ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

Ihre E-Mail wurde erfolgreich gesendet. Bitte prüfen Sie Ihren Maileingang.

Leider ist ein Fehler beim E-Mail-Versand aufgetreten. Bitte versuchen Sie es erneut.

Vorgang fortführen?

Exportieren
Filter
  • Ultrastructure  (1.615)
  • Drosophila  (737)
  • Angiosperms  (680)
  • Springer  (3.026)
  • Nature Publishing Group
  • 1
    ISSN: 1432-2285
    Schlagwort(e): Cambial activity ; Frost hardiness ; Phenology ; Salix ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary The ultrastructure of cells in the cambial region of Salix dasyclados Wim. (clone 78056) was studied during the development of winter hardiness and the onset of cambial activity in spring. Plants were grown at relative growth rates (RG) of 8% and 12% respectively, resulting in different nitrogen content in the stems. Frost hardiness of the plants was estimated by standardized freezing tests. Plants with a higher nitrogen status ceased growth later and started re-growth earlier in spring than plants with lower nitrogen content. Differences in ability to withstand low temperatures during autumn and spring were found between plants grown in the two nutrient treatments. During the development of frost hardiness in the autumn, the number of meristematic cells in the cambial region decreased. The cessation of meristematic activity was accompanied by cell wall thickening and ultrastructural changes in the cells. Frost hardiness increased from the ability to survive -6° C in October to survival of -80° C at the beginning of December. From November to February the cambial region comprised a layer of 2–3 thick-walled cells with conspicuous ultrastructural features. Starch accumulated in plastids in September, decreased during November to March and then increased again in accordance with changes of frost hardiness. Onset of cambial activity began between the end of March and the beginning of April, as shown by increased vacuolization of meristematic cells and mitotic activity. By April, the starch content had increased and lipolysis was observed. Frost hardiness had decreased, and plants with low and high nitrogen content were able to survive -15° C and -10° C, respectively. After budburst, all axillary shoot parts were damaged at temperatures below-3° C.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 2
    ISSN: 1432-2285
    Schlagwort(e): Conifer ; Fluoride ; Nitrogen ; Sulphur dioxide ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Effects of SO2, aqueous fluoride (NaF) and a solution of nitrogen compounds (NH4NO3) on the visible symptoms, pollutant accumulation and ultrastructure of Scots pine (Pinus sylvestris L.) and Norway spruce [Picea abies (L.) Karst.] seedlings were studied in an open-air experiment lasting for 3 consecutive years. Visible injury symptoms were most pronounced in combination exposures and whenever F was applied. Visible symptoms correlated well with needle pollutant concentrations. Exposure to NaF increased needle F contents particularly when F was applied with SO2 or NH4NO3. This suggests that a reduction in N or SO2 emissions, in F polluted areas, could improve the condition of conifers via decreased accumulation of phytotoxic F in the needles. Norway spruce needles accumulated 2–10 times as much S and F as those of Scots pine. Microscopic observations showed various changes in the needle mesophyll cell ultrastructure. In both species, exposure to SO2 increased significantly the amount of cytoplasmic vacuoles, suggesting detoxification of excess sulphate or low pH. F treatments resulted in a significant enlargement of plastoglobuli in Scots pine and a darkening of plastoglobuli in Norway spruce. All exposures enhanced the accumulation of lipid bodies. An increased portion of translucent plastoglobuli was most pronounced in N treatments. Many of the ultrastructural changes and visible symptoms appeared only as number of years exposed increased, indicating that long-term experiments are needed. Both visible symptoms and ultrastructural changes pointed to the more pronounced sensitivity of Norway spruce compared to Scots pine. Ultrastructural results mostly supported earlier qualitative observations of F, N and SO2 effects on needle mesophyll cell ultrastructure. However, no reduction of thylakoids in SO2 containing exposure or curling of thylakoids in F exposure could be detected in the present study.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 3
    ISSN: 1432-2285
    Schlagwort(e): Nuclear crystalloid inclusions ; Olea europaea ; Cytochemistry ; Ultrastructure ; Glycoprotein
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary The nuclei of mesophyll cells of olive trees contain numerous sizeable crystalloid inclusions. Cytochemical examination using epoxy resin-embedded, semithin-sectioned tissue indicated the presence of proteins and oligoor polysaccharides in these inclusions. Their electron microscopical analysis revealed a crystalline substructure consisting of intersected subunits of high order. The spacing of the lattice fibrils and the angles of intersection were determined and used to establish a model of the unit cell of crystallization. It is suggested that the nuclear crystalloids of olive trees consist of glycoprotein molecules. They differ from the intranuclear crystalloids observed in other species predominantly in the high density of their subunit arrangement.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 4
    ISSN: 1432-2285
    Schlagwort(e): Air pollutants ; Chloroplasts ; Fluoride ; Olive tree leaves ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary Leaves of olive trees growing in the vicinity of the Aluminium Factory of Greece were ultrastructurally investigated in order to determine any malformations caused by environmental air pollutants, especially hydrogen fluoride, in comparison with control samples and normal seasonal senescence. Estimation of some elements accumulated by these leaves showed that they contained high amounts of F and Al attributable to the operation of the nearby factory. The most seriously effected cell components were found to be the mesophyll chloroplasts that show a dilation of the intrathylakoid space, increase of the number of plastoglobuli, discoloration of plastoglobuli, accumulation of large starch grains and an overall disorganized appearance of the organelle. The nuclear crystalloid inclusions have unusual shapes, while the vacuoles contain a fibrillar/granular material that increases their electron density. It is concluded that the ultrastructural malformations are caused by a combination of environmental stresses and air pollutants.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 5
    Digitale Medien
    Digitale Medien
    Springer
    Zoomorphology 104 (1984), S. 304-309 
    ISSN: 1432-234X
    Schlagwort(e): Ultrastructure ; Gills ; Epithelial cells ; Polychaeta
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The ultrastructure of gill epidermal cells of Diopatra neapolitana and their relationship with blood spaces are described. The existence of a basal infolding complex, related to the blood spaces, is also reported. A possible involvement of these cells in osmoregulation and ion interchange, apart from their well-known role in respiration, is suggested.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 6
    Digitale Medien
    Digitale Medien
    Springer
    Sexual plant reproduction 1 (1988), S. 208-216 
    ISSN: 1432-2145
    Schlagwort(e): Megagametophyte ; Synergids ; Brassica campestris ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary In Brassica campestris, both synergids of the ovule degenerate before the arrival of the pollen tube. Synergid degeneration does not depend on pollination. At the non-degenerated stage, the synergids are completely filled with a complexly organized cytoplasm containing numerous mitochondria with many cristae, a large number of dictyosomes with many associated vesicles, and a very extensive rough endoplasmic reticulum. The degenerative changes that occur in the cytoplasm of the synergids are characterized by a loss of visibility of the membranes of the endoplasmic reticulum and the simultaneous formation of dense deposits on the surrounding membranes of the mitochondria. Locally, the plasma membranes of the synergids disappear, and some ground plasma of the synergids penetrates into the space between the plasma membranes of the egg cell and the central cell.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 7
    Digitale Medien
    Digitale Medien
    Springer
    Sexual plant reproduction 10 (1997), S. 368-373 
    ISSN: 1432-2145
    Schlagwort(e): Key words Egg-cell isolation (angiosperm) ; Micromanipulation ; Plumbagozeylanica ; Viable egg ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract  A protocol for isolating viable eggs in Plumbago zeylanica by mechanical dissection is reported. The optimum solution for isolation was 0.8 M mannitol + 10 mM MOPS + 10 mM CaCl2, (pH 4.5–5.0) with an osmolality of 860–940 mmol/kg. Eggs retain their viability for at least 24 h. Isolated eggs were true protoplasts without cell walls and could tolerate osmolality of 437 mmol/kg to 965 mmol/kg. Observation of the isolated eggs using transmission electron microscopy indicated that they were well preserved and reflected the ultrastructure of physiologically active cells, displaying features similar to those of in vivo egg cells. Notable differences include the absence of a filiform apparatus and the accumulation of dense particles in the plastids, which was most conspicuous in egg cells that were damaged during isolation.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 8
    Digitale Medien
    Digitale Medien
    Springer
    Sexual plant reproduction 11 (1998), S. 121-130 
    ISSN: 1432-2145
    Schlagwort(e): Key words Egg cell ; Parthenogenesis ; Synergid ; Ultrastructure ; Wheat ; Zygote
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract  The ultrastructure of the egg apparatus of the sexual (aestivum)-Salmon line (aS) and the isogenic but alloplasmic (kotschyi)-Salmon line (kS) of the Salmon system of wheat was studied by transmission electron microscopy 3 days before and during anthesis. Additionally, the zygotic stage of aS, 17 h after pollination, was included. Metabolic activity of egg cells from the sexual line aS was low 3 days before anthesis and increased dramatically after pollination and fertilization. This timing of increased activity was evident because of changes occurring in the egg cell nucleus and nucleolus, polysomes, endoplasmic reticulum and Golgi apparatus, and the completion of the cell wall around the zygote. In contrast to the sexual line, the egg cell of the parthenogenetic line showed high activity 3 days before anthesis. The metabolic and ultrastructural characters observed in the nucleus and cytoplasm of the kS line 3 days before and during anthesis corresponded with those of the isogenic sexual line aS during anthesis and 17 h after pollination, respectively. High metabolic activity observed in the persistent synergid of kS may be connected with the occurrence of additional embryos in seeds (twins) of this line.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 9
    Digitale Medien
    Digitale Medien
    Springer
    Sexual plant reproduction 11 (1998), S. 284-291 
    ISSN: 1432-2145
    Schlagwort(e): Key words Abies ; Egg cell ; Plastid inheritance ; RFLP ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract  The ultrastructure of egg cells in Abies alba was examined to elucidate the lack of maternal inheritance of plastids. Before fertilization, maternal plastids are absent in the perinuclar zone containing mainly mitochondria and smooth endoplasmic reticulum. During egg cell development the maternal plastids are transformed into large inclusions which are situated mostly towards the periphery of the egg cell, and finally disintegrate. As a consequence, they do not participate in zygote formation. RFLP analysis of cpDNA of parental trees and their F1 interspecific hybrids (A. alba×A. numidica, A. alba×A. nordmanniana, A. nordmanniana×A. Alba) using HindIII and BamHI showed a paternal mode of cpDNA inheritance. Paternal inheritance has also been found with PCR/RFLP analysis of cpDNA from parental trees and their hybrids (A. alba×A. pinsapo, A. pinsapo×A. alba, A. pinsapo×A. numidica) using ApaI and HaeIII digests, as well as in the crosses of A. cephalonica×A. nordmanniana, A. nordmanniana×A. cephalonica, A. cephalonica×A. numidica using TagI digests.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 10
    Digitale Medien
    Digitale Medien
    Springer
    Sexual plant reproduction 12 (1999), S. 99-109 
    ISSN: 1432-2145
    Schlagwort(e): Key words Arabidopsis thaliana ; Megasporogenesis ; Meiosis ; Ultrastructure ; Cellular polarity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract  In this study, megasporogenesis of the plant model Arabidopsis thaliana was investigated by electron microscopy for the first time. The data described here could constitute a reference for future investigations of Arabidopsis mutants. During the beginning of meiosis the megaspore mother cell shows a polarity created by unequal distribution of organelles in the cytoplasm. Plastids accumulate in the chalazal region and long parallel saccules of endoplasmic reticulum, small vacuoles and some dictyosomes are found in the micropylar region. Plasmodesmata are abundant in the chalazal cell wall. The nucleus is almost centrally localized and contains a prominent excentric nucleolus and numerous typical synaptonemal complexes. After the second division of meiosis the four megaspores are separated by thin cell walls crossed by numerous plasmodesmata and do not show significant cellular organization. The young functional megaspore is characterized by a large nucleus and a large granular nucleolus. The cytoplasm is very electron dense due to the abundance of free ribosomes and contains the following randomly distributed organelles: mitochondria, a few short saccules of endoplasmic reticulum, dictyosomes and undifferentiated plastids. However, there is no apparent polarity, except for the distribution of some small vacuoles which are more abundant in the micropylar region of the cell. The degenerating megaspores are extremely electron dense and do not show any substructure.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 11
    Digitale Medien
    Digitale Medien
    Springer
    Sexual plant reproduction 2 (1989), S. 154-166 
    ISSN: 1432-2145
    Schlagwort(e): Helianthus annuus ; Unfertilized ovule culture ; Parthenogenesis ; Ultrastructure ; Proembryo
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Electron microscope studies have been conducted on the parthenogenesis induced by in vitro culture of unfertilized ovules of sunflower (Helianthus annuus). In comparison with the state of the egg prior to inoculation, some eggs 5 days after culture show striking ultrastructural changes, which include, among others, nuclear migration, an increase in the number and activity of the organelles, a loss of polarity and wall formation at the chalazal end of the cell. Most of these changes are similar to those that occur normally in the zygote, indicating that parthenogenic development has been triggered in these eggs. Such eggs have been termed activated and are presumed to be capable of undergoing parthenogenesis. The parthenogenic proembryos which result share some features in common with zygotic proembryos. In addition, some parthenogenic proembryos exhibit unique properties not found in zygotic proembryos. These include embryos that consist of two parts differing markedly in density, an inversion of polarity, the frequent occurrence of autophagic vacuoles, the thickening of cell walls, a centripetal growth mode of wall formation, the appearance of an incomplete cell wall, free nuclear division, amitosis and degeneration. We believe that these ultrastructural peculiarities are the effects of in vitro culture.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 12
    Digitale Medien
    Digitale Medien
    Springer
    Sexual plant reproduction 2 (1989), S. 193-198 
    ISSN: 1432-2145
    Schlagwort(e): Polymorphism ; Ultrastructure ; Pollen grains ; Canna indica L ; Tannin
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Our investigations on Canna indica L. indicate that the pollen of this species is polymorphic: there are two types of pollen — a larger type and a comparatively smaller type. Transmission electron microscopy (TEM) revealed the presence of small vacuoles containing tannic substances in the generative cell (GC) of the larger grains: the GC of the mature grain contained a higher quantity of tannins than the GC of the immature grain. Mitochondria, lipid bodies, rough endoplasmic reticulum (RER) and microtubular bundles were present in the cytoplasm of the GC. Numerous mitochondria, lipid bodies and plastids were also present in the vegetative cell (VC), with the mitochondria clustered around the vegetative nucleus. The plastids were observed to be associated with the RER cisterns. During the maturation process, the number of starch grains contained in the plastids decreased.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 13
    Digitale Medien
    Digitale Medien
    Springer
    Sexual plant reproduction 4 (1991), S. 28-35 
    ISSN: 1432-2145
    Schlagwort(e): Tapetal cells ; Brassica oleracea L ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The ultrastructure of the secretory, binucleate tapetum of Brassica oleracea in the micro spore mother cell (MMC) stage through to the mature pollen stage is reported. The tapetal cells differentiate as highly specialized cells whose development is involved in lipid accumulation in their final stage. They start breaking down just before anther dehiscence. Nuclei with dispersed chromatin, large nucleoli and many ribosomes in the cytoplasm characterize the tapetal cells. The wall-bearing tapetum phase ends at the tetrade stage. The dissolution of tapetal walls begins from the inner tangential wall oriented towards the loculus and proceeds gradually along the radial walls to the outer tangential one. The plasmodesmata transversing the radial walls between tapetal cells persist until the mature microspore, long after loss of the inner tangential wall. After wall dissolution, the tapetal protoplasts retain their integrity and position within the anther locule. The tapetal cell membrane is in direct contact with the exine of the microspores/pollen grains and forms tubular evaginations that increase its surface area and appear to be involved in the translocation of solutes from the tapetal cells to the microspores/ pollen grains. The tapetal cells exhibit a polarity expressed by spatial differentiation in the radial direction.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 14
    Digitale Medien
    Digitale Medien
    Springer
    Sexual plant reproduction 4 (1991), S. 176-181 
    ISSN: 1432-2145
