Distribution of heterochromatin in a reconstructed karyotype of Vicia faba as identified by banding- and DNA-late replication patterns

1) The distribution pattern of heterochromatin characterized by Giemsa-banding, Quinacrine-banding and DNA-late replication has been studied in a reconstructed karyotype of Vicia faba with all chromosome pairs interdistinguishable. 2) By means of two Giemsa-banding methods both an interstitial and a centromeric Giemsa-banding pattern are described. The former one comprehends 14 marker and 18 additional bands of lower but characteristic visualization frequencies. The centromeric Giemsa-banding pattern consists of 7 bands, located in the centromeric and in the secondary constrictions of the metaphase chromosomes. Chromosomes with banding patterns intermediate between the interstitial and the centromeric Giemsa-banding have also been observed. 3) Quinacrine-banding revealed 10–12 brightly fluorescent bands and 1–2 regions of dim fluorescence. Most Q-bands occupy chromosomal positions also characterized by interstitial Giemsa bands. 4) The DNA-late replication pattern, analyzed both by autoradiography and by FPG-technique, revealed 9 late replicating chromosome regions; all of these correspond positionally to the sites of interstitial Giemsa bands. 5) The results are discussed with respect to (a) the relationships between the banding- and the DNA-late replication pattern; (b) banding and heterochromatin characteristics; (c) the correlations between the distribution of chromatid aberrations and special types of heterochromatin. — The patterns of heterochromatin distribution found are in basic conformity with the corresponding patterns reported for the standard karyotype of Vicia faba. The heterochromatin type characterized by both Giemsabanding and late replication is characteristic of all those chromosome regions which after mutagen treatments show up as aberration hot spots. Positional correlations between interstitial Giemsa marker bands and chemically induced isochromatid breaks are indicative of preferential aberration clustering in heterochromatin/euchromatin junctions.     

Analysis of chromatin-associated fiber arrays

The distribution of constitutive heterochromatin has been investigated in four chromosomal races of the grasshopper Caledia captiva (2n= 23 /24 ) by the C-banding technique. Each of the four races was found to have a distinctive banding pattern which is associated with the inter-racial differences in chromosomal rearrangements. — The Ancestral race has a telocentric chromosome complement with large procentric C-bands which are structurally double on six pairs of chromosomes. The centromeres are unstained. — The General Purpose race has a C-banding pattern very similar to that seen in other Acridine grasshoppers with the majority of its chromosomes showing a centromeric localisation of the bands. — The two southern races, which show a complex polymorphism for presumed pericentric inversions on all twelve chromosomes, also show an unusually high level of interstitial and terminal C-bands. The different locations and numbers of these bands allow unambiguous identification of all the chromosome pairs within the complement. — In two cases, there is good evidence to indicate that a C-band redistribution between acrocentric and metacentric chromosomes has occurred by pericentric inversion. Furthermore, C-band variation on the long arm of the metacentric X-chromosome indicates the presence of a large paracentric inversion. This double inversion system has involved over 95% of the X-chromosome. — The interstitial and terminal C-bands probably have not resulted from heterochromatin movement within the complement but, more likely, have arisen by saltatory duplication of pre-existing sequences on the chromosome. — A new nomenclature system for banded chromosomes is proposed which allows most kinds of chromosomal restructuring and rearrangement to be adequately enumerated.     

Cytogenetics of the chinese giant salamander,Andrias davidianus (Blanchard): the evolutionary significance of cryptobranchoid karyotypes

