Identification of Renner complexes and duplications in permanent hybrids of Gibasis pulchella (Commelinaceae)

Discovery of permanent hybridity in the very large chromosomes of Gibasis pulchella (Commelinaceae) has allowed specific identification of segmental interchanges in complex heterozygotes. The interchanges are confined to terminal regions, are sometimes very small, and may be unequal in size. Breakpoints have occurred close to major C-bands, probably at euchromatin/heterochromatin boundaries. Complete and disjunctional ring formation at meiosis results in the segregation of two Renner complexes, each of which can be specifically identified with C-banding. The complex carrying the interchanges is usually transmitted through the pollen. Certain chromosomes that have undergone more extensive change than the rest of the complement may have some special significance. There is evidence of small duplications within heterozygous genomes. Permanent hybridity in different organisms may have quite different origins, possibly initiated by major karyotype repatterning following the activation of transposons that generate chromosome breakage.Abbreviations p Short arm - q long arm - M metacentric - SM submetacentric - BS bisatellited chromosome in population 4 - UB unbanded chromosome in population 4 - II bivalent; closed meiotic ring configuration, e.g., 10, ring of ten - ch open chain configuration - NOR nucleolus organising region     

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.     

Chromosomal identification and meiotic behavior of reciprocal translocations in a rye polymorphic population. Evolutionary implications

Summary The spontaneous interchange polymorphism of rye cultivar Ailés is composed, as can be deduced from the chromosomal identification of the interchanges analyzed, of several different reciprocal translocations in which the chromosomes of its haploid complement are involved with a similar frequency, except for chromosomes 4R and 6R. Several features of chromosome behavior at metaphase I, such as configuration and orientation of quadrivalents and frequency of chiasmata, were analyzed in structural heterozygotes for different interchanges. The two main factors affecting the orientation of quadrivalents at metaphase I proved to be the morphology of these chromosome associations at metaphase I and, in particular, the frequency of bound chromosome arms that they showed. A genotypic control of alternate orientation of quadrivalents independent of chiasmata frequency was not detected. In addition, the frequency of alternate orientation shows no relation to the fitness. Possible evolutionary implications of the results obtained are discussed.     

Interchange-trisomics in barley

Observations on morphology, sterility and cytology of some interchangetrisomics obtained from the progeny of radiation induced interchangeheterozygotes in a 6-rowed barley (Hordeum vulgare L.) var. K₁₂ are described. The different interchange trisomics show distinct phenotypic expression and have been classified as bushy, slender, robust, semi-erect and pseudonormal on the basis of their gross morphology, leaf characteristics, awn and spike lengths. All interchange trisomics show pollen and ovule sterility which varies between plants. Meiotic behaviour is described. The five different interchange trisomics appear to have different extra chromosomes.     

Anther development and the orientation of the interchange quadrivalent in pearl millet

The effects of developmental stage of the anther, ageing of the plant, inbreeding and season on meiotic segregation of an interchange chain quadrivalent were studied in pearl millet, Pennisetum americanum (L.) Leeke. The frequency of adjacent orientation (and segregation) increased with developmental stage of the anther, independent of other factors. Plant age and degree of inbreeding had no demonstrable effects, but there was an indication that high temperature favoured adjacent orientation. Chromosome contraction as measured by change in chromosome length appeared to be negligible during metaphase-anaphase. Therefore, increased adjacent orientation cannot readily be explained by metaphase reorientation resulting from the straightening of chromosomes caused by an increase in their rigidity. It is probable that the unoriented or mal-oriented quadrivalents observed regularly at early metaphase I continue to straighten out prior to their delayed orientation. When they finally orientate late in metaphase, their orientation will more likely be adjacent than alternate.     

Cytogenetics of double cross hybrids between Pennisetum americanum — P. purpureum amphiploids and P. americanum x Pennisetum squamulatum interspecific hybrids

