A CYTOGENETIC ANALYSIS OF CERTAIN POLYPLOIDS IN GRINDELIA (COMPOSITAE)

Two diploid taxa, Grindelia procera and G. camporum, and 3 tetraploid ones, G. camporum, G. hirsutula, and G. stricta, have been studied to ascertain their interrelationships. Meiosis in diploid parental strains was regular, the common chromosome configuration being 5 rod bivalents and 1 ring bivalent. The average chiasmata frequency per chromosome was 0.60. Pollen fertility was about 90% in all strains examined. Diploid interspecific hybrids had normal meiosis with an average chiasmata frequency of 0.56 per chromosome. No heterozygosity for inversions or interchanges was detected, and pollen fertility was above 85%. Meiosis in parental tetraploid strains was characterized by the presence of quadrivalents in addition to a complementary number of bivalents. The average chiasmata frequency per chromosome was 0.59 and pollen fertility was generally about 80%. Tetraploid interspecific hybrids also had quadrivalents, normal meiosis, and high pollen fertility. Close genetic relationships between the diploids and between the tetraploids are indicated, and geographical, ecological, and seasonal barriers to gene exchange exist. Attempts to obtain hybrids between diploids and tetraploids were successful in a few cases. The hybrids were tetraploid and had normal meiosis and fertility similar to parental and F₁ tetraploids. Their origin was by the union of unreduced gametes of the diploid female parent and normal pollen from the tetraploid parent. On the basis of chromosome homology, normal meiosis, plus high fertility exhibited in the diploid, tetraploid, and diploid X tetraploid interspecific hybrids, these species of Grindelia are considered to be a part of an autopolyploid complex. Gene exchange between diploids and diploids, tetraploids and tetraploids, and diploids and tetraploids is possible. Tetraploid G. camporum may have originated by hybridization between G. procera and diploid G. camporum with subsequent doubling of chromosomes and selection for the combined characteristics of the diploids.     

Cytology of the tetraploidAllium ampeloprasum with chiasma localization

Allium ampeloprasum cultivated in Kashmir is a tetraploid. The somatic complement of the cultivar consists of 32 median or submedian chromosomes, of which 8 have secondary constrictions. The tetraploid karyotype exhibits a great deal of heterozygosity which is taken as an evidence in support of the allopolyploid nature of the species. The tetraploid form is represented by the genomic formula AAAA. The three genomes show a great deal of similarity and are therefore taken to represent three varieties which have given rise to this cultivar through hybridity. — Despite this, no multivalents are formed by the species during meiosis. The shift from multivalent to bivalent type of pairing is attributed to the localization of chiasmata around the centromere. This type of chiasmata localization is a means adopted by some polyploid species to stabilize as diploids.     

Cytological investigations of the effect of colchicine on meiosis in Lilium hybrid cv. “Black Beauty” microsporocytes

Using colchicine, two methods have been successfully applied for the induction of tetraploid meiocytes at premeiotic mitosis in the near achiasmate diploid hybrid cultivar Black Beauty of Lilium. The experiments were aimed at understanding whether the achiasmate condition is attributable to insufficient homology for effective pairing or to some genie defect in order to interpret the data obtained from molecular studies. Cytological observations demonstrate a strong correlation between the induction of tetraploidy and subsequent chiasma formation. The chiasma frequency per cell in untreated diploid control meiocytes ranged from 0 to 8 (mean 2.25), while in colchicine treated undoubled cells sampled 14±2 days after the start of treatment it ranged from 0 to 2 (mean 0.148). By comparison, the chiasma frequency per cell in colchicine-doubled tetraploid cells ranged from 29 to 51 (mean 42.24), such cells showing complete or near complete bivalent pairing. These results, similar to those reported previously for other higher plant species, demonstrate that the achiasmatic condition in Black Beauty is not due to a genie defect. The methods developed have made possible hitherto inaccessible biochemical analyses of meiocytes that had been treated with colchicine or other chemicals at premeiotic stages.     

