Growth of Hyphal Branching Systems in Coprinus disseminatus

Apical portions of hyphal branching systems of Coprinus disseminatuswere observed at the margins of colonies extending at a constantrate under one set of environmental conditions. Growth was consistentlymonopodial, the main hyphae continuing to extend in the colonymargin at a constant rate. Primary branch initiation occurredat regular intervals, closely associated with cell divisionof the parent hypha, and initiation of secondary branches tookplace in the older parts of the system. Extension rates of main,primary branch, and secondary branch hyphae were distinct, beingin the proportions 100: 66: 18. In the majority of systems successivebranches of the same category closely resembled one anotherand changes in extension rate of primary branches were smallfrom soon after initiation up to a length of 750µ. Ina minority of systems branch behaviour was less regular, somebranches increasing in extension rate whilst others decreased.Changes in older parts of the systems were not followed. young primary branch hyphae were consistently narrower thanmain hyphae. Although extension rate was correlated with hyphaldiameter for main and for branch hyphae separately, the extensionrate of equally wide hyphae was significantly higher for mainas compared with branch hyphae. Furthermore the wider, faster-extendingbranch hyphse temded tp arise from the wider, faster-extendingmain hyphae. The significance of these findings is discussed.     

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 dikaryotization in Schizophyllum commune

The growth, duplication and fate of multikaryotic hyphae bearing true clamp connections, as derived from compatible matings of Schizophyllum commune, were studied by phase contrast microscopy. The nuclei (N) of multikaryotic apices maintained a near central position during hyphal growth. True clamp connection formation occurred with near synchronous mitosis followed by septal synthesis across the clamp neck and main hyphal axis. Nuclear progeny after mitosis in a hexakaryon included 6 N in the apex, 1 N in the clamp and 5 N in the penultimate cell; the solitary nucleus in the clamp later entered the penultimate cell. Similar events occurred for clamp connection formation and mitosis in the trikaryon, quadrikaryon or pentakaryon, whether in the apex or primary branches. Nuclear content of the multikaryotic apex (2 N through 10 N) had no apparent effect on the rate of individual hyphal growth. Reduction of the nuclear number in a trikaryon occurred by long-term entrappment of a solitary nucleus in the clamp and subsequent outgrowth of the dikaryotic penultimate cell. Occasionally, more than one nucleus became entrapped in the clamp cell. The ephemeral nature of the multikaryon was indicated by the fact that older cultures appeared to be exclusively dikaryotic hyphae at the colony periphery.     

Oldest fossil basidiomycete clamp connections

A rachis of the fossil filicalean fern Botryopteris antiqua containing abundant septate hyphae with clamp connections is preserved in a late Visean (Mississippian; ~330 Ma) chert from Esnost (Autun Basin) in central France. Largely unbranched tubular hyphae pass from cell to cell, but may sometimes produce a branch from a clamp connection. Other clamp-bearing hyphae occur clustered in individual cells or small groups of adjacent host cells. These hyphae may be tubular, catenulate with numerous hyphal swellings, or they may display a combination of both. The Visean hyphae with clamp connections predate Palaeancistrus martinii, the heretofore oldest direct fossil evidence of Basidiomycota, by some 25 Ma.     

Cyclic AMP control of hierarchical growth pattern of hyphae inNeurospora crassa

Wild-typeNeurospora crassa shows a clear hyphal dominance growth pattern with a hierarchy of hyphal diameters containing wide main hyphae, narrow primary branch hyphae, and still narrower secondary branches. Mutants (cr-1), lacking cyclic AMP, lack this size hierarchy when grown in medium without cyclic AMP. When grown in media containing sufficient cyclic AMP or 8-bromocyclic AMP to correct other morphological aberrations, these mutants still lack hierarchical growth. When grown in the presence of very high levels (3 mM) of 8-bromocyclic AMP, there is a long delayed formation of hyphae of different diameters. It is suggested that differences in cyclic AMP concentrations among the hyphae of wild type may be central to the production of the hierarchical growth pattern.     