Cytogenetic aspects of the cryptobranchid salamander Andrias davidianus of western China have been studied, including chromosome number and morphology, C-band patterns, meiosis, and the chromosomal localization of ribosomal 5S RNA genes. Our data regarding chromosome number (2n=60) and general chromosome morphology largely confirm the results of Morescalchi et al. (1977). The karyotype consists of 16 pairs of macrochromosomes that decrease gradually in relative length to 14 pairs of microchromosomes. Telocentric chromosomes are a conspicuous feature of the karyotype, representing more than half the genome. Differential staining reveals that all of the chromosomes, except four pairs of microchromosomes, have C-band heterochromatin in their centromeric regions, the amount varying irrespective of chromosome size. Faint bands of interstitial and telomeric C-band heterochromatin are found in mitotic chromosomes but are not seen in meiotic preparations. In C-banded mitotic preparations from a female, one of the smallest macrochromosome pairs is heteromorphic in respect to C-band heterochromatin and centromere position. In situ hybridization of an iodinated 5S RNA probe to meiotic chromosome preparations reveals that this repeated gene is clustered near the telomeric region of chromosome 7, a medium size telocentric, a location corresponding to a band of heterochromatin. Studies of spermatocytes indicate that the process of meiosis in A. davidianus closely resembles that of more advanced salamanders, and that the microchromosomes are meiotically stable. The significance of microchromosomes and chromosome morphology in the reorganization of salamander genomes during evolution is discussed on the basis of cytogenetic data available for A. davidianus and various other primitive and advanced salamanders.     

The salivary gland chromosomes of Dasyneura crataegi (Diptera: Cecidomyiidae)

Four distinctly crossbanded, stout polytene chromosomes are present in the nuclei of both the basal reservoir region and gland proper region of salivary glands of young larvae of the Cecidomyid Dasyneura crataegi. In older larvae, asynchronous progressive splitting of the chromosomes into oligotene fibrils occurs, underlining their truly polytene nature. Three nucleoli are present, located on two of the chromosomes. A series of massive puffs is also organised by one of the nucleolar chromosomes. Three other features of interest shown by the chromosomes of this species are (a) the centromeric association of only two, the nucleolar organising, chromosomes of the four present; (b) the high breakability of the centromeric regions of these two chromosomes; and (c) the marked heterochromatin proliferation which is found at these regions in older larvae. As in most Cecidomyids, the salivary glands are of complex structure with anterior basal reservoir and posterior gland proper zones. Marked differences in the relative and absolute sizes of these two regions are found during the development of the glands, which indicate that their names are inappropriate to their probable functions.     

Heterochromatin variation in Cryptobothrus chrysophorus

The endemic grasshopper Cryptobothrus chrysophorus is widely distributed throughout S.E. Australia and its populations display an extensive and spectacular pattern of autosomal variation. While the standard telocentric complement of three long (L1–3), six medium (M4–9) and two short (S10–11) autosome pairs is present throughout most of its range, two quite distinct chromosome races can be defined within this species. Populations in the northern part of its distribution (northern N.S.W. and southern Queensland-northern race) are differentiated from the remainder (southern race) by fixed blocks of distal heterochromatin on autosomes M4, 5, 6, 8 and 9 and by differences in the character of the megameric M7 chromosome. Additionally, while many populations in both races show a polymorphic system of supernumerary segments on the two smallest autosomes (S10–11), that found in the northern race is both more variable and more complex. On the other hand all the populations of the southern race we have examined are polymorphic for a series of centric shifts which convert telocentrics into acro- or meta-centrics. These occur more commonly in the megameric M7 and the two smallest autosomes (S10–11) although in one population (Forbes Creek, N.S.W.) at least 12 different shifts involving 8 of the autosomes (L3, M4, 5, 6, 7, 8, 9 and S10) are known. By contrast, in the northern erace only the small autosomes (S10–11) show centric shifts. These several floating and fixed variants thus involve all chromosomes of the standard set other than the two largest autosomes (L1–2) and the X-chromosome, which appear to be invariate. Finally, morphologically distinct supernumerary (B) chromosomes, intermediate in size between the standard S10 and the M9 elements, are found in both races but are especially common in Tasmania, the most southerly point of the species range. These B-chromosomes are partly heterochromatic and partly euchromatic so that they too add to the considerable heterochromatin variation in this species.     