Chromosome mosaics and the recovery of the original strain from octoploidHordeum murinum

Summary Plants with chromosome numbers (2n=18–54) lower than that of the normal 2n=56 were found in the C₁ progeny of colchicine induced octoploid form ofHordeum murinum. Pollen mother cells in three octoploid plants had reduced chromosome complements at meiosis. Some of these plants had the original chromosome number of 2n=28. A number of these cells had regular bivalent pairing at first metaphase. Evidence indicated independent as well as nonindependent assortment of chromosomes at somatic reduction, the latter type resulting in ancestral type pollen mother cells (14^II) and gametes respectively. Since normal tetraploid plants were recovered in the progeny (C₂) of chromosome mosaics, ancestral type fully balanced egg cells must have also been formed. It is believed that the recovered tetraploids originated presumably from the fusion of double reduced gametes. Break-down diploids occurring occasionally among progenies of autoploids may originate from the fusion of such gametes.With 7 Figures in the TextContribution No. 107 from the Genetics and Plant Breeding Research Institute, Research Branch, Canada Department of Agriculture, Ottawa, Ontario, Canada.     

Cytological studies of diploid and tetraploidTheobroma cacao

The chromosomes of diploid and established artificial autotetraploidT. cacao were examined with particular attention to their shapes and relative sizes at mitotic metaphase, as well as their association during metaphase of male meiosis. Bivalent formation was observed in the diploid, and although there was low apparent chiasma frequency, disjunction was regular. In the two established autotetraploids studied, there was a high frequency of bivalents as compared with trivalents and quadrivalents. Pollen fertility as measured by its germination on agar was between 38 and 64 percent (diploid 90–98.5 percent). Fruit set was between 11.5 and 19.1 percent (diploid 74 percent), and mature bean number was approximately half the ovule number counted (diploid 90 percent). Seed germination was, however, never less than 77 percent at any particular sowing and almost all the seedlings had 4x chromosome number. It is suggested that an improvement in the yield capacity of the autotetraploid might be possible by crossing C₁ tetraploid individuals selected on the basis of the frequency of bivalent formation, as well as uniformity in pollen size and fertility.     

Greek classicism in living structure? Some deductive pathways in animal morphology

Classical temples in ancient Greece show two deterministic illusionistic principles of architecture, which govern their functional design: geometric proportionalism and a set of illusion-strengthening rules in the proportionalism's stochastic margin. Animal morphology, in its mechanistic-deductive revival, applies just one architectural principle, which is not always satisfactory. Whether a Greek Classical situation occurs in the architecture of living structure is to be investigated by extreme testing with deductive methods.Three deductive methods for explanation of living structure in animal morphology are proposed: the parts, the compromise, and the transformation deduction. The methods are based upon the systems concept for an organism, the flow chart for a functionalistic picture, and the network chart for a structuralistic picture, whereas the optimal design serves as the architectural principle for living structure. These methods show clearly the high explanatory power of deductive methods in morphology, but they also make one open end most explicit: neutral issues do exist.Full explanation of living structure asks for three entries: functional design within architectural and transformational constraints. The transformational constraint brings necessarily in a stochastic component: an at random variation being a sort of free management space. This variation must be a variation from the deterministic principle of the optimal design, since any transformation requires space for plasticity in structure and action, and flexibility in role fulfilling. Nevertheless, finally the question comes up whether for animal structure a similar situation exists as in Greek Classical temples. This means that the at random variation, that is found when the optimal design is used to explain structure, comprises apart from a stochastic part also real deviations being yet another deterministic part. This deterministic part could be a set of rules that governs actualization in the free management space.     