    Schlagwort(e): Pollen ; Brassica napus ; Mitoses ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Brassica napus pollen development during the formation of the generative cell and sperm cells is analysed with light and electron microscopy. The generative cell is formed as a small lenticular cell attached to the intine, as a result of the unequal first mitosis. After detaching itself from the intine, the generative cell becomes spherical, and its wall morphology changes. Simultaneously, the vegetative nucleus enlarges, becomes euchromatic and forms a large nucleolus. In addition, the cytoplasm of the vegetative cell develops a complex ultrastructure that is characterized by an extensive RER organized in stacks, numerous dictyosomes and Golgi vesicles and a large quantity of lipid bodies. Microbodies, which are present at the mature stage, are not yet formed. The generative cell undergoes an equal division which results in two spindle-shaped sperm cells. This cell division occurs through the concerted action of cell constriction and cell plate formation. The two sperm cells remain enveloped within one continuous vegetative plasma membrane. One sperm cell becomes anchored onto the vegetative nucleus by a long extension enclosed within a deep invagination of the vegetative nucleus. Plastid inheritance appears to be strictly maternal since the sperm cells do not contain plastids; plastids are excluded from the generative cell even in the first mitosis.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 15
    Digitale Medien
    Digitale Medien
    Springer
    Sexual plant reproduction 4 (1991), S. 226-234 
    ISSN: 1432-2145
    Schlagwort(e): Male germ unit ; Sperm cells ; Isolation ; Pollen tubes ; Brassica napus ; Pollen-tube inner plasma membrane ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Sperm cells of pollen tubes grown both in vivo and in vitro form a male germ unit. Extensions from both sperm cells of each pollen tube are closely associated with the tube nucleus. A high yield (2.7 × 104. 20 mg−1 pollen grains germinated) of intact sperm cells was obtained following release by osmotic shock from pollen tubes grown in vitro. Structural integrity of isolated sperm was maintained by isolation at low temperature in an osmotically balanced medium. At 4° C many isolated sperm pairs were still enclosed within the pollentube inner plasma membrane. Sperm cells not enclosed within this membrane no longer remained connected as a pair. During isolation vesicles formed on the sperm cell surface from disruption of the fibrillar components bridging the periplasmic space. Both in the pollen tube and after isolation the sperm nucleus is in close association with at least one region of the sperm plasma membrane. Sperm isolated at room temperature showed the presence of nucleopores, and nuclei were euchromatic, instead of heterochromatic as in intact sperm in the pollen tube.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 16
    Digitale Medien
    Digitale Medien
    Springer
    Sexual plant reproduction 5 (1992), S. 27-33 
    ISSN: 1432-2145
    Schlagwort(e): Isolated generative cells ; Ultrastructure ; Microtubule ; Immunofluorescence microscopy ; Allemanda neriifolia
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The ultrastructure of isolated generative cells ofAllemanda neriifolia at interphase and prophase was studied. The microtubule organization of the isolated cells was also investigated by immunofluorescence microscopy with a monoclonal anti-α-tubulin. After the generative cells had been isolated from the growing pollen tubes by osmotic shock, most of the cells were at prophase and only a few were at interphase. The interphase cell is spindle shaped and contains an ellipsoidal nucleus. In addition to the usual organelles, the cytoplasm of the interphase cell contains numerous vesicles (each measuring 40–50 nm in diameter) and two sets of longitudinally oriented microtubule bundles — one in the cortical region and the other near the nucleus. Most of the prophase cells are spherical in shape. Based on the ultrastructure and the pattern of microtubule cytoskeleton organization three types of prophase cells can be recognized. (1) Early prophase cell, which contains the usual organelles, numerous vesicles, and a spherical nucleus with condensed chromosomes. Longitudinally oriented microtubule bundles can no longer be seen present in the early prophase cell. A new type of structure resembling a microtubule aggregate appears in the cytoplasm. (2) Mid prophase cell, which has a spherical nucleus containing chromosomes that appear more condensed than those seen in the early prophase cell. In addition to containing the usual organelles, the cytoplasm of this cell contains numerous apparently randomly oriented microtubules. Few vesicles are seen and microtubule aggregates are no longer present. (3) Late prophase cell, typified by the lack of a nuclear envelope. Consequently, the chromosomes become randomly scattered in the cytoplasm. Microtubules are still present and some become closely associated with the chromosomes. The changes in the ultrastructure and in the pattern of microtubule organization in the interphase and prophase cells are discussed in relation to the method of isolation of the generative cells.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 17
    Digitale Medien
    Digitale Medien
    Springer
    Sexual plant reproduction 5 (1992), S. 86-88 
    ISSN: 1432-2145
    Schlagwort(e): Sex chromosome markers ; Y-chromosome ; Angiosperms ; Silene latifolia ; Melandrium album
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary In order to obtain markers for the Y chromosome ofSilene latifolia, we pooled equal weights of leaf tissue from 18 female siblings into one sample and repeated the process with 18 male siblings. Pooling was intended to provide a common genetic background for each sample, leaving the absence or presence of the Y chromosome as the primary difference between the two samples. DNA was extracted from each sample and subjected to polymerase chain reaction (PCR) amplification with arbitrary 10 bp primers. Four of 60 primers used gave an amplification with the male DNA not found among those from the female DNA. Each of these was subsequently shown to provide a reliable marker for the Y chromosome.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 18
    Digitale Medien
    Digitale Medien
    Springer
    Sexual plant reproduction 5 (1992), S. 131-137 
    ISSN: 1432-2145
    Schlagwort(e): Pollen grain ; Generative cell ; Formation and detachment ; Ultrastructure ; Polystachia pubescens ; Orchidaceae
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The formation and nature of the generative cell wall and the detachment mode of the generative cell from the intine in Polystachia pubescens were observed by LM and TEM. Vesicles evenly positioned within the phragmoplast fuse to form a cell plate that divides the microspore into the generative and vegetative cell. This cell plate consists of callose. Before the generative cell leaves the intine, however, the callose is completely resorbed and is not replaced by any other substance. The generative cell becomes detached from the intine by moving towards the centre of the pollen grain. A constriction formed thereby gives the generative cell a bulb-like appearance and leads ultimately to the generative cell being pinched off. Plasma-filled vesicles originating from the generative cell remain between the intine and the plasma membrane of the vegetative cell.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 19
    ISSN: 1432-2145
    Schlagwort(e): Wheat pollen ; Chemical hybridizing agents ; Male sterility ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Phenylcinnoline carboxylate compounds SC-1058 and SC-1271 cause complete male sterility in wheat when applied at suitable dosages at the pre-meiotic stage of anther development. Anthers from treated and untreated plants were compared using light and electron microscopy from the pre-meiotic stage through the formation of nearly mature pollen. Overall anther development is gradually slowed in treated plants and pollen development is generally arrested in the late prevacuolate or early vacuolate microspore stage, although the first pollen mitosis does sometimes occur. The sporopollenin-containing exine walls are thinner, and show abnormally developed foot and tectum layers with sparse connecting baculi. Microspore cytoplasm degenerates and the cells eventually collapse. At the early, prevacuolate, free microspore stage treated tapetal cells hypertrophy, expanding into the locule. They contain abnormally large vacuoles that appear to form from the fusion of secretory vesicles, and some vacuoles contain electrondense deposits. The sporopollenin-containing orbicular wall and Ubisch bodies are retarded in their development and are structurally deformed. Acetolysis of whole anthers and of thick sections shows that the sporopollen-in-containing structures of treated materials are greatly reduced in thickness and are less rigid than in the control. We conclude that application of these compounds causes interference with the secretory function of tapetal cells which supplies sporopollenin cell-wall polymers to the exine of the microspores and to the tapetal orbicular wall and associated Ubisch bodies. Interference with the tapetal secretion of other nutrients required for microspore development is strongly suggested.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 20
    Digitale Medien
    Digitale Medien
    Springer
    Sexual plant reproduction 6 (1993), S. 191-198 
    ISSN: 1432-2145
    Schlagwort(e): Micropyle ; Transfer cells ; Ultrastructure ; Nucellus ; Poaceae
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Several kinds of outgrowth from the grass ovule are known. Attention is focused here on one outgrowth that occurs within or around the micropyle and is of nucellar origin. Grass species in which it is currently known to occur are listed and examples of variants briefly described. Attention is concentrated upon Pennisetum, where the cell structure is described in detail with a series of electron photomicrographs. The tissue representing an aggregation of these transfer cells is newly named with the term ‘embellum’, and its significance for pollen tube growth is considered.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 21
    Digitale Medien
    Digitale Medien
    Springer
    Sexual plant reproduction 8 (1995), S. 197-204 
    ISSN: 1432-2145
    Schlagwort(e): Apomixis ; Apospory ; Aposporous initial ; Aposporous embryo sac ; Ultrastructure ; Panicum
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The nucellar ultrastructure of apomictic Panicum maximum was analyzed during the meiocytic stage and during aposporous embryo sac formation. At pachytene the megameiocyte shows a random cell organelle distribution and sometimes only an incomplete micropylar callose wall. The chalazal nucellar cells are meristematic until the tetrad stage. They can turn into initial cells of aposporous embryo sacs. The aposporous initials can be recognized by their increased cell size, large nucleus, and the presence of many vesicles. The cell wall is thin with few plasmodesmata. If only a sexual embryo sac is formed, the nucellar cells retain their meristematic character. The aposporous initial cell is somewhat comparable to a vacuolated functional megaspore. It shows large vacuoles around the central nucleus and is surrounded by a thick cell wall without plasmodesmata. In the mature aposporous embryo sac the structure of the cells of the egg apparatus is similar to each other. In the chalazal part of the egg apparatus the cell walls are thin and do not hamper the transfer of sperm cells. Structural and functional aspects of nucellar cell differentiation and aposporous and sexual embryo sac development are discussed.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 22
    ISSN: 1432-2145
    Schlagwort(e): Key words Somatic embryogenesis ; Ultrastructure ; Pennisetum ; Poaceae ; Morphometrics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract  Ultrastructural changes during zygotic and somatic embryogenesis in pearl millet (Pennisetum glaucum [L.] R. Br.) were quantified using morphometric techniques. The total area per cell profile and the cell volume percentage of the whole cell, endoplasmic reticulum (ER), Golgi bodies, mitochondria, nuclei, lipids, plastids, starch grains and vacuoles were measured and comparisons made between three zygotic and three somatic embryo developmental stages. All measurements were taken from scutellar or scutellar-derived cells. Zygotic embryogenesis was characterized by increases in cell size, lipids, plastids, starch, Golgi bodies, mitochondria and ER. Somatic embryogenesis was characterized by two phases of cell development: (1) the dedifferentiation of scutellar cells involving a reduction in cell and vacuole size and an increase in cell activity during somatic proembryoid formation and (2) the development of somatic embryos in which most cell organelle quantities returned to values found in late coleoptile or mature predesiccation zygotic stages. In summary, although their developmental pathways differed, the scutella of somatic embryos displayed cellular variations which were within the ranges observed for later stages of zygotic embryogenesis.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 23
    Digitale Medien
    Digitale Medien
    Springer
    Mycorrhiza 10 (2000), S. 15-21 
    ISSN: 1432-1890
    Schlagwort(e): Anthoceros punctatus ; Arbuscular mycorrhiza ; Bryophytes ; Glomus ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Glomus claroideum (Schenck & Smith emend. Walker & Vestberg) were investigated for ability to form arbuscular mycorrhiza-like symbioses with the hornwort Anthoceros punctatus (L.). Spores were transferred to a cellulose acetate filter on water agar and a small portion of an Anthoceros thallus was placed directly upon the spores. Light-microscope observations 20 days after inoculation revealed branched hyphae growing within the thallus. After 45 days, arbuscules and vesicles were studied by light- and electron-microscopy. After 60 days in water agar culture, the colonised Anthoceros thalli were transferred to a low-nutrient medium agar. Hyphae spread in the agar and newly formed spores were observed 5 weeks after the transfer. After 4 months, about 1000 spores were formed in each Petri dish. This is the first report of an experimentally established arbuscular mycorrhiza-like symbiosis between an identified fungus belonging to the Glomales and a bryophyte.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 24
    ISSN: 1432-1424
    Schlagwort(e): Drosophila ; per mutants ; pertransgenic ; Lucifer Yellow injections ; Gap junctions
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Abstract Larval salivary gland cells of Drosophila melanogaster were injected with a fluorescent dye to assess strengths of intercellular communication among such cells, as influenced by mutations at the period locus and by a per transgene. This clock gene had been reported to increase the extent of dye transfer when mutated such that it shortens the period of biological rhythms; the previous study also showed that a per-null mutant decreased the strength of transfer among salivary gland cells. Our re-examination of this feature of larval physiology—in observer-blind analyses, using the per s and per o mutants as well as two per-normal strains—revealed no appreciable differences in extents of dye transfer among these four genotypes. These results are discussed in the context of emerging findings which suggest that the period gene's product controls pacemaker functioning as an intracellularly acting entity.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 25
    Digitale Medien
    Digitale Medien
    Springer
    Journal of comparative physiology 186 (2000), S. 347-357 
    ISSN: 1432-1351
    Schlagwort(e): Key words Crustacean ; Sensorimotor ; Ultrastructure ; Multilamellar sheath ; Myelinated axons
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract Speed of nerve impulse conduction is greatly increased by myelin, a multi-layered membranous sheath surrounding axons. Myelinated axons are ubiquitous among the vertebrates, but relatively rare among invertebrates. Electron microscopy of calanoid copepods using rapid cryofixation techniques revealed the widespread presence of myelinated axons. Myelin sheaths of up to 60 layers were found around both sensory and motor axons of the first antenna and interneurons of the ventral nerve cord. Except at nodes, individual lamellae appeared to be continuous and circular, without seams, as opposed to the spiral structure of vertebrate and annelid myelin. The highly organized myelin was characterized by the complete exclusion of cytoplasm from the intracellular spaces of the cell generating it. In regions of compaction, extracytoplasmic space was also eliminated. Focal or fenestration nodes, rather than circumferential ones, were locally common. Myelin lamellae terminated in stepwise fashion at these nodes, appearing to fuse with the axolemma or adjacent myelin lamellae. As with vertebrate myelin, copepod sheaths are designed to minimize both resistive and capacitive current flow through the internodal membrane, greatly speeding nerve impulse conduction. Copepod myelin differs from that of any other group described, while sharing features of every group.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 26
    Digitale Medien
    Digitale Medien
    Springer
    Journal of comparative physiology 166 (1989), S. 179-187 
    ISSN: 1432-1351
    Schlagwort(e): Blowfly ; Drosophila ; Photoreceptor ; Lanthanum ; trp mutant
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The effect of lanthanum on the light response of blowfly (Calliphora erythrocephala) photoreceptors was studied. The electrophysiological behaviour of the photoreceptors in the presence of La can be summarized as follows: 1. Upon long stimulation the photoreceptors responded with a ‘transient receptor potential’, i.e. the cells depolarized at the onset of the stimulus and then repolarized to (or below) the resting potential. This effect was dependent on stimulus intensity and occurred only at high intensities. During illumination membrane noise was reduced. 2. The light-induced changes in membrane potential were paralleled by changes in membrane resistance. 3. The time course of the receptor response was slowed down. 4. Light adaptation led to an increase in response latency. 5. The recovery of the receptor response after light adaptation was slowed down. 6. The sensitivity of the receptor cells measured by the response to short light stimuli was reduced. In summary, the electrophysiological behaviour of Calliphora photoreceptors in the presence of La was very similar to that of the photoreceptors of the trp (transient receptor potential) mutant of Drosophila melanogaster. This result suggests that La and trp mutation affect the same cellular processes in the photoreceptors.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 27
    Digitale Medien
    Digitale Medien
    Springer
    Planta 133 (1976), S. 15-19 
    ISSN: 1432-2048
    Schlagwort(e): Tropaeolum, Embryogenesis ; Differentiation ; Plastids ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Embryogeny in the nasturtium is characterized by the development of a large, tripartite suspensor and storing cotyledons. A light and electron microscopic study revealed an early diversification of the plastids in the various regions of the suspensor and the embryo proper. Amyloplasts are found in the developing cotyledons of the heart-like embryo, while chloroplasts occur within the meristematic part of the embryo and the adjacent portion of the suspensor. The cells between the meristem and the storing cotyledons display undifferentiated leukoplasts, whereas leukoplasts with an electron-dense matrix occur in the basal cell mass of the embryo-suspensor. Etioplasts develop in several cells of the placental haustorium of the suspensor. The carpel haustorium shows rather undifferentiated leukoplasts, which are transformed into electron-dense plastids during autolysis of the suspensor. This early plastidal differentiation in discussed with respect to its control and functional significance.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 28