Telomere and centromere association tendencies in the human male metaphase complement

Summary Generalized distances between centromeres and between telomeres were statistically analyzed (x ² tests) in 100 trypsin-banded metaphase figures derived from normal males.Analysis of association tendencies on the first column of obtained c-c, p-p, q-p, and p-q histograms showed significant heterochromatin attraction not only between nonacrocentrics and acrocentrics but also between two nonacrocentric chromosome pairs (1 and 16). However since, not all c-heterochromatin-rich chromosomes were involved in associations (pair 5), and conversely, since chromosomes without an important centromeric heterochromatin block were involved in associations (pairs 8 and 11), it is probable that centromeric heterochromatin is not the only factor responsible for chromosome association. Moreover associations occur not only at the centromeres; in our circle analysis of the binding capacity of the telomeres or centromere of one chromosome pair with the telomeres or the centromeres of all other chromosome pairs, we also found preferential associations for T(4,13), T(9,15), T(11,15), T(13,19) T(15,19), T(17,18), T(17,22), and T(19,20).We therefore suggest that heterochromatin is not the only reason for chromosome association and that telomeres may also play an important part in this process.     

Chromosomes and DNA of Mus: Terminal DNA synthetic sequences in three species

The DNA replication patterns of the terminal S phase of three species of Mus were analyzed by tritiated thymidine autoradiography. The centromeric heterochromatin of M. fulvidiventris is the latest component to finish DNA synthesis. The Y chromosome finishes replication earlier than the centromeric heterochromatin. The centromeric heterochromatin of M. musculus, on the other hand, is not the latest component to finish DNA synthesis. At the very late S phase, grains are found in the euchromatic arms instead of the heterochromatic areas. The hot X and the hot Y can be identified in the majority of, but not all, cases. The heterochromatic short arms of the autosomes in M. dunni finish DNA replication earlier than many areas in the euchromatic long arms and the heterochromatin of the sex chromosomes. This indicates that in M. dunni there are at least two types of heterochromatin. The late-replicating zones in the euchromatic long arms are distinctly banded. This banded grain pattern can be seen in all Mus species observed, but in M. dunni it is most exaggerated. Late-replicating chromosome segments can be demonstrated also by 2+ cycles of BUdR incorporation and Giemsa staining.     

Organization and evolution of alpha satellite DNA from human chromosome 11

The human alpha satellite repetitive DNA family is organized as distinct chromosomal subsets located at the centromeric regions of each human chromosome. Here, we describe a subset of the alpha satellite which is localized to human chromosome 11. The principal unit of repetition of this alpha satellite subset is an 850 bp XbaI fragment composed of five tandem diverged alphoid monomers, each 171 bp in length. The pentamer repeat units are themselves tandemly reiterated, present in 500 copies per chromosome 11. In filter hybridization experiments, the Alpha 11 probes are specific for the centromeric alpha satellite sequences of human chromosome 11. The complete nucleotide sequences of two independent copies of the XbaI pentamer reveal a pentameric configuration shared with the alphoid repeats of chromosomes 17 and X, consistent with the existence of an ancestral pentameric repeat common to the centromeric arrays of at least these three human chromosomes.     

Unterschiedliche Mutationsspektren verschiedener reiner linien der Sippe 50 vonAntirrhinum Majus L. nach gleicher Behandlung mit R?ntgenstrahlen

Ohne ZusammenfassungHerrn Professor Dr. Dr. h.c.Hans Kappert zum 75. Geburtstag gewidmet.Der Deutschen Forschungsgemeinschaft danke ich für die Unterstützung dieser Arbeit.     

The mitochondrially encoded "phantom ATPase" of S. cerevisiae. II. A heterogeneous mitochondrial ATPase population in situ.

Summary The mitochondrial ATPase from a PHO 1 mutant (OLI 2, PHO 1, OLI 4 region on mit DNA of S. cerevisiae) was further examined. A new purification method using Lysolecithin instead of Triton allowed us to solubilize and separate a heterogeneous ATPase population from PHO 1-mitochondria: the major abnormal fraction had extremely low oligomycin-sensitivity (but normal specific immunological reactivity), while a minor normal fraction (representing about 20% of the initial mitochondrial ATPase activity) had high sensitivity and affinity for oligomycin.Moderate urea treatment of PHO 1-mitochondria leads to partial loss of ATPase activity and a concomitant increase of oligomycin-sensitivity, suggesting that a heterogeneous ATPase population exists in situ in the mitochondrial membrane: part of the major abnormal ATPase fraction is selectively inactivated by urea, producing a concomitant enrichment in the initially minor normal ATPase fraction.If the minor normal ATPase fraction is the only one capable of in vivo ATP synthesis, the deficient but oligomycin-sensitive cell growth and oxidative phosphorylation in vitro are readily explained.Further structural studies are under way to ascertain whether the minor normal ATPase fraction is strictly identical to the wild type, in which case PHO 1 is a regulatory gene, or not, in which case PHO 1 is a structural gene.     

