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.     

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,     

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.     

Karyological characterization of meiosis, post-meiotic mitosis and nuclear migration in the ectomycorrhizal fungus Rhizopogon roseolus (= R. rubescens)

Karyological characteristics during basidiosporogenesis of Rhizopogon roseolus, a member of the hypogeous Agaricomycetes, were studied by light and transmission electron microscopy. More than 1000 tissue fragments of young basidiomata were stained with HCl-Giemsa and observed by a light microscopy to evaluate nuclear behavior. Basidium morphology in the hymenium was observed by transmission electron microscopy. Meiosis and post-meiotic mitosis took place in the center of the basidium. Sterigmata appeared when the first meiotic division occurred, and the center of the basidium became constricted when the second meiotic division occurred. Asynchronous nuclear migration from the basidium into the basidiospores occurred after post-meiotic mitosis, producing eight uninucleate basidiospores. The nucleus migrated patchily into basidiospores. The pattern of post-meiotic mitosis of R. roseolus, in which post-meiotic mitosis took place in the center of the basidium, is reported for the first time.     

Nuclear Degeneration during Ballistospore Formation of Cronartium asclepiadeum (Uredinales)*

When basidia of Cronartium asclepiadeum (Uredinales) develop basidiospores, nuclei migrate from the basidial cells into the basidiospores. A mitotic nuclear division yields two nuclei in the basidiospore. One of these nuclei degenerates if the basidiospore develops a secondary ballistospore. Several stages in the degeneration of the nuclei can be recognized: (1) Condensation of chromatin, (2) separation of the nucleus into a portion containing the chromatin and a portion containing the nucleoplasm by an invagination of the nuclear envelope, (3) reduction of nuclear volume, (4) enveloping and (5) twisting of nuclear membranes around the degenerating nucleus, (6) homogenization of the chromatin with reduction of the nuclear envelope, and reduction of the enclosing membrane complex from a multilamellar structure to a single membrane layer, and (7) invagination or splitting off of the spiralled membranes. The nuclear behavior during early developmental stages of secondary spore formation is similar to that of budding basidiomycetous yeasts. Basidiomycetes producing ballistospores may possibly have arisen from those whose reproducing phase is yeast-like.     

Electron microscopic studies on a unique cytokinetic structure in tetrasporocytes of the red algaHarveyella sp. (Cryptonemiales,Choreocolaceae)

Summary A unique type of cytokinesis is described in tetrasporocytes of the alloparasitic red alga,Harveyella sp. Cytokinesis takes place immediately after four post-meiotic nuclei are formed and may result from coalescence of endoplasmic reticulum cisternae. As a result of this cisternal fusion, a double-membraned cleavage channel is formed. This channel lacks wall material and is usually oriented tetrahedrally. Membranes of the peripheral portions of the cleavage channel fuse with the existing tetrasporocyte plasmalemma, delimiting four tetraspores. Subsequently, wall material is secreted within the preformed cleavage channels to form a continuous tetraspore wall between adjacent tetraspores. Wall secretion usually occurs in a centrifugal direction, beginning at the juncture of the cleavage channels, but it also may be random or centripetal. Dictyosome activity is absent during the first wall secretion stage but contributes to secondary wall deposition.Portions of this study were conducted at the University of Washington's Friday Harbor Laboratories, Friday Harbor, Washington.     

The characteristics of shuttling RNAs confirmed

Shuttling RNAs are recognized as molecules that migrate against steep concentration gradients from one nucleus (through the cytoplasm) into another nucleus in the same cell. In previous work these molecules were identified through experiments involving the separation of two kinds of nuclei utilizing differences in the nuclei that may have produced misleading results. In the experiments reported here normal, randomly-chosen ameba (A. proteus) nuclei containing [³²P]RNA were implanted into unlabeled normal, randomly-chosen cells and, after suitable incubation, the labeled RNAs present in each kind of nucleus were characterized by gel electrophoresis. The previously obtained results were confirmed: i.e. (a) the recipient cell nuclei acquired the same four small, distinct RNAs, which are recognized as shuttling ones because they migrate from one nucleus to the other; (b) the grafted nuclei possess, in addition to the four shuttling RNAs, three small, distinct RNAs, which are recognized as non-shuttling RNAs. New evidence also is presented to show that the acquisition by a nucleus of labeled RNAs in the above kind of experiment is not a result of new synthesis of RNAs from the labeled turnover products emanating from the transplanted nucleus.     

