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181.
The hyphal walls of three mycobionts, isolated from the lichens Xanthoria parietina, Tornabenia intricata and Sarcogyne sp. were investigated by two techniques: microautoradiography of fungal colonies exposed to radioactive carbohydrate precursors; and binding, in vivo, of fluorescein conjugated lectins to hyphal walls of such colonies.N-[3H] acetylglucosamine was readily incorporated into tips, young hyphal walls and septa of the three mycobionts and the free-living fungus Trichoderma viride, but not into Phytophthora citrophthora, indicating that chitin is a major component of the mycobionts' hyphal walls. All three mycobionts, but neither of the free-living fungi, incorporated [3H] mannose and [3H] mannitol into their hyphal walls.Fluorescein-conjugated wheat germ agglutinin was bound to the hyphal walls of the three mycobionts and T. viride, but not to the walls of P. citrophthora; the binding pattern was similar to the grain pattern obtained in autoradiographs after short N-[3H] acetylglucosamine labelling. As wheat germ agglutinin binds specifically to chitin oligomers, the lectin binding tests further confirmed that chitin is a mycobiont hyphal wall component.Binding characteristics of several fluorescein-conjugated lectins to the three mycobionts indicated that this technique can yield useful information concerning the chemical composition of hyphal wall surfaces.List of abbreviations FITC
fluorescein isothiocyanate
- WGA
wheat germ agglutinin
- TCA
trichloroacetic acid
- PNA
peanut agglutinin
- LA
lotus agglutinin
- Glc NAc
N-acetylglucosamine
- ConA
concanavalin A
- SBA
soybean agglutinin
- WBA
waxbean agglutinin
Part of an M.Sc. thesis submitted by A. Braun to the Department of Botany, Tel Aviv University. 相似文献
182.
A developmental electron microscopic study of the parasitism of Rolylenchulus reniforrnis in resistant ''Peking'' and susceptible ''Lee'' soybeans was made during a 21-day period under controlled conditions. Within 2 days of inoculation, the nematode had penetrated the cortical cells to the endodermis where it inserted its stylet, secreted and initiated syncytial formation and cell hypertrophy. Syncytia primarily involved pericycle tissues and, to a lesser extent, xylem parenchyma and endodermis. When identifiable, the cell into which the nematode stylet was inserted to initiate syncytial development was endodermal. Susceptible tissues exhibited two basic phases of development during this infection period: (i) an initial phase represented by partial cell wail lysis and separation; and (ii) an anabolic phase, characterized by organelle proliferation and development accompanied by secondary wall deposits, which provided nutrition for sessile female development. The resistant or hypersensitive reaction (HR) lacked the anabolic phase found in the susceptible reaction, and was characterized by an extension and usually accelerated type of Iysis found in the first phase of the syncytial development. The HR was usually very evident 4 days after inoculation, and could be identified by an almost complete lysis of the cell walls and cytoplasm. The possibility that the initial cell of the developing syncytium or "prosyncyte" may influence a susceptible or resistant reaction is discussed. Successive stages of cell wall dissolution and the deposition of secondary cell walls are described. 相似文献
183.
Fredrick C. Colley Lie Kian Joe Viqar Zaman E.U. Canning 《Journal of invertebrate pathology》1975,26(1):11-20
A nuclear-polyhedrosis virus (NPV) of the silkworm, Bombyx mori, which forms an icosahedral inclusion body, was transmitted to larvae of the rice stem borer, Chilo suppressalis. Serial passages of Bombyx NPV in the alternate host by injecting the supernatant of diseased hemolymph produced inclusion bodies with cuboidal and other shapes that differed from the original shape formed in Bombyx. These different shapes increased with times of passages, and after the twelfth passage, only cuboidal inclusion bodies were formed. The icosahedral inclusion bodies in B. mori and the cuboidal inclusion bodies in C. suppressalis occluded singly enveloped virions of the same size (350 × 75 nm), but the cuboidal inclusion bodies contained only a few virions and a large number of membraneous spherical structures. The formation process of the cuboidal inclusion body differed from that of the icosahedral. At first, irregularly branched inclusion bodies containing “vacant” spaces appeared in the infected nuclei. The bodies grew larger with the deposition of protein in the spaces between the branches, and this was accompanied with the occlusion of a large number of membraneous structures formed in the vicinity of the inclusion bodies, which became cuboidal in shape. 相似文献
184.
Microscopy and sequencing-based technologies are providing increasing insights into chromatin architecture. Nevertheless, a full comprehension of chromosome folding and its link with vital cell functions is far from accomplished at the molecular level. Recent theoretical and computational approaches are providing important support to experiments to dissect the three-dimensional structure of chromosomes and its organizational mechanisms. Here, we review, in particular, the String&Binders polymer model of chromatin that describes the textbook scenario where contacts between distal DNA sites are established by cognate binders. It has been shown to recapitulate key features of chromosome folding and to be able at predicting how phenotypes causing structural variants rewire the interactions between genes and regulators. 相似文献
185.