    ISSN: 1432-2048
    Schlagwort(e): Festuca ; Frost damage ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Tillers of Festuca arundinacea Schreb. were subjected to-8°C in a bath of methylated spirits for three-quarters of an hour. They were thawed at room temperature and some material taken from the shoot apical meristem and leaf blade for electron microscopy. Similar material was taken from control plants for electron microscopy. Nine tillers subjected to-8°C and thawed subsequently failed to regrow. Nine control tillers regrew. All the treated meristem cells and about half the treated leaf mesophyll cells were extensively altered. Their nuclei were contracted, organelles were swollen or partly disrupted, plasmalemma and nuclear membranes were broken or absent and vacuoles were sometimes disrupted. Strongly osmiophilic material accumulated in the vicinity of membranes. About half the leaf mesophyll cells differed from the control mesophyll cells only in having more spherosomes and narrower thylakoids. Parallels with other ultrastructural studies of stress damage and the indications the results give of possible primary damaging events are discussed.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 29
    ISSN: 1432-2048
    Schlagwort(e): Endosperm ; Galactomannan ; Secretion ; Ultrastructure ; Trigonella
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The mode of deposition (secretion) of galactomannan in the cells of the seed endosperm ofTrigonella foenum-graecum has been studied by electron microscopy. In cells which are just beginning to secrete galactomannan there are stacks of rough endoplasmic reticulum (ER). The intracisternal space (containing the enchylema) of the rough ER then swells, becomes vacuolated and forms a voluminous network, with “pockets” of cytoplasm entrapped within poculiform rough ER. The enchylema contains material which reacts with periodate-thiocarbohydrazidesilver proteinate in a very similar manner to the galactomannan already deposited in the cell wall. It appears that the galactomannan is formed in the intracisternal space of the rough endoplasmic reticulum and then expelled outside the plasmalemma. This mode of deposition contrasts with that of other plant cell wall polysaccharides whose secretion is mediated by Golgi vesicles.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 30
    Digitale Medien
    Digitale Medien
    Springer
    Planta 188 (1992), S. 403-413 
    ISSN: 1432-2048
    Schlagwort(e): Cyanobacterium ; Gunnera ; Infection process ; Nostoc ; Symbiosis ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The symbiosis between Gunnera and Nostoc was reconstituted using G. chilensis Lam. and G. manicata Linden, respectively, and three different Nostoc strains. Six stages characterised by specific modifications in both the cyanobiont and the host were recognised during the infection process. Mucilage-secreting stem glands developed on the Gunnera stems independent of the presence of cyanobacteria (Stage I). Soon after addition of the Nostoc isolates to the plant apices, an abundant differentiation of motile hormogonia commenced. The cyanobacteria accumulated in the mucilage on the surface of the gland (Stage II), and the hormogonia then proceeded into the stem tissue through intercellular channels (Stage III). At the channel bases, Nostoc was detected between the cell walls of small, densely cytoplasmic Gunnera cells and also in elaborate folds of these (Stage IV). The Gunnera cell walls subsequently dissolved adjacent to the cyanobacteria and Nostoc entered the host cells (Stage V). Once the intracellular association was formed, a high proportion of the vegetative Nostoc cells differentiated into heterocysts (Stage VI). Nostoc changed from being rich in inclusions (particularly cyanophycin) while on the gland surface into a comparatively “non-storing” form during penetration and the early intracellular stages. Bacteria were numerous on the gland surface, fewer in the channels, and were never detected within the Gunnera cells, indicating the existence of specific recognition mechanisms discriminating between conceivable microsymbionts. Mechanisms behind mutual adaptations and interactions between the two symbionts are discussed.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 31
    Digitale Medien
    Digitale Medien
    Springer
    Planta 188 (1992), S. 155-163 
    ISSN: 1432-2048
    Schlagwort(e): Bradyrhizobium ; Electron microscopy ; Glycine (root nodules) ; High-pressure freezing ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract High-pressure freezing of chemically untreated nodules of soybean (Glycine max (L.) Merr.), in sharp contrast to chemical fixation and prefixation, appears to preserve the ultrastructure close to the native state. This is supported by the observation that the peribacteroid membrane of high-pressure-frozen samples is tightly wrapped around the bacteroids, a finding that is fully consistent with the current views on the physiology of oxygen and metabolite transport between plant cytosol and bacteroids. In soybean root nodules, the plant tissue and the enclosed bacteria are so dissimilar that conventional aldehyde-fixation procedures are unable to preserve the overall native ultrastructure. This was demonstrated by high-pressure freezing of nodules that had been pre-fixed in glutaraldehyde at various buffer molalities: no buffer strength tested preserved all ultrastructural aspects that could be seen after high-pressure freezing of chemically untreated nodules.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 32
    Digitale Medien
    Digitale Medien
    Springer
    Theoretical and applied genetics 50 (1977), S. 125-127 
    ISSN: 1432-2242
    Schlagwort(e): Drosophila ; Mutants ; Radiation ; Lethals ; Dose-Response
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The mutagenic efficiency of ionizing radiations has been tested on different lines of Drosophila melanogaster. It has been shown that differential lethal effects are obtained when irradiated females from different lines are mated to flies carrying heterozygous lethal genes. The results seem not to be attributable to differential expression of the lethality in the various crosses performed with the irradiated flies. This might suggest that gene activity is involved in the expression of the mutagenic effects of radiations.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 33
    Digitale Medien
    Digitale Medien
    Springer
    Theoretical and applied genetics 80 (1990), S. 321-325 
    ISSN: 1432-2242
    Schlagwort(e): Heterosis ; Genetic distance ; Drosophila ; Inbreeding
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The aim of the experiment was to determine if the estimated genetic distance between two populations could be used to predict the amount of heterosis that would occur when they were crossed. Eight lines of known relatedness to each other were produced by eight generations of sib mating and sub-lining. This produced lines that varied in coefficient of coancestry from zero to 0.78. Fourteen reciprocal crosses of these lines were used to measure heterosis for larval viability and adult fecundity. Gene frequencies at six polymorphic enzyme loci were used to estimate the genetic distances between lines, which were then compared with the known degrees of coancestry. The estimated genetic differences were poorly correlated with the known coancestry coefficients (r=0.4), possibly due to the small number of loci typed. Also genetic distances were only about 1/3 of what was expected. Selection acting on blocks of genes linked to the enzyme loci probably prevented the expected increase in homozygosity. Coancestry coefficient was correlated with heterosis (r=0.44–0.71). This level of correlation implied differences in heterosis among parent lines with the same level of coancestry. This variability is expected if a small number of loci explain most of the heterosis. The average level of heterosis was less than expected after eight generations of sib mating. This is most likely due to selection opposing the increase in homozygosity caused by inbreeding. The combination of these two imperfect correlations resulted in no significant correlation between genetic distance estimated from markers and heterosis.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 34
    Digitale Medien
    Digitale Medien
    Springer
    Theoretical and applied genetics 77 (1989), S. 123-127 
    ISSN: 1432-2242
    Schlagwort(e): Inbreeding depression ; Drosophila ; Natural selection
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary This experiment was designed to study the relationship between rate of inbreeding and observed inbreeding depression of larval viability, adult fecundity and cold shock mortality in Drosophila melanogaster. Rates of inbreeding used were full-sib mating and closed lines of N=4 and N=20. Eight generations of mating in the N=20 lines, three generations in the N=4 lines and one generation of full-sib mating were synchronised to simultaneously produce individuals with an expected level of inbreeding coefficient (F) of approximately 0.25. Inbreeding depression for the three traits was significant at F=0.25. N=20 lines showed significantly less inbreeding depression than full-sib mated lines for larval viability at approximately the same level of F. A similar trend was observed for fecundity. No effect of rate of inbreeding depression was found for cold shock mortality, but this trait was measured with less precision than the other two. Natural selection acting on loci influencing larval viability and fecundity during the process of inbreeding could explain these results. Selection is expected to be more effective with slow rates of inbreeding because there are more generations and greater opportunity for selection to act before F=0.25 is reached. Selection intensities seem to have been different in the three traits measured. Selection was most intense for larval viability, less intense for fecundity and, perhaps, negligible at loci influencing cold shock mortality.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 35
    Digitale Medien
    Digitale Medien
    Springer
    Theoretical and applied genetics 77 (1989), S. 253-259 
    ISSN: 1432-2242
    Schlagwort(e): Heterosis ; Selection ; Drosophila ; Genotype x environment
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Experiments were designed to examine whether heterosis would occur in crosses of Drosophila melanogaster populations adapted to 18 °C or 28 °C environments. Crosses were examined in parental environments, an intermediate environment (23 °C) and a mixed environment (alternating 18°/28°C). Parental populations did not show divergence for larval viability, cold shock or high temperature mortalities when tested in a common environment. However, the 28 °C population was less fecund than the 18 °C population, but had higher larval competitive ability and higher adult longevity. Heterosis for viability, cold shock mortality and high temperature mortality occurred in crosses between a population adapted to 18 °C and another adapted to 28 °C, but not in crosses between two populations adapted to the same temperature. The results suggest that, in the absence of drift, heterosis is expected in crosses between lines or populations with different histories of selection but not between lines with the same selection histories.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 36
    Digitale Medien
    Digitale Medien
    Springer
    Theoretical and applied genetics 80 (1990), S. 569-575 
    ISSN: 1432-2242
    Schlagwort(e): Heterosis ; Genetic distance ; Drosophila
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary An experiment was performed to test the hypothesis that the genetic distance between populations estimated from enzyme loci could be used to predict the amount of heterosis that would occur in crosses between these populations. A partial diallel cross using 11 populations of Drosophila melanogaster from the AustralianPacific region and from England was carried out. Heterosis for larval viability, fecundity, cold shock mortality, and an index of these three traits was recorded. When two populations originating from the same location were crossed, no heterosis occurred, but otherwise heterosis was significant for all traits. For larval viability, a similar low level of heterosis occurred in all crosses. For cold shock mortality, the level of heterosis varied widely and fecundity showed a pattern intermediate between these two. The geographic distance between the sites from which populations originated was not correlated with the amount of heterosis in their crosses. There was a tendency for populations from ecologically different environments to show heterosis in crosses. Genetic distance based on ten enzyme loci was correlated with heterosis for cold shock mortality and the combined trait index. These results can be explained by the hypothesis that genes affecting larval viability are subject to strong, uniform selection in all populations, which limits the extent to which gene frequencies can drift apart. However, genes affecting cold shock mortality and the enzyme loci are subject to different selection pressures in different environments. This divergent selection combined with genetic drift causes divergence in gene frequency and heterosis.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 37
    Digitale Medien
    Digitale Medien
    Springer
    Theoretical and applied genetics 83 (1992), S. 821-826 
    ISSN: 1432-2242
    Schlagwort(e): Drosophila ; Balancers ; Inversions ; Translocations ; Meiosis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary We used a screen for maternally generated late embryonic lethals as a new method for the isolation of inversions that are suitable for the balancing of mutations in Drosophila hydei. The recovery of several inversions by this method demonstrates that female meiosis in D. hydei apparently differs from meiosis in female D. melanogaster, since in D. hydei the defective chromosomes which are generated by a single crossing-over within a paracentric inversion can be recovered via the egg nucleus. In addition, the classic method of crossingover suppression was used in order to isolate more inversions and to improve the balancing capacities of inversions. We succeeded in constructing chromosomes that allow the balancing of mutations on nearly the whole genome of D. hydei. We discuss here whether or not this method is suited for application to other organisms.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 38
    ISSN: 1432-2242
    Schlagwort(e): DNA fingerprinting ; Repetitive DNA ; Genotype identification ; Angiosperms
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Oligonucleotides hybridizing to simple repetitive DNA patterns are highly informative as probes for DNA fingerprinting in all investigated animal species, including man. Here we demonstrate the applicability of this technique in higher plants. The oligonucleotide probes (GTG)5 and (GATA)4 were used to investigate the differences in DNA fingerprint patterns of the following angiosperm species: Triticum aestivum, Secale cereale, Hordeum vulgare, Beta vulgaris, Petunia hybrida, Brassica oleracea, and Nicotiana tabacum. Two species, Hordeum vulgare as a monocot and Beta vulgaris as a dicot, were analyzed in more detail. Their genomes differ considerably in both amount and organization of the simple repetitive sequences (GATA)n, (GACA)n, (GTG)n, and (CT)n due to the evolutionary distance of these two species. Furthermore, several lines and cultivars of Beta vulgaris and Hordeum vulgare can clearly be distinguished on the basis of their highly polymorphic patterns of these repetitive sequences.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 39
    ISSN: 1432-1939
    Schlagwort(e): Nested subsets ; Drosophila ; Community structure ; Species-area relationships
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Nested subset structure has been studied in archipelagoes and fragmented habitats, and has been attributed to differential colonization and extinction rates among species and nested environmental tolerances. In this experiment, we tested for nestedness in assemblages of mycophagous fly larvae. Twenty mushrooms in each of three size classes (4.8–6.0 g, 10–15 g, 21–32 g) were placed on moist potting soil in experimental cups. The cups were placed in oak and pine forests in Greenville, S.C., USA for 5 days, where they were available to ovipositing flies. Upon collection, the mushrooms were incubated in the laboratory for 3 weeks and all emerging flies were sorted by species, counted, and weighed. A random placement analysis was conducted to determine whether the species richness pattern was a sampling artifact of the species abundance distributions. The actual species richness pattern did not conform to the random placement model; most mushrooms contained significantly fewer species than predicted by random sampling. The communities were strongly nested as measured by two different indices, and the nestedness pattern was related to mushroom size. Small mushrooms usually produced no flies or a single species, Dohrniphora sp. (Phoridae). Medium and large mushrooms typically produced more species-rich communities that usually contained the phorid and Drosophila putrida, D. tripunctata, and Leucophenga varia. This core guild was nested within a more diverse assemblage that included D. falleni, Mycodrosophila dimidiata, a muscid, and two Leptocera sp. (sphaeroceridae). These patterns are tentatively explained in the context of nested desiccation tolerances, mediated by differences in mushroom size.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 40
    Digitale Medien
    Digitale Medien
    Springer
    Oecologia 108 (1996), S. 262-272 
    ISSN: 1432-1939
    Schlagwort(e): Drosophila ; Temperature performance ; Life history ; Thermal environment
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The variability of morphological and lifehistory traits in Drosophila melanogaster and D. subobscura, two sympatric Drosophila species of different climatic origin, were investigated with regard to seasonal and daily temperature and humidity fluctuations to assess thermal sensitivity and the responses of freeliving organisms to oscillating temperatures. Temperature and humidity were measured continuously at the site where Drosophila were observed throughout the day, and thus represent a realistic picture of the temperature environment of these animals. A phenotypic model (gaussian curve) of temperature performance was fitted to daily fecundities and provided estimates of the position of temperature optimum and of the maximum and the breadth of performance for both species. D. melanogaster had a higher optimum temperature than D. subobscura. A trade-off between the maximum and the breadth of performance was detected both within and between the species.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 41
    Digitale Medien
    Digitale Medien
    Springer
    Oecologia 108 (1996), S. 552-561 
    ISSN: 1432-1939
    Schlagwort(e): Drosophila ; Colonization ; Ecology ; Succession ; Guild
