Meiotic Chromosome Configurations Research Articles

Triploid Property of Senno (Lychnis senno Siebold et Zucc., Caryophyllaceae), a Traditional Ornamental Plant Conserved in Japan

‘Senno’ (Lychnis senno Siebold et Zucc., Caryophyllaceae), is a traditional and endangered ornamental plant species and presently only eleven strains have been confirmed to be under cultivation in nine localities in Chugoku and Kyushu districts of Japan. Analyses on chromosome number and nuclear DNA contents using flow cytometry revealed that all of the strains are triploid (2n = 36). The average of meiotic chromosome configuration (10.1III + 1.9II + 1.9I) observed in one strain indicated that ‘Senno’ is an autotriploid. Chromosome bridges, lagging chromosomes and micronuclei were observed in microsporogenesis. Although about 70 % of pollen showed stainability with cotton blue solution, ‘Senno’ plants conserved in Japan did not produce any viable seeds by self-pollination. The origin of the ‘Senno’ conserved in Japan is discussed.

Genetic stability and maintenance of Raphanus sativus lines with an added Brassica rapa chromosome

AbstractThe genetic stability and maintenance of Raphanus sativus‐Brassica rapa monosomic chromosome addition lines (a‐h‐types MALs, 2n = 19, BC2), developed by backcrossing the synthesized amphidiploid Raphanobrassica (Raphanus sativus × Brassica rapa, 2n = 38, RRAA) with R. sativus cv. ‘Shogoin’ (2n = 18, RR), was investigated. Transmission of the added alien chromosome through selected smaller seeds (SSS) and the inheritance of morphological traits and random amplified polymorphic DNA (RAPD)‐specific markers together with meiotic chromosome configuration and seed fertility were also investigated for three successive generations (BC3 to BC5). The distinctive traits and the RAPD‐specific markers of the eight types of MAL were substantially inherited and stably maintained throughout three generations, although a few variant plants (2n =18) resembling MALs (2n = 19) and hyperploidal plants (2n = 26 and 2n = 37) were generated in the earlier generations of BC3 and BC4 in comparison with BC5. The average transmission rates for three generations ranged from 26% for both the b‐type and the d‐type to 44% for the e‐type through SSS. On the other hand, the transmission rates through randomly selected seeds (RSS) were lower, ranging from 6.5% for the f‐type to 23.5% for the b‐type. In meiosis, more than 90% of PMCs showed the 9II +1I pairing configuration at metaphase I throughout three generations. For seed fertility, when backcrossed with the radish cv. ‘Shogoin’, the values were approximately 180% to 500% with the mode around 300% with the seed harvested from a pod increasing with the advancing generations. Genetic recombination between the radish chromosomes and the added chromosome is probably rare, suggesting that the added chromosome is mostly maintained unaltered in the background of the radish genome.

Effects of aromatase inhibition on in vitro follicle and oocyte development analyzed by early preantral mouse follicle culture.

In vivo studies on folliculogenesis have documented a relation among intrafollicular steroid content, follicle growth, and oocyte development. This study examined how profound changes in androgen/estrogen ratio would affect mouse in vitro follicular development. Arimidex, a potent follicular aromatase inhibitor was used for this purpose. Early preantral follicles were cultured for 12 days up to the preovulatory stage. Oocyte's meiotic maturation, spindle and chromosome configurations, in vitro fertilization and preimplantation embryo development were evaluated. Compared to controls, Arimidex reduced E2 concentration in follicle culture medium by a factor 1000, and an expected simultaneous accumulation of testosterone was measured in the conditioned medium. Arimidex treatment provoked a dose-dependent earlier differentiation of the granulosa cells as judged by an earlier antrallike cavity formation and slightly elevated basal progesterone secretion. Follicle survival exceeded 98% in all groups and all follicles responded normally to HCG/EGF addition on day 12 by cumulus mucification. By the HCG ovulatory challenge, progesterone output was reduced in Arimidex supplemented groups suggesting preovulatory luteinization. These results indicate that in vitro mouse follicles can develop normally under very low levels of estrogens and that a local androgen increase by a factor 3 is not atretogenic. Oocyte growth did not differ among culture conditions. Arimidex treatment induced a dose dependent enhancement of GVBD and polar body formation rate in response to HCG at the end of culture. Spindle and chromosome analyses demonstrated that in all groups, 90% of the oocytes which extruded a polar body had also reached the MII stage. While most of the cultured MII oocytes had a normal spindle and well aligned chromosomes, significantly less oocytes were fertilized in the groups cultured in the presence of Arimidex. Once fertilized, however, there was found to be no difference for preimplantation embryo development between controls and Arimidex treatment. These data suggest that in mice a pronounced estrogenic environment is not essential for in vitro folliculogenesis. Drastic changes in the intrafollicular steroid concentrations do not disrupt meiotic maturation nor compromise early preimplantation development, but adversely affect fertilization of in vitro grown oocytes.

