Spore formation and karyological characterization of basidiosporogenesis,meiosis, post-meiotic and nuclear migration mitosis in Coprinus comatus

In Coprinus comatus, we sampled and observed different maturity stages of basidium to find the possible causes of binucleate basidiospores by microscopy using the HCI-Giemsa and DAPI staining methods. In basidium, following karyogamy, a single nucleolus was observed. We found evidence suggesting post-meiotic mitosis following nuclear migration in the spores. Post-meiotic mitosis occurred in the basidiospores, resulting in four binucleate basidiospores. This indicates that the basidiospore is a monokaryon, and that C. comatus shows the same pattern of basidiospore formation as Coprinopsis cinerea. This type of nuclear behavior was defined as pattern D, one of six distinct patterns (pattern A–F) of nuclear behavior during basidiosporogenesis have been described for basidiomycetes by Campos and Costa in 2010.     

Nucleolar behaviour during division in the homobasidiomycetidae

Summary

The nucleoli of Oudemansiella mucida and Nolanea cetrata become disassociated from the parent chromatin during both mitosis and meiosis. Disassociation of the nucleoli from the post-meiotic nuclei at the onset of migration is taken, along with other evidence, to indicate that the third nuclear division is initiated in the basidium and completed in the basidiospores. It is postulated that the coincidence of migration and the third nuclear division arises from the inability of nucleoli to pass through the sterigmata. This view is supported by observations made by the authors on other members of the Homobasidiomycetidae.     

Meiosis,basidiospore development and post-meiotic mitosis in the basidiomycete,Phallus impudicus

The meiotic spindles of Phallus impudicus had a similar ultrastructure to those seen in other basidiomycetes. After meiosis the basidal apex differentiated to form a number of broadly based protuberances which subsequently developed into basidiospores (up to 9 per basidium). The nuclei then underwent a post-meiotic mitosis within the cytoplasm of each basidiospore. After this mitosis one nucleus remained in the basidiospore and a complete septum developed at the base. The significance of this arrangement of meiosis, spore production and post-meiotic mitosis is discussed with respect to the taxonomy and life cycle of this unusual basidiomycete.     

Basidiospore formation in monokaryotic fruiting bodies of a mutant strain of Coprinus macrorhizus

The process of basidiospore formation in a mutant strain Fis^c of Coprinus macrorhizus, a heterothallic species of Basidiomycete, which forms monokaryotic fruiting bodies was examined. A single nucleus in a young basidium divided mitotically and two daughter nuclei were fused subsequently. The fused nucleus then divided meiotically forming four basidiospores on a basidium. The typical chromosome behaviours in the first meiotic prophase were observed. Synaptonemal complexes were observed in a basidium at the first meiotic prophase. A continuous illumination of fruiting bodies was effective to arrest meiosis in monokaryotic fruiting bodies at the particular stage of meiotic division.     

Meiosis in the basidiomycetous fungus,Coprinus atramentarius

Summary Stages in meiosis ofCoprinus atramentarius have been studied using the electron microscope. Serial sections of late pachytene nuclei showed a diglobular spindle pole body adjacent to the nuclear membrane. After Prophase I the two globular ends of the SPB enlarged and became positioned towards the apex of the basidium and the first meiotic spindle formed across the basidium apex. The two spindles of the second meiotic division formed in the same plane but at 90° to the original spindle of the first division.     

Microspectrophotometric study and kinetics of autogamy during encystment of Tetrahymena rostrata

The process of autogamy that accompanies encystment in Tetrahymena rostrata was divided into five stages; A: first meiotic division, B: second meiotic division. C: post-meiotic division and fusion of the pronuclei, D: first and second synkaryon's mitosis and E: macronuclear-polyploidization. In this communication the kinetics of these phases is reported. The degeneration of the old-macronucleus begins about the second meiotic division (stage-B), and the development of the new-macronucleus progressively rises during about 15h.     