Algorithmic Generation of Freely Jointed Hard Sphere Chains and Properties of Inertial Tensors

Abstract

A statistical algorithm, capable of generating a large number of freely jointed hard sphere chains, is presented. This is the first of a series of algorithms being developed to model unfolded proteins by different modes of hard sphere chains. The aim of these studies is to systematically investigate the effects of different factors, such as atomic radii, bond angles, torsion angles, chain length, etc., on the conformation of unfolded proteins and other random polymers. As continuous models, various types of hard sphere chains enable one to isolate the aforementioned factors one at a time for investigation and thus are advantageous over discrete lattice models. In particular, the freely jointed hard sphere chain model allows one to evaluate the excluded volume effect. As a first step in this endeavor, the average determinant D(N,r) and the average trace T(N, r) of the inertial tensor A of the random chains were calculated at various sphere radii r and chain lengths N. It is found that both the average determinant D(N,r) and the average trace T(N,r) scale linearly with chain length N. after logarithmic transformation. However, the critical exponent of D(N,r) increases with r faster than that of T(N,r) as a result of the non-commutativity between the det operator and the average operator < >. The significance of the algorithm and the results obtained on understanding random polypeptide chains are discussed.     

NUCLEAR BEHAVIOR IN THE BASIDIOMYCETE,VOLVARIELLA VOLVACEA

The basidiospores of the straw mushroom are typically uninucleate and its vegetative hyphae are generally multinucleate. There is a marked reduction of nuclear number in the trama and subhymenium. Interphase nuclei exist in two forms, each of which undertakes a particular mode of division. The “diffused” nuclei divide by conventional mitosis while the “constricted” ones divide amitotically. In metaphase of mitosis nine chromosomes were seen both in polar and lateral view. This haploid number confirms the nine bivalents found in basidia during meiosis. A unique characteristic of this fungus is that the diploid nucleus, the two postkaryotic nuclei and the four postkaryotic nuclei may be enclosed by a well-defined nuclear envelope during division.     

金针菇担孢子核相及遗传属性的研究

以3个不同的金针菇菌株为材料,研究了其担孢子的核相及遗传属性。荧光染色观察显示,担孢子核相以双核为主,双核孢子、单核孢子和无核孢子分别占80.2%、7.5%和12.3%。源于单孢分离物的菌丝为有隔膜、无锁状联合的多核菌丝。在交配试验中,源于不同菌株单孢分离物的菌丝原生质体的配对形成具锁状联合的菌落,而源于同一单孢分离物的菌丝原生质体的配对则形成无锁状联合的菌落,暗示担孢子中的两个核具有相同的交配型。RAPD分析显示,源于同一单孢分离物的菌丝原生质体为10个随机引物所扩增的图谱彼此完全相同,印证了担孢子中的双核是同质的。此外,观察表明,一个担子上着生有4个担孢子。因此,金针菇是一种具4个含同质双核担孢子的四极性蕈菌。     

Electron microscope studies on Tomentella II. Hyphal anastomosis and reproductive organs

Light and electron microscope observations were made on the hyphal anastomosis, basidia and basidiospores ofTomentella bombycina andT. fuscoferruginosa. Three different types of anastomosis were observed and the presence of nuclei at the anastomosis area was seen in most cases. The probasidial cell appeared tetranucleate and nuclear migration to the sterigmata took place when basidiospore genesis was initiated. The basidiospores showed from 1 to 4 nuclei, but the nuclear identification on the electron microscope was difficult in mature basidiospores.T. fuscoferruginosa basidiospore cell wall appeared to be formed by one single layer, while theT. bombycina basidiospore wall showed three well-delimited layers with different electron density.