Direct microscopic studies of clamp connection formation in growing hyphae of Schizophyllum commune

Summary Photomicroscopic studies of clamp connection formation were collated with microscopic measurements of apical extension and mitosis in rapidly growing dikaryotic hyphae of Schizophyllum commune. Intercalary clamp connection formation was described in sub-terminal regions of the dikaryon. Conventional (i.e., rearward) clamp initiation was compared to forward clamp connection formation. Primary branch emergence was observed from clamp connections in growing hyphae and contrasted to sub-basidial branching in the hymenium of dikaryotic fruit-bodies.     

Light and electron microscope study of unilateral mating between a secondary mutant and a wild-type strain ofSchizophyllum commune

Summary After hyphal fusions between the secondary mutant and wild-type strains ofSchizophyllum commune some of the fused hyphae show several nuclei per cell and dissolved septa. These hyphae are designated migration hyphae because they are evidently the main routes of nuclear exchange between the two strains. On the wild-type side of the mating the nuclei spread gradually from the main part of the migration hyphae into the side branches, which develop into an extensive network with many anastomoses. The first cells with pseudoclamps or clamp connections are observed in this network.On the mutant side of the mating the branching is less developed and the number of anastomoses is smaller. The cross walls of the septa are poorly dissolved, and nuclear aggregations occur in the hyphae. No development of clamp connections or pseudoclamps is observed. It is suggested that the unilateral mating response of the secondary mutant strain might possibly be caused by the failure of the septa in the mutant hyphae to dissolve, which inhibits the distribution of the nuclei into the side branches of migration hyphae.     

Isolation of a homothallic mutant in <Emphasis Type="Italic">Lentinula edodes</Emphasis>

To obtain a homothallic mutant in Lentinula edodes, basidiospores derived from the common Bmut dikaryon (A1B1mut × A2B1mut) were treated with UV irradiation. Of a total of approximately 5000 monosporous cultures recovered, a single basidiospore isolate was found to produce the hyphae bearing clamp connections without mating. This mutant strain could form fruit bodies, and all its single basidiospore isolates developed into colonies with clamp connections. Such homothallic behaviors were transmitted from the mutant strain to the next generation. During the germination and following hyphal elongation in a single basidiospore of mutant strain, clamp connections were clearly detected in multicellular hyphae, which contained two nuclei in each cell. Their clamp connections were morphologically variable, viz., pseudo, abnormal, and true clamps. Amplified fragment length polymorphism (AFLP) profiles among the basidiospore isolates of mutant strain were identical, indicating that the mutant strain produced isogenic basidiospore progeny. Contribution no. 385 from the Tottori Mycological Institute     

Branching is coordinated with mitosis in growing hyphae of Aspergillus nidulans

Filamentous fungi like Aspergillus nidulans can effectively colonize their surroundings by the formation of new branches along the existing hyphae. While growth conditions, chemical perturbations, and mutations affecting branch formation have received great attention during the last decades, the mechanisms that regulates branching is still poorly understood. In this study, a possible relation between cell cycle progression and branching was studied by testing the effect of a nuclei distribution mutation, cell cycle inhibitors, and conditional cell cycle mutations in combination with tip-growth inhibitors and varying substrate concentrations on branch initiation. Formation of branches was blocked after inhibition of nuclear division, which was not caused by a reduced growth rate. In hyphae of a nuclei distribution mutant branching was severely reduced in anucleated hyphae whereas the number of branches per hyphal length was linearly correlated to the concentration of nuclei, in the nucleated hyphae. In wild type cells, branching intensity was increased when the tip extension was reduced, and reduced when growing on poor substrates. In these situations, the hyphal concentration of nuclei was maintained and it is suggested that branching is correlated to cell cycle progression in order to maintain a minimum required cytoplasmic volume per nucleus and to avoid the formation of anucleated hyphae in the absence of nuclear divisions. The presented results further suggest the hyphal diameter as a key point through which the hyphal element regulates its branching intensity in response to the surrounding substrate concentrations.     