Cytogenetics of pearl millet

Summary The somatic karyotype of pearl millet Pennisetum americanum (L.) Leeke. (2n = 14) has been studied in several cultivars, but few cytological markers have been discovered which could help in the easy identification of the chromosomes. Analysis of pachytene bivalents permits such identification but is feasible only in a few cultivars. Recently, several lines having telocentric chromosomes have been produced and classified but their potentialities as cytogenetic tools have yet to be explored. Some African populations of pearl millet carry B-chromosomes in their karyotype. Cytogenetics of B-chromosomes has been reported in great detail. Bs undergo spontaneous changes to produce deficient- and iso-chromosomes. The main effect of B-chromosomes is on chiasma frequency which is exerted by the relative amounts of chiasma promoting euchromatin and the chiasma depressing heterochromatin in the Bs. Haploid plants occur occasionally and sometimes show a low degree of seed set, offering a possibility of establishing homozygous inbred lines. Cytogenetics of several spontaneous and induced autotetraploids have been reported. In general quadrivalent formation between the seven sets of four homologues was random. Seed set of the autotetraploids could be improved by selection; improved seed fertility was found to be associated with increased chiasma frequency, increased quadrivalent frequency and regular distribution of chromosomes at anaphase I. Genes controlling morphological characters of plant phenotype segregate independent of those controlling fertility and in pearl millet polyploidy per se is not limiting to plant vigour. Primary trisomics represent the best studied among the aneuploids of pearl millet. All the seven primary trisomics have been identified and described. Some were used in assigning genes to specific chromosomes but in general trisomies have poor vigour and fertility, and show low frequency of transmission. Apart from B-chromosomes, cytogenetics of interchanges has been the best studied aspect of pearl millet. The frequency of co-orientation of an interchange complex at metaphase I, which determines the fertility or sterility of the interchange heterozygote, is influenced by the genetic background and thus is theoretically amenable for selection leading to improved fertility of the heterozygote. Interchange tester-stocks have been assembled which can be used to identify the chromosomes involved in any newly obtained interchange. A complex interchange line involving all the chromosomes of the complement has also been produced, but the ring-of-fourteen produces total male and female sterility.Genotypic control of mitosis and meiosis has been reported, with reference to chromosome numerical mosaicism, multiploid sporocytes, desynapsis and chromosome fragmentation, and male sterility. Pearl millet being a largely outbreeding species, forced inbreeding was mainly found to result in loss of morphological vigour and reduction in mean chiasma frequency per PMC. Interspecific hybrids between pearl millet and several related species have been cytologically investigated and homology of the seven chromosomes of pearl millet with seven of the fourteen chromosomes of P. purpureum has been demonstrated. Cytogenetic evidence from haploids, autopolyploids and interspecific hybrids has indications to suggest that the haploid number of x = 7 is derived from x = 5, but the evidence is inconclusive and needs critical evaluation.     

Fertility and selection in tetraploid Lolium

Selection over five generations increased the fertility (seed set) in a population of tetraploid Lolium perenne from 67.57 per cent in the second (C ₂) to 73.95 per cent in the seventh (C ₇) generation. The increased fertility is associated with a high quadrivalent frequency and a low frequency of bivalents, trivalents and univalents. The high quadrivalent frequency in the selected population was achieved partly by a slight overall increase in chiasma frequency but mainly by a redistribution of chiasmata.     

Über Konstitution und Erbgang eines neuen Delphinidinglycosids „Floridorin“ aus der Garteniris-Sorte cv. ‘Floridor’ (Cayeux 1929)

Zusammenfassung Bei der diploiden hohen Garten-Iris cv. Floridor (Cayeux 1929) wurde als bisher einziger Sorte ein neues Delphinidinglycosid Floridorin aufgefunden. Seine chemische Konstitution wurde als Delphinidin-3-Glukose-Rhamnose-p-Cumarsäure aufgeklärt. Es fand sich zusammen mit dem schon von uns aufgeklärten Anthozyan Tulipanin (Delphinidin-3-Glucose-Rhamnose). Das Hauptanthozyan der anderen Garten-Iris ist das von uns neuerdings nachuntersuchte Violanin. Die Untersuchungen wurden mit bereits von uns angegebenen neueren Methoden ausgeführt, wie der stufenweisen Hydrolyse und dem oxidativen Abbau. Das neue Floridorin zeigte bei den diploiden Garten-Iris einen monohybriden rezessiven Erbgang gegen Violanin. Die Blüten der Sorten, die Floridorin enthalten, sind schon mit dem Auge an einem charakteristischen taubenblauen Farbton zu erkennen.