Meiotic Chromosome Configurations of XY and "XO" Type Males from Four Species of the Genus Chymomyza(Diptera, Drosophilidae) with a Description of the Karyotype of C. rufithorax.

The karyotype of Chymomyza rufithorax, a species belonging to the procnemis species group of the genus Cymomyza (Diptera, Drosophilidae), is the fundamental one of Cymomyza species, consisting of a pair of rods with a proximal constriction (X chromosome), 2 pairs of large metacentric chromosomes, and a pair of dots. In males of this species, the X chromosome does not have a synaptic mate, and the chromosome number is 7. Therefore the male of this species belongs to the “XO” type, which has been reported for only 3 species in the genus Chymomyza. Meiotic chromosome configurations of the “XO” type males from C. rufithorax and C. obscuroides and the XY males from C. pararufithorax and C. costata were described. XY pairing was found in the XY males, but an X chromosome univalent was observed in the “XO” type males. Meiotic pairing configurations of other autosomes in the “XO” males were found to be similar to those in XY males. These data suggest that the Y chromosome or its pairing site might have degenerated or been eliminated from the genome during the course of speciation.

Chromosome Differentiation in Drosera, Subgenus Rorella, Section Rossolis.

The Drosera chromosomes studied were not localized-centromeric but diffused-centromeric. Among the Drosera taxa studied, only D. filiformis (2n=20) had 20 weak CMA-negative orDAPI-positive large bands more than 2.97 μm2 area each at the same site of 20 chromosomes. Thus, its hybrid with D. intermedia (=Drosera × hybrida, 2n=20) had ten CMA weakly-negative orDAPI-positive bands more than 3.00 μm2 each in the same site of ten chromosomes which could be of the gamete of D. filiformis. Drosera petiolaris (2n=14) displayed the meiotic chromosome configuration of six circular bivalents with four distinct chromatids held each other with end-to-end association and two univalents at metaphase I, while D. rotundifolia (2n=20) displayed ten ring-shaped bivalents, that were quite similar to the bivalents of the localized-centromeric chromosomes. These differences in CMA-positive and DAPI-negative bands, IBAS-area, and meiotic chromosome behavior might be correlated with chromosome differentiation and speciation in the species of Drosera of the Northern and the Southern Hemispheres.

Chromosome configuration during in vitro maturation of goat, sheep and buffalo oocytes

The competence of meiotic chromosome configuration at the time of co-culture of oocytes with spermatozoa is an essential prerequisite for successful in vitro fertilization (IVF). Although this technology has been used in several livestock species, various intrinsic and extrinsic factors affecting the high repeatablity of IVF have yet to be understood. The present study was conducted to determine the appropriate time for coculture of oocytes and spermatozoa in order to optimize the fertilization rate in sheep, goats and buffalo. Oocytes were collected from the ovaries of slaughtered animals. The oocytes were divided into 10 groups and cultured for maturation in TCM-199 supplemented with estrous cow serum for different durations at 38.5 · 0.5|C in a CO 2 incubator. Sheep and goat oocytes were removed from culture medium after 0,6,12,22,24,26,28,30,32 and 36 and buffalo oocytes after 0,6,12,16,20,22,24,26,28, and 36 h. The oocytes were treated with hypotonic solution (0.75M KCl) and fixed in Carony's fixative on glass slides. The fixed oocytes were stained with Giemsa solution, and the meiotic chromosomes were evaluated under a compound microscope at x1000 magnification. Observations were recorded on a total of 1328 oocytes (sheep, 409; goat, 727 and buffalo, 192). The sequential configurations of diffused chromatin, pachytene, diplotene (along with nucleoli), diakinesis and metaphase II (MII) were analyzed at different durations of culture. Control oocytes (fixed at 0 h without incubation) were mostly at the pachytene stage, and as the duration of culture increased the instances of diplotene, diakinesis and finally MII increased. Oocytes at the MII stage of meiosis are known to be at the optimal stage of development for co-culture with spermatozoa and successful in vitro fertilization. On the basis of sequential configuration of chromosomes, it was found that the optimal duration of in vitro maturation of oocytes is 32, 30 and 24 h for sheep, goats and buffalo, respectively.