Evidence for the independent regulation of hyphal extension and branch initiation in Fusarium graminearum A3 5

Abstract Addition of 100 μM choline chloride to the medium increased (by approx. 36%) both the length of the hyphal growth unit ( G a measure of mycelial branching) and the mean hyphal extension rate ( E ) of Fusarium graminearum but did not increase the maximum rate of extension of the hyphae ( E _max). The paramorphogen, edifenphos (Hinosan) reduced G and E without affecting specific growth rate (μ). However, when mycelia were treated with edifenphos plus choline, μ was reduced, G was increased by approx. 35%, but E and E _max were not affected. The results suggest that the primary effect of edifenphos is inhibition of hyphal extension, whilst the primary effect of choline is inhibition of branch initiation.     

The Development and Behaviour of Mycelial Strands in Merulius lacrymans (Wulf.) Fr.: II. Hyphal Behaviour during Strand Formation

The system of hyphal branching by Merulius lacrymans was observedin mycelium which had grown from a wood food-base on to glassslides during incubation in sterile moist chambers. A hierarchyof branches and sub-branches arose from the region of clampconnexions, or nodes, of relatively wide main hyphae. Therewas evidence that the sequence of branches occurring at nodesin basipetal succession represented the time sequence of branchdevelopment at any one node. Later-formed branches at any nodewere smaller than earlier branches, but such earlier branchesusually became smaller towards the tip as growth continued.Mycelial strands were built up by growth and branching of thigmo-tropicallysensitive ‘tendril’ hyphae in association with thewide main hyphae. Tendril hyphae were characteristically narrow,thin-walled hyphae arising both as later-formed branches fromthe nodes of the main hyphae and as the narrowed tips of earlierbranches. Although this branching behaviour could be seen amongstaerial hyphae growing over agar media, hyphae growing in contactwith or within the agar behaved differently and did not formstrands.     

Multinucleate nature,and mating by use of isozyme analysis inPoria cocos

Double staining study of nuclei and cell walls inPoria cocos indicated that the hyphal cells were multinucleate and had no clamp connections. Isozyme analysis of alcohol dehydrogenase (ADH) in 52 natural isolates revealed that there were three types of banding patterns: type I, five bands; type II, one slow band; type III, one fast band. Regenerants expressing type-II or type-III ADH-isozyme pattern were obtained from type-I isolates via protoplast manipulation. When the type-II regenerants were mated with the type-III regenerants, hyphae of type-I phenotype appeared. These data indicated that these type-II and type-III regenerants derived from protoplasts of the type-I isolates were primary hyphae. These primary hyphal cells were also multinucleate. Inter-strain mating ofP. cocos was performed and confirmed by ADH-isozyme analysis. Confronting cultures of a type-III regenerant derived from protoplasts of a type-I isolate and a type-II regenerant derived from a type-II isolate resulted in type-I hyphae.     

中国大孔菌属小记

<正>1 INTRODUCTION Megasporoporia Ryvarden & J.E. Wright is characterized by large pores, long and cylindrical to ellipsoid basidiospores, clamp connections on generative hyphae, and by dextrinoid skeletal hyphae     

中国哈宁管菌属(担子菌纲)的首次报道

报道了中国担子菌纲一新记录属——哈宁管菌属Henningsomyces,并对采集于云南省迪庆州香格里拉县千湖山冷杉倒木上的一新记录种雪白哈宁管菌Henningsomyces candidus进行了详细描述。该菌最典型的形态特征是担子果由许多白色小管直立排列而成,菌丝体为一体系,同时具有简单分隔和锁状联合,担孢子薄壁、光滑、近椭圆形,菌管口的菌丝呈明显的树状分枝。     

Ectopic expression of a constitutively active Cdc42 small GTPase alters the morphology of haploid and dikaryotic hyphae in the filamentous homobasidiomycete Schizophyllum commune