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On the constitution and inheritance of a new delphinidine glycoside Floridorin from the cultivated iris variety cv. Floridor (Cayeux 1929)Studies on anthocyanins LI

Summary The diploid tall bearded garden Iris cv. Floridor (Cayeux 1929) proved to be thus far the only variety with a different anthocyanine, called Floridorin. Its chemical structure has been found to be delphinidine-3-glucose-rhamnose-p-coumaric-acid. It occurs together with tulipanine already analyzed by us as delphinidine-3-glucose-rhamnose. The main anthocyanine of thePogoniris garden varieties proved to be violanin the structure of which has been studied by us lately. The investigations were carried out by some newer methods, such as partial hydrolysis and oxidative degradation already published by us. The new Floridorin gives a monohybrid recessive Mendelian ratio with other diploid varieties ofPogoniris colored by violanine. The varieties colored by Floridorin show a characteristic greyish blue coloration which can be recognized with the naked eye.

     

Octoploidy inCoffea arabica

Morphology and cytology of three octoploid forms ofCoffea arabica were studied. A comparison of the morphological characters of natural allotetraploids and the derived octoploids indicates that there is a reduction in size from tetraploidy to octoploidy. The inferiority in vegetative vigour and high sterility of the octoploids suggests that the optimum chromosome number has been reached in nature at the tetraploid level.Occurrence of a high frequency of quadrivalents in meiosis of the octoploids presently studied is contrary to the reports of earlier workers where quatrivalents were not observed. The significance of quadrivalent formation is discussed.     

Chromosome painting in meiosis reveals pairing of specific chromosomes in polyploid <Emphasis Type="Italic">Solanum</Emphasis> species

Analysis of chromosome pairing has been an important tool to assess the genetic similarity of homologous and homoeologous chromosomes in polyploids. However, it is technically challenging to monitor the pairing of specific chromosomes in polyploid species, especially for plant species with a large number of small chromosomes. We developed oligonucleotide-based painting probes for four different potato chromosomes. We demonstrate that these probes are robust enough to monitor a single chromosome throughout the prophase I of meiosis in polyploid Solanum species. Cultivated potato (Solanum tuberosum, 2n?=?4x?=?48) is an autotetraploid. We demonstrate that the four copies of each potato chromosome pair as a quadrivalent in 66–78% of the meiotic cells at the pachytene stage. Solanum demissum (2n?=?6x?=?72) is a hexaploid and has been controversial regarding its nature as an autopolyploid or allopolyploid. Interestingly, no hexavalent pairing was observed in meiosis. Instead, we observed three independent bivalents in 83–98% of the meiotic cells at late diakinesis and early metaphase I for the four chromosomes. These results suggest that S. demissum has evolved into a cytologically stable state with predominantly bivalent pairing in meiosis.     

Chromosome association and fertility in tetraploid ryegrass

In colchicine treated diploid ryegrass,Lolium perenne L. (2n=14), in addition to normal diploids, tetraploids and mixoploids, cytologically aberrant plants were observed. The latter included one aneuploid (2n=25), four translocation heterozygotes (diploid and mixoploid), and one mixoploid desynaptic plant which was a chimera of normal and desynaptic tissues as shown by successive clonal propagations. The normal diploids had chromosome association of 7 II, with an average chiasmata frequency of 12 per pollen mother cell and had 85.6 per cent pollen fertility. The tetraploids showed a mean chromosome association of 0.88 I, 4.83 II, 0.29 III and 3.91 IV, with an average chiasmata frequency of 25 per microsporocyte, and had 83.8 per cent fertile pollen. In the tetraploids, pollen fertility was negatively correlated with quadrivalent frequency and positively so with bivalent and trivalent frequencies, there being no significant correlation with univalent frequency. Among the most frequent types of quadrivalents, only the alternate chain quadrivalent frequency was positively correlated (r=+.9297) with the plllen fertility. On this basis, an increased pollen fertility in the succeeding generations of tetraploids could result from a decrease in the frequency of quadrivalent types other than the alternate chains.     