Topology of microtubules and actin in the life cycle of Xanthophyllomyces dendrorhous (Phaffia rhodozyma)

The morphology of budding and conjugating cells and associated changes in microtubules and actin distribution were studied in the yeast Xanthophyllomyces dendrorhous (Phaffia rhodozyma) by phase-contrast and fluorescence microscopy. The non-budding interphase cell showed a nucleus situated in the central position and bundles of cytoplasmic microtubules either stretching parallel to the longitudinal cell axis or randomly distributed in the cell; none of these, however, had a character of astral microtubules. During mitosis, the nucleus divided in the daughter cell, cytoplasmic microtubules disappeared and were replaced by a spindle. The cytoplasmic microtubules reappeared after mitosis had finished. Actin patches were present both in the bud and the mother cell. Cells were induced to mate by transfer to ribitol- containing medium without nitrogen. Partner cells fused by conjugation projections where actin patches had been accumulated. Cell fusion resulted in a zygote that produced a basidium with parallel bundles of microtubules extended along its axis and with actin patches concentrated at the apex. The fused nucleus moved towards the tip of the basidium. During this movement, nuclear division was taking place; the nuclei were eventually distributed to basidiospores. Mitochondria appeared as vesicles of various sizes; their large amounts were found, often lying adjacent to microtubules, in the subcortical cytoplasm of both vegetative cells and zygotes.     

THE QUADRIPOLAR MICROTUBULE SYSTEM AND MEIOTIC SPINDLE ONTOGENY IN HORNWORTS (BRYOPHYTA: ANTHOCEROTAE)

Ontogeny of the meiotic spindle in hornworts was studied by light microscopy of live materials, transmission electron microscopy, and indirect immunofluorescence microscopy. As in monoplastidic meiosis of mosses and Isoetes, the single plastid divides twice, and the four resultant plastids migrate into the future spore domains where they organize a quadripolar microtubule system (QMS). Additionally, a unique axial microtubule system (AMS) was found to parallel the plastid isthmus at each division in meiosis, much as in the single plastid division of mitosis. This finding is used to make a novel comparison of mitotic and meiotic spindle development. The AMS contributes directly to development of the mitotic spindle, whereas ontogeny of the meiotic spindle is more complex. Nuclear division in meiosis is delayed until after the second plastid division; the first AMS disappears without spindle formation, and the two AMSs of the second plastid division contribute to development of the QMS. Proliferation of microtubules at each plastid results in the QMS consisting of four cones of microtubules interconnecting the plastids and surrounding the nucleus. The QMS contributes to the development of a functionally bipolar spindle. The meiotic spindle is comparable to a merger of two mitotic spindles. However, the first division spindle does not terminate in what would be the poles of mitosis; instead the poles converge to orient the spindle axis midway between pairs of non-sister plastids.     

Sheathed nuclear division in primary spermatocytes of Orgyia antiqua (Lepidoptera, Insecta)

The restructuring of spermatocytes during the first meiotic division is examined in the moth Orgyia antiqua (Lymantriidae, Lepidoptera) using transmission electron microscopy. Particular emphasis was placed on the behaviour of the perispindle membrane system. These membranes develop from layers of smooth endoplasmic reticulum wrapped around the prophase I nucleus and are retained until early telophase I. The original nuclear envelope is dissolved in metaphase I. Polar fenestrae in the perispindle membrane stacks are filled with numerous irregular membrane elements. The formation of new nuclear envelopes around the daughter nuclei takes place inside the perispindle membrane system. Finally, the membrane stacks rupture concomitantly with spindle elongation in late telophase I. Thus, division of primary spermatocytes in Orgyia antiqua has a surprising degree of similarity with the so-called closed mitosis. This mode of division is typical for many protozoa, algae and fungi. In the pertinent cells, the original nuclear envelope persists around the spindle area during nuclear division. In order to distinguish the closed mitosis from the situation in Orgyia antiqua spermatocytes, the term 'sheathed nuclear division' is suggested for the latter.     