The Chromosomes of Baicalasellus Angarensis (Isopoda, Asellidae)

To elucidate the cytotaxonomic relationships of endemic Baicalian asellides, the mitotic and meiotic chromosome configurations of Baicalasellus angarensis (Isopoda) were investigated. It was shown that the haploid chromosome number of B. angareresis is: n = 8; sex chromosomes have not been found. The karyotype of B. angarensis was found to be strikingly similar to the karyotype of Asellus aquaticus. It differs from the latter only by the morphology of a single chromosome pair and the number of chiasmata in metaphase 1. On the other hand, it differs markedly from the Japanese Asellus hilgendorfi. Possible implications of this finding on the current view of the origin of Baicalian isopods are discussed.

Cytogeography and meiotic chromosome configurations of six intraspecific aneuploids ofCarex conica Boott (Cyperaceae) in Japan

Chromosome numbers were determined for 340 plants ofCarex conica from 83 populations in Japan. Six aneuploids, 2n=32, 33, 34, 36, 37 and 38, were found. Plants with even diploid chromosome numbers 2n=32, 34, and 36 were the most common and had different geographical distributions. Individuals with 2n=32 were from islands in the Seto Inland Sea and nearby coastal areas of the Chugoku District of Honshu; those with 2n=34 were from the Kanto, Chubu and Kinki Districts of Honshu; those with 2n=36 were from the mountainous areas of Chugoku, Shikoku and Kyushu Districts. Canonical discriminant analysis of 17 morphological characters demonstrated that the plants with 2n=32 were clearly distinct from those with 2n=34 or 36. All four aneuploids with even chromosome numbers showed normal bivalent pairing at meiotic metaphase I and probably represent cytogenetically stable cytodemes. Plants with 2n=33 had one heteromorphic trivalent and 15 bivalents, indicating a structural mutation. At mitotic metaphase I, one chromosome was markedly larger than the others, suggesting that the 2n=33 plants arose from 2n=34 plants by fusion of two chromsomes. The plant with 2n=37 was intermediate in morphology betweenCarex conica (2n=36) andC. morrowii (2n=38) and probably originated as an interspecific hybrid between these species.

Origin, evolution and genome differentiation in Guizotia abyssinica and its wild species

Guizotia abyssinica, G. schimperi and G. scabra are diploid species (2n=2x=30) characterised by 15 bivalents during prophase-I/metaphase-I of meiosis. The former species is cultivated whereas the latter two are wild. Interspecific hybrids between these three species were generated and the F1 hybrids were analysed to assess cytogenetic relationships and crop evolution within the genus Guizotia. Meiotic chromosome configurations at diakenesis/metaphase-I in the pollen mother cells of hybrids averaged 0.25I + 14.60II + 0.15IV for G. abyssinica x G. schimperi, 0.05I + 13.6II + 0.14III + 0.58IV for G. abyssinica x G. scabra, and 0.8I + 12.7II + 0.08III + 0.88IV for G. schimperi x G. scabra. Based upon the results of our investigations we conclude that the genomes of G. abyssinica and G. schimperi are similar and homologous, whereas the G. scabra genome is only partially homologous to that of G. abyssinica/G. schimperi. Furthermore, the crop species G. abyssinica might have originated from G. schimperi through selection and cultivation; chromosome translocations appear to have played a significant role in the divergence and differentiation of these three species.

