was 0.87. Pollen sterility was 6.00 percentages.

Meiotic studies in <em>Solanum sisymbrifolium</em> Lamk

Meiotic studies in two populations of Solanum sisymbrifolium were caried out in detail each from Railway track at Gaya railway station and from Lal Darwaja of Munger. Meiosis showed anomalies like multivalent and univalent at metaphase-I and soe pollen other cells showed abnormalities like clumping of chromosomes, precocious separation of chromosomes and translocation chains and rings while at anaphase-I,12:12chromosomes were recorded in most of the pollen mother cells. About 15% of the PMC at this stage were found to be abnormal.

Cytotoxic potential of <em>Cissus quandrangularis</em> on <em>Allium cepa</em> root meristem

<p>Apoptosis is a developmental and regulated process which may occur as a result of the cytogenetic changes in the cell. <em>Cissus quandrangularis</em> is a xerophytic plant that belongs to the family Vitaceae, commonly distributed throughout the hotter parts of India and Sri Lanka. An attempt had been made to explore the apoptosis-mediated cytotoxic potential of <em>C.</em> <em>quadrangularis</em> on <em>Allium cepa</em>. Cytogenetic activities of the plant were revealed using DAPI staining and <em>in situ</em> visualization of cell death was carried out with the help of Evans blue staining. The presence of clastogenic (nuclear lesions, chromosome bridges, chromosome breakage and pulverization of chromosomes) and non-clastogenic abberations (ball metaphase, stellate metaphase, chromosome clumping and early movement of chromosomes) observed under fluorescent microscope shows the cytotoxic effect of the plant extract. The quantification of cell death was measured by reading absorbance at 600 nm using the spectrophotometer. The cytotoxic effects on <em>Allium</em> root tips shows the apoptotic potential of the plant extract and the present study enlightens the anticancer potential of the plant.</p><p> </p><p> </p><p> </p><p> </p><h2> </h2><h2> </h2><p> </p><p> </p><p> </p><p> </p><p> </p><p> </p><p> </p><p> </p><p> </p><p> </p><p> </p><p> </p><p> </p><p> </p>

Cytogenetic analysis of five recommended and released Philippine varieties of sugarcane (Saccharum officinarumL.) and their parentals

AbstractMeiotic chromosomal behavior of five recommended and released Philippine varieties of sugarcane and their parents, namely VMC 95-09 (Q 90 × Unidentified), PSR 97-45 (VMC 74-292 × CP 72-1312), PSR 00-343 (VMC 84-947 × Unidentified), PSR 00-161 (VMC 86-550 × VMC 87-599), and PSR 00-34 (VMC 84-194 × PHIL 89-43) were characterized and analyzed. Samples were collected from the tassel source of Philippine Sugar Research Institute Foundation Inc. (PHILSURIN) located in Negros Occidental, Philippines. Gametic number for each variety was determined at diakinesis and at least 50 cells per meiotic stage was analyzed. All varieties exhibited chromosome mosaicism at diakinesis with n = 40–60. Chromosome clumping was observed at diakinesis of Q 90 (68%), CP 72-1312 (35%), and PSR 97-45 (22%) pollen mother cells. High frequency of bivalent formation (68–100%) was observed, both in parents and hybrids, indicating that chromosome pairing is autosyndetic. Irregularities at meiosis were also observed at high frequen...

Mutagens induced chromosomal damage in Lablab purpureus (L.) Sweet var. typicus

Cytological analysis with respect to meiotic behaviour is considered to be the one of the most dependable indices to estimate the potency of mutagens and to elucidate the response of various genotypes to a particular mutagen. Seeds of Lablab purpureus (L.) Sweet var. typicus cv. CO(Gb)14 were subjected to different doses/concentrations of gamma rays and EMS. The effects of different mutagenic treatments on meiosis were studied on treated and control plants. Various types of meiotic aberrations such as stickiness, clumping of chromosomes, laggards, ring chromosomes and precocious movements were observed in the mutagenic treatments. As increase in the concentration, the frequency of cells showing chromosomal aberrations shows a linear increase up to a certain level. However, the EMS treatments proved to be more effective in inducing meiotic aberrations as compared to gamma rays.