Modulation of natural killer activity by thymosin alpha 1 and interferon

Summary A single injection of -interferon (-IFN) (30 000 units/mouse), a major biological modifier of natural killer (NK) cytolytic activity, strongly stimulated NK activity in normal mice, as expected, while the same treatment did not statistically alter the NK response in cyclophosphamide (CY)-suppressed animals.We investigated the possibility of thymosin ₁ cooperating with -IFN in boosting NK activity in CY-suppressed animals.The results show that treatment with thymosin ₁ (200 g/kg) for 4 days, followed by a single injection of -IFN 24 h before testing, strongly restored NK activity in CY-suppressed mice. Thymosin ₁ was, moreover, able to accelerate the recovery rate of NK activity in bone marrow reconstituted murine chimeras.Taken together the data support the concept that the synergic effect between thymosin ₁ and -IFN could be the result of effects on differentiation of the NK lineage at different levels.     

Spermatogonia and the cycle of the seminiferous epithelium in the nine-banded armadillo

Summary The cycle of the seminiferous epithelium of the nine-banded armadillo can be divided into ten stages. As in most mammals, only one stage is observed per tubular cross-section. The process of spermiogenesis can be divided into thirteen steps according to the development of the acrosomal system and the flagellum. Four generations of spermatogonia are observed in the germinal epithelium: 1) stem cells, 2) type A, 3) intermediate, and 4) type B spermatogonia. The stem cell is characterized by a highly irregular nucleus and the presence of glycogen in its cytoplasm. The type A spermatogonium contains an oblong nucleus with one or two shallow infoldings of the nuclear membrane. The intermediate spermatogonium contains an ovoid nucleus characterized by one or two nuclei and heterochromatin scattered in the nucleoplasm. The nucleus of the type B spermatogonium is more spherically shaped with a centrally placed nucleolus and heterochromatin associated with the nuclear envelope.The author wishes to acknowledge the technical assistance of Teri Lane     

Cytological analysis on the distribution and origin of the alien chromosome pair conferring blue aleurone color in several European common wheat (Triticum aestivum L.) strains

Summary Meiotic chromosome pairing and Giemsa C-banding analyses in crosses of several European blue-grained wheat strains with Chinese Spring double ditelosomic and other aneuploid lines showed that Triticum aestivum Blaukorn strains Berlin, Probstdorf, Tschermak, and Weihenstephan are chromosome substitutions, in which the complete wheat chromosome 4A pair is replaced, whereas the strains Brünn and Moskau are 4B substitutions. The alien chromosome pair in all of these strains is an A genome chromosome (4A) from diploid Triticum monococcum or T. boeoticum not present in common tetraploid and hexaploid cultivated wheats. The Blaukorn strain Weihenstephan W 70a86 possesses, in addition to a rye chromosome pair 5R compensating for the loss of part of chromosome 5D, a 4A/5DL translocation replacing chromosome pair 4B of wheat.     

Genetic analysis of gliadin-encoding genes reveals gene clusters as well as single remote genes

Summary Analysis of F₂ grains from two different crosses has revealed a complex organization of the family of gliadin-coding genes located on chromosomes of the first homoeological group in hexaploid wheat. Chromosome 1A of variety Bezenchukskaya 98 was found to carry at least five gliadin-coding genes of which three genes form a cluster controlling the synthesis of the GLD1A1 block. Two additional genes are located on the both sides of this cluster and recombine with it at frequencies of 5±1.3% and 13±2.9%. Gliadinencoding genes recombining with the main clusters were also found on chromosomes 1B and 1A in the Bezenchukskaya 98 and Saratovskaya 210 varieties, respectively. In Chinese Spring, widely used in genetic studies, we discovered a recombination between genes located on chromosome 1A and controlling the synthesis of - and -gliadins. Varieties and biotypes of one variety may differ by the presence or absence of such selfish (not included in clusters) gliadin components. The similarity of organization of prolamine-coding genes on chromosomes in different cereals is considered.     