Evidence on the Saltatory Origin of the G Genome in Wheat: the Description of a Triticum timopheevi-like Mutant

A spontaneously occurring somatic mutant of Triticum turgidumdicoccoides showed close morphological resemblance to T. timopheevi(AAGO). The hybrid between the mutant and the T. turgidum dicoccoides‘ mother’ plant was completely sterile, with verylow pollen fertility (0·33 percent). It exhibited a reasonablyhigh frequency of trivalents and quadrivalents at first metaphaseof meiosis, indicating that the mutation involved substantiallevels of chromosome rearrangement. The hybrid between the mutantand T. timopheevi had reasonably high fertility (53·5per cent) and high pollen fertility (86·6 per cent) andalmost regular bivalent formation at first metaphase of meiosis. It is proposed that T. timopheevi could have arisen in consequenceof somatic macromutation from T. turgidum dicoccoides givingrise to spontaneous speciation. The G genome of T. timopheeviis possibly monophyletic in origin, arising from rearrangementof chromosomes of the B genome of tetraploid wheat. Triticum turgidum dicoccoides, wheat, G genome, mutant     

Differential meiotic behaviour of diploid and tetraploid cells in a partially asynaptic mutant

A partially asynaptic individual of the grasshopperEuchorthippus pulvinatus (2n = 16 + X) was analysed at meiosis, using a Giemsa C-banding technique. Long chromosomes formed univalents less frequently than did medium and short ones. Homologues which succeeded in forming bivalents showed reduced chiasma frequency, the long chromosomes being affected by most. Changes in chiasma distribution were also observed. The presence of univalents at metaphase I seems to affect the function of the spindle, since most cells at the second division were unreduced. Cytokinesis was also subsequently suppressed in a great number of these products of restitution, resulting in the formation of diploid and tetraploid spermatids. Fifteen tetraploid metaphase I cells were also found in which pairing level and chiasma frequency were almost twice the average value in normal diploid individuals. The nature of this mutant is discussed.     

加拿大披碱草和圆柱披碱草BC1植株的细胞遗传学鉴定

以加拿大披碱草(2n=4x=28)和圆柱披碱草(2n=6x=42)为材料,对其BC1植株染色体数目、配对构型以及花粉育性和结实性等进行了鉴定。结果显示:BC1代85%以上细胞染色体数目为28条(2n=4x=28);BC1植株的花粉母细胞减数分裂中期Ⅰ染色体配对行为较规则,其平均染色体构型分别为0.04Ⅰ 13.98Ⅱ,且环状二价体多于棒状二价体;BC1植株的花粉可育率和自然结实率分别为84.83%和70.98%,说明BC1植株的育性已得到恢复,为其后代优良株系的选育奠定了基础。     

Meiotic irregularities in diploid and tetraploid plants of <Emphasis Type="Italic">Lolium multiflorum</Emphasis> Lam.

The genus Lolium comprises several species of economical importance in temperate countries, mostly due to their high nutritional value and adaptability to cold environments, including southern regions of Brazil. Recently, several diploid cultivars and populations, as well as synthetic tetraploid cultivars have been explored. In order to viabilize or to direct crossings, it is important that the accessions present regular meiosis, thus, producing viable pollen grains. In this way, this study aimed at investigating the meiosis of nine accessions of Lolium multiflorum used in breeding programs, seeking to evaluate its viability in future crossings. The meiosis of diploid plants (2n?=?2×?=?14) is more regular than the artificially tetraploidized genotypes (2n?=?4×?=?28). In the tetraploids, univalent, bivalent, and multivalent configurations were observed. The irregularities were associated to mixoploidy, irregular segregation of chromosomes, spindle disorders, asynchrony, micronuclei, and cellular fusion and formation of syncyte. The abnormalities affected the meiotic index of tetraploid cultivars, characterizing them as unstable. Nevertheless, both diploid and tetraploid genotypes are considered able to participate in crossings because, although there are abnormalities, they do not occur at levels that could affect the production of viable pollen grains.     

Extensive nonhomologous meiotic synapsis between normal chromosome axes of an rcp(3;6)(p14;q21) translocation in a hairless Mexican boar

Due to its low fertility, expressed as small litter size, a Mexican hairless boar was subjected to cytogenetic investigation. Analysis of G-banded mitotic chromosomes revealed a reciprocal chromosome translocation, rcp(3;6) (p14;q21). Synaptonemal complex analysis showed a regular pairing behavior of the translocation chromosome axes, always resulting in a quadrivalent configuration. However, due to extensive nonhomologous pairing between the axes of nonderivative chromosomes 3 and 6, the quadrivalent mostly had an asymmetrical cross-shaped morphology. The nonhomologous pairing occurred not only at mid and late pachytene, but also at the earliest stage of pachytene. It seems that early pachytene heterosynapsis is a common phenomenon in the pairing behavior of pig reciprocal translocations. Therefore, heterosynapsis may reduce apoptosis of germ cells due to partial absence of homologous synapsis during the pairing phase of meiosis. The frequency of spermatocytes showing quadrivalent configurations with unpaired axial segments apparently did not affect germ cell progression in the boar, since fairly normal testicular histology was noticed.     