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Zusammenfassung Licht- und elektronmikroskopische Beobachtungen sind an der Hyphalanastomose, Basidia und Basidiosporen vonTomentella bombycina undT. fuscoferruginosa gemacht worden. Drei verschiedene Typen von Anastomose sind festgestellt worden und die Gegenwart der Kerne war in der Fläche der Anastomose in den meisten Fällen sichtbar. Die probasidiale Zelle erschien vierkernig und eine Kernwanderung zu den Sterigmata fand statt, wenn Basidiosporengenese eingeleitet war. Die Basidiosporen zeigten 1 bis 4 Sporen, aber die Identifikation der Kerne war durch Elektronmikroskopie in reifen Basidiosporen schwierig.T. fuscoferruginosa formed die Zellwand der Basidiospore durch eine einzige Schicht, während die Zellwand der Basidiospore vonT. bombycina drei gut begrenzte Schichten mit verschiedenen Elektrondichtigkeit zeigte.

     

Stereum sanguinolentum: Is it an amphithallic basidiomycete?

Monobasidiospore isolates were prepared from basidiocarps of Stereum sanguinolentum. Five isolates per basidiome were paired with each other and with isolates from the trama. Interbasidiome pairings of the trama isolates and of a selection of single-spore isolates also were performed. Thin sections of the hymenium were stained with DAPI and examined by fluorescence microscopy to study the nuclei in the basidia. Spore prints were stained with DAPI to count the number of nuclei per spore. SEM was used to determine the number of basidiospores per basidium. All intrabasidiome pairings were compatible. In contrast, interbasidiome pairings, except one, were incompatible, independent of whether single-spore or trama isolates were paired. Fertile basidiomes were formed in single-basidiospore cultures. Basidia were regularly four-spored. On average, 5% of the basidiospores possessed one nucleus, 82% two, 2% three and 1% four nuclei. Ten percent of the spores appeared to be empty. Karyogamy, meiosis and postmeiotic mitosis were observed in the basidia. Nuclei resulting directly from meiosis, i.e., without having undergone postmeiotic mitosis, sometimes were observed in the sterigmata or spore primordia. The high number of vegetative compatibility groups (VCG) of S. sanguinolentum observed in this study and earlier studies is difficult to explain without sexual or parasexual recombination. We suppose that the majority of spores with ≥2 nuclei are amphithallic, possessing at least one nucleus of each mating type. Recombination could occur by exchange of nuclei among VCGs via anastomoses between homothallic compartments. Transfer of nuclei from heterothallic to homothallic mycelia or matings between homothallic mycelia, which originate from monokaryotic spores, might be other paths for gene exchange.     

Inheritance of Restriction Fragment Length Polymorphisms in Agaricus Brunnescens

The cultivated mushroom, Agaricus brunnescens, is secondarily homothallic; most basidia produce only two basidiospores, each of which receives two of the four post meiotic nuclei. The segregation of restriction fragment length polymorphisms (RFLPs) detected by four plasmid probes carrying single-copy nuclear DNA of Agaricus was followed in seven parental strains including commercial, wild-collected, and artificially synthesized heterokaryons. Of a total of 367 single-spore progeny examined, 351 (95.6%) were heteroallelic at all RFLP loci heteroallelic in the respective parents. Of the 16 segregant isolates, ten (2.7% of the total) were homoallelic at all segregating loci assayed, suggesting that these isolates were most probably derived from rare spores that had received only a single postmeiotic nucleus. Some of these ten isolates had recombinant genotypes. Only five isolates (1.4% of the total) showed homoallelism at one of the loci heteroallelic in the parent, while remaining heteroallelic at other loci. These five genotypes suggest that a crossover had occurred between a marker locus and its respective centromere. Taken together, the results suggest that meiosis in A. brunnescens is accompanied by low levels of recombination and that nonsister nuclei are preferentially incorporated into basidiospores after meiosis II.     

