Control of erythritol dehydrogenase in Schizophyllum commune

Summary An NAD-dependent erythritol dehydrogenase was detected in cell-extracts of basidiospore germinants of Schizophyllum commune following culture on either meso-erythritol or glycerol as sole carbon sources. Induction of erythritol dehydrogenase was also observed in purely vegetative mycelium (str. 845 or str. 699). Erythritol dehydrogenase was not observed in ungerminated basidiospores or germinants which arose on d-glucose, d-mannitol, sorbitol, ribitol, xylitol, d-arabitol or l-arabitol. NAD-coupled polyol dehydrogenases for all the latter sugar alcohols were observed in ungerminated basidiospores, germinants, and vegetative mycelium of S. commune cultured on d-glucose. Basidiospore germination on d-glucose plus meso-erythritol led to a 90% decrease in erythritol dehydrogenase and the specific activity of ribitol dehydrogenase was directly comparable to that seen in d-glucose germinants. Storage experiments of crude extracts of meso-erythritol germinants indicated differential enzyme decay of dehydrogenases for d-mannitol, sorbitol and erythritol while the respective enzymes could be further distinguished by heat-stability as well as preferential utilization of analogues of NAD. DEAE-cellulose column chromatography led to separation of sorbitol dehydrogenase which was also active with xylitol, erythritol dehydrogenase, and mannitol dehydrogenase which was also active with d-arabitol.     

Reversion of protoplasts from dikaryotic mycelium ofSchizophyllum commune

Summary Morphological observations on the reversion of homokaryotic protoplasts obtained from dikaryotic mycelium ofSchizophyllum commune reveal that part of the morphogenetic processes operative in clamp formation are transiently expressed in the absence of heterokaryotic conditions. Often the homokaryotic revertants start off to produce simple septa and then 21form pseudoclamps for some time before they revert permanently to the normal monokaryotic morphology with simple septa. Heterokaryotic revertants often form pseudoclamps before reverting to the normal dikaryotic morphology with true clamps.     

POLYOLS IN SCHIZOPHYLLUM COMMUNE

Sugars and sugar alcohols present in extracts of the wood-rotting mushroom Schizophyllum commune were identified by paper chromatography during fruiting, basidiospore germination, and growth of vegetative mycelium. Homokaryotic fruitbodies and dikaryotic fruits derived from several compatible matings of S. commune contained mannitol and arabitol. Basidiospores shed from dikaryotic fruits also contained mannitol and arabitol while the latter disappeared during spore germination. Vegetative mycelium (strain 699) contained glucose, fructose, mannitol and glycerol while these compounds as well as arabitol occurred in mycelium of strain 845. Polyols are not, therefore, associated exclusively with the sporulation process in S. commune.     

Control of arabitol formation in Schizophyllum commune development

Summary Dikaryotic cells of S. commune synthesized polyols throughout the life cycle when grown on glucose, cellobiose, or cellulose. Basidiospores contained arabitol and mannitol which were depleted during germination. The mannitol content of the young germlings rose to normal levels within a day; arabitol accumulation remained depressed for 5 to 7 days and then returned to normal levels characteristic of vegetative cells. Individual homokaryons differed in their production of intracellular polyols, which, unlike germlings, remained constant with cultural age. Homokaryon (str. 699) produced low levels of arabitol but high levels of glycerol while another homokaryon (str. 845) was the reverse. Mixtures of these homokaryons as well as the dikaryon (699×845) produced arabitol and glycerol levels intermediate between the parent homokaryons. High concentrations of glucose did not change the nature of the polyols produced. Arabitol formation could be induced prematurely in germlings or elevated in the dikaryon by growth on acetate or ethanol. Both homokaryons responded to growth on acetate with elevated arabitol production; acetate induction of arabitol formation was repressed in all types of cells if glucose were added simultaneously with acetate. Maltose, cellobiose, and trehalose also stimulated arabitol formation in young germlings, suggesting that glucose repression was the cause of decreased arabitol formation in basidiospore germlings. There was no correlation between the formation of arabitol and the derepression of isocitrate lyase or change in specific activities of alkaline and acid phosphatase in germlings grown on various carbon sources.     