Changes in metabolism and hormone trafficking during exposure of endocrine cells to elevated ammonium

Endocrine cell cultures have potential in bioprocessing, for the production of biologically active hormones, and in tissue engineering, for the development of implantable artificial tissues for long-term restoration of endocrine function. To optimize such systems, it is necessary to develop a thorough understanding of how inherently present environmental stresses, such as nutrient depletion and metabolite accumulation, affect the cells. This work focuses on the effects of the metabolite ammonium on indicators of endocrine cell metabolism and on the processing, storage and secretion of regulated secretory proteins. Experiments were conducted on recombinant insulin-producing mouse pituitary AtT-20 cells and mouse insulinoma TC3 cells. Exposure for 24–48 hours to 6 mM of exogenous ammonium resulted in higher rates of glucose consumption by both AtT-20 and TC3 cells, while the formation of additional ammonium generally decreased relative to ammonium-free controls. When TC3 cells were discharged of their intracellular insulin stores, the presence of ammonium during a subsequent recharge completely inhibited addition of new insulin-related peptides to the stores, as we had observed previously for both cell lines. There was a correlation between insulin-related peptides stored in TC3 cells during recharging and the amount that could be released upon secretagogue stimulation. Using a combination of radioimmunoassay and high performance liquid chromatography, we found that intracellular insulin and insulin-related peptides changed in the same fashion. Intracellular mechanisms that may be producing the observed results are discussed.Abbreviations IRP insulin-related peptides - HPLC high performance liquid chromatography - DAMP 3-(2,4-dinitroanilino)-3 amino-N-methyldipropylamine     

Allopolyploid of tetraploidphaseolus species ×p. calcaratus cross

Allopolyploids were raised by oolchicine treatment of vegetative buds in the triploid hybrid of tetraploidPhaseolus species xP. calcaratus cross. They had 70 per cent pollen fertility and produced many viable seeds. The average chromosome configuration per cell at MI in them was 1.56_IV + 0.01m + 29.30_II + l.llr. It has been concluded that the increased fertility in allopolyploids was due to more regular meiosis and the low frequency of quadrivalents indicated the occurrence of preferential pairing.     

“Homologies” between non-homologous chromosomes in the grasshopper Caledia captiva

Cytological studies of hybrids between three chromosomal forms of the grasshopper, Caledia captiva, have revealed a clear case of pairing and exchange between non-homologous chromosomes. The genomes of each of the three chromosomal forms are readily identifiable by their marked differences in morphology and in the pattern of C-heterochromatin distribution. The testes of inter-racial F₁ hybrid males contain both diploid and tetraploid meiocytes within the same individual. Multiple chromosome associations are a regular feature of all diploid cells. In many cases, these multiples involve two or more non-homologous chromosomes from within the same haploid genome. Such associations reveal unambiguous evidence of meiotic exchange and chiasmata. The X chromosome is frequently observed to associate with an autosome, and anaphase I cells provide evidence of X/autosome exchanges. A correlation exists between the position of the exchange event in non-homologous pairs and the location of heterochromatin. In tetraploid meiocytes, pairing is by strict homology only, giving rise to cells with 22 bivalents plus an XX bivalent or two univalent X chromosomes. Segregation patterns in tetraploid cells are entirely normal and result in the production of diploid gametes. In the male, the increased ploidy level was observed to arise following an endoreduplication process which takes place pre-meiotically in the spermatogonial cells. The finding that non-homologous chromosomes from within the same haploid genome can pair and cross over during meiosis clearly shows that some caution must be taken when interpreting multiple associations as evidence of interchange heterozygosity in hybrids.