Postovulatory aging of human ova: II. Spontaneous division of the first polar body

Two oocytes recovered from the Fallopian tube at 24 and 50 h following the LH peak in plasma were examined by light microscopy and transmission electron microscopy. The possibility of fertilization was excluded by clinical and morphologic evidence. In the earliest specimen, the first polar body showed condensed nuclear chromatin, without nuclear envelope, and is interpreted as entering interphase. In the other specimen, the first polar body was undergoing division, which is interpreted as spontaneous second meiotic division.     

CYTOLOGICAL STUDIES IN LACCARIA (AGARICALES). I. MEIOSIS AND POSTMEIOTIC MITOSIS

In the genus Laccaria, basidial formation, dikaryotic basidia, karyogamy, and meiosis were generally similar to structures and phenomena reported for other Agaricales. The haploid nuclei of dikaryotic basidia resided side by side in the basidium prior to karyogamy. Following karyogamy a single nucleolus was observed in L. montana (four-spored species); several nucleoli remained in the nucleus of L. tortilis (two-spored species). The haploid number of chromosomes for L. montana appeared to be n = 9. Postmeiotic mitosis typically occurred in the basidiospores resulting in binucleate basidiospores for four-spored species and quadrinucleate basidiospores for two-spored species. Postmeiotic mitosis sometimes occurred in the sterigmata and basidia proper. In instances where postmeiotic mitosis occurred in basidia, mature basidiospores were not formed and the basidia were collapsed, and contained up to eight nuclei.     

长根小奥德蘑双孢菌株与四孢菌株核相变化的比较

用双苯并咪唑（Hoechst 33258）染色法分别对长根小奥德蘑Oudemansiella radicata双孢菌株和四孢菌株的菌丝、子实体、担孢子进行染色观察,结果表明：双孢长根小奥德蘑菌丝细胞多为单核,无锁状联合;原担子中单核进行一次有丝分裂形成两个横向或纵向排列的子核,这2个子核分别进入2个担孢子中,留下无核的空担子;成熟担孢子具有一个核。四孢长根小奥德蘑菌丝细胞大多数为双核,具有锁状联合;进入原担子中的两个单倍性细胞核先发生核配,形成一个二倍性的核,再经过减数分裂形成四个染色体减半的单倍性子核,     

THE BASIDIA OF EXIDIA NUCLEATA. II. DEVELOPMENT

The basidia of Exidia nucleate, were studied by light and electron microscopy. The basidium arises from a basal clamp-connection as a subcylindrical, dikaryotic structure but soon becomes sphaeropedunculate. Mitochondria, endoplasmic reticulum, and compact lamellar systems are more abundant and more evenly dispersed in diploid probasidia than in dikaryotic probasidia, whereas vacuoles in the apical regions are larger in dikaryotic probasidia. Oil globules are few or absent in the earlier stages but increase in size and number throughout basidial development. Karyogamy results in a diploid nucleus approximately twice the volume of haploid nuclei. Although indications were noted of reorganization of the nuclear envelope during the terminal stages of reduction division, available evidence does not suggest a prolonged loss of the nuclear envelope during division. Internal wall formation is centripetal, at least in those stages observed. In areas of active wall formation, a conspicuous zone devoid of mitochondria, oil globules, and endoplasmic reticulum was noted consistently. The circumscribing wall of a hypobasidial segment is composed of 2 lamellae of contrasting electron-density and is separated from the walls of adjacent hypobasidial segments and the wall delimiting the enucleate stalk by a median electron-transparent lamella. Although extensive vacuolation occurs in the hypobasidial segments as the nuclei and most of the cytoplasm pass through the epibasidia into the basidiospores, evidence of active nuclear migration was observed. Each basidiospore contains a nucleus, mitochondria, endoplasmic reticulum, and numerous oil globules.     