Summary Pearl millet, Pennisetum americanum L. Leeke-napiergrass, Pennisetum purpureum Schum. amphiploids (2n=42) were crossed with pearl millet X Pennisetum squamulatum Fresen. interspecific hybrids (2n=41) to study the potential of germplasm transfer from wild Pennisetum species to pearl millet. These two interspecific hybrids were highly cross-compatible and more than two thousand trispecific progenies were produced from 17 double crosses. All doublecross hybrids were perennial and showed a wide range of morphological variations intermediate to both parents in vegetative and inflorescence characteristics. Some crosses resulted in sublethal progenies. Chromosomes paired mainly as bivalents (¯x15.88) or remained as univalents. At metaphase I, trivalents, quadrivalents, an occasional hexavalent and a high frequency of bivalents indicated some homeology among the genomes of the three species. Delayed separation of bivalents, unequal segregation of multivalents, lagging chromosomes, and chromatin bridges were observed at anaphase I. Although approximately 93% of the double-cross hybrids were male-sterile, pollen stainability in male-fertile plants ranged up to 94%. Seed set ranged from 0 to 37 seed per inflorescence in 71 plants under open-pollinated conditions. Apomictic embryo sac development was observed in double-cross progenies when crosses involved a pearl millet x P. squamulatum apomictic hybrid as pollen parent. These new double-cross hybrids may serve as bridging hybrids to transfer genes controlling apomixis and other plant characteristics from the wild Pennisetum species to pearl millet.     

Induction of segmental interchanges in pearl millet (Pennisetum typhides)

Summary Dry seeds of two varieties of Pennisetum typhoides (2n=14), Tift 23-B and Bil-3B, were treated with gamma rays, diethyl sulphate (DES) and ethylene imine (EI) at their approximate LD₅₀ dosages and the pollen mother cells of the M₁ (first generation immediately after the seed treatment) plants were analysed at diakinesis for multivalent configurations resulting from segmental interchanges. While quadrivalents and trivalents were commonly found in all the mutagenic treatments, hexavalents were seen in the gamma-ray treatment only. Ring quadrivalents were common in all the treatments and their frequency was higher in gamma-ray treatment than in the treatments with the chemical mutagens of which EI produced more quadrivalents than DES. The variety BIL3B was more responsive to all the mutagens used than Tift-23B in which, excepting in gamma-ray treatment, no multivalents were observed in EI and DES treatments.The quadrivalents induced by different mutagens were of different types involving different chromosomes, indicating some kind of specificity of the mutagens in causing chromosome breaks. Thus, in EI-induced quadrivalents the nucleolar chromosome, the shortest chromosome of the complement, was involved, whereas in the case of DES and gamma rays it was the longest chromosome of the complement that was involved in the quadrivalent. Apparently the breaks must have been produced in different chromosomes preferentially.Self-pollinated seeds of two heterozygotes whose interchanges were induced by EI and gamma rays were given a second cycle treatment with gamma rays, again at the LD₅₀ dosage (35 kR), and interchange stocks involving different chromosomes, up to a maximum of eight chromosomes were realized. Alternate use of EI and gamma rays offered better possibilities of obtaining inter-change heterozygotes involving more, if not all, chromosomes in a ring than two successive treatments with gamma rays alone.     

Synthesis and secretion of caseins by the mouse mammary gland: Production and characterization of new polyclonal antibodies

Polyclonal antibodies to mouse - and /-caseins were raised in rabbits. These antibodies display tissue- and species specificity as shown by immunoblotting. Immunohistochemical analyses demonstrate that both - and /-caseins were synthesized and secreted from virtually all lactating mammary epithelial cells, in a pattern very similar to that of the mouse -lactalbumin. Residual amounts of caseins were located also in the apical surface of epithelial cells surrounding the ducal lumen of virgin mammary gland sections. In contrast to the significant level of -casein in the milk, the amount of this protein compared to - or -caseins was extremely low in medium conditioned for 24 h by mammary explants of mid-pregnant mice immediately after explantation or after 4 days.     

Centromere orientation,reorientation, and segregation in an interchange quadrivalent during anther development in pearl millet

Prometaphase I orientation, reorientation and anaphase I segregational behaviour of a chain-forming interchange quadrivalent involving one of the long chromosomes and the long arm of the seventh (nucleolar) chromosome was studied during anther development in pearl millet. The data obtained from 34 anthers showed that by early prometaphase I about 90% of the bivalents have attained stable bipolar orientation but about 48% of the quadrivalents are mal-oriented. There seems to be an interaction between bivalents and quadrivalents during mal-orientation and reorientation. The mal-oriented bivalents reoriented before the quadrivalents. For quadrivalent mal-orientation four types, 4/0, 3/1, 2/1/1/1 and 2/2 (adjacent 1), were distinguished in addition to the regular types, adjacent 2 and alternate. Based on their potential to reorient, the order of the mal-oriented quadrivalent types was 4/0 > 3/1 > 2/1/1; 2/2 led to anaphase I disjunction as for an adjacent 1 segregation. The data from 36 anthers at anaphase I showed alternate segregation of chromosomes in nearly 50% of pollen mother cells (PMCs) up to a developmental index of about 65. In late anthers about 35% PMCs showed alternate segregation. This suggests that the PMCs that reached metaphase I later had more adjacent 2 orientations since mal-oriented configurations delay meiotic development, and implies preferential reorientation behaviour of the maloriented quadrivalent types.     