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The guild of “cosmopolitan” Drosophila coexist almost worldwide and yet the mechanisms that underlie this coexistence are unknown. The larval resource of the guild is decaying fruit and vegetables, but the species show little specialization and can coexist on a single resource, such as oranges. In southern California the guild includes D. simulans (SIM), D. melanogaster (MEL), D. pseudoobscura (OBS), D. immigrans (IMM), D. hydei (HYD) and D. busckii (BUS). These species show consistent differences in their colonization of decaying organges, differences that may promote their coexistence. This study tested whether the colonization pattern of a species is determined primarily by attraction to specific resource types (decayed or fresh organges), by ability to colonize new resource patches, or by dependence on a successional sequence of Drosophila species. The experiments compared oranges that were pre-aged prior to a colonization period and showed that the colonization pattern of each species (except OBS) was driven primarily by its decay-dependent attraction to oranges. While OBS exhibited a pattern of colonization independent of pre-aging, the remaining species all showed some preference for older (7-day pre-aged) over fresh oranges. Their overall pattern of attraction, ordered by high relative abundance on fresher organges, was SIM〉MEL=IMM〉HYD=BUS. BUS, a specialist on decaying plant material, was the only species that showed a preference for 11-day over 7-day oranges. Pre-aging the oranges under covers, to prevent prior colonization by Drosophila, did not change the interspecific pattern of colonization, indicating that microbial decay was driving the changes in attraction. The patterns of attraction separated two ecologically similar pairs (SIM from MEL; IMM from HYD) and published data on ethanol tolerance show that, in each pair, the earliest colonizer has the lower tolerance. This suggests an important interplay between colonization patterns and physiological optima.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 42
    ISSN: 1432-1432
    Schlagwort(e): Histone H2A ; Histone variant ; Intron position ; Drosophila ; Tetrahymena
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Genomic clones ofDrosophila andTetrahymena histone H2A variants were isolated using the corresponding cDNA clones, (van Daal et al. 1988; White et al. 1988). The site corresponding to the initiation of transcription was defined by primer extension for bothDrosophila andTetrahymena genomic sequences. The sequences of the genomic clones revealed the presence of introns in each of the genes. TheDrosophila gene has three introns: one immediately following the initiation codon, one between amino acids 26 and 27 (gln and phe), and one between amino acids 64 and 65 (glu and val). TheTetrahymena gene has two introns, the positions of which are identical to the first two introns of theDrosophila gene. The chicken H2A.F variant gene has been recently sequenced and it contains four introns (Dalton et al. 1989). The first three of these are in the same positions as the introns in theDrosophila gene. The fourth intron interrupts amino acid 108 (gly). In all cases the sizes and the sequences of the introns are divergent. However, the fact that they are in conserved positions suggests that at least two of the introns were present in the ancestral gene. A phylogenetic tree constructed from the sequences of the variant and major cell cycle-regulated histone H2A proteins from several species indicates that the H2A variant proteins are evolutionarily separate and distinct from the major cell cycle-regulated histone H2A proteins. The ancestral H2A gene must have duplicated and diverged before fungi and ciliates diverged from the rest of the eukaryote lineage. In addition, it appears that the variant histone H2A proteins analyzed here are more conserved than the major histone H2A proteins.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 43
    Digitale Medien
    Digitale Medien
    Springer
    Journal of molecular evolution 28 (1988), S. 145-150 
    ISSN: 1432-1432
    Schlagwort(e): Alcohol dehydrogenase ; Drosophila ; Enzyme kinetics ; Product inhibition ; Microevolution
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Because natural populations ofDrosophila melanogaster are polymorphic for different allozymes of alcohol dehydrogenase (ADH) and becauseD. melanogaster is more tolerant to the toxic effects of ethanol than its sibling speciesD. simulans, information regarding the sensitivities of the different forms of ADH to the products of ethanol degradation are of ecological importance. ADH-F, ADH-S, ADH-71k ofD. melanogaster and the ADH ofD. simulans were inhibited by NADH, but the inhibition was relieved by NAD+. The order of sensitivity of NADH was ADH-F〈ADH-71k, ADH-S〈ADH-simulans with ADH-F being about four times less sensitive than theD. melanogaster enzymes and 12 times less sensitive than theD. simulans enzyme. Acetaldehyde inhibited the ethanolto-acetaldehyde activity of the ADHs, but at low acetaldehyde concentrations ethanol and NAD+ reduced the inhibition. ADH-71k and ADH-F were more subject to the inhibitory action of acetaldehyde than ADH-S and ADH-simulans, with ADH-71k being seven times more sensitive than ADH-S. The pattern of product inhibition of ADH-71k suggests a rapid equilibrium random mechanism for ethanol oxidation. Thus, although the ADH variants only differ by a few amino acids, these differences exert a far larger impact on their intrinsic properties than previously thought. How differences in product inhibition may be of significance in the evolution of the ADHs is discussed.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 44
    Digitale Medien
    Digitale Medien
    Springer
    Journal of molecular evolution 28 (1989), S. 220-224 
    ISSN: 1432-1432
    Schlagwort(e): Drosophila ; Foldback element ; Transposable element
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Foldback elements are a family of transposable elements described inDrosophila melanogaster. The members of this dispersed repetitive family have terminal inverted repeats that sometimes flank a central region. The inverted repeats of all the family members are homologous. The study of the distribution and conservation of the foldback elements in differentDrosophila species shows that this distribution is different from that of the hybrid dysgenesis systems (PM and IR). Sequences homologous to foldback elements were observed by Southern blots and in situ hybridization in all species of themelanogaster subgroup and in some species of themontium andtakahashii subgroups. The element was probably already present before the radiation of these subgroups. No evidence of horizontal transmission of the foldback element could be observed.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 45
    Digitale Medien
    Digitale Medien
    Springer
    Journal of molecular evolution 18 (1982), S. 310-314 
    ISSN: 1432-1432
    Schlagwort(e): Neutral mutation theory ; Natural selection ; Protein evolution ; Levene model ; Environmental variability ; Genetic variability ; Drosophila
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary If a phenotypic character is under stabilizing selection, the selective disadvantage of a nonoptimal genotype will decrease exponentially to zero as the proportion of phenotypic variation that is environmental in origin -V e /V p - increases. Under the modified mutation-drift hypothesis of genetic polymorphism, the proportion of mutations that are effectively neutral and average heterozygosity should increase with this ratio. Invertebrates, because of their small size, fast development, and low degree of homeostasis (relative to vertebrates), are expected to show a larger environmental component of phenotypic variation than vertebrates. This may help explain why invertebrates are in general more genetically variable than vertebrates and why, when laboratory populations ofDrosophila are maintained in heterogeneous environments, genetic variability is lost less rapidly than when they are kept in constant conditions.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 46
    Digitale Medien
    Digitale Medien
    Springer
    Journal of molecular evolution 22 (1985), S. 252-271 
    ISSN: 1432-1432
    Schlagwort(e): Drosophila ; Mitochondrial DNA ; Mitochondrial genes ; Nucleotide sequence ; Gene arrangement ; Genetic code ; Codon-anticodon interaction ; Ribosomal RNA genes ; Transfer RNA genes
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The sequence of the 16,019 nucleotide-pair mitochondrial DNA (mtDNA) molecule ofDrosophila yakuba is presented. This molecule contains the genes for two rRNAs, 22 tRNAs, six identified proteins [cytochrome b, cytochrome c oxidase subunits I, II, and III (COI-III), and ATPase subunits 6 and 8] and seven presumptive proteins (URF1-6 and URF4L). Replication originates within a region of 1077 nucleotides that is 92.8% A+T and lacks any open reading frame larger than 123 nucleotides. An equivalent to the sequence found in all mammalian mtDNAs that is associated with initiation of second-strand DNA synthesis is not present inD. yakuba mtDNA. Introns are absent fromD. yakuba mitochondrial genes and there are few (0–31) intergenic nucleotides. The genes found inD. yakuba and mammalian mtDNAs are the same, but there are differences in their arrangement and in the relative proportions of the complementary strands of the molecule that serve as templates for transcription. Although theD. yakuba small and large mitochondrial rRNA genes are exceptionally low in G and C and are shorter than any other metazoan rRNA genes reported, they can be folded into secondary structures remarkably similar to the secondary structures proposed for mammalian mitochondrial rRNAs.D. yakuba mitochondrial tRNA genes, like their mammalian counterparts, are more variable in sequence than nonorganelle tRNAs. In mitochrondrial protein genes ATG, ATT, ATA, and in one case (COI) ATAA appear to be used as translation initiation codons. The only termination codon found in these genes is TAA. In theD. yakuba mitochondrial genetic code, AGA, ATA, and TGA specify serine, isoleucine, and tryptophan, respectively. Fifty-nine types of sense codon are used in theD. yakuba mitochondrial protein genes, but 93.8% of all codons end in A or T. Codon-anticodon interactions may include both G-A and C-A pairing in the wobble position. Evidence is summarized that supports the hypothesis that A and T nucleotides are favored at all locations in theD. yakuba mtDNA molecule where these nucleotides are compatible with function.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 47
    Digitale Medien
    Digitale Medien
    Springer
    Journal of molecular evolution 24 (1986), S. 83-88 
    ISSN: 1432-1432
    Schlagwort(e): Transposons ; Polymorphism ; Drosophila ; Southern technique
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The genomic distributions of the copia, 297, 412, mdg 1, and B 104 transposable elements have been compared by the Southern technique among two Oregon R and four Canton SDrosophila laboratory lines that have been maintained separately for defined periods of a few years. The heterogeneity of the autoradiographic patterns suggests that multiple transposition events have occurred during the time of separation. The hypothesis that transposition could be induced by, variations of environmental parameters is discussed.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 48
    ISSN: 1432-1432
    Schlagwort(e): Chloroplast 4.5S rRNA ; Cytosolic and chloroplast 5S rRNAs ; 5.8S rRNA ; 18S rRNA ; Nucleotide sequences ; Phylogenetic trees ; Angiosperms ; Gymnosperms ; Monocotyledons ; Dicotyledons
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Complete or partial nucleotide sequences of five different rRNA species, coded by nuclear (18S, 5.8S, and 5S) or chloroplast genomes (5S, 4.5S) from a number of seed plants were determined. Based on the sequence data, the phylogenetic dendrograms were built by two methods, maximum parsimony and compatibility. The topologies of the trees for different rRNA species are not fully congruent, but they share some common features. It may be concluded that both gymnosperms and angiosperms are monophyletic groups. The data obtained suggest that the divergence of all the main groups of extant gymnosperms occurred after the branching off of the angiosperm lineage. As the time of divergence of at least some of these gymnosperm taxa is traceable back to the early Carboniferous, it may be concluded that the genealogical splitting of gymnosperm and angiosperm lineages occurred before this event, at least 360 million years ago, i.e., much earlier than the first angiosperm fossils were dated. Ancestral forms of angiosperms ought to be searched for among Progymnospermopsida. Genealogical relationships among gymnosperm taxa cannot be deduced unambiguously on the basis of rRNA data. The only inference may be that the taxon Gnetopsida is an artificial one, andGnetum andEphedra belong to quite different lineages of gymnosperms. As to the phylogenetic position of the two Angiospermae classes, extant monocotyledons seem to be a paraphyletic group located near the root of the angiosperm branch; it emerged at the earliest stages of angiosperm evolution. We may conclude that either monocotyledonous characters arose independently more than once in different groups of ancient Magnoliales or that monocotyledonous forms rather than dicotyledonous Magnoliales were the earliest angiosperms. Judging by the rRNA trees, Magnoliales are the most ancient group among dicotyledons. The most ancient lineage among monocotyledons leads to modern Liliaceae.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 49
    Digitale Medien
    Digitale Medien
    Springer
    Journal of molecular evolution 16 (1980), S. 37-46 
    ISSN: 1432-1432
    Schlagwort(e): Evolution ; Drosophila ; Temperature ; Mitochondrial enzymes ; Kinetic properties
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The evolutionary behavior of two mitochondrial enzymes (L-glycerol 3-phosphate:cytochrome c oxidoreductase E.C.1.1.1.95,αGPO, and L-malate: NAD+ oxidoreductase, E.C.1.1.1.37, m-MDH) obtained from several temperate and tropicalDrosophila species was examined by comparing their catalytic properties, which related to temperature (Km-Ea-Q10-Thermostability). MitochondrialαGPO or m-MDH obtained either from temperate or from tropical species was found to exhibit similar catalytic properties while for both cytosolic enzymes, theαGPDH and s-MDH, Km patterns were similar among species from the same thermal habitat and different between thermal habitats. In combination with other observations reported in the literature these facts support the view that the function, and probably the structure, of mitochondrial enzymes are better conserved in evolution than those of the corresponding enzymes found in the cytosol. It is proposed that the relative invariance of the mitochondrial enzymes structure is probably linked to a necessary relative invariance of molecular interactions inside the mitochondrion.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 50
    Digitale Medien
    Digitale Medien
    Springer
    Journal of molecular evolution 20 (1984), S. 251-264 
    ISSN: 1432-1432
    Schlagwort(e): Drosophila ; Genome evolution ; 68C Glue gene cluster ; Drosophila melanogaster species subgroup
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The 68C puff is a highly transcribed region of theDrosophila melanogaster salivary gland polytene chromosomes. Three different classes of messenger RNA originate in a 5000-bp region in the puff; each class is translated to one of the salivary gland glue proteins sgs-3, sgs-7, or sgs-8. These messenger RNA classes are coordinately controlled, with each RNA appearing in the third larval instar and disappearing at the time of puparium formation. Their disappearance is initiated by the action of the steroid hormone ecdysterone. In the work reported here, we studied evolution of this hormone-regulated gene cluster in themelanogaster species subgroup ofDrosophila. Genome blot hybridization experiments showed that five other species of this subgroup have DNA sequences that hybridize toD. melanogaster 68C sequences, and that these sequences are divided into a highly conserved region, which does not contain the glue genes, and an extraordinarily diverged region, which does. Molecular cloning of this DNA fromD. simulans, D. erecta, D. yakuba, andD. teissieri confirmed the division of the region into a slowly and a rapidly evolving protion, and also showed that the rapidly evolving region of each species codes for third instar larval salivary gland RNAs homologous to theD. melanogaster glue mRNAs. The highly conserved region is at least 13,000 bp long, and is not known to code for any RNAs.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 51
    ISSN: 1432-1432
    Schlagwort(e): Drosophila ; per gene ; Repeated sequence ; Threonine-glycine ; Length polymorphism ; Minisatellite
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Single-fly polymerase chain reaction amplification and direct DNA sequencing revealed high levels of length polymorphism in the threonine-glycine encoding repeat region of theperiod (per) gene in natural populations ofDrosophila melanogaster. DNA comparison of two alleles of identical lengths gave a high number of synonymous substitutions suggesting an ancient time of separation. However detailed examination of the sequences of different Thr-Gly length variants indicated that this divergence could be understood in terms of four deletion/insertion events. InDrosophila pseudoobscura a length polymorphism is observed in a five-amino acid degenerate repeat, which corresponds tomelanogaster's Thr-Gly domain. In spite of the differences betweenD. melanogaster andD. pseudoobscura in the amino acid sequence of the repeats, the predicted secondary structures suggest evolutionary and mechanistic constraints on theper protein of these two species.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 52
    Digitale Medien
    Digitale Medien
    Springer
    Journal of molecular evolution 33 (1991), S. 156-162 
    ISSN: 1432-1432
    Schlagwort(e): Drosophila ; Mitochondrial DNA ; Nucleotide sequence ; Nonsynonymous substitutions ; Phylogeny ; A+T content
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The nucleotide sequence of a segment of the mitochondrial DNA from threeDrosophila species (D. erecta, D. eugracilis, andD. takahashii), belonging to different subgroups of themelanogaster group has been determined. The segment encompasses three complete tRNA genes (tRNAtrp, tRNAcys, and tRNAtyr) and portions of two protein-coding genes: the subunit 2 of the NADH dehydrogenase (ND2) and the subunit 1 of the cytochrome oxidase (COI). Comparisons also involve homologous sequences already known for four otherDrosophila species of themelanogaster group. Length differences were confined in the intergenic region where a long stretch of AT repeats was observed in one of the species analyzed. The three tRNA genes exhibit very different evolutionary rates, the most slowly evolving one, tRNAtyr, is adjacent to the 5′ end of COI; tRNAs in similar positions have been previously shown to evolve slowly because they are probably involved in transcript processing. Although the rate of synonymous substitutions was very similar between ND2 and COI genes there were strong discrepancies between them in terms of the number of nonsynonymous substitutions. Differences have also been found in G+C content of the genes, which are likely to be linked to different selective pressures. There is a reduction in G+C content in the region where selective constraints are reduced. This suggests the existence of different levels of constraints along the sequenced segment. An overall analysis of the types of substitutions showed a decrease in A+T content during the course of evolution of the species.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 53