Meiotic chromosome behavior of Haworthia limifolia

Haworthia limifolia is a xerophytic plant belonging to the family Liliaceae and is indigenous to Africa. It is use extensively for its medicinal properties like antibacterial, antifungal properties and used for the treatment of sores, superficial burns, as a blood purifier and to promote pregnancy in women and cattles. In present investigation chromosomal behaviour of H. limifolia in meiosis was studied. In diplotene stage chiasmata was observed showing the possibilities of genetic recombination. Chromosome clumps were observed in diakinesis indicating sticky nature of chromosomes. Meiotic abnormalities like stickiness, precocious movement, formation of bridges and laggards were also reported in both meiosis I and II. A fairly high percentage of pollen sterility that is 73.41% was recorded resulting in failure of fruit formation. This plant could be designated as facultative apomict (Swanson, 1957) as the only means of reproduction found was asexual or vegetative.

201 ROLE OF THE NITRIC OXIDE SYSTEM IN EFFECTS OF PROLACTIN AND GROWTH HORMONE ON METAPHASE-II CHROMOSOMES IN BOVINE OOCYTES AGING IN VITRO

Aging of mammalian oocytes is the time-dependent process of cytological and molecular transformations leading to a decline in the ovum quality and developmental capacity. We have previously shown that 2 related pituitary hormones, prolactin (PRL) and growth hormone (GH), may decelerate abnormal changes in the morphology of metaphase II (MII) chromosomes in bovine cumulus-enclosed oocytes (CEO) aging in vitro. The goal of the present research was to examine the involvement of different isoforms of nitric oxide synthase (NOS) in the actions of PRL and GH on MII chromosomes in aging bovine oocytes. Bovine CEO were matured for 20 h in TCM 199 containing 10% FCS, 10 μg mL–1 porcine FSH, and 10 μg mL–1 ovine LH. After IVM, CEO or denuded oocytes (DO) were cultured for 24 h in the aging medium of TCM 199 supplemented with 10% FCS (control). In experimental groups, the medium contained either 50 ng mL–1 bovine PRL or 10 ng mL–1 bovine GH and/or NOS inhibitors. The following inhibitors were applied: (1) N-propyl-l-arginine (NPLA; an inhibitor of neuronal NOS (nNOS), 5 μM) and (2) L-NAME (an effective inhibitor of both endothelial NOS (eNOS) and nNOS, 20 μM). Destructive changes of MII chromosomes in oocytes were assessed by the following morphological signs: decondensation, partial adherence, chromosome clumping into a single mass, and fragmentation. The total activity of NOS in oocytes was determined by NADPH-diaphorase staining. The data from 4–5 replicates were analysed by ANOVA. During CEO aging in the control medium, the rate of MII oocytes with destructive changes of chromosomes rose from 16.8 ± 2.1% to 58.5 ± 1.4% (P < 0.001), whereas both PRL and GH reduced this rate up to 42.0 ± 1.3% and 46.5 ± 1.6%, respectively (P < 0.001). The nNOS inhibitor NPLA abolished (P < 0.001) the inhibitory effect of PRL on abnormal modifications of chromosomes in CEO but did not affect the frequency of these modifications in the control or GH-treated groups. In the absence of the hormones, L-NAME (the eNOS+nNOS inhibitor) decreased the rate of aging CEOs with chromosome abnormalities from 58.5 ± 1.4% to 41.2 ± 2.5% (P < 0.001), acting unidirectionally with PRL and GH. Meanwhile, L-NAME enhanced (P < 0.05) the suppressing effect of PRL on destructive changes of MII chromosomes but did not influence the similar effect of GH. At the same time the chromosome morphology in senescent DOs was unaffected by the hormones or NOS inhibitors. Furthermore, the total activity of NOS in oocytes separated of cumulus after 24 h of aging was similar in the control and experimental groups. Thus, the inhibitory effect of GH on abnormal modifications of MII chromosomes in aging bovine oocytes may be related to a reduction of the eNOS activity in cumulus cells, whereas the respective effect of PRL is likely to be achieved by both inactivation of eNOS and activation of nNOS. This research was supported by RFBR (No. 13–04–01888).

Cytogenetic mechanism for the aneuploidy and mosaicism found in tetraploid Pacific oyster Crassostrea gigas (Thunberg)