Transfer of germ plasm from the secondary to the primary gene pool in pennisetum

Summary Germ plasm from the A-genome of Pennisetum purpureum Schum. (AABB) of the secondary gene pool was transferred to cultivated pearl millet (AA) [P. glaucum (L.) R. Br.] by pollinating cytoplasmicnuclear male-sterile (cms) pearl millet with fertile allohexaploid pearl millet x P. purpureum hybrids (AAAABB). Certain allohexaploids used as pollinators on cms pearl millet resulted in 14-chromosome diploid pearl millet progenies. Three types of diploid pearl millet plants were produced in addition to the expected 28-chromosome AAAB-genome plants: (1) cms plants with only the A-genome, (2) cms plants with the A- and A-genomes, and (3) fertile plants with the A- and A-genomes. The latter group has allowed the utilization of genes for fertility restoration, stiff stalk, maturity, height, and morphological characteristics from the A-genome of P. purpureum in the pearl millet breeding program. Production of monoploid gametes by the allohexaploids appeared to be genetically controlled.     

Verhalten tierischer Zellen in der Gewebekultur gegenüber einem basisch substituierten Benzimidazolderivat mit fluorochromierenden Eigenschaften

Zusammenfassung 33258 Hoechst, ein basisch substituiertes Benzimidazolderivat, beeinflußt Mitosen und Interphasezellen permanenter Zellinien in der Gewebekultur. Es kommt zu Mitosestörungen in der Anaphase und Telophase durch Verklumpen von Chromosomen, zu Zellvergrößerungen und zur Wachstumshemmung. Diese reversiblen und irreversiblen Veränderungen beruhen auf Verbindungen der Substanz mit der DNS der Zellkerne. Weiter wird über die Verwendung der Substanz als Fluorochrom zur Analyse von DNS-Schädigungen in Interphasezellen und an Mitosechromosomen berichtet.

---

On the influence of a benzimidazol derivative (fluorochrome) on cell lines in tissue culture

Summary 33258 Hoechst, a benzimidazol derivative influences mitotic and interphase cells of permanent cell lines in tissue culture. Mitotic anomalities observed during anaphase and telophase are clumping of chromosomes, cell enlargement and inhibition of growth. These reversible and irreversible changes are due to the reaction between the substance and the DNA in the nucleus. Further is reported about the utilization of the substance as fluorochrome to analyse DNA damage in interphase cells and mitotic chromosomes.

     

<Emphasis Type="Italic">Fusarium</Emphasis> species of the <Emphasis Type="Italic">Gibberella fujikuroi</Emphasis> complex and fumonisin contamination of pearl millet and corn in Georgia,USA

This study was designed to identify and compare the Fusarium species of the Gibberella fujikuroi complex on pearl millet (Pennisetum glaucum (L.) R. Br) and corn (Zea mays L.) crops grown in southern Georgia, and to determine their influence on potential fumonisin production. Pearl millet and corn samples were collected in Georgia in 1996, 1997 and 1998. Three percent of the pearl millet seeds had fungi similar to the Fusarium species of the G. fujikuroi species complex. One hundred and nineteen representative isolates visually similar to the G. fujikuroi species complex from pearl millet were paired with mating population A (Fusarium verticillioides (Sacc.) Nirenberg), mating population D (F. proliferatum (Matsushima) Nirenberg) and mating population F (F. thapsinum (Klittich, Leslie, Nelson and Marasas) tester strains. Successful crosses were obtained with 50.4%, 10.1% and 0.0% of these isolates with the A, D and F tester strains, while 39.5 of the isolates did not form perithecia with any tester strains. Two of the typical infertile isolates were characterized by DNA sequence comparisons and were identified as Fusarium pseudonygamai (Nirenberg and ODonnell), which is the first known isolation of this species in the United States. Based on the pattern of cross-compatibility, conidiogenesis, colony characteristics and media pigmentation, a majority of the infertile isolates belong to this species. Fumonisins FB₁ and FB₂ were not detected in any of the 81 pearl millet samples analyzed. The species of the G. fujikuroi species complex were dominant in corn and were isolated from 84%, 74% and 65% of the seed in 1996, 1997 and 1998, respectively. Representative species of the G. fujikuroi species complex were isolated from 1996 to 1998 Georgia corn survey (162, 104 and 111 isolates, respectively) and tested for mating compatibility. The incidence of isolates belonging to mating population A (F. verticillioides) ranged from 70.2% to 89.5%. Corn survey samples were assayed for fumonisins, and 63% to 91% of the 1996, 1997 and 1998 samples were contaminated. The total amount of fumonisins in the corn samples ranged from 0.6 to 33.3 g/g.     