Meiotic chromosome pairing and synaptonemal complex transformation in Culex pipiens oocytes

The synaptonemal complexes of the oocytes of the mosquito Culex pipiens quinquefasciatus have been reconstructed from serial sections. A diffuse structure, probably a chromocenter composed of centromeric heterochromatin, was present during pachytene. As no synaptonemal complexes were visible inside the chromocenter the continuity of the 2 arms of a bivalent was lost. The telomeric ends were clustered in a small area of the nuclear membrane in a bouquet arrangement; they were associated in pairs, and sometimes joined through a special structure. One pair was composed of the 2 telomeres of the shortest bivalent and a ring configuration was thus formed. The other 2 chromosomes may form one or two rings. During a short transitional stage, after the disappearence of the synaptonemal complexes, several thousand annuli, 1200–1500 A in diameter, were present in the nuclei. The annuli disappeared as material originating mainly from the transverse filaments of the synaptonemal complexes formed a capsule around the chromosomes during diplotene.     

Population cytogenetics of the genus Caledia (Orthoptera: Acridinae)

The acridine grasshopper, Caledia captiva exists as two chromosomal races in south-east Queensland. One of these, the Moreton race inhabits the coastal region to the east of the Great Dividing Range. All chromosomes of the complement (2n=11II+XO/XX) have been involved in centromeric rearrangement, which transforms the acro- and telocentric chromosomes into submeta- and metacentric elements. The second, or Torresian race is widely distributed through southern Papua, Arnhem Land, Cape York Peninsula and down the east coast of Australia as far south as Brisbane. This race, which is characterised by a completely acro- and telocentric chromosome complement, approaches the Moreton race in south-east Queensland where the two races are separated by less than 1 km, along a front of at least 150 km. Evidence is presented to show that chromosome introgression is occurring across the contact zone and this takes place in one direction only, namely the Torresian chromosomes are infiltrating into the Moreton race but not reciprocally. Furthermore, the introgression of chromosomes across the zone is limited to certain members of the Torresian complement and even then these successful chromosomes show highly variable degrees of penetrance into the Moreton race. It is proposed that a tension zone exists between these two races which is maintained by the interaction of (a) ecological tolerance differences on either side of the zone and (b) by partial competitive exclusion due to the interracial differences in phenology. This case of parapatric association with limited hybridisation is unique in its clarity due to the marked differences in the appearance of the chromosome complements of these races which permits direct assessment of the behaviour of most members of the genome in hybrids and their derivatives.     

The fine structure of chickpea (Cicer arietinum L.) chromosomes as revealed by pachytene analysis

A standard pachytene karyotype of chickpea (Cicer arietinum L.) is presented for the first time. Individual pachytene chromosomes were identified and described in detail. An idiogram was prepared on the basis of chromosome length, arm ratio, and distribution of heterochromatin and euchromatin. Chickpea pachytene chromosomes belong to the differentiated type with darker staining heterochromatin proximal to and lighter staining euchromatin distal to the centromeres. Chromosomes were numbered from 1 to 8 following a descending order of length. The total length of the chromosome complement at pachytene was 335.33 , and chromosome size ranged from 58.05 to 30.53 .     

Centromeric association of a microchromosome in a Turner syndrome patient with a pseudodicentric Y

A 12-year-old patient with Turner syndrome was found to have a complex mosaicism for a microchromosome (MC) and a psu dic(Y)(q11). The MC was smaller than Yp, appeared pale in G, C and late replicating bands, had a pair of small centromeric dots, was associated with other chromosomes in most metaphases, and was rather stable both in size and during mitosis. The psu dic(Y) was Cd-positive only at the active centromere, had two pericentromeric heterochromatic regions, and lacked the Yq12 band. No cells with both abnormal chromosomes were found. To evaluate the association of the MC with all ordinary chromosomes, 857 G-banded cells with the marker were screened. The MC was considered as associated whenever the distance between it and other chromosome(s) was equal to, or smaller than, 18p. Out of 848 associations registered, 489 (57.7%) were centromeric, 202 (23.8%) telomeric, and 157 (18.5%) interstitial; i.e., centromeric associations were overrepresented (P < 0.001) and showed a random distribution, except for an excessive involvement of chromosome 8. This association pattern, also exhibited by two similar MCs in human beings, the minute Y of a marsupial and certain B chromosomes in plants, probably reflects the Rabl orientation of chromosomes in interphase.     