Cytological and genetic studies of the life cycle of Saccharomycopsis lipolytica

Summary In the alkane yeast Saccharomycopsis lipolytica (formerly: Candida lipolytica) the variability in the ascospore number is caused by the absence of a correlation between the meiotic divisions and spore wall formation. In four spored yeasts, after meiosis II, a spore wall is formed around each of the four nuclei produced by meiosis II. However, in the most frequently occurring two spored asci of S. lipolytica, the two nuclei are already enveloped by the spore wall after meiosis I due to a delay of meiosis II. This division takes place within the spore during the maturation of the ascus. In this case germination of the binucleate ascospore is not preceded by a mitosis. It follows that the cells of the new haploid clones are mononucleate. In the three spored asci, which occur rarely, only one nucleus is surrounded by a spore wall after meiosis I; the other nucleus undergoes meosis II before the onset of spore wall formation. The result is one binucleate and two mononucleate spores. In the one spored asci the two meiotic divisions occur within the young ascospore, i.e. spore wall formation starts immediately after development of the ascus. These cytological observations were substantiated by genetic data, which in addition confirmed the prediction that binucleate spores may be heterokaryotic. This occurs when there is a postreduction of at least one of the genes by which the parents of the cross differ. This also explains the high frequency of prototrophs in the progeny on non-allelic auxotrophs since random spore isolates are made without distinguishing between mono-and binucleate spores. The possibility of analysing offspring of binucleate spores by tetrad analysis is discussed. These findings enable us to understand the life cycle of S. lipolytica in detail and we are now in a position to start concerted breeding for strain improvement especially with respect to single cell protein production.     

Cytology of teliospore germination and basidiospore formation inUromyces appendiculatus var.appendiculatus

Summary The cytology of teliospore germination and basidiospore formation inUromyces appendiculatus var.appendiculatus was characterized with light and fluoroscence microscopy. Meiosis of the diploid nucleus occurred in the metabasidium. The four haploid daughter nuclei migrated into the basidiospore initials where they underwent a post meiotic mitosis. Each basidiospore was delimited from the meatabasidium by a septum at the apex of the sterigma. Seventy-five percent of mature basidiospores were binucleate, 24.5% uninucleate, and 0.5% trinucleate. Mature, released basidiospores measured 16×9 m, were smooth-surfaced, and reniform to ovate-elliptical in shape.This study represents portion of a dissertation submitted by the senior author to the Faculty of Biology of the University of Constance in March, 1983, in partial fulfillment of the requirements for the degree of Doctor of Natural Sciences (Dr. rer. nat.).     

Lebendbeobachtungen der Chromosomen-Aufregulation bei der Gallmücke Heteropeza pygmaea (Cecidomyiidae,Diptera)

In male-determined, paedogenetically developing eggs of Heteropeza pygmaea a restitutive fertilization takes place after meiosis. Two small nuclei of maternal origin (somatic nuclei) and the egg nucleus migrate to the center of the egg chamber. Their chromosomes then form the metaphase plate of the primary cleavage nucleus. The in vitro observations and the analysis of photomicrographs and time lapse films revealed that the metaphase stage can be reached in three different ways: 1. The egg nucleus and the two somatic nuclei form one common spindle. 2. The egg nucleus forms a spindle and the two somatic nuclei together form another one. The two spindles then fuse in late prometaphase and form a single spindle. 3. The egg nucleus alone forms a spindle. The chromosomes of the somatic nuclei migrate to the equator of this spindle. This variation in the restitutive fertilization is explained by an increasing asynchrony between the development of the egg nucleus and the slower somatic nuclei from the first to the third type.     

The cytoskeleton and polarization during pollen development in Carex blanda (Cyperaceae)

Patterns of cytoskeletal organization during distinct polarizations that characterize pollen development in the sedge Carex blanda (Cyperaceae) were studied by correlated methods of immunohistochemistry and confocal and transmission electron microscopy. As is typical of the family Cyperaceae, Carex produces a unique pollen type known as a pseudomonad in which all four microspores of the tetrad are enclosed within the wall of a single pollen grain. Only one member of the tetrad is functional and the other three abort. The pseudomonads are precisely oriented in the locule with the functional microspore in the wide abaxial portion of the wedge-shaped cytoplasm adjacent to the tapetum, and the degenerative microspores are packed tightly in the pointed adaxial portion. A unique sequence of post-meiotic developmental events reflects both intracellular and intercellular polarity. Development includes: (1) random placement of tetrad nuclei in the coenocytic sporocyte after meiosis, (2) interrupted cytokinesis resulting in a tetrad of nuclei that migrates as a unit into the narrow adaxial tip, (3) completion of unequal cytokinesis and centering of the functional nucleus in the wide abaxial portion of the microsporocyte via a radial array of microtubules and microfilaments, (4) unequal mitosis resulting in a small generative cell at the proximal surface of the functional microspore (adjacent to the abortive microspores), and (5) recentering of the vegetative nucleus in the abaxial cytoplasm via a radial cytoskeletal array.