Chromosome constitution was investigated in adult tetraploid Pacific oyster produced by blocking the first polar body of triploid eggs which were fertilized with haploid sperms. A high incidence of aneuploid and heteroploid mosaics were found among the offspring. Of 20 individuals identified, only 9 (45%) were eutetraploid which contained 40 chromosomes; 2 (10%) were aneuploid (hypotetraploid), which contained 39 and 38 chromosomes, respectively; and 9 (45%) were heteroploid mosaics. One mosaic was consisted of cells containing 40 and 39 chromosomes, respectiovely (1:1 in cell number), while the other 8 were consisted of cells containing chromosomes varying between tetraploid and triploid. It was also interesting to note that 3 mosaics even contained some diploid cells with 20 chromosomes. A certain number of cells of 2 tetraploids and 8 mosaics spread with 32–37 well-scattered and some clumped chromosomes at metaphase. The percentage of aneuploid cells with chromosomes varying between triploid and tetraploid correlated significantly with that of heteroploid mosaics cells with clumping chromosomes (P<0.05). Our findings suggested that reversion existed in both tetraploid and triploid oyster and chromosome clumping may underline the chromosome elimination in tetraploid oyster. It seems that the reversing cells, at least some of them, continuously eliminate their chromosomes until the most stable diploid state is established.

Influence of particle size and reactive oxygen species on cobalt chrome nanoparticle-mediated genotoxicity

Patients with cobalt chrome (CoCr) metal-on-metal (MOM) implants may be exposed to a wide size range of metallic nanoparticles as a result of wear. In this study we have characterised the biological responses of human fibroblasts to two types of synthetically derived CoCr particles [(a) from a tribometer (30 nm) and (b) thermal plasma technology (20, 35, and 80 nm)] in vitro, testing their dependence on nanoparticle size or the generation of oxygen free radicals, or both. Metal ions were released from the surface of nanoparticles, particularly from larger (80 nm) particles generated by thermal plasma technology. Exposure of fibroblasts to these nanoparticles triggered rapid (2 h) generation of reactive oxygen species (ROS) that could be eliminated by inhibition of NADPH oxidase, suggesting that it was mediated by phagocytosis of the particles. The exposure also caused a more prolonged, MitoQ sensitive production of ROS (24 h), suggesting involvement of mitochondria. Consequently, we recorded elevated levels of aneuploidy, chromosome clumping, fragmentation of mitochondria and damage to the cytoskeleton particularly to the microtubule network. Exposure to the nanoparticles resulted in misshapen nuclei, disruption of mature lamin B1 and increased nucleoplasmic bridges, which could be prevented by MitoQ. In addition, increased numbers of micronuclei were observed and these were only partly prevented by MitoQ, and the incidence of micronuclei and ion release from the nanoparticles were positively correlated with nanoparticle size, although the cytogenetic changes, modifications in nuclear shape and the amount of ROS were not. These results suggest that cells exhibit diverse mitochondrial ROS-dependent and independent responses to CoCr particles, and that nanoparticle size and the amount of metal ion released are influential.

Genetic and biochemical biomarkers in the macrophyte Bidens laevis L. Exposed to a commercial formulation of endosulfan

Previous studies in the wetland macrophyte Bidens laevis L have demonstrated that the insecticide endosulfan induces a high frequency of somatic chromosome aberrations in anaphase-telophase (CAAT) but no DNA changes as determined by the single cell gel electrophoresis (Comet) assay. Thus, cytogenetic biomarkers appear to be more sensitive to the toxic effects of the insecticide than the DNA molecule in the studied species. For this reason, the goals of this study were to use cytogenetic biomarkers--CAAT and abnormal metaphase--and defense biomarkers such as the activity of the antioxidant enzymes--guaiacol peroxidases (POD), glutathione reductase, and microsomal and cytosolic (m- and c-) glutathione-S-transferase (GST)--to evaluate in B. laevis effects caused by a commercial formulation of endosulfan. The frequency of CAAT was increased at 5, 10, 50, and 100 μg/L endosulfan with respect to the negative controls by 3.1, 2.5, 2.5, and 3.2-fold, respectively while the frequency of abnormal metaphases was also increased at the same concentrations by 3.5, 2.8, 3.2, and 11.3-fold, respectively. In addition to these aneugenic effects, other abnormalities such as C-mitosis and chromosome clumping were observed at 10 μg/L endosulfan. On the other hand, POD induction at 0.02, 0.5, 5, and 10 μg/L and m-GST inhibition at 0.5, 10, and 50 μg/L in plants exposed during 24 h to endosulfan were observed but all of these responses were highly variable. In conclusion, only cytogenetic biomarkers like CAAT in B. laevis can serve potentially as early warning systems to detect environmentally relevant concentrations of endosulfan in aquatic ecosystems.