Molecular evolutionary characterization of an Activator (Ac)-like transposable element sequence from pearl millet (Pennisetum glaucum) (Poaceae)

We present data on the evolution of the Ac/Ds family of transposable elements in select grasses (Poaceae). A defective Ac-like element was cloned from a DNA library of the grass Pennisetum glaucum (pearl millet) and its entire 4531 bp sequence has been determined. When the pearl millet Ac-like sequence is aligned with the maize Ac sequence, it is found that there is approximately 70% DNA similarity in the central region spanning most of maize Ac exon II and all of exon III. In addition, there are two smaller regions of similarity at the Ac terminii. Besides these three major structural similarities, Pennisetum Ac has two large regions, one 5 and one 3, that show little similarity to Zea Ac. Furthermore, most of the sequences corresponding to intron II in maize Ac are absent in pearl millet Ac. Kimura's evolutionary distance between the central region of maize and pearl millet Ac sequences is estimated to be 0.429±0.020 nucleotide substitutions per site. This value is not significantly different from the average number of synonymous substitutions for coding regions of the Adh1 gene between maize and pearl millet, which is 0.395±0.051 nucleotide substitutions per site. If we assume Ac and Adh1 divergence times are equivalent between maize and pearl millet, then the above calculations suggest Ac-like sequences have probably not been strongly constrained by natural selection. Conserved DNA and amino acid sequence motifs are also examined. The level of DNA sequence divergence between maize and pearl millet Ac sequences, the estimated date when maize and pearl millet diverged (25–40 million years ago), coupled with their reproductive isolation/lack of current genetic exchange, all support the theory that Ac-like sequences have not been recently introduced into pearl millet from maize. Instead, Ac-like sequences were probably present in the progenitor of maize and pearl millet and have thus existed in the grasses for at least 25 million years.     

Trisomic categories in pearl millet (Pennisetum americanum (L.) Leeke)

Summary In pearl millet [Pennisetum americanum (L.) Leeke], in the open pollinated and crossed progenies of autotriploids, desynaptics and translocation heterozygotes, two primary trisomics, one each of secondary and tertiary trisomics, two primary trisomics with interchanges, two interchange secondary trisomics, and three interchange tertiary trisomics were located. These categories were determined on the basis of chromosomal associations formed at meiosis. In one other trisomic, its category, whether tertiary or interchange trisomy, could not be determined. Some of these categories, like the secondary trisomy and interchange tertiary trisomy, are reported for the first time.     

Natural variants of pearl millet (Pennisetum typhoides) with altered levels of set II alcohol dehydrogenase activity

Two linked genes, Adh1 and Adh2, specify three sets of ADH isozymes in pearl millet. Set I is a homodimer specified by Adh1, Set III is a homodimer specified by Adh2, and Set II is a heterodimer consisting of one ADH1 subunit and one ADH2 subunit. Dry seeds exhibit only Sets I and II. Anaerobic treatment of seeds greatly increases the activity of Sets I and II and causes the Set III isozymes to be expressed. In the investigation reported here, the ADH zymogram phenotypes of 112 inbred pearl millet lines were analyzed. Two kinds of naturally occurring ADH variant strains were observed: in the low-activity variant, Set II activity is low in the dry seed, and no Set III activity is present upon anaerobic treatment. In the high-activity variant, Set II activity is high and Set III isozymes are expressed in the dry seed. The mutation in the high-activity strain appears to affect the product of Adh2 and not the product of Adh1. Dominance tests show that the mutations in both types of variant strains act in cis. These observations and linkage tests indicate that the mutations are closely linked to or at the Adh2 locus.This work was supported by a PHS National Research Service Award Training Grant in Genetics to the Biology Department of the University of Oregon.     