Life cycle and nuclear behavior in three rust fungi (Uredinales)

Kuehneola japonica has a microcyclic life cycle with a regular alternation of generations. Single basidiospore inoculations onto Rosa wichuraiana resulted in teliospore production, indicating its homothallic nature. Dikaryotization in a vegetative mycelium in the host seemed to occur through nuclear division that was not followed by septum formation. Karyogamy and meiosis took place through teliospore and metabasidium development; this fungus was considered to reproduce genetically homogeneous progenies. Puccinia lantanae and P. patriniae were also microcyclic in their life cycle; however, these fungi differed from K. japonica in the mode of nuclear behavior. In the former two fungi, both vegetative and reproductive cells were uninucleate. No karyogamy was observed, and nuclear division in the metabasidium development was thought to be mitotic. In P. lantanae, a basidiospore was formed on a sterigma, whereas a whiplike hypha emerged from each metabasidium cell in P. patriniae. Inoculations of Justicia procumbens with a single basidiospore of P. lantanae resulted in teliospore production. The fungus seemed to remain uninucleate, either haploid or diploid, throughout the life cycle. Thus, reproduction was considered to be apomictic. Received: August 16, 2001 / Accepted: October 1, 2001     

Griseofulvin-induced alterations in site of dividing nuclei and structure of septa in a dikaryon ofSchizophyllum commune

Summary Ultrastructural study of a dikaryon of the basidiomyceteSchizophyllum commune showed that treatment with griseofulvin affected the site of the dividing nuclei and the location and structure of the septa. The microtubules were considered to be the primary target of griseofulvin, since they participate in nuclear division and movement in the hyphae, and their assembly is known to be in other organisms than fungi inhibited by griseofulvin. It is pointed out that dikaryotic hyphae with two nuclei and a clamp connection per cell are more sensitive indicators of the effect of griseofulvin than homokaryotic hyphae, whose structure is less complex.     

Antigenic differences due to the incompatibility factors inSchizophyllum commune

Summary A serological comparison of proteins extracted from a dikaryon and from its isogenic, homokaryotic component strains demonstrated differences that are attributable to tetrapolar incompatibility in the Basidiomycete,Schizophyllum commune.With 1 Figure in the TextThis work was supported by the Deutsche Forschungsgemeinschaft, Bad Godesberg Germany.Senior Fulbright Research Grantee in the Federal Republic of Germany and Fellow of the John Simon Guggenheim Memorial Foundation, 1960–1961     

Kinetic studies of septum synthesis,erosion and nuclear migration in a growing B-mutant of Schizophyllum commune

Summary Microscopic measurements of apical growth and primary branch elongation were compared with nuclear movements, septum synthesis and erosion in a growing B-mutant of Schizophyllum commune. Apical growth, mitosis, septum formation, and intercalary cell division were similar to wild-type hyphae. Nuclear replication and new cross-wall formation also occurred in either apical cells bounded by eroding septa or in subterminal cells adjoined by eroded septa. An anucleate subterminal unit of the B-mutant hypha was invaded by a migrant nucleus which subsequently replicated and laid down a new septum in this region. Septum erosion occurred as early as 1 h following synthesis. Cellular granules and filaments were implicated in both septum synthesis and erosion.     

Nuclear distribution in Alternaria tenuis

Nuclear distribution and behaviour during vegetative growth and spore formation inAlternaria tenuis was studied utilising the HCl — Giemsa staining technique. The vegetative mycelium and conidia are predominantly monokaryotic. Anastomoses, followed by nuclear migrations, have been recorded. Intercellular nuclear migrations have only been observed in germinating conidia. Nuclear behaviour during conidial formation indicates that the conidia are homokaryotic. Cytological differences have been found in different monocoidal isolates of A. tenuis.     

Two morphological markers indicating dikaryosis in Schizophyllum commune

Summary In the wood destroying basidiomycete Schizophyllum commune a method is described to recognize the onset of dikaryosis rapidly in using recessive genetic markers. The gene ai ⁺/ai causes in its mutant recessive allele (ai) the production of dark coloured fruit bodies. This can be made use of to evaluate macroscopically the formation of a dikaryon. Another useful marker is the gene rd ⁺/rd. The recessive allele (rd) causes phenotypically the formation of a round looking mycelium instead of the fringed looking mycelium, the wild type. This genetic marker which is closely linked to the A-incompatibility factor is therefore also qualified to detect the onset of dikaryosis without much effort.     