Plastid polarity and meiotic spindle development in microsporogenesis ofSelaginella

Summary Microsporogenesis inSelaginella was studied by fluorescence light microscopy and transmission electron microscopy. As in other examples of monoplastidic meiosis the plastids are involved in determination of division polarity and organization of microtubules. However, there are important differences: (1) the meiotic spindle develops from a unique prophase microtubule system associated with two plastids rather than from a typical quadripolar microtubule system associated with four plastids; (2) the division axes for first and second meiotic division are established sequentially, whereas as in all other cases the poles of second division are established before those of first division; and (3) the plastids remain in close contact with the nucleus throughout meiotic prophase and provide clues to the early determination of spindle orientation. In early prophase the single plastid divides in the plane of the future division and the two daughter plastids rotate apart until they lie on opposite sides of the nucleus. The procytokinetic plate (PCP) forms in association with the two slender plastids; it consists of two spindle-shaped microtubule arrays focused on the plastid tips with a plate of vesicles at the equatorial region and a picket row of microtubules around one side of the nucleus. Second plastid division occurs just before metaphase and the daughter plastids remain together at the spindle poles during first meiotic division. The meiotic spindle develops from merger of the component arrays of the PCP and additional microtubules emanating from the pair of plastid tips located at the poles. After inframeiotic interphase the plastids migrate to tetrahedral arrangement where they serve as poles of second division.Abbreviations AMS axial microtubule system - FITC fluorescein isothiocyanate - MTOC microtubule organizing center - PCP procytokinetic plate - QMS quadripolar microtubule system - TEM transmission electron microscope (microscopy)     

Division spindle and centrosomal plaques during mitosis and meiosis in some Ascomycetes

The behaviour of the division spindle and centrosomal plaques is described in four species of Ascomycetes (Ascobolus immersus, Ascobolus stercorarius, Podospora anserina and Podospora setosa) studied by light and electron microscopy. Two unique features of the kinetical apparatus were observed: presence of centrosomal plaques and intranuclear location of the spindle. In all types of mitoses (mycelium, crosier and postmeiotical mitosis) the apparatus is structurally identical to that found in meiosis. The centrosomal plaques, present in all divisions, are always contiguous with the nuclear envelope and never show centrioles similar to those commonly found in Metazoa and Protozoa. During metaphase and anaphase the plaque is constituted of two zones situated on each side of the nuclear envelope: an electron opaque outer zone and inner one less opaque in which most of the microtubules end. In Podospora the outer zone appears in sections as consisting of two dark layers separated by a clear one. Two dispositions of plaques are possible: either they are entirely contiguous with the nuclear envelope (Ascobolus) or only partially so, the remainder being perpendicular to the nuclear envelope (Podospora). — The localisation of the plaques in the ascus was determined by light and electron microscopy. The nuclear envelope was shown to remain intact during division. It was possible to observe that the sporal wall of each spore originated from the same unique double membrane formed in the ascus during the meiotic second division and postmeiotical mitosis. This fact is of genetical interest for the study of morphological and physiological characters of the spores.     

Ultrastructure of basidium and nucleus associated organelle in Filobasidiella neoformans: Its application as a taxonomic character

Filobasidiella neoformans, the teleomorph of Cryptococcus neoformans, was observed using electron microscopy to confirm its phyletic status. No septa were found in the basidium of F. neoformans. Mature basidiospores were encapsulated by a relatively thick cell wall. Basidiospores directly budded from the basidium without sterigma formation, and no hilar appendix was noted. A lateral component of a synaptonemal complex was observed. As for mitotic apparatus, a spherical nucleus associated organelle (NAO), 0.12 m in diameter, was found in the hemispherical depressive area of the nuclear envelope. Therefore, this fungus seems to have both characteristics of the Holobasidiomycetidae and of the primitive Basidiomycotina such as the Teliomycetes.     