A New Intergeneric Hybrid between Triticum aestivum L. and Agropyron fragile (Roth) Candargy: Variation in A. fragile for Suppression of the Wheat Ph-Locus Activity

New intergeneric hybrids were obtained between Triticum aestivum L. cv. Tukuho’ (2n = 6x = 42, AABBDD) and Agropyron fragile (Roth) Candargy PGR 8097 (2n = 4x = 28, PPPP) at a frequency of 1.06 %, through the use of direct embryo culture and in ovulo embryo culture. Such hybrids could be used to transfer barley yellow dwarf virus (BYDV) resistance and winterhardiness into bread wheat. The somatic chromosome number in all the hybrid plants was 2n = 5x = 35, as expected. Considerable variation in chromosome pairing was observed among the different hybrid plants. Average meiotic chromosome configuration at metaphase I was 17.29 Is + 6.57 rod Us + 1.97 ring Us + 0.18 III + 0.03 IV + 0.002 VI. The high level of chromosome pairing in some F1 hybrids was attributed to Ph-suppressor gene(s) present in A. fragile. The hybrids could not be backcrossed to wheat, but amphiploid seeds have been obtained by colchicine treatment.

Tetrasomic inheritance and chromosome pairing behaviour in the naturally occurring autotetraploid Heuchera grossulariifolia (Saxifragaceae)

Inheritance patterns at four allozyme loci and chromosome pairing behaviour at diakinesis were examined in the naturally occurring autotetraploid Heuchera grossulariifolia. Segregation patterns for Tpi, Pgi, Pgm-2, and Lap deviated significantly from all possible disomic models. All patterns were consistent with tetrasomic inheritance of these marker loci. No chromatid segregation was detected electrophoretically. Meiotic chromosome configurations at diakinesis in 45 cells were compared with a previously published model to test for autopolyploid-like chromosome pairing. Using the observed chiasma frequencies, the frequency of quadrivalents was consistent with the expectations for an autotetraploid. We suggest that the low frequency of quadrivalents at diakinesis in Heuchera grossulariifolia is due to small chromosome size, which results in a low chiasma frequency.Key words: autopolyploidy, tetrasomic inheritance, chromosome pairing, isozyme genetics, Heuchera.

The genus Rubus (Rosaceae) in South Africa. IV. Natural hybridiza­ tion

The genus Rubus L. is represented in southern Africa by the subgenera Eubatus Focke and Idaeobatus Focke. A combination o f morphological data, data on the reproductive systems of some collections and meiotic chromosome behaviour indicates that a hybrid swarm in the eastern Transvaal was formed subsequent to the hybridization between R. cuneifolius Pursh. taxon B (subgenus Eubatus) and R. longepedicellatus (C. E. Gust.) C. H. Stirton (subgenus Idaeobatus). Other examples of intra- and intersubgeneric hybridization were found during this study of the South African material. These instances, with examples found in the literature, indicate that the subgeneric subdivisions of Rubus are artificial. Three different methods were used to analyse the meiotic chromosome configurations. The genome relationship system of Alonso Kimber (1981) and Kimber Alonso (1981) and the modification of the binomial system of Jackson Casey (1980) by Spies (1984) proved to be the most sensitive for distinguishing between alio-, segmental alio- and autoploids.

Karyology of the northern Baltic peracaridan Crustacea

Abstract To elucidate cytotaxonomic relationships of the species of Isopoda, Amphipoda, and Mysidacea inhabiting the northern Baltic Sea, their mitotic or meiotic chromosome configurations were investigated using orceine squash and Giemsa-stained air spread techniques. The twenty one examined species and their haploid chromosome numbers were Idotea granulosa (n = 28), I. baltica and I. chelipes (n = 29), Mesidotea entomon (n = 30), Jaera ischiosetosa (n = 15), Asellus aquaticus (n = 8), Gammarus oceanicus, G. locusta, G. salinus, G. zaddachi, and G. duebeni (n = 26–27), Calliopius laeviusculus (n = 9), Leptocheirus pilosus (n = 11), Corophium volutator (n = 14), Pontoporeia femorata (n = 14), P. affinis (n = 26), Neomysis integer (n = 34), Mysis mixta, M. relicta, and Praunus inermis (n = 52) and P. flexuosus (n = 49). The observed karyological features are in accordance with phylogenetic reconstructions based on morphology and zoogeographical histories of the species. Mysids are the connecting link with ...

Cytogenetical studies on African rice, Oryza glaberrima Steud. 1. Colchicine-induced autotetraploid.