Tracing neurons with a kinesin-β-galactosidase fusion protein

Summary We have analyzed the development of neuronal projections inDrosophila by fusing the gene encodingDrosophila kinesin, a microtubule-associated motor protein, toEscherichia coli lacZ, and employing the resulting chimeric protein as a reporter molecule for labelling cells by the enhancer-trap method. Expression of kinesin--galactosidase in neurons has afforded a detailed view of the morphologies and projections of neurons. The images of cells provided by this method will facilitate anatomical and genetic investigations of theDrosophila nervous system as well as other cell types. Correspondence to: Y.N. Jan     

Evolution and improvement of cultivated amaranths

Summary Of the four interspecific hybrids, three (A. graecizans var. graecizans X A. tricolor cv. Purple leaf, A. lividus var. lividus X A. tricolor var. viridis and A. gracilis X A. tricolor cv. Purple leaf) were studied cytologically. In all the three, differentiation between the parents is chiefly a result of interchanges and paracentric inversions. The interchange complexes may involve from four (A. gracilis X A. tricolor cv. Purple leaf) to fourteen (A. lividus var. lividus X A. tricolor var. viridis) chromosomes, indicating that the parents differ from each other in 1 to 6 interchanges. Because of the small size of the chromosomes, it is possible that crossing-over in interchange for small segments is restricted. The particular parental species representing the ancestral condition from which others were derived or compounded is difficult to pin-point. With preferential pairing and the restoration of fertility in the amphidiploid A. lividus-tricolor, it became clear that it is very likely that the interchanged segments are small and sterility in the hybrid is entirely chromosomal.This situation is in strong contrast to that in Sect. Amaranthus, where the single male flower per glomerule and huge showy inflorescences lead to more cross-pollination; coupled with this are strong morphological divergences between taxa and less genetic differentiation. In the Sect. Blitopsis, there are a number of male flowers per glomerule and small non-showy axillary inflorescences, leading to self-pollination, and less morphological but strong genetic differentiation by interchanges and inversions.     

Comparative study ofTriticum aestivum andT. timopheevi genomes using C-banding technique

The somatic chromosomes ofTriticum timopheevi and those of two varieties ofT. aestivum, Chinese Spring and Bezostaya-1, have been identified by a Giemsa staining technique. The data suggest thatT. timopheevi and tetraploid wheats had a common ancestor from which their genomes differentiated due to chromosomal aberrations and the increase of heterochromatin in the chromosomes of theT. timopheevi G-genome. The differences between the chromosomes of the AB and AG genomes result in substitutions and large translocations between these chromosomes in interspecific hybrids.     

Territorial behavior of the red admiral,Vanessa atalanta (Lepidoptera: Nymphalidae) I. The role of climatic factors and early interaction frequency on territorial start time

We examined the relative importance of climatic factors and population density to territorial start time ofVanessa atalanta males. Start time varies with solar altitude and therefore with seasons. We removed seasonal effects by converting start times to corresponding solar altitudes. Start time solar altitude correlates primarily with ambient temperature (T _a) and secondarily with substrate temperature (T _s), regardless of cloud cover. Overcast cloud cover resulted in later not earlier start times as expected from reduced solar radiation (R) levels. R may affect start time indirectly by affectingT _s and later start times under overcast skies may be a result ofT _s. Start times under solid overcast but not under broken overcast were different than under clear skies, suggesting thatV. atalanta males can use dim sun or blue patches in broken overcast as a start time cue. Early interaction frequency is correlated withT _a and wind direction, but not with start time itself, suggesting that male population density is unimportant compared with climatic factors. We conclude thatV. atalanta has a climate-dependent start time but, also, that maintaining a relatively fixed daily schedule is more important to males than is achieving an optimal body temperature while perching.     

C(alpha) chemical shift tensors in helical peptides by dipolar-modulated chemical shift recoupling NMR

The C chemical shift tensors of proteins contain information on the backbone conformation. We have determined the magnitude and orientation of the C chemical shift tensors of two peptides with -helical torsion angles: the Ala residue in G*AL (=–65.7°, =–40°), and the Val residue in GG*V (=–81.5°, =–50.7°). The magnitude of the tensors was determined from quasi-static powder patterns recoupled under magic-angle spinning, while the orientation of the tensors was extracted from C–H and C–N dipolar modulated powder patterns. The helical Ala C chemical shift tensor has a span of 36 ppm and an asymmetry parameter of 0.89. Its ₁₁ axis is 116° ± 5° from the C–H bond while the ₂₂ axis is 40° ± 5° from the C–N bond. The Val tensor has an anisotropic span of 25 ppm and an asymmetry parameter of 0.33, both much smaller than the values for -sheet Val found recently (Yao and Hong, 2002). The Val ₃₃ axis is tilted by 115° ± 5° from the C–H bond and 98° ± 5° from the C–N bond. These represent the first completely experimentally determined C chemical shift tensors of helical peptides. Using an icosahedral representation, we compared the experimental chemical shift tensors with quantum chemical calculations and found overall good agreement. These solid-state chemical shift tensors confirm the observation from cross-correlated relaxation experiments that the projection of the C chemical shift tensor onto the C–H bond is much smaller in -helices than in -sheets.