Flow Karyotyping of Wheat Addition Line “T240” with a Haynaldia villosa 6VS Telosome

To construct a chromosome-specific DNA library of chromosome 6VS from Haynaldia villosa, a wheat alien chromosome addition line T240 with a 6VS chromosome arm and its parental common wheat cv. CA921 were used to optimize protocols for preparing chromosome suspension amenable to flow sorting of the 6VS chromosome. Our results showed that root tips incubated sequentially in Hogland’s solution containing 1.25 mM hydroxyurea (DNA synthesis inhibitor) for 18 h, a hydroxyurea-free period for 2 h, and 1 μM trifluralin for 4 h (metaphase blocking reagent) increased the metaphase index (MI) by up to 62 % . Many metaphase chromosomes were released to form a chromosome suspension when root tips fixed in 2 % paraformaldehyde were treated in a homogenizer at 9,500 rpm for 10–15 s. Most of the released chromosomes had intact morphology. The background solution of chromosome suspension was clear and relatively few of cell debris and chromosome clumps. Univariate flow karyotypes were established with chromosome suspension flow through FACS Vantage 2000 SE flow cytometer. The flow karyotype of CA921 consisted of four chromosome peaks, whereas that for T240 had a fifth peak. This fifth peak in T240 contained the telosome, which was further confirmed to be 6VS through fluorescence in situ hybridization.

Cytogenetic mechanism for reversion of triploids to heteroploid mosaics in Crassostrea gigas (Thunberg) and Crassostrea ariakensis

AbstractTriploid oyster induction has been very successful.However, during ¢eld culture, a certain proportionof triploids apparentlyloses one set of chromosomes,‘reverting’to diploid^triploid mosaics.The revertantswill lose theiraquaculture advantages due to the re-covery of reproductive ability. Mitotic chromosomeswere observed in mosaics of Crassostrea gigas andCrassostrea Ariakensis to elucidate the cytogeneticmechanism of reversion. Most individuals showed amodal number of 30 in triploid cells and varyingnumbers of chromosomes in other cells. From all15mosaics of C.gigas and16 mosaics ofC. ariakensis in-dividuals, high proportions of aneuploid cells withvarious numbers of chromosomes were observed.Most of the aneuploid cells were hypotriploid cellswith 26^29 chromosomes. Notably, in 10 out of 15C. gigas and 9 out of16 C. ariakensis ,somecellscon-sisted of 20^26 well-spread chromosomes and 3^10chromosome ‘clumps’. Individuals with more chro-mosome clumps tended to have higher percentagesof hypotriploid cells. The correlation between thesetwo categories of cells was signi¢cant (Po0.05) in C.gigasand highlysigni¢cant ( Po0.01) in C.ariakensis.Thus, we conclude that some chromosomes areeliminated during mitotic divisions because theyclump together and are thus unable to undergo nor-mal segregation.Keywords: triploid oyster, reversion, mechanism,chromosome eliminationIntroductionTriploid induction has become one of the most im-portant and successful genetic breeding techniquesin aquaculture (Thorgaard1983;Thorgaard & AllenJr1986).The use of triploidy is based onthe principlethattriploidsaresterilebecauseoftheoddnumberofchromosome sets (Thorgaard 1983; Allen Jr 1987).There are severaladvantages of sterility.The ¢rst ad-vantagederivesfromthefactthatsteriletriploidscanmaintain higher market quality and often highergrowth rates during the reproductive season, whennormal diploids consume much of their energy onproducing gametes, thereby reducing £esh qualityand the somatic growth rate.The second advantageis that undesirable population proliferation of cul-turedstockscanbecontrolled,reducingtheopportu-nityfor‘geneticpollution’.Thethirdadvantageisthatsterilityaiords the possibilityof biological control ofreproduction, i.e. genetically modi¢ed organisms ornon-native species can be introduced to foreign en-vironments without risktonative species.Triploidoysterhasbeenthemostsuccessfulexam-ple for the application of triploidy in aquaculture(AllenJr1988; AllenJr, Downing & Chew1989). Uptoa few years ago, the primary method for producingtriploid oysters was to inhibit the second polar body(PB2) extrusion of newly fertilized eggs with cyto-chalasin B (CB) (chemical triploids, Allen Jr et al.1989). This method does not produce100% triploidsbecause some of the eggs may escape treatment forvariousreasons.Recently,theproductionof100%tri-