Cytogenetical study on the colchicine-induced autotetraploid of Oryza glaberrima was carried out. As compared with the diploid, the autotetraploid increased in stomata length, length of penultimate leaf blade, pollen diameter and seed size; decreased in plant height, first internode length, number of panicles, number of spikelets per panicle, pollen stainability and seed fertility. The differences between them were conspicuous in number of panicles, number of spikelets per panicle, seed fertility and seed size. The autotetraploid had multipored pollen grains and awned seeds, which was different qualitatively from the diploid. In pollen mother cells of the autotetraploid, 2 to 12 IV were observed at the stage of diakinesis to metaphase I, and 8IV+8 II most frequently. The mean meiotic chromosome configuration was 7.63IV+0.08 III+8.51 II+0.23 I. The meiotic chromosome configurations observed in the present study could be explained by a hypothesis postulated by Jackson and Casey (1980, 1982) with random pairing among four homologous chromosome arms and a maximum two chiasmata per bivalent.

Chromosome damage induced by artificial seed aging in barley

Barley (Hordeum vulgare L. 'Himalaya') seeds were artificially aged under two storage conditions (32 °C/12% moisture content (m.c.) and 38 °C/18% m.c.) to study the behavior of induced chromosomal aberrations during plant growth. The frequencies of aberrant anaphases at first mitosis in root tips were correlated with loss of germinability. However, after 3 and 5 weeks' growth, aberration frequency declined. In plants grown from artificially aged seeds, the frequency of aberrant anaphases appeared to be stabilized at about 1% after 5 weeks' growth, in spite of the large differences in the frequencies at first mitosis. This suggests that because of their genetic imbalance, cells with chromosomal aberrations induced by seed aging were being excluded during plant growth. Meiotic chromosome configurations at MI were normal (7 II) in all plants studied, although a few precocious separations were found. Meiotic aberrations were found at AI-TI, AII-TII and the tetrad stages in the pollen mother cells of plants grown from the control and artificially aged seeds. However, there were no clear differences among the control and the two aging treatments. It was obvious that some cells with meiotic chromosomal aberrations were lost between the AI-TI and AII-TII stages, and still more between the AII-TII and tetrad stages. The frequency of tetrads with micronuclei in plants produced from artificially aged seeds was the same as in the control. The plants grown from artificially aged seeds showed high pollen fertility (95.2 to 97.0%) and seed fertility (90.1 to 97.2%) which was comparable to the control values (97.4 and 97.9%) respectively, indicating no special effects of seed aging. Anaphase cells of the first mitosis in the next (A2) generation were analyzed to study the transmission of chromosomal aberrations through mitotic and meiotic cell divisions in the A1 generation. Aberrant anaphases in the progeny from the artificially aged seeds were not higher than those of the control progeny. This indicates that the chromosomal aberrations induced by seed aging are not transmitted to the next generation.

Temperature and chiasma formation in Rhoeo spathacea var. variegata

A clone of Rhoeo spathacea var. variegata was exposed to a constant temperature of 37°C to examine the effects of high temperature on the chiasma frequency. Rhoeo was chosen for this study for its unusual meiotic chromosome configurations (rings and chains) at diakinesis and the first metaphase which permitted the calculation of terminal-chiasma frequency, and for its genetic homogeneity among plants in a clone. Plants treated for 12 h and 24 h at 37°C had similar mean terminal-chiasma frequencies to that of controls (10.93±0.11, 10.95±0.09 and 10.64±0.07 respectively), while those treated for 36 h, 48 h or 60 h had lower mean terminal-chiasma frequencies than that of controls (8.06±0.18, 4.25±0.15, 0.76±0.07 and 10.64±0.07 respectively). Analysis of variance was performed to find out whether the mean terminal-chiasma frequencies resulted from different treatments were significantly different from one another. The results of the analysis indicated that prolonged exposures to high temperature significantly reduced the chiasma frequencies.