Internal motion time scales of a small, highly stable and disulfide-rich protein: A 15N, 13C NMR and molecular dynamics study

Motions of the backbone CH and threonine CH bonds of toxin were investigated using natural abundance 13C NMR and molecular dynamics. Measurement of the 13C longitudinal and transverse relaxation rates employed ACCORDION techniques together with coherence selection by pulsed field gradients and sensitivity enhancement through the use of preservation of equivalent pathway, thus allowing a considerable reduction of the required spectrometer time. 13C R1, R2, 1H13C NOE were obtained, as well as the variations of R1(90° ) as a function of the rf field strength. These data were compared to those recorded by 1H and 15N NMR on a labelled sample of the toxin [Guenneugues et al. (1997) Biochemistry, 36, 16097–16108]. Both sets of data showed that picosecond to nanosecond time scale motions are well correlated to the secondary structure of the protein. This was further reinforced by the analysis of a 1 ns molecular dynamics simulation in water. Several CH and threonine CH experimentally exhibit fast motions with a correlation time longer than 500 ps, that cannot be sampled along the simulation. In addition, the backbone exhibits motions on the microsecond to millisecond time scale on more than half of its length. Thus, toxin , a highly stable protein (Tm=75°C at acidic pH) containing 61 amino acids and 4 disulfides, shows important internal motions on time scales ranging from 0.1–0.5 ps, to 10–100 ps, 1 ns, and about 30 s to 10 ms.     

Contrasting leaf and ‘ecosystem’ CO2 and H2O exchange in Avena fatua monoculture: Growth at ambient and elevated CO2

Elevated CO₂ (ambient + 35 Pa) increased shoot dry mass production in Avena fatua by 68% at maturity. This increase in shoot biomass was paralleled by an 81% increase in average net CO₂ uptake (A) per unit of leaf area and a 65% increase in average A at the ecosystem level per unit of ground area. Elevated CO₂ also increased ecosystem A per unit of biomass. However, the products of total leaf area and light-saturated leaf A divided by the ground surface area over time appeared to lie on a single response curve for both CO₂ treatments. The approximate slope of the response suggests that the integrated light saturated capacity for leaf photosynthesis is 10-fold greater than the ecosystem rate. Ecosystem respiration (night) per unit of ground area, which includes soil and plant respiration, ranged from-20 (at day 19) to-18 (at day 40) mol m^-2 s^-1 for both elevated and ambient CO₂ Avena. Ecosystem below-ground respiration at the time of seedling emergence was -10 mol m^-2 s^-1, while that occuring after shoot removal at the termination of the experiment ranged from -5 to-6 mol m^-2 s^-1. Hence, no significant differences between elevated and ambient CO₂ treatments were found in any respiration measure on a ground area basis, though ecosystem respiration on a shoot biomass basis was clearly reduced by elevated CO₂. Significant differences existed between leaf and ecosystem water flux. In general, leaf transpiration (E) decreased over the course of the experiment, possibly in response to leaf aging, while ecosystem rates of evapotranspiration (ET) remained constant, probably because falling leaf rates were offset by an increasing total leaf biomass. Transpiration was lower in plants grown at elevated CO₂, though variation was high because of variability in leaf age and ambient light conditions and differences were not significant. In contrast, ecosystem evapotranspiration (ET) was significantly decreased by elevated CO₂ on 5 out of 8 measurement dates. Photosynthetic water use efficiencies (A/E at the leaf level, A/ET at the ecosystem level) were increased by elevated CO₂. Increases were due to both increased A at leaf and ecosystem level and decreased leaf E and ecosystem ET.