Clathrin is essential for meiotic spindle function in oocytes

In the mammalian ovary, oocytes are arrested at prophase of meiosis I until a hormonal stimulus triggers resumption of meiosis. During the subsequent meiotic maturation process, which includes completion of the first meiotic division and formation of the second metaphase spindle, oocytes acquire competence for fertilization. Recently, it was shown that clathrin, a cytosolic protein complex originally defined for its role in intracellular membrane traffic, is also involved in the stabilization of kinetochore fibers in mitotic spindles of dividing somatic cells. However, whether clathrin has a similar function in meiotic spindles in oocytes has not been investigated previously. Our results show that endogenous clathrin associates with the meiotic spindles in oocytes. To study the function of clathrin during meiotic maturation, we microinjected green fluorescent protein-tagged C-terminal and N-terminal dominant-negative clathrin protein constructs into isolated porcine oocytes prior to in vitro maturation. Both protein constructs associated with meiotic spindles similar to endogenous clathrin, but induced misalignment and clumping of chromosomes, occurrence of cytoplasmic chromatin and failure of polar body extrusion. These data demonstrate that clathrin plays a crucial role in meiotic spindle function in maturing oocytes, possibly through spindle stabilization.

Nuclear and non-nuclear interactions in F_1 hybrid populations of three Solanum species in the subgenus Leptostemonum,section Melongena (Solanaceae)

Reciprocal crosses involving Solanum gilo Raddi, S. anguivi Lam. and S. macrocarpon L., subg. Leptostemonum (Dunal) Bitter sect. Melongena Dunal were produced in order to assess inherent nuclear and non-nuclear influences on hybrid fitness, the extent of genomic change, and species compatibility. Hybrids expressed intermediacy and overlaps in leaf, petiole, petal, and plant height dimensions. Maternal influence was dominant in growth habit, leaf shape and texture, flower colour, and fruit size, while paternal control was limited to fruit colour in Solanum gilo × S. macrocarpon. Pollen viability was reduced from 97.3%-86.5% in parents to 53.8%-20.5% in hybrids. S. gilo × S. macrocarpon produced single-flowered inflorescence, whereas the reciprocal S. macrocarpon × S. gilo developed the ability to perennate, indicating the heterogeneity of the parental genome. Fruits of the hybrids were intermediate or smaller, and had fewer seeds. They were wrinkled in S. gilo × S. macrocarpon, with many aborted seeds. Meiosis was irregular, with few laggards, and isolated uni- and bivalent chromosomes associated with foreign genes in the parent species. Conversely, multivalent and chromosome clumps revealed the extent of homogenization of the parental genomes and species affinity. The maternal genome exerted profound influence on hybrid phenotype and fitness, and should inform and direct future hybridization efforts.

Microsporogenesis and meiotic abnormalities in the hybrid complex of Phlomis composita (Lamiaceae)

The extent of chromosome structural differences such as permanent translocations and paracentric inversions has been studied in the hybrid complex of Phlomis composita and its putative parental taxa P. lychnitis and P. crinita. They are detected as meiotic abnormalities during microsporogenesis. In total, 117 plants from 19 populations in Andalusia (southern Spain) and Levante (eastern Spain) were studied for ploidy level, chromosome clumping, multivalent or univalent formation, late bivalent disjunction with bridges, chromatin bridges and fragments, irregular polysporads and variable pollen size. All individuals had the diploid chromosome number 2n = 20, with no significant difference in the frequencies of the above meiotic abnormalities either at taxon or population levels. However, very different frequencies were observed on the regional scale between populations in Andalusia and Levante. The results are discussed within the theoretical framework of homoploid hybrid or recombinational speciation. © 2003 The Linnean Society of London, Botanical Journal of the Linnean Society, 2003, 143, 79−85.

Glutathione oxidation is associated with altered microtubule function and disrupted fertilization in mature hamster oocytes.

We hypothesized that depletion of glutathione (GSH) with diamide, a relatively specific GSH oxidant, may alter the meiotic spindle apparatus in mature hamster oocytes. Immunofluorescent analysis of oocytes exposed to diamide for 1.5 or 3 h revealed time- and concentration-dependent disruption of spindle morphology accompanied by chromosome clumping. In oocytes first cultured in diamide for 1.5 h and then in diamide-free medium for 1.5 or 3 h, microtubules appeared to repolymerize, but normal spindle structure was not regained. HPLC confirmed that diamide oxidized oocyte GSH under conditions identical to those associated with spindle-related abnormalities. Exposure of oocytes to 25 or 50 microM diamide before in vitro fertilization did not affect their ability to undergo fertilization. A significant proportion of the fertilized oocytes that had been exposed to 50 microM diamide before insemination exhibited abnormal multiple female pronuclei with an apparently normal male pronucleus. These observations indicate that mature hamster oocytes are susceptible to oxidative stress during the critical period that precedes fertilization and provide further evidence that GSH plays important roles in oocyte spindle function and pronucleus development.