    Digitale Medien
    Digitale Medien
    Springer
    Journal of molecular evolution 30 (1990), S. 273-280 
    ISSN: 1432-1432
    Schlagwort(e): Genome evolution ; Molecular evolutionary rates ; Insect DNA ; Drosophila
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary DNA-DNA hybridization studies of insects, more specificallyDrosophila and cave crickets, have revealed interesting patterns of genome evolution that contrast markedly with what has been seen in other taxa, especially mammals and birds. Insect genomes are composed of sections of single-copy DNA with extreme variation in rates of evolutionary change. This variation is more extreme than between introns and exons; introns fall into the relatively conserved fraction of the genome. Attempts to calculate absolute rates of change inDrosophila DNA have all led to estimates some 5–10 times faster than those found in most vertebrates; this is true even for the more conservative part of the nuclear genome. Finally we point out that morphological similarity, chromosomal similarity, and/or ability to form interspecific hybrids is often associated with quite high levels of single-copy DNA divergence in insects as compared to mammals and birds.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 54
    ISSN: 1432-1939
    Schlagwort(e): Competition ; Environment ; Fitness ; Genetic variation ; Drosophila
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The outcome of interspecific competition of two closely related species may depend upon genetic variation in the two species and the environment in which the experiment is carried out. Interspecific competition in the two sibling species, Drosophila melanogaster and D. simulans, is usually investigated using longterm laboratory stocks that often have mutant markers that distinguish them. To examine competition in flies that genetically more closely resemble flies in nature, we utilized freshly caught wildtype isofemale lines of the two species collected at the same site in San Carlos, Mexico. Under ordinary laboratory conditions, D. melanogaster always won in competition. However, in hotter and drier conditions, D. simulans competed much more effectively. In these environmental conditions, there were genetic differences in competitive ability among lines with the outcome of competition primarily dependent upon the line of D. melanogaster used but in some cases also influenced by the line of D. simulans used. Differences in the measures of productivity and developmental time did not explain the differences in competitive ability among lines. This suggests that the outcome of competition was not due to differences in major fitness components among the isofemale lines but to some other attribute(s) that influenced competitive ability. When lines of flies were combined, the outcome of competition was generally consistent with competitive outcomes between pairs of lines. In several cases, the combination of lines performed better than the best of the constituent lines, suggesting that competitive ability was combined heterotically and that the total amount of genetic variation was important in the outcome of interspecific competition.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 55
    Digitale Medien
    Digitale Medien
    Springer
    Oecologia 111 (1997), S. 529-534 
    ISSN: 1432-1939
    Schlagwort(e): Key words Competition ; Multi-species ; Dynamics ; Drosophila ; Triangular co-ordinates
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract We report a series of experiments with three competing species and a novel graphical analysis that explores the dynamics of this simple multi-species system. The three competing species (Drosophila hydei, D. immigrans and D. virilis) were maintained in five very large cages, on a natural fruit resource. The analytic method involved constructing a “dynamic surface”, by interpolation, from the population trajectories. Within the dynamic surface constructed from the five experiments a small “equilibrium area” (an area of point vectors) could be identified. The implications of both the method and the results are discussed.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 56
    Digitale Medien
    Digitale Medien
    Springer
    Oecologia 75 (1988), S. 516-520 
    ISSN: 1432-1939
    Schlagwort(e): Drosophila ; Picornavirus ; Fertility ; Embryonic and larvo-pupal death rate
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Drosophila C virus (DCV) has a considerable impact on ovarian morphogenesis inDrosophila melanogaster host populations. This virus also affects the developmental time and the fresh weight of infected females. In order to investigate the hypothesis that DCV may play a role in the dynamics ofDrosophila populations, the fertility and embryonic and larvo-pupal death rates of a host population and that of five DCV-free populations were determined. A comparison of two populations, one of them DCV-free, the other infected, suggested that the fertility of the DCV-infected flies was higher than that of uninfected flies, despite a greater larvo-pupal death rate. Fertility of the infected flies was greater among the infected population than for the DCV-free populations. The DCV-free populations originated from five different localities. The virus clearly does have an impact on the biotic potential of its host population. This paper reports for the first time a positive interaction between a viral population and a host population as it increases certain parameters of host population dynamics.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 57
    ISSN: 1432-1939
    Schlagwort(e): Yeast ; Drosophila ; Host plants ; Communities ; Vectors
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The yeast communities from slime fluxes of three deciduous trees (Prosopis juliflora, Populus fremontii and Quercus emoryi) and the necroses of two cacti (Opuntia phaeacantha and Carnegiea gigantea) were surveyed in the region of Tucson, Arizona. In addition, the yeasts carried by dipterans associated with the fluxes or necroses (Drosophila carbonaria, D. brooksae, D. nigrospiracula, D. mettleri, and Aulacigaster leucopeza) were sampled. The results indicate that each host sampled had a distinct community of yeasts associated with it. The dipterans, which can act as vectors of the yeasts, deposited yeasts from other sources in addition to those found on their associated hosts. It is argued that host plant physiology is relatively more important than the activity of the vector in determining yeast community composition. Furthermore, the average number of yeast species per flux or necrosis is not different from the average number of yeast species per fly. It is hypothesized that the vector may affect the number of species per individual flux or not, and that the number is lower than the rot or necrosis could potentially support.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 58
    ISSN: 1432-1939
    Schlagwort(e): Hymenoptera ; Eucoilidae ; Leptopilina heterotoma ; Infochemicals ; Kairomone ; Drosophila
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Parasitoids that forage for herbivorous hosts by using infochemicals may have a problem concerning the reliability and detectability of these stimuli: host stimuli are highly reliable but not very detectable at a distance, while stimuli from the host's food are very detectable but generally not very reliable in indicating host presence. One solution to this problem is to learn to link highly detectable stimuli to reliable but not very detectable stimuli. Ample knowledge is available on how associative learning aids foraging parasitoids in the location of suitable microhabitats. However, in this paper we report on another solution to the reliability-detectability problem and present evidence for an essential, but as yet overlooked, aspect of Drosophila parasitoid ecology. For the first time it is shown that a parasitoid of Drosophila larvae spies on the communication system of adult Drosophila flies to locate potential host sites: naive parasitoids strongly respond to a volatile aggregation pheromone that is deposited in the oviposition site by recently mated female flies. Thus, the parasitoids resort to using highly detectable information from a host stage different from the one under attack (i.e. infochemical detour). The function and ecological implications of these findings are discussed.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 59
    ISSN: 1432-1939
    Schlagwort(e): Drosophila ; Polymorphism ; Stenocereus ; Host-plant-shift ; Developmental homeostasis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Chromosomally polymorphic populations of Drosophila mojavensis from Baja California feed and breed on agria cactus, Stenocereus gummosus; whereas, monomorphic Arizona populations are associated exclusively with organ pipe cactus, S. thurberi. The effects of this host plant shift in expanding the kinds of feeding and breeding sites were assessed by manipulating larval density and recording differences in egg to adult development time and viability, and adult thorax size in both populations on artificially rotted substrates of both cactus species. Older agria rots increased development time but had no effect on viability. Organ pipe rots were qualitatively poorer substrates than agria rots for both monomorphic and polymorphic populations of D. mojavensis, especially at higher larval densities causing longer egg to adult development times, lower viabilities, and smaller thorax sizes than agria. The Baja population expressed shorter development times, higher viabilities, and smaller thorax sizes than the Arizona population on both cactus substrates. No evidence for cactus host race formation was found. The Baja population was less sensitive to increasing larval densities for all fitness characters studied on both cactus substrates indicating greater developmental homeostasis than in the monomorphic Arizona population. These data support the hypothesized central-marginal population structure within this species coincident with the distribution of host plants and lend insight into the process of adaptive divergence at different life history stages caused by host plant shifts.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 60
    Digitale Medien
    Digitale Medien
    Springer
    Oecologia 75 (1988), S. 400-404 
    ISSN: 1432-1939
    Schlagwort(e): Vectoring ; Drosophila ; Cactophilic yeasts ; Dispersal ; Community structure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary At two locations in the Sonoran Desert, yeasts were sampled from species of Drosophila, the flies' cactus hosts, and other neighboring sources of cactophilic yeasts to determine the relation between the yeasts vectored by the fly and the yeasts found in their breeding sites. D. mojavensis, D. nigrospiracula, and D. mettleri vectored yeast assemblages significantly more similar to the yeast species found on the rot from which the flies were collected than to the yeasts found on other rots from the flies host cactus or other rotting cactus at the same site. Rots with Drosophila had fewer yeast species than those without flies, suggesting that flies were associated with younger rots. Rots with flies and the Drosophila also had more yeast species with the capability to produce ethyl acetate than rots without flies. The results support the contention that cactophilic Drosophila feed on a subset of the yeasts available in an area, and may act to maintain differences among the yeast communities found on different species of cactus.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 61
    ISSN: 1432-1939
    Schlagwort(e): Parasitoid ; Host suitability ; Phylogeny ; Leptopilina ; Drosophila
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Decaying petioles of giant hogweed,Heracleum mantegazzianum Sommier & Levier, are used as a breeding site by six species ofDrosophila and the drosophilidScaptomyza pallida. The most numerous parasitoid species associated with this community isLeptopilina australis. BecauseL. australis was previously unknown in western Europe, we present the characters to distinguish it form its close relativeL. clavipes. Experiments on host species selection and survival ofL. australis showed that this parasitoid mainly usesD. limbata as host. Olfactometer experiments showed thatL. australis is attracted by the odour of decaying hogweed stalks, especially when these contain larvae ofD. limbata. L. australis is also strongly attracted by the odour of stinkhorns, a habitat in which it has never been found in nature.D. phalerata is the dominant fly species in stinkhorns, and is not a host ofL. australis. We offer a possible functional explanation for this unexpected habitat choice, by showing thatD. transversa andD. kuntzei, both species found to breed in fungi, are also suitable hosts forL. australis. We also discuss habitat choice with regard to a proposed phylogeny of theLeptopilina species in temperate Europe. Finally, we discuss niche overlap ofL. australis with the otherLeptopilina species.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 62
    ISSN: 1432-1939
    Schlagwort(e): Drosophila ; Microbial associations ; Resource partitioning
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The distributions of five Drosophila species and four components of the microflora have been compared across a total of 48 traps baited with four different fruit and vegetable substrates in two domestic compost heaps in Canberra (Australia). Large and consistent differences are found, both among the Drosophila and among the microbial classes, in their distributions across traps baited with different substrates. Moreover the distribution of each Drosophila species shows a unique set of strong associations with the microbial distributions. Thus the distributions of both D. simulans and D. melanogaster are found to be strongly negatively correlated with the abundance of bacteria while D. simulans is also strongly positively correlated with the titre of fermenter yeasts. D. immigrans is strongly positively correlated both with bacteria and with non-fermenter yeasts. D. hydei is positively correlated with nonfermentery yeasts and D. busckii is negatively correlated with fermenter yeasts. Moulds are the only microbial class not consistently associated with the distribution of any of the Drosophila species. The correlations with the other microbial classes are sufficient to explain the majority of the abundance differences of the Drosophila species among the trap types. It is therefore proposed that the clear partitioning of the fruit resources by the Drosophila is due to their differing primary interactions with the microflora.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 63
    Digitale Medien
    Digitale Medien
    Springer
    Oecologia 92 (1992), S. 183-187 
    ISSN: 1432-1939
    Schlagwort(e): Drosophila ; Resource exploitation ; Decaying-herbage breeding ; Host choice
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The Drosophila fauna of a deciduous flood plain forest rich in undergrowth near the river Isar, close to Munich, Germany, was surveyed in summer 1990. Decaying herbage baits (decay artificially induced) were set out to study the exploitation of that resource by Drosophila. Sixteen plant species belonging to several families dominant in the collecting area were tested. All attracted and produced drosophilid flies. Ten Drosophila species utilized decaying plant material as breeding sites; at least eight of the ten are polyphagous. Decaying stalks and leaves of Angelica sylvestris (Apiaceae) were examined in detail. In the case of the most frequent species of Drosophila attracted to A. sylvestris, the number of adults collected did not correlate with the number of flies emerging from the substrate. This was particularly true of D. limbata and D. phalerata. When oviposition and larval development of D. limbata and D. phalerata on A. sylvestris was tested in the laboratory, the number of offspring per female was the same in both species. The difference between these two species of the quinaria group in the exploitation of A. sylvestris in the field is therefore not due to differential suitability of the substrate.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 64
    Digitale Medien
    Digitale Medien
    Springer
    Journal of comparative physiology 172 (1993), S. 303-308 
    ISSN: 1432-1351
    Schlagwort(e): Drosophila ; Photoreception ; Magnetoreception ; Magnetic compass orientation ; Geomagnetic field
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract 1. Wildtype Oregon-R Drosophila melanogaster were trained in the ambient magnetic field to a horizontal gradient of 365 nm light emanating from one of the 4 cardinal compass directions and were subsequently tested in a visually-symmetrical, radial 8-arm maze in which the magnetic field alignment could be varied. When tested under 365 nm light, flies exhibited consistent magnetic compass orientation in the direction from which light had emanated in training. 2. When the data were analyzed by sex, males exhibited a strong and consistent magnetic compass response while females were randomly oriented with respect to the magnetic field. 3. When tested under 500 nm light of the same quantal flux, females were again randomly oriented with respect to the magnetic field, while males exhibited a 90° clockwise shift in magnetic compass orientation relative to the trained direction. 4. This wavelength-dependent shift in the direction of magnetic compass orientation suggests that Drosophila may utilize a light-dependent magnetic compass similar to that demonstrated previously in an amphibian. However, the data do not exclude the alternative hypothesis that a change in the wavelength of light has a non-specific effect on the flies' behavior, i.e., causing the flies to exhibit a different form of magnetic orientation behavior.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 65
    Digitale Medien
    Digitale Medien
    Springer
    Journal of comparative physiology 174 (1994), S. 267-280 
    ISSN: 1432-1351
    Schlagwort(e): Electric fish ; Pacemaker ; GABA ; Glutamate ; Ultrastructure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract The medullary pacemaker nucleus of Hypopomus triggers each electric organ discharge (EOD) by a single command pulse. It consists of electrotonically coupled ‘pacemaker’ cells, which generate the rhythm, and ‘relay’ cells, which follow the pacemaker cells and excite the spinal motoneurons of the electric organ. The pacemaker cells receive two inputs from the complex of the diencephalic prepacemaker nucleus (PPn), a GABA-ergic inhibition and a glutamatergic excitation. Relay cells, on the other hand, receive two glutamatergic inputs, one from a subnucleus of the PPn, the PPn-C, and a second from the sublemniscal prepacemaker nucleus (SPPn). We have labelled afferents to the pacemaker nucleus by injecting HRP to specific sites of the prepacemaker complex. By using immunogold-labelled antibodies and en-grid staining techniques, we demonstrated GABA and glutamate immunoreactivity in labelled synaptic profiles of ultra-thin sections of the pacemaker nucleus. The two types of synapses were interspersed on the surfaces of pacemaker cells, with GABA-immunoreactive synapses apparently representing the GABA-mediated input of the ‘PPn-I’, an inhibitory subdivision of the PPn, and glutamate-immunoreactive synapses representing the input of the ‘PPn-G’, an excitatory subdivision of the PPn. Only glutamate-immunoreactive synapses were found on relay cells.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 66