Nuclear and Non-nuclear Factors influencing Clamp Connection Formation in Coprinus disseminatus

Matings between sister single spore lines of Coprinus disseminatusshowed a cryptic tetrapolar pattern. The two groups of matingsthat resulted in formation of mycelia with clamp connections(apparent dikaryons) differed in rate of nuclear penetrationduring mating. In one group penetration occurred at rates comparablewith nuclear migration in other species and in the other groupit was often extensive but at a rate similar to, or less than,the dikaryon growth-rate. No differences were detected betweenthese two groups in stability, colony extension rate, frequencyof clamp connections, proportions of true clamp connectionsand pseudoclamps, or number of nuclei per hyphal tip cell. Cytological studies and the isolation of hyphal tips showedthat both groups of apparent dikaryons were heterokaryotic di-or trikaryons. The di- and trikaryotic conditions co-existedin the same mycelium, but adjacent cells of individual branchingsystems usually contained equal numbers of nuclei. Within apparentdikaryons the number and kinds of nuclei per cell were similarin hyphae with clamp connections and those with simple septa.Treatments that prevented clamp connection formation did notalter the nuclear status of most of the hyphae. Irregularities in nuclear distribution were infrequent and mostwere associated with pseudoclamps. Forty per cent of nodes withprobable pseudoclamps yielded homokaryotic branches, which wereof either constituent mating type. There was some indicationthat irregularities in nuclear distribution could also occurduring divisions associated with simple septa.     

Direct studies of nuclear movements in Schizophyllum commune

Summary Measurements of nuclear positions in apical cells of homokaryotic mycelia and dikaryotic mycelium of Schizophyllum commune showed that nuclei occupied a near central position in most cases. Forward nuclear movements observed in living hyphal apices occurred at rates within the range of hyphal growth and could account for the maintenance of centrally located nuclei. Opposed nuclear movements followed mitosis and greatly exceeded the rate of hyphal growth. Septum disruption and rapid nuclear movements characterized an A _xB_mut homokaryon. Neither cytoplasmic streaming nor actively participating granules or filaments could account for any of these nuclear movements.     

Corn Smut Dikaryon in Culture

A TYPICAL smut life cycle has three phases—diploid, haploid and dikaryon¹. Diploid spores (teliospores) formed in the host tissue are a resting phase. They undergo meiosis at germination to form haploid vegetative cells which are usually yeast-like. The dikaryon is the pathogenic phase and is made up of cells with two haploid nuclei. It is initiated by the fusion of two compatible non-pathogenic haploid cells and the formation of an infection hypha by the fusion product.     

Meiotic-like Recombination in Vegetative Dikaryons of SCHIZOPHYLLUM COMMUNE

A total of 65 Schizophyllum commune dikaryons of three different genotypes were synthesized, maintained on agar plates, prevented from fruiting, and macerated. The macerate was plated. Germlings of homokaryotic morphology were isolated using no chemical or genetic selection, grown, and tested for recombinant genotypes. Crossover types were plentiful among the homokaryons with recombinant genotypes, indicating that meiotic-like processes in vegetative dikaryons are common and may be as important as conventional basidial meiosis in the origin of recombinant strains.     

The septal pore cap is an organelle that functions in vegetative growth and mushroom formation of the wood‐rot fungus Schizophyllum commune

Mushroom‐forming basidiomycetes colonize large areas in nature. Their hyphae are compartmentalized by perforated septa, which are usually covered by a septal pore cap (SPC). Here, we describe, for the first time, the composition and function of SPCs using the model system Schizophyllum commune. The SPC of S. commune was shown to consist of a proteinaceous matrix covered by a lipid membrane. The matrix was demonstrated to define the ultrastructure of the SPC and to consist of two main proteins, Spc14 and Spc33. Gene spc14 encodes a protein of 86 amino acids, which lacks known domain, signal or localization sequences. Gene spc33 encodes a 239 and a 340 amino acid variant. Both forms contain a predicted signal anchor that targets them to the ER. Immuno‐localization showed the presence of Spc33 in the SPC but not in ER. From this and previous reports it is concluded that the SPC is derived from this organelle. Inactivation of spc33 resulted in loss of SPCs and the inability to close septa. The latter may well explain why vegetative growth and mushroom formation were severely reduced in strains in which spc33 was inactivated.     