Tissue culture in Haworthia

Plants regenerated on two different media (NK and I) from the calluses of simple or cloned subcultures, which were originated from a single stock callus of Haworthia setata derived from its flower bud, were observed for eight characters, i.e., somatic chromosome number in root tips, growth vigor, leaf shape, leaf color, number of stomata per unit leaf area, esterase zymogram, chromosome association at meiotic metaphase I in pollen mother cells, and pollen fertility. From these regenerates plants with different characters from those of the parental plant were obtained. With regards to chromosomal aberrations, tetraploids, aneuploids, plants with a part of the chromosome segment deleted, with reciprocal and non-reciprocal translocations, or with paracentric inversions and those showing sub-chromatid aberrations at meiosis were obtained. The NK medium tended to regenerate more tetraploids and less plants carrying translocation than the I medium.Chromosome variabilities in somatic cells of the regenerates correlated with those of the calluses, from which they regenerated, while they did not correlate with either the meiotic irregularities (chromosome association at MI) or pollen fertility of the regenerates. From these facts, it was concluded that a rather large number of callus cells participate in the regeneration of an individual plant, although, however, only a few limited types of the cells form its germ line.Polyploidy affected growth vigor, leaf shape, stomata number and chromosome association at MI, but its effects were not detected on other characters. Chromosomal aberrations at the diploid level produced no clear changes in the regenerate's phenotype except in meiotic chromosome configuration and pollen fertility.Most chromosomal variants obtained in the present study are already reported in plants collected from wild populations, but plants with the deletion of a whole chromosome (karyotype 7L+6S) or chromosome segment (7L+1M+6S and 14L+2M+12S) have never been reported: this fact suggests that tissue culture is a powerful tool for producing plants with novel karyotypes.

Cytological Studies in Cultivated Species of Camellia : III. Tetraploid Species and Hybrids between Diploid Species and Hexaploid Species

Pairing between the homologous chromosomes in some cultivated clones of Camellia gralethamialea was found to be complete and normal at metaphase I. The comparative study of meiosis revealed the presence of some univalents, trivalents, or quadrivalents in a tetraploid cultivar of C. japoleica and 10 tetraploid hybrids between diploid species and hexaploid species. Majority of the hybrid combinations showed similar patterns of chromosome associations at metaphase I: the most common configuration was 30u, and the mean numbers of chiasmata per bivalent were quite high, 1.9-2. O. Thus, among 30 bivalents 15 suggested allosyndetic pairing between one genome from diploid parent and one genome from hexaploid parent. Metaphase chromosome pairing in meiosis I in the tetraploid hybrids of Camellia studied was not sufficient to assign distinct genome formulas for the properties of different chromosome sets in various species. The presence of sterility and partial sterility shown in a tetraploid cultivar of C. japonica and 10 tetraploid hybrids might be due to both genetic and unstable meiotic chro-mosome configurations at metaphase I as well as developing petaloidy.

Cytological Studies in Cultivated Species of Camellia : I. Diploid Species and their Hybrids

The diploid species and cultivars of Calefellia studied showed complete and normal chromosome pairing at metaphase I in meiosis. Thirteen F1 hybrid combinations between diploid species of Camellia showed similar patterns of meiotic chr-omosome configurations and chiasma frequencies at metaphase I. These hybrid combinations showed a single chromosome configuration of 15I_I In these hybrid combinations the chiasma frequencies deviated only slight from those of their parents. Metaphase chromosome pairing in meiosis I in hybrids of Calvzellia was not sufflcient to assign distinct genome fermulas for the properties of different chromosome sets in various s pecies. The presence of partial pollen sterility shown in many cultivated taxa of diploid Camellia was not correlated with chromosome configurations at metaphase I in PMC's. The sterility and partial sterility shown in diploid Caleeellia taxa might be due to eithel-genetic differences or cryptic structulal difEerences or chromosomal differences. Since cultivated Camellia is longeval tree or shrub and is artificially selected for economic purposes, all genetical and cytological factors discussed have been accumulated and foimed into more complicated genomic constitutions.

Meiotic Chromosome Behaviours of Auto-pentaploid Rice Plant Derived from Anther Culture

A pentaploid rice plant designated A4 by Nishi and Mitsuoka (1969) showed chromosome-mosaicism in MI of PMCs. When reckoned 2n numbers from the meiotic chromosome configurations, various aneuploid cells ranging from 33 to 99 were observed in one and the same anther-locule.Morphologically it resembles tetraploid, but anthesis is quite different. As it is similar to cleistogamy, fertilization has never taken place, resulting in the parthenocarpy. When crossed with the pollens of normal diploids, it set only imperfect seeds having no germinating ability. This plant was characterized by the formation of multi-germ-pores on the pollen grain.