    Digitale Medien
    Digitale Medien
    Springer
    Journal of comparative physiology 175 (1994), S. 267-278 
    ISSN: 1432-1351
    Schlagwort(e): Drosophila ; Bang sensitivity ; Mechanotransduction ; Adaptation ; Sensory coding
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract Bang-sensitive mutants of Drosophila melano gaster (bas 1, bssMW1, eas2, tko25t) display seizure followed by paralysis when subjected to mechanical shock. However, no physiological or biochemical defect has been found to be common to all of these mutants. In order to observe the effects of bang-sensitive mutations upon an identified neuron, and to study the nature of mechanically induced paralysis, we examined the response of a mechanosensory neuron in these mutants. In each single mutant and the double mutant bas 1 bssMW1, the frequency of action potentials in response to a bristle displacement was reduced. This is the first demonstration of a physiological defect common to several of the bang-sensitive mutations. Adaptation of spike frequency, cumulative adaptation to repeated stimulation (fatigue) and the time course of recovery from adaptation were also examined. Recovery from adaptation to a conditioning stimulus was examined in two mutants (bas 1 and bss MW1), and initial recovery from adaptation was greater in both mutants. Quantification of receptor potentials was complicated by variability inherent in extracellular recording conditions, but examination of the waveform and range of amplitudes did not indicate clear mutant defects. Therefore the differences observed in the spike response may be due to an alteration of the transfer from receptor potentials to action potential production. DNA sequence analysis of tko and eas has indicated that they encode apparently unrelated biochemical products. Our results suggest that these biochemical lesions lead to a common physiological defect in mechanoreceptors. Although this defect does not provide a straightforward explanation for bang sensitivity, the altered cellular process may lead to bang sensitivity through its action in different parts of the nervous system.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 67
    Digitale Medien
    Digitale Medien
    Springer
    Journal of comparative physiology 175 (1994), S. 687-693 
    ISSN: 1432-1351
    Schlagwort(e): rdgB ; Maxillary palp ; Drosophila ; Electrophysiology ; Olfaction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract We describe the kinetics of odorant response in the maxillary palp of Drosophila, and show that the rate of recovery from odorant stimulation is affected by mutation of the rdgB (retinal degeneration B) gene. We use immunocytochemistry to confirm that the rdgB gene product is expressed in the maxillary palp. rdgB has recently been shown to encode a protein with Ca2+-binding sites and sequence similarity to rat brain phosphatidylinositol transfer protein; it is located near the rhabdomeric membranes in photoreceptor cells, where it has been suggested to play a role in membrane transport. The delay in recovery kinetics that we observe in olfactory tissue may reflect a defect in membrane restoration at the conclusion of the olfactory transduction cascade. The use of common molecules in the physiology of two olfactory organs, and in both visual and olfactory physiology, is discussed.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 68
    Digitale Medien
    Digitale Medien
    Springer
    Journal of comparative physiology 178 (1996), S. 513-522 
    ISSN: 1432-1351
    Schlagwort(e): Potassium channel ; Photoreceptor ; Calliphora ; Drosophila ; Shaker
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract Single electrode current and voltage clamp recordings in Calliphora, and whole-cell voltage clamp recordings in Drosophila were used to characterise the voltage-gated K channels in both major classes of photoreceptors, R7/8 (long visual fibres, LVFs) and R1-6 (short visual fibres, SVFs). R7/8 were identified by their unique spectral properties, ca. 3–4 fold higher input resistances and 3–4 fold lower cell capacitance. In Calliphora SVFs possess both fast and slow activating delayed rectifier potassium conductances. Drosophila SVFs possess a slowly inactivating delayed rectifier (IKs), a very rapidly inactivating A channel encoded by the Shaker gene (IA), and, in a minority of cells, a third K conductance with intermediate kinetics (IKf). In both specs the LVFs lack the slowest component, but exhibit the faster K conductance(s) with properties indistinguishable from those in the SVFs. These findings add to established evidence demonstrating the significant role played by potassium channels in tuning the photoreceptor membrane. The results also suggest that R1-6 photoreceptors and R7/8 form inputs to visual subsystems tuned to different temporal frequencies.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 69
    Digitale Medien
    Digitale Medien
    Springer
    Journal of comparative physiology 175 (1994), S. 179-191 
    ISSN: 1432-1351
    Schlagwort(e): Drosophila ; Neuromuscular ; Haemolymph ; Membrane potential ; Synaptic potential
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract Neuromuscular preparations from third instar larvae of Drosophila are not well-maintained in commonly used physiological solutions: vacuoles form in the muscle fibers, and membrane potential declines. These problems may result from the Na∶K ratio and total divalent cation content of these physiological solutions being quite different from those of haemolymph. Accordingly haemolymph-like solutions, based upon ion measurements of major cations, were developed and tested. Haemolymph-like solutions maintained the membrane potential at a relatively constant level, and prolonged the physiological life of the preparations. Synaptic transmission was well-maintained in haemolymph-like solutions, but the excitatory synaptic potentials had a slower time course and summated more effectively with repetitive stimulation, than in standard Drosophila solutions. Voltage-clamp experiments suggest that these effects are linked to more pronounced activation of muscle fiber membrane conductances in standard solutions, rather than to differences in passive muscle membrane properties or changes in postsynaptic receptor channel kinetics. Calcium dependence of transmitter release was steep in both standard and haemolymph-like solutions, but higher external calcium concentrations were required for a given level of release in haemolymph-like solutions. Thus, haemolymph-like solutions allow for prolonged, stable recording of synaptic transmission.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 70
    Digitale Medien
    Digitale Medien
    Springer
    Journal of comparative physiology 175 (1994), S. 587-596 
    ISSN: 1432-1351
    Schlagwort(e): Wing beat frequency ; Optomotor responses ; Landing response ; Drosophila
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract The present study shows that the wing beat frequency of Drosophila is visually controlled and modulated in response to different optomotor stimuli. Whereas rotational large field stimuli do not appear to modulate wing beat frequency, single rotating vertical stripes increase or decrease wing beat frequency when moving back-to-front or front-to-back, respectively. Maximal modulations occur at lateral stripe positions. Expansion stimuli eliciting the landing response cause a marked increase in wing beat frequency. Parameters of this frequency response depend in a graded fashion on certain stimulus properties, and the frequency response co-habituates with the landing response. Several results indicate that the frequency response is an integral component of the landing response, although it can also occur when the characteristic front leg extension is not observed. The complex spatial input integration underlying the frequency response and other motor components of the landing response cannot easily be explained by a system of large field integration units, but might indicate the existence of local expansion detectors.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 71
    Digitale Medien
    Digitale Medien
    Springer
    Journal of comparative physiology 175 (1994), S. 761-766 
    ISSN: 1432-1351
    Schlagwort(e): Olfactory behavior ; Antenna ; Maxillary palp ; Olfaction ; Drosophila
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract Maxillary palps have been proposed as secondary olfactory organs, after the antennae, in Drosophila melanogaster. Our study tries to establish the quantitative importance of both organs as olfactory information mediators. Dose-response curves for three odorants: ethyl acetate, propionaldehyde and benzaldehyde were carried out for comparing olfaction in either complete animals or flies surgically deprived of antennae. Antennaless flies tested in our behavioral assay showed indifferent, attractant and repellent responses depending on concentration, similarly as normal flies do. However, they clearly displayed less sensitivity than normal flies. The range of concentrations they were able to perceive was correlated to antennal sensitivity approximately by a factor 1∶10 for ethyl acetate and benzaldehyde, and between 1∶10 and 1∶100 at high concentrations of propionaldehyde. A complementary experiment was performed to test changes in olfactory behavior produced by removing maxillary palps in the presence of antennae. At high concentrations of odorant, responses to ethyl acetate and propionaldehyde experienced small changes when both palps were removed. Results are compatible with a summation model of all olfactory information reaching the brain either through antennae or palps.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 72
    Digitale Medien
    Digitale Medien
    Springer
    Journal of comparative physiology 176 (1995), S. 355-364 
    ISSN: 1432-1351
    Schlagwort(e): Drosophila ; Giant fiber ; Escape Olfactory ; Flight
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract We have monitored the patterns of activation of five muscles during flight initiation of Drosophila melanogaster: the tergotrochanteral muscle (a mesothoracic leg extensor), dorsal longitudinal muscles #3, #4 and #6 (wing depressors), and dorsal ventral muscle #Ic (a wing elevator). Stimulation of a pair of large descending interneurons, the giant fibers, activates these muscles in a stereotypic pattern and is thought to evoke escape flight initiation. To investigate the role of the giant fibers in coordinating flight initiation, we have compared the patterns of muscle activation evoked by giant fiber stimulation with those during flight initiations executed voluntarily and evoked by visual and olfactory stimuli. Visually elicited flight initiations exhibit patterns of muscle activation indistinguishable from those evoked by giant fiber stimulation. Olfactory-induced flight initiations exhibit patterns of muscle activation similar to those during voluntary flight initiations. Yet only some benzaldehyde-induced and voluntary flight initiations exhibit patterns of muscle activation similar to those evoked by giant fiber stimulation. These results indicate that visually elicited flight initiations are coordinated by the giant fiber circuit. By contrast, the giant fiber circuit alone cannot account for the patterns of muscle activation observed during the majority of olfactory-induced and voluntary flight initiations.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 73
    Digitale Medien
    Digitale Medien
    Springer
    Journal of comparative physiology 176 (1995), S. 611-623 
    ISSN: 1432-1351
    Schlagwort(e): Ligand-gated channel ; Chloride channel ; Histamine ; Drosophila ; Visual ecology
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract The large monopolar cells (LMCs) of the first optic neuropil (lamina) in insects respond to the photoreceptor neurotransmitter histamine with an increase in chloride conductance. We have compared the properties of this conductance from a range of diptera from different visual environments:Tipula paludosa (slow flying, crepuscular),Drosophila melanogaster (slow-flying diurnal), and 3 fast-flying diurnal speciesMusca domestica,Calliphora vicina andLucilia sericata. In whole-cell recordings of dissociated LMCs, histamine-induced currents were elicited using a multichannel parallel perfusion device, allowing rapid determination of the dose-response function, characterised by affinity (K d) and Hill coefficient (n).Calliphora,Lucilia andMusca had the steepest dose response curves (n = 2.8) and the lowest affinity for histamine (K d 35–50 μM); the crepuscularTipula had a significantly higher affinity (K d = 16 μM) and lower Hill coefficient (n = 1.8).Drosophila had a high affinity (K d 24 μM), and a high Hill coefficient (n = 2.5). In excised inside-out patch recordings all species showed similar single channel properties (conductance 40–60 pS, mean open time 〈 1 ms). The low Hill coefficient inTipula would be expected to result in lower synaptic gain. We suggest this may be an adaptation to prevent the LMC's response bandwidth being filled with the high levels of photon noise typical of photoreceptors adapted for low light levels. The lower affinity for histamine found in the more photopic species suggests that the concentration of histamine (and therefore presumably number of synaptic vesicles released from the photoreceptors) should be higher. This might improve signal-to-noise ratio by decreasing the contribution of the shot event noise introduced by stochastic release of synaptic vesicles.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 74
    Digitale Medien
    Digitale Medien
    Springer
    Journal of comparative physiology 176 (1995), S. 611-623 
    ISSN: 1432-1351
    Schlagwort(e): Ligand-gated channel ; Chloride channel ; Histamine ; Drosophila ; Visual ecology
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract The large monopolar cells (LMCs) of the first optic neuropil (lamina) in insects respond to the photoreceptor neurotransmitter histamine with an increase in chloride conductance. We have compared the properties of this conductance from a range of diptera from different visual environments: Tipula paludosa (slow flying, crepuscular), Drosophila melanogaster (slow-flying diurnal), and 3 fast-flying diurnal species Musca domestica, Calliphora vicina and Lucilia sericata. In whole-cell recordings of dissociated LMCs, histamine-induced currents were elicited using a multichannel parallel perfusion device, allowing rapid determination of the dose-response function, characterised by affinity (K d) and Hill coefficient (n). Calliphora, Lucilia and Musca had the steepest dose response curves (n = 2.8) and the lowest affinity for histamine (K d 35–50 μM); the crepuscular Tipula had a significantly higher affinity (K d = 16 μM) and lower Hill coefficient (n = 1.8). Drosophila had a high affinity (K d 24 μM), and a high Hill coefficient (n = 2.5). In excised inside-out patch recordings all species showed similar single channel properties (conductance 40–60 pS, mean open time 〈 1 ms). The low Hill coefficient in Tipula would be expected to result in lower synaptic gain. We suggest this may be an adaptation to prevent the LMC's response bandwidth being filled with the high levels of photon noise typical of photoreceptors adapted for low light levels. The lower affinity for histamine found in the more photopic species suggests that the concentration of histamine (and therefore presumably number of synaptic vesicles released from the photoreceptors) should be higher. This might improve signal-to-noise ratio by decreasing the contribution of the shot event noise introduced by stochastic release of synaptic vesicles.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 75
    Digitale Medien
    Digitale Medien
    Springer
    Journal of molecular evolution 35 (1992), S. 51-59 
    ISSN: 1432-1432
    Schlagwort(e): Drosophila ; Gart locus ; Chironomus tentans ; Purine nucleotide biosynthesis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The Drosophila Gart locus consists of two genes. One gene encodes three enzymes in the de novo purine nucleotide biosynthesis pathway [glycinamide ribonucleotide synthetase (GARS), aminoimidazole ribonucleotide synthetase (AIRS), and glycinamide ribonucleotide transformylase (GART)]. The second gene lies within an intron of the purine gene and encodes a cuticle protein. To investigate the evolution of the Gart locus, the Chironomus tentans homolog was cloned by screening a genomic DNA library with a polymerase chain reaction product. This study shows that the interesting structural features of this locus conserved in two distant Drosophila species are not found in the Chironomus homolog. These features include the cuticle protein gene nested within an intron and the existence of an alternative transcript to yield a monofunctional enzyme. In addition, the extremely rapid divergence of coding sequence seen for members of the tandemly duplicated AIRS domain in Drosophila is found to be much less rapid in Chironomus.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 76
    Digitale Medien
    Digitale Medien
    Springer
    Journal of molecular evolution 36 (1993), S. 127-135 
    ISSN: 1432-1432
    Schlagwort(e): Transposable elements ; Drosophila ; Gypsy ; Horizontal transfer ; In situ hybridization ; Molecular evolution
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Characterization of sequences homologous to theDrosophila melanogaster gypsy transposable element was carried out inDrosophila subobscura (gypsyDS). They were found to be widely distributed among natural populations of this species. From Southern blot and in situ analyses, these sequences appear to be mobile in this species.GypsyDS sequences are located in both euchromatic and heterochromatic regions. A completegypsyDS sequence was isolated from aD. subobscura genomic library, and a 1.3-kb fragment which aligns with the ORF2 of theD. melanogaster gypsy element was sequenced. Comparisons of this sequence in three species (D. subobscura, D. melanogaster, and D. virilis) indicate that there is greater similarity between theD. subobscura-D. virilis sequences than betweenD. subobscura andD. melanogaster. Molecular divergence ofgypsy sequences betweenD. virilis andD. subobscura is estimated at 16 MY, whereas the most likely divergence time of these two species is more than 60 MY. These data strongly suggest thatgypsy sequences have been horizontally transferred between these species.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 77
    Digitale Medien
    Digitale Medien
    Springer
    Journal of molecular evolution 36 (1993), S. 214-223 
    ISSN: 1432-1432
    Schlagwort(e): Drosophila ; Mitochondrial DNA ; Length polymorphisms ; A+T-rich region ; Tandem duplicated sequences ; Nucleotide sequences ; Secondary structures
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary In the twelve Drosophila obscura group species studied, belonging to the affinis, obscura, and pseudoobscura subgroups, the mitochondrial DNA length ranges from 15.8 to 17.2 kb. This length polymorphism is mainly due to insertions/deletions in the variable region of the A+T-rich region. In addition, one species (D. tristis) possess a tandem duplication of a 470-bp fragment that contains the replication origin. The same duplication has occurred at least twice in the Drosophila evolutionary history due to the fact that the repetition is analogous to repetitions found in the four species of the D. melanogaster complex. By comparing the nucleotide sequence of the conserved region in D. ambigua, D. obscura, D. yakuba, D. teissieri, and D. virilis, we show the presence of a secondary structure, likely implied in the replication origin, which could favor the generation of this kind of duplications. Finally, we propose that the high A and T content in the variable region of the A + T-rich region favors the formation of less-stable secondary structures, which could explain the generation of minor insertion/deletions found in this region.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 78