Dante Poy Martín J. Ramírez Peter Michalik Luis N. Piacentini 《Journal of morphology》2020,281(2):250-257
Genital traits are among the fastest to evolve, and the processes that drive their evolution are intensively studied. Spiders are characterized by complex genitalia, but the functional role of the different structures during genital coupling is largely unknown. Members of one of the largest spider groups, the retrolateral tibial apophysis (RTA) clade, are characterized by a RTA on the male palp, which is thought to play a crucial role during genital coupling. However, the RTA was lost in several families including the species-rich wolf spiders (Lycosidae) leading to the hypothesis that the genital coupling is achieved by alternative mechanisms. Here, we investigate the genital interactions during copulation in the wolf spider Agalenocosa pirity (Zoicinae) on cryofixed mating pairs using electron, optical and X-ray microscopy and compare our findings with other lycosids and entelegyne spiders. We found an unprecedented coupling mechanism for lycosid spiders involving the palea and a membranous cuticle folding adjacent to the epigynal plate. Additionally, we show an uncommon coupling between the median apophysis and the contralateral genital opening, and confirmed that the terminal apophysis acts as functional conductor, as previously hypothesized for males of Zoicinae. Phylogenetic mapping of RTA indicated that the basal tibial process found in Agalenocosa is a secondary acquisition rather than a modified RTA. 相似文献
186.
Abstract The cell wall of Candida albicans contains mannoproteins that are covalently associated with β-1,6-glucan. When spheroplasts were allowed to regenerate a new cell wall, initially non-glucosylated cell wall proteins accumulated in the medium. While the spheroplasts became osmotically stable, β-1,6-glucosylated proteins could be identified in their cell wall by SDS-extraction or β-1,3-glucanase digestion. At later stages of regeneration, β-1,3-glucosylated proteins were also found. Hence, incorporation of proteins into the cell wall is accompanied by extracellular coupling to β-1,6-/β-l,3-glucan. The SDS-extractable glucosylated proteins probably represent degradation products of wall proteins rather than their precursors. Tunicamycin delayed, but did not prevent the formation of β-1,6-glucosylated proteins, demonstrating that β-1,6-glucan is not attached to N -glycosidic side-chains of wall proteins. 相似文献
187.
Satoru Masuda Shigefumi Kuwahara Toshio Suguro Kenji Mori 《Bioscience, biotechnology, and biochemistry》2013,77(11):2515-2520
The (S)-enantiomer of the sex pheromone of the yellow scale (Aonidiella citrina), (S,E)-6-isopropyl-3,9-dimethyl-5,8-decadienyl acetate, was stereoselectively synthesized from (R)-(+)-citronellic acid. 相似文献
188.
Molecular graphics and molecular mechanics techniques have been used to study the mode of ligand binding and mechanism of action of the enzyme phospholipase A2. A substrate-enzyme complex was constructed based on the crystal structure of the apoenzyme. The complex was minimized to relieve initial strain, and the structural and energetic features of the resultant complex analyzed in detail, at the molecular and residue level. The minimized complex was then used as a basis for examining the action of the enzyme on modified substrates, binding of inhibitors to the enzyme, and possible reaction intermediate complexes. The model is compatible with the suggested mechanism of hydrolysis and with experimental data about stereoselectivity, efficiency of hydrolysis of modified substrates, and inhibitor potency. In conclusion, the model can be used as a tool in evaluating new ligands as possible substrates and in the rational design of inhibitors, for the therapeutic treatment of diseases such as rheumatoid arthritis, atherosclerosis, and asthma. 相似文献
189.
Abstract Murine monoclonal antibodies (mAbs) were selected against a cell wall glycoprotein of Saccharomyces cerevisiae . One of the mAbs (92-276/018) specifically identified S. cerevisiae and the sibling species S. paradoxus, S. pastorianus and S. bayanus in immunofluorescence studies and immunoblot analyses, while no other yeast genera except Saccharomyces were recognized. Further analysis indicated that the mAb 92-276/018 reacts with an epitope in the carbohydrate chain of the cell wall glycoproteins. 相似文献
190.
John H. Pazur Michael E. Tay Beverly A. Pazur Frank J. Miskiel 《Journal of Protein Chemistry》1987,6(5):387-399
Sets of isomeric anti-lactose antibodies with specificity for the lactose units of a cell wall polysaccharide fromStreptococcus faecalis strain N were induced in rabbits immunized with a vaccine of nonviable cells of the organism. Such sets of anti-lactose antibodies
were isolated from the serum of immunized animals by affinity chromatography on lactosyl-Sepharose. Gel electrofocusing experiments
showed that the preparations consisted of multiprotein components. One preparation of antibodies of 13 isomers was separated
into homogeneous components by liquid isoelectrofocusing. The individual isomeric antibodies exhibit specificity for the lactose
units of the antigenic polysaccharide, possess isoelectric points in the range of 5.9–8.0, and belong to the IgG class of
immunoglobulins, and each member yields one light chain and one heavy chain on dissociation in sodium dodecyl sulfate (SDS)
and mercaptoethanol. These results have been interpreted as evidence for the assembly of the chains of isomeric antibodies
by a single-chain pairing mechanism. 相似文献