Ultrastructure of developing basidiospores in <Emphasis Type="Italic">Rhizopogon roseolus</Emphasis> (= <Emphasis Type="Italic">R. rubescens</Emphasis>)

The ultrastructure of developing basidiospores in Rhizopogon roseolus is described. When viewed in the fruiting body chamber using scanning electron microscopy, basidiospores appear narrowly ellipsoid and have smooth walls. Eight basidiospores are usually produced on the apex of each sterigma on the basidium. Transmission electron micrographs showed that basidiospores formed by movement of cytoplasm (including the nuclei) via the sterigmata, and then each basidiospore eventually became separated from its sterigma by an electron-lucent septum. The sterigma and basidium subsequently collapsed, resulting in spore release. Freshly released spores retained the sterigmal appendage connected to the collapsed basidium. After spore release, the major ultrastructural changes in the spore concerned the lipid bodies and the spore wall. During maturation, lipid bodies formed and then expanded. Before release, the spore wall was homogeneous and electronlucent, but after release the spore wall comprised two distinct layers with electron-dense depositions at the inner wall, and the dense depositions formed an electron-dense third layer. The mature spore wall complex comprised at least four distinct layers: the outer electron-lucent thin double layers, the mottled electron-dense third layer, and the electron-lucent fourth layer in which electron-lucent granular substances were dispersed.     

Entamoeba histolytica: cell cycle and nuclear division

The cell cycle of Entamoeba histolytica, the duration of its phases, and the details of the nuclear division stages are described in this paper. Trophozoites from clone L-6, strain HM1:IMSS, were synchronized by colchicine. Synchrony was observed immediately after treatment and cultures remained synchronous for at least three replicative cycles with synchrony indexes between 13 and 15 hr. The stages of nuclear division were studied by light and electron microscopy. Four stages of the nuclear division were defined: prophase, early anaphase, late anaphase, and telophase. No metaphase stage was observed by light or electron microscopy. One of the first events in the nuclear division was the presence of a bud close to the juxtanuclear body, which grew to a daughter nucleus. The karyosome and the nuclear membrane remained throughout the mitotic process. Bundles of intranuclear microtubules were observed forming a "V" from the center of the nucleus to one of the poles, and associated with them, 12 to 16 chromosomes-like structures appeared. The results of these studies strongly suggest that division of E. histolytica involved a pleuromitotic process which is carried out in about 120 min.     

Studies of sporogenesis in the rhodophyta

Summary Post-meiotic tetraspore mother cells of Corallina officinalis L. have been studied by light and electron microscopy. During the course of post-meiotic cellular reorganisation each nucleus becomes surrounded by a complex of precisely oriented endoplasmic reticulum, termed nuclear endoplasmic reticulum. A distinctive feature of this relationship is an electron dense substance in contact with the nuclear surface and extending as groundplasm between the ER cisternae as far as the outer limits of the complex, where it gives place to the ribosome-containing matrix of the general cytoplasm. There is circumstantial evidence to indicate that the extracisternal electron dense material is a product of nucleo-cytoplasmic interaction, and that it is involved in the assembly of ribosomes.The nuclear endoplasmic reticulum appears to be active in the production of smaller swollen cisternal elements, which form frequently anastomosing reticular tracts in the regions between adjacent nuclei. There is structural evidence of vesicular transport of material from the swollen cisternae to the proximal (forming) face of the Golgi apparatus.These events are thought to be of fundamental importance in achieving the cellular reorganisation and transformation which occurs after the second meiotic division.The authors thank Mr. D. C. Williams for technical assistance. One of us (MCP) gratefully acknowledges the financial support provided by a Natural Environment Research Council Studentship.     

Timing of DNA replication during the meiotic process in monokaryotic basidiocarps of Coprinus macrorhizus

By applying the method of fluorescent microscopy to propidium iodide stained cells, change in the relative amount of DNA in a basidium was examined during the meiotic process in Coprinus macrorhizus. In the monokaryotic basidiocarp of the mutant strain Fis^c, mitotic DNA replication was first induced soon after a 3h-illumination period on the 10th day of culture, and subsequently meiotic DNA replication occurred after karyogamy.