    Digitale Medien
    Digitale Medien
    Springer
    Journal of molecular evolution 37 (1993), S. 483-495 
    ISSN: 1432-1432
    Schlagwort(e): Drosophila ; mastermind ; Gene comparison ; Triplet repeat ; Homopolymer ; Protein evolution ; Repeat length variation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Runs of identical amino acids encoded by triplet repeats (homopolymers) are components of numerous proteins, yet their role is poorly understood. Large numbers of homopolymers are present in the Drosophila melanogaster mastermind (mam) protein surrounding several unique charged amino acid clusters. Comparison of mam sequences from D. virilis and D. melanogaster reveals a high level of amino acid conservation in the charged clusters. In contrast, significant divergence is found in repetitive regions resulting from numerous amino acid replacements and large insertions and deletions. It appears that repetitive regions are under less selective pressure than unique regions, consistent with the idea that homopolymers act as flexible spacers separating functional domains in proteins. Notwithstanding extensive length variation in intervening homopolymers, there is extreme conservation of the amino acid spacing of specific charge clusters. The results support a model where homopolymer length variability is constrained by natural selection.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 79
    ISSN: 1432-1432
    Schlagwort(e): Artemia franciscana ; Artemia salina ; Artemia parthenogenetica ; Mitochondrial DNA evolution ; Cytochrome c oxidase I ; Cytochrome b ; Drosophila ; Arthropods ; Parthenogenesis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract From the cloned mitochondrial DNAs (mtDNAs) isolated from two bisexual species, one Mediterranean, Artemia salina, and one American, Artemia franciscana, and two parthenogenetic (diploid and tetraploid) strains of Artemia parthenogenetica collected in Spain, physical maps have been constructed and compared. They are extremely different among themselves, much more than the differences between Drosophila melanogaster and D. yakuba and in the same range of different mammalian species such as mouse/rat or man/cow. The nucleotide sequences of two regions of mtDNA encoding parts of the cytochrome c oxidase subunit I (COI) and cytochrome b (Cytb) genes have been determined in the two bisexual species and the two parthenogenetic strains. Comparisons of these sequences have revealed a high degree of divergence at the nucleotide level, averaging more than 15%, in agreement with the differences found in the physical maps. The majority of the nucleotide changes are silent and there is a strong bias toward transitions, with the C↔T substitutions being highly predominant. The evolutionary distance between the two Artemia parthenogenetica is high and there is no clear relationship with any of the bisexual species, including the one present nowadays in Spain. Using a combination of molecular (mtDNA) and morphological markers it is possible to conclude that all of these Artemia isolates should be actually considered as belonging to different species, even the two Artemia parthenogenetica diploidica and tetraploidica.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 80
    Digitale Medien
    Digitale Medien
    Springer
    Journal of molecular evolution 32 (1991), S. 454-462 
    ISSN: 1432-1432
    Schlagwort(e): Alcohol dehydrogenase gene ; Drosophila ; Gene structure ; Evolutionary trends ; Nucleotide substitution rate
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The study of individual genes is essential to a comprehensive understanding of genome evolution. The wealth of information on alcohol dehydrogenase (Adh) inDrosophila makes this gene particularly suitable for such analysis. We have characterized more than 4 kb of the genomicAdh region inDrosophila ambigua and compared this region toDrosophila mauritiana andDrosophila pseudoobscura. The presence of two genes,Adh and 3′ORF (open reading frame), has been confirmed and some of their essential features have been inferred from primary structural analysis. Inter- and intraspecific comparisons have led us to support that both genes may have diverged from an ancient precursor. They appear to be evolving independently, and show a species-specific pattern. TheAdh in theobscura group species lacks amino acids three and four when compared to the species of themelanogaster group and has accumulated most of its amino acid replacements in the third exon. Neither characteristic is observed when any other group species are compared, which suggests that these may be particular features of the evolution of theobscura group. The 3′ORF is highly conserved among the three species analyzed, although variability in the length of the third exon and the nucleotide substitution rate, which is much higher than inAdh, are worth noting. According to our data, both mutation/fixation rates and the distribution of mutations vary over time, which makes it difficult to predict the evolutionary dynamics of specific genome regions.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 81
    ISSN: 1432-1432
    Schlagwort(e): Drosophila ; Muscle-myosin heavy-chain gene ; Alternative exons ; Synonymous substitutions ; Amino acid substitutions ; Evolution ; Testis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The muscle-myosin heavy-chain (mMHC) gene of Drosophila hydei has been sequenced completely (size 23.3 kb). The sequence comparison with the D. melanogaster mMHC gene revealed that the exonintron pattern is identical. The protein coding regions show a high degree of conservation (97%). The alternatively spliced exons (3a-b, 7a-d, 9a-c, 11a-e, and 15a-b) display more variations in the number of nonsynonymous and synonymous substitutions than the common exons (2, 4, 5, 6, 8, 10, 12, 13, 14, 16, 17, and 19). The base composition at synonymous sites of fourfold degenerate codons (third position) is not biased in the alternative exons. In the common exons there exists a bias for C and against A. These findings imply that the alternative exons of the Drosophila mMHC gene evolve at a different, in several cases higher, rate than the common ones. The 5′ splice junctions and 5′ and 3′ untranslated regions show a high level of similarity, indicating a functional constraint on these sequences. The intron regions vary considerably in length within one species, but the corresponding introns are very similar in length between the two species and all contain stretches of sequence similarity. A particular example is the first intron, which contains multiple regions of similarity. In the conserved regions of intron 12 (head-tail border) sequences were found which have the potential to direct another smaller mMHC transcript.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 82
    ISSN: 1432-1432
    Schlagwort(e): Drosophila ; Glucose repression ; Amylase gene ; Interspecific promoter function ; Conserved cis-acting elements
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Previous studies have demonstrated that the expression of the α-amylase gene is repressed by dietary glucose in Drosophila melanogaster. Here, we show that the α-amylase gene of a distantly related species, D. virilis, is also subject to glucose repression. Moreover, the cloned amylase gene of D. virilis is shown to be glucose repressible when it is transiently expressed in D. melanogaster larvae. This cross-species, functional conservation is mediated by a 330-bp promoter region of the D. virilis amylase gene. These results indicate that the promoter elements required for glucose repression are conserved between distantly related Drosophila species. A sequence comparison between the amylase genes of D. virilis and D. melanogaster shows that the promoter sequences diverge to a much greater degree than the coding sequences. The amylase promoters of the two species do, however, share small clusters of sequence similarity, suggesting that these conserved cis-acting elements are sufficient to control the glucose-regulated expression of the amylase gene in the genus Drosophila.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 83
    Digitale Medien
    Digitale Medien
    Springer
    Journal of molecular evolution 34 (1992), S. 130-140 
    ISSN: 1432-1432
    Schlagwort(e): Drosophila ; Sophophora ; cDNA-DNA hybridization ; Phylogenetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary We have performed DNA-DNA hybridization experiments among several species of Drosophila using the evolutionarily conserved portion of the genome representing sequences coding for amino acids of proteins. This was done by using as tracer, radioactively labeled complementary DNA that was reverse transcribed from adult mRNA. We show that this procedure extends phylogenetically the distance over which the technique can be applied to fast-evolving groups such as Drosophila. The major phylogenetic conclusions are (1) the subgenus Sophophora is a monophyletic lineage; (2) within Sophophora the melanogaster subgroup is closer to the obscura group than either group is to the willistoni group; (3) the subgenus Drosophila is complex with most major lineages originating deep in the phylogeny; the subgenus may not be monophyletic; (4) as with most groups classically placed in Drosophila, the Hawaiian Drosophila originate early, supporting the notion that this lineage is older than the extant islands; and (5) the virilis/repleta lineage is monophyletic within Drosophila.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 84
    Digitale Medien
    Digitale Medien
    Springer
    Journal of molecular evolution 37 (1993), S. 525-543 
    ISSN: 1432-1432
    Schlagwort(e): Drosophila ; Zaprionus ; Phylogeny ; Ribosomal RNA sequences
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Nucleotide sequences of 72 species of Drosophilidae were determined for divergent D1 and D2 domains (representing 200 and 341 nucleotides respectively in D. melanogaster) of large ribosomal RNA, using the rRNA direct sequencing method. Molecular phylogenetic trees were reconstructed using both distance and parsimony methods and the robustness of the nodes was evaluated by the bootstrap procedure. The trees obtained by these methods revealed four main lineages or clades which do not correspond to the taxonomical hierarchy. In our results, the genus Chymomyza is associated with the subgenus Scaptodrosophila of the genus Drosophila and their cluster constitutes the most ancient clade. The two other clades are constituted of groups belonging to the subgenus Sophophora of the genus Drosophila: the so-called Neotropical clade including the willistoni and saltans groups and the obscura-melanogaster clade itself split into three lineages: (1) obscura group + ananassae subgroup, (2) montium subgroup, and (3) melanogaster + Oriental subgroups. The fourth clade, the Drosophila one, contains three lineages. D. polychaeta, D. iri, and D. fraburu are branched together and constitute the most ancient lineage; the second lineage includes the annulimana, bromeliae, dreyfusi, melanica, mesophragmatica, repleta, robusta, and virilis groups. The third lineage is composed of the immigrans and the cardini, funebris, guaramunu, guarani, histrio, pallidipennis, quinaria, and tripunctata groups. The genera Samoaia, Scaptomyza, and Zaprionus are branched within the Drosophila clade. Although these four clades appear regularly in almost all tree calculations, additional sequencing will be necessary to determine their precise relationships.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 85
    Digitale Medien
    Digitale Medien
    Springer
    Journal of molecular evolution 36 (1993), S. 315-326 
    ISSN: 1432-1432
    Schlagwort(e): Drosophila ; Fushi tarazu ; Functional constraints ; Regulatory elements
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary We have studied the evolutionary changes occurring in the noncoding regions around the developmentally important fushi tarazu (ftz) gene in a total of 11 species in the genus Drosophila. Previous molecular developmental studies have identified DNA elements both 3′ and 5′ to the coding region which are important in proper regulation of expression of the Drosophila melanogaster ftz gene. We show here that these same elements are the most evolutionarily conserved regions in the vicinity of the gene homologs. Parts of some control elements are more conserved than exonic sequences. Not only is there sequence conservation, but the relative position, orientation, and distances among the control elements remain conserved. One quite significant difference does exist between the two major subgenera studied, Sophophora and Drosophila: namely, an inversion of the ftz unit with respect to other genes in the Antennapedia complex, ANT-C. As a comparison, we applied similar analysis to a “housekeeping” gene-rosy (ry), or Xdh. In contrast, DNA sequences 5′ to the ry coding region revealed little evolutionary conservation. These studies bear out the proposition that functionally important DNA sequences remain more conserved through evolutionary time than do less functionally important sequences. This proposition could be tested in the present case because we could predict a priori from the developmental studies which DNA regions should be most conserved.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 86
    ISSN: 1432-1432
    Schlagwort(e): Alcohol dehydrogenase ; Drosophila ; Drosophila lebanonensis ; Gene expression ; Codon usage ; Phylogenetic relationships
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The region of the genome of D. lebanonensis that contains the Adh gene and the downstream Adh-dup gene was sequenced. The structure of the two genes is the same as has been described for D. melanogaster. Adh has two promoters and Adh-dup has only one putative promoter. The levels of expression of the two genes in this species are dramatically different. Hybridizing the same Northern blots with a specific probe for Adh-dup, we did not find transcripts for this gene in D. lebanonensis. The level of Adh distal transcript in adults of D. lebanonensis is five times greater than that of D. melanogaster adults. The maximum levels of proximal transcript are attained at different larval stages in the two species, being three times higher in D. melanogaster late-second-instar larvae than in D. lebanonensis first-instar larvae. The level of Adh transcripts allowed us to determine distal and proximal initiation transcription sites, the position of the first intron, the use of two polyadenylation signals, and the heterogeneity of polyadenylation sites. Temporal and spatial expression profiles of the Adh gene of D. lebanonensis show qualitative differences compared with D. melanogaster. Adh and Adh-dup evolve differently as shown by the synonymous and nonsynonymous substitution rates for the coding region of both genes when compared across two species of the melanogaster group, two of the obscura group of the subgenus Sophophora and D. lebanonensis of the victoria group of the subgenus Scaptodrsophila. Synonymous rates for Adh are approximately half those for Adh-dup, while nonsynonymous rates for Adh are generally higher than those for Adh-dup. Adh shows 76.8% identities at the protein level and 70.2% identities at the nucleotide level while Adh-dup shows 83.7% identities at the protein level and 67.5% identities at the nucleotide level. Codon usage for Adh-dup is shown to be less biased than for Adh, which could explain the higher synonymous rates and the generally lower nonsynonymous substitution rates in Adh-dup compared with Adh. Phylogenetic trees reconstructed by distance matrix and parsimony methods show that Sophophora and Scaptodrosophila subgenera diverged shortly after the separation from the Drosophila subgenus.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 87
    ISSN: 1432-1432
    Schlagwort(e): Drosophila ; dec-1 eggshell gene ; Wild-type variants ; Repeated region ; DNA sequencing
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Thedec-1 eggshell gene inDrosophila melanogaster encodes follicle cell proteins required for proper eggshell assembly. As shown by Southern and Northern analyses thedec-1 gene occurs in four alleles (Fcl-4) among wild-type strains. Its second exon has a distinct feature in the form of 12 repeats with 78–91 nucleotides; the first five show nearly 100% homology. DNA sequence comparison of the repeated region of the alleles revealed that the length polymorphisms are caused by changes in the numbers of the first five repeats. The results suggest that the alleles have been generated by unequal intragenic crossing-over and/or slippage during DNA replication and that the allelic length variants have arisen independently. The possiblilty that the most common allele,FC1, has a selective advantage over the other alleles is discussed.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 88
    Digitale Medien
    Digitale Medien
    Springer
    Journal of molecular evolution 39 (1994), S. 452-465 
    ISSN: 1432-1432
    Schlagwort(e): Drosophila ; Y chromosome ; Male fertility genes ; Lampbrush loops ; Germ line ; Transposable elements ; Gypsy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract During the evolution of the Y chromosome of Drosophila hydei, retrotransposons became incorporated into the lampbrush loop pairs formed by several of the male fertility genes on this chromosome. Although insertions of retrotransposons are involved in many spontaneous mutations, they do not affect the functions of these genes. We have sequenced gypsy elements that are expressed as constituents of male fertility gene Q in the lampbrush loop pair Nooses. We find that these gypsy elements are all truncated and specifically lost those sequences that may interfere with the continuity of lampbrush loop transcription. Only defective coding regions are found within the loop. Gypsy is not transcribed in loops of many other Drosophila species harboring the family. These results suggest that any contribution of gypsy to the function of male fertility gene Q does not depend on a conserved DNA sequence.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 89
    Digitale Medien
    Digitale Medien
    Springer
    Journal of molecular evolution 39 (1994), S. 478-488 
    ISSN: 1432-1432
    Schlagwort(e): Mitochondrial DNA ; Nucleotide sequences ; Drosophila ; Rapid phyletic radiation ; Molecular phylogeny
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Approximately 2 kb corresponding to different regions of the mtDNA of 14 different species of the obscura group of Drosophila have been sequenced. In spite of the uncertainties arising in the phylogenetic reconstruction due to a restrictive selection toward a high mtDNA A+T content, all the phylogenetic analysis carried out clearly indicate that the obscura group is formed by, at least, four well-defined lineages that would have appeared as the consequence of a rapid phyletic radiation. Two of the lineages correspond to monophyletic subgroups (i.e., afftnis and pseudoobscura), whereas the obscura subgroup remains heterogeneous assemblage that could be reasonably subdivided into at least two complexes (i.e., subobscura and obscura).