Chlamydospores of Schizophyllum commune

Summary The detection of chlamydospores of Schizophyllum commune in liquid medium is described. The short thick walled cells are formed by intercalary septation which leads also to modification of the septal complex. The chemical composition of the cell walls of chlamydospores is similar to the composition of the vegetative mycelium.     

Electron microscopic observation of the sporangial structure of strains of Actinoplanaceae

Lechevalier, Hubert A. (Rutgers, The State University, New Brunswick, N.J.), Mary P. Lechevalier, and Pauline E. Holbert. Electron microscopic observation of the sporangial structure of strains of Actinoplanaceae. J. Bacteriol. 92:1228-1235. 1966.-Eight strains of Streptosporangium spp. and one strain each of Spirillospora albida and an Ampullariella-like Actinoplanes sp. were observed by electron microscopy. The sporangiospores of all these organisms had a smooth surface. All formed their sporangia by the ingrowth of a hypha inside a bag formed by the extension of the outer sheath of the sporangiophore. The sporogenic hypha was not branched in strains of Streptosporangium but was branched in S. albida and the Actinoplanes sp. Spore formation was by septation of the intrasporangial hyphae. When it occurred, septation took place by the same annular ingrowth of the cell wall common in gram-positive bacteria. The septum at the apex of the sporangiophore was formed before the others. Septation was seen to occur between two fully formed septa, indicating almost simultaneous formation of large segments dividing again, almost simultaneously, into smaller spore-sized segments.     

Distinguishing homokaryons and heterokaryons in Phellinus sulphurascens using pairing tests and ITS polymorphisms

Phellinus sulphurascens Pilát causes laminated root rot of coniferous species in both western North America (WNA) and Asia. Accurate somatic incompatibility tests for mapping population structures have been difficult to conduct for P. sulphurascens because no single, unambiguous criterion has allowed differentiation of homokaryotic and heterokaryotic isolates. In a population study of P. sulphurascens in WNA, two types of ITS sequences were found in the single spore and vegetative isolates. All single spore isolates (SSIs) had either ITS type-1 or type-2 whereas some vegetative isolates had both ITS types. The segregation pattern for inheritance of ITS, which we observed in SSIs from eight basidiocarps, suggested that each ITS type occurred in a different nucleus and that each basidiospore inherited only one ITS type. In four SSIs from Russia and eight heterokaryotic isolates from Japan, nine different ITS types, referred to as type-3 to -11, were detected. A variety of pairing tests conducted between known Asian and WNA homokaryon and heterokaryon isolates did not always give consistent results with respect to fungal mat morphologies and formation of demarcation lines. However, the ITS types that occurred after pairing tests did follow consistent patterns. Thus, using ITS polymorphisms and pairing tests between Asian tester isolates and 49 vegetative isolates from WNA, we were able to accurately distinguish between homokaryotic and heterokaryotic isolates.     

Control of fungal development. II. Kinetics of growth during dikaryosis in Schizophyllum commune

This paper describes a method for mating colonies of Schizophyllum commune so that the mating process in sets of individual colonies occurs synchronously. This technique has permitted us to define the kinetics of growth during dikaryosis, the transition from the homokaryotic to the dikaryotic stage of the life cycle. Homokaryons and established dikaryons have essentially the same exponential growth rates. We find that, during the transition from the homokaryon to the dikaryon, there is a period of distinctly slower growth, and it is during this period that the morphology typical of the dikaryon first becomes apparent. Growth kinetics for the transition from the homokaryon to the common-A heterokaryon are also established. This method will permit us to study sequential biochemical and physiological events occurring during these two developmental transitions.     

Fine structure of vegetative mycelium and spores of Nocardia spp

The fine structure of a fragmenting and sporulating mycelium of cultures of actinomycetes possessing biochemical properties characteristic of the genus Nocardia--a cell wall of type IV and lipid LCN a--was studied. It was found that fragmenting hyphae are similar in structure to the vegetative hyphae of known actinomycetes. Sporulation takes place through the simultaneous division of a sporulating hypha by numerous septa. Spores differ from vegetative cells in the presence of a thickened electron-dense cell wall, dense internal contents, and the presence of vacuoles.