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 90
    ISSN: 1432-1432
    Schlagwort(e): Concerted evolution ; Molecular drive ; Drosophila ; rDNA spacers ; PCR length polymorphism ; MVR-PCR mapping
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Polymerase chain reaction (PCR)-amplified, sequenced, and digitally typed intergenic spacers (IGSs) of the ribosomal (r)DNA in D. melanogaster reveal unexpected features of the mechanisms of turnover involved with the concerted evolution of the gene family. Characterization of the structure of three isolated IGS length variants reveals breakage “hot spots” within the 330-base-pair (bp) subrepeat array found in the spacers. Internal mapping of variant repeats within the 240-bp subrepeat array using a novel digital DNA typing procedure (minisatellite variant repeat [MVR]-PCR) shows an unexpected pattern of clustering of variant repeats. Each 240-bp subrepeat array consists of essentially two halves with the repeats in each half identified by specific mutations. This bipartite structure, observed in a cloned IGS unit, in the majority of genomic DNA of laboratory and wild flies and in PCR-amplified products, has been widely homogenized yet is not predicted by a model of unequal crossing over with randomly placed recombination breakpoints. Furthermore, wild populations contain large numbers of length variants in contrast to uniformly shared length variants in laboratory stocks. High numbers of length variants coupled to the observation of a homogenized bipartite structure of the 240-bp subrepeat array suggest that the unit of turnover and homogenization is smaller than the IGS and might involve gene conversion. The use of PCR for the structural analysis of members of the rDNA gene family coupled to digital DNA typing provides powerful new inroads into the mechanisms of DNA turnover affecting the course of molecular evolution in this family.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 91
    Digitale Medien
    Digitale Medien
    Springer
    Journal of molecular evolution 41 (1995), S. 1152-1159 
    ISSN: 1432-1432
    Schlagwort(e): Synonymous substitutions ; Nonsynonymous substitutions ; Estimation methods ; Confidence intervals ; Drosophila
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract A method for estimating the numbers of synonymous (Ks) and nonsynonymous (Ka) substitutions per site is proposed. The method is based on the Li's (J Mol. Evol. 36:96–99, 1993) and Pamilo and Bianchi's (Mol. Biol. Evol. 10:271–281, 1993) method, but a putative source of bias is solved. It is proposed that the number of synonymous substitutions that are actually transitions or transversions should be computed by separating the twofold degenerate sites into two types of sites, 2S-fold and 2V-fold, where only transitional and transversional substitutions are synonymous, respectively. Kimura's (J. Mol. Evol. 16:111–120, 1980) two-parameter correcting method for multiple substitutions at a site is then applied using the overall observed synonymous transversion frequency to estimate both the numbers of synonymous transversional (Bs) and transitional (As) substitutions per site. This approach, therefore, also minimizes stochastic errors. Computer simulations indicate that the method presented gives more accurate Ks and Ka estimates than the aforementioned methods. Furthermore, the obtention of confidence intervals for divergence estimates by computer simulation is proposed.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 92
    Digitale Medien
    Digitale Medien
    Springer
    Journal of molecular evolution 9 (1977), S. 279-298 
    ISSN: 1432-1432
    Schlagwort(e): 5S RNA ; Drosophila ; Evolution ; Secondary structure ; Development
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The nucleotide sequence ofDrosophila melanogaster 5S RNA has been determined and appears to be homogeneous both in the KC cell line and in the insect at different developmental stages. Experimental evidence on the conformation of this molecule is in agreement with a general class of 5S RNA models.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 93
    Digitale Medien
    Digitale Medien
    Springer
    Journal of molecular evolution 32 (1991), S. 421-428 
    ISSN: 1432-1432
    Schlagwort(e): Alcohol dehydrogenase ; Amino acid sequence ; Phylogenetic relationships ; Drosophila
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Increasing data onDrosophila alcohol dehydrogenase (ADH) sequences have made it possible to calculate the rate of amino acid replacement per year, which is 1.7×10−9. This value makes this protein suitable for reconstructing phylogenetic relationships within the genus for those species for which no molecular data are available such asScaptodrosophila. The amino acid sequence ofDrosophila lebanonensis is compared to all of the already knownDrosophila ADHs, stressing the unique characteristic features of this protein such as the conservation of an initiating methionine at the N-terminus, the unique replacement of a glycine by an alanine at a very conserved position in the NAD domain of all dehydrogenases, the lack of a slowmigrating peptide, and the total conservation of the maximally hydrophilic peptide. The functional significance of these features is discussed. Although the percent amino acid identity of the ADH molecule inDrosophila decreases as the number of sequences compared increases, the conservation of residue type in terms of size and hydrophobocity for the ADH molecule is shown to be very high throughout the genusDrosophila. The distance matrix and parsimony methods used to establish the phylogenetic relationships ofD. lebanonensis show that the three subgenera,Scaptodrosophila, Drosophila, andSophophora separated at approximately the same time.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 94
    Digitale Medien
    Digitale Medien
    Springer
    Journal of molecular evolution 33 (1991), S. 450-456 
    ISSN: 1432-1432
    Schlagwort(e): Drosophila ; Mariner ; Transposable elements
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The abundance of the transposable elementmariner differs dramatically in the genomes of the closely related speciesDrosophila simulans, D. mauritiana, D. sechellia, andD. melanogaster. Natural populations ofD. simulans andD. mauritiana have 1–10 and 20–30 copies per diploid genome, respectively, and the insertion sites are polymorphic. The element has not been found inD. melanogaster. In this paper we show thatD. sechellia, a species endemic to the Seychelles Islands, contains only twomariner elements that are at fixed sites in the genome. One element, inserted in chromosome 2R at 51A1–2, contains three deletions and is missing much of the 3′ end. The other element, inserted in chromosome 3L at 64A10–11, is the full length of 1286 bp. Although the sequence of the full-length element is polymorphic in populations ofD. sechellia, at least some of the sequences are closely related to elements fromD. simulans andD. mauritiana that are known to be active. However, judging from the progeny of crosses betweenD. sechellia andD. simulans, the biological activity of the full-lengthD. sechellia element appears to be low, either because of the nucleotide sequence of the element or because of its position in the genome, or both.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 95
    ISSN: 1432-1432
    Schlagwort(e): Evolution ; Gene regulation ; Drosophila ; Adaptation ; Enzymes
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract In an effort to understand the forces shaping evolution of regulatory genes and patterns, we have compared data on interspecific differences in enzyme expression patterns among the rapidly evolving Hawaiian picture-winged Drosophila to similar data on the more conservative virilis species group. Divergence of regulatory patterns is significantly more common in the former group, but cause and effect are difficult to discern. Random fixation of regulatory variants in small populations and/or during speciation may be somewhat more likely than divergence driven by selection. Within the picture-winged group, we also have compared enzymes that fulfill different metabolic roles. There are highly significant differences between individual enzymes, but no obvious correlations to functional categories.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 96
    ISSN: 1432-1432
    Schlagwort(e): CpG suppression ; GC content ; Angiosperms ; Isochores ; GC bias ; Mutational pressure ; Error-prone repair ; Transcriptionally coupled repair
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Nuclear protein coding sequences from gymnosperms are currently scarce. We have determined 4 kb of nuclear protein coding sequences from gymnosperms and have collected and analyzed 〉60 kb of nuclear sequences from gymnosperms and nonspermatophytes in order to better understand processes influencing genome evolution in plants. We show that conifers possess both biased and nonbiased genes with respect to GC content, as found in monocots, suggesting that the common ancestor of conifers and monocots may have possessed both biased and nonbiased genes. The lack of biased genes in dicots is suggested to be a derived character for this lineage. We present a simple but speculative model of land-plant genome evolution which considers changes in GC bias and CpG frequency, respectively, as independent processes and which can account for several puzzling aspects of observed nucleotide frequencies in plant genes.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 97
    Digitale Medien
    Digitale Medien
    Springer
    Journal of molecular evolution 42 (1996), S. 369-375 
    ISSN: 1432-1432
    Schlagwort(e): Transposable elements ; Drosophila ; Tirant ; Retrotransposon
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract In this paper we report a new retrotransposon-like element ofDrosophila melanogaster calledTirant. This sequence is moderately repeated in the genome of this species and it has been found to be widely dispersed throughout its distribution area. From Southern blot andin situ analyses, this sequence appears to be mobile inD. melanogaster, since its chromosome location and the hybridization patterns vary among the different strains analyzed. In this way, partial sequencing ofTirant ends suggests that it is a retrotransposon, since it is flanked by two LTRs. The presence of sequences homologous toTirant has been also investigated in 28 species of the genusDrosophila by means of Southern analyses. These sequences were only detected in species frommelanogaster andobscura groups. These data suggest that ancestral sequences ofTirant appeared after the Sophophora radiation and before the divergence of those groups.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 98
    ISSN: 1432-1432
    Schlagwort(e): Drosophila ; Lcp gene family ; Gene homogenization ; CAAT-box motifs ; Gene phylogeny ; Sex chromosomes
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The larval cuticle protein genes (Lcps) represent a multigene family located at the right arm of the metacentric autosome 2 (2R) inDrosophila melanogaster. Due to a chromosome fusion theLcp locus ofDrosophila miranda is situated on a pair of secondary sex chromosomes, theX2 andneo-Y chromosome. Comparing the DNA sequences fromD. miranda andD. melanogaster organization and the gene arrangement ofLcp1-Lcp4 are similar, although the intergene distances vary considerably. The greatest difference betweenLcp1 andLcp2 is due to the occurrence of a pseudogene inD. melanogaster which is not present inD. miranda. Thus the cluster of the fourLcp genes existed already before the separation of themelanogaster andobscura group. Intraspecific homogenizations of different cluster units must have occurred repeatedly between theLcp1/Lcp2 andLcp3/Lcp4 sequence types. The most obvious example is exon 2 of theLcp3 gene inD. miranda, which has been substituted by the corresponding section of theLcp4 gene rather recently. The homogenization must have occurred before the translocation which generated theneo-Y chromosome.Lcp3 ofD. melanogaster has therefore no orthologous partner inD. miranda. Rearrangements in the promoter regions of theD. miranda Lcp genes have generated new, potentially functional CAAT-box motifs. Since three of theLcp alleles on theneo-Y are not expressed andLcp3 is expressed only at a reduced level, it is suggestive to speculate that the rearrangements might be involved ascis-regulatory elements in the up-regulation of theX2-chromosomalLcp alleles, inDrosophila an essential process for dosage compensation. TheLcp genes on theneo-Y chromosome have accumulated more base substitutions than the corresponding alleles on theX2.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 99
    ISSN: 1432-1432
    Schlagwort(e): Drosophila ; Cuticle proteins (LCP) ; Conserved protein motifs ; Gene phylogeny ; Sex chromosomes
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The larval cuticle proteins (LCPs) are encoded by a multigene family,Lcp1-4, located at the right arm of the metacentric autosome 2 (2R) inDrosophila melanogaster. Due to a chromosome fusion theLcp locus ofDrosophila miranda is situated on a pair of secondary sex chromosomes, theX2 andneo-Y chromosomes. Comparing the deduced amino acid sequences of the autosomalD. melanogaster loci with the sex-chromosomal loci ofD. miranda, we were able to trace the evolution of theLcp loci with respect to their different chromosomal inheritance. The length of the signal peptide is conserved in all four LCPs, while the size of the mature LCPs varies. Conserved protein motifs became obvious from the alignment, indicating regions of structural and functional importance. Analyzing intra- and interspecific sequence similarities of theLcp gene families allowed us to reconstruct the phylogeny of the gene cluster. Alignment with cuticle amino acid sequences originating from divergent insect species reveals motifs already present in the primordial insect LCPs. These motifs indicate different levels of constraint acting during the evolution of the LCPs.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 100
    ISSN: 1432-1432
    Schlagwort(e): Evolution ; Expression patterns ; α-Amylase ; Glucose repression ; Starch induction ; Intra- and interspecific variation ; Drosophila ; Gene expression ; Regulatory genes
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Intraspecific variation of α-amylase activity in D. melanogaster and D. immigrans, which is distantly related to D. melanogaster, and interspecific variation of α-amylase activity in 18 Drosophila species were examined. The amount of intraspecific variation of α-amylase activities measured in terms of coefficient of variation in D. melanogaster and D. immigrans was one-half and one-tenth or less, respectively, of the interspecific variation in 18 Drosophila species. We also surveyed the response patterns of α-amylase activity to dietary carbohydrates at the larval and adult stages. The levels of α-amylase activity depended on both repression by dietary glucose (glucose repression) and induction by dietary starch (starch induction). In general, our data suggest that glucose repression was conserved among species at both stages while starch induction was mainly observed in larvae, although the degree of the response depended on species. In D. lebanonensis lebanonensis and D. serrata, larvae expressed electrophoretically different α-amylase variants (isozymes) from those of adult flies. These results may suggest that the regulatory systems responsible both for the response to environment and developmental expression are different among species in Drosophila.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
Schließen ⊗
Diese Webseite nutzt Cookies und das Analyse-Tool Matomo. Weitere Informationen finden Sie hier...