Cloning of the Cdc42 gene from Schizophyllum commune enabled investigation of the role of ScCdc42 in the regulation of vegetative growth and sexual reproduction in this fungus, which has a well-characterized hyphal cell structure, cytoskeleton, and mating system. Ectopic expression of the constitutively active Sccdc42(G12V) or Sccdc42(Q61L) alleles from native or inducible ScCel1 promoters in haploid hyphae had dramatic effects on hyphal morphology, cytoskeletal structure, and Cdc42 localization. For transformants with constitutively active Sccdc42, polar tip growth of apical cells in the leading hyphae was normal but polar tip growth in side branches was altered, implying different regulation of polarity establishment in the two groups of apical cells. Branch emergence at exceptional sites and isotropic growth of cells near the septum indicated that ScCdc42 regulates branch site selection and subsequent hyphal development. Poor dikaryotization along with irregular clamp connections in mates expressing Sccdc42(G12V) or Sccdc42(Q61L) suggested that Cdc42 also contributes to efficient mating in S. commune.     

Roles of Ca2+ in hyphal and yeast-form growth inCandida albicans. Growth regulation by altered extracellular and intracellular free Ca2+ concentrations

The dimorphic fungusCandida albicans has both a yeast form and a hyphal form. When yeast-form cells were starved and then transferred to aN-acetylglucosamine medium, the formation of true hyphae from the unbudded yeast-form cells was induced. Removal of Ca²⁺ from the medium with EGTA inhibited hyphal formation by 50%, resulting in only thin and short hyphae. Externally applied excess Ca²⁺ (>10⁻²M) also affected the hyphal formation, resulting in formation of pseudohyphae. This effect required a high concentration of Ca²⁺ but was Ca²⁺-specific. Deprivation of Ca²⁺ also inhibited yeast-form growth. Interestingly, such cells had abnormally wide bud necks and became defective in cell separation. To measure cytosolic free Ca²⁺, fura-2 was introduced into hyphal cells by electroporation. Its normal value was estimated to be about 100 nM. The electroporation caused transient elevation of cytosolic free Ca²⁺ concentration and transient cessation of hyphal growth. There was a close correlation between the timing of recovery of Ca²⁺ concentration and that of the resumption of hyphal growth. Our results demonstrate the importance of extracellular and intracellular free Ca²⁺ for the growth ofC. albicans.     

Development of Aspergillus parasiticus and formation of aflatoxin B1 under the influence of conidiogenesis affecting compounds

The influence of various inhibitors of hyphal growth, sporulation and biosynthesis of aflatoxin B₁ in Aspergillus parasiticus NRRL 2999 was studied. 6-Thioguanine, dl-ethionine, fluoroacetic acid and phenylboric acid, inhibitors of maturation of fungal conidiophores and of conidiogenesis, were added at various concentrations to malt extract agar. Lower concentrations of 6-thioguanine and dl-ethionine did not inhibit the growth of hyphae and the sporulation. Phenylboric acid reduced conidiogenesis more than hyphal growth. The yields of aflatoxin B₁ were significantly reduced. Additions of fluoroacetic acid did not greatly affect the growth of hyphae but totally inhibited the production of conidia and concurrently significantly reduced the formation of aflatoxin B₁. An interrelation between conidiogenesis and onset of secondary metabolism in A. parasiticus is evident.     

Fine structure of the cell walls of Polyporus myllitae Cke. et Mass.

Following a brief survey of the wall structure of the vegetative hyphae of a number of basidiomyeetes, attention is focused upon Polyporus myllitae Cke. et Mass. After removal of the outer amorphous layer by various chemical treatments, the underlying surface is seen to consist of an interwoven network of microfibrils. There is no evidence of any preferred angle of orientation. However, on what is believed to be the inner surface of the hyphal wall, microfibrils show a strong tendency towards a transverse orientation. The resulting structure is compatible with the multi-net concept of cell wall growth of Houwink and Koelofsen. There is no obvious change in microfibril orientation in passing along a hypha towards its tip. Electron-opaque cross-walls partition hyphae, sometimes separate a branch from a parent hypha, and occur in clamp connections. The cross-wall consists of microfibrils underlying, or embedded in, an amorphous matrix. They are circularly arranged around a single central pore which has a thickened rim.     

Immunofluorescence microscopy of the microtubule cytoskeleton during conjugate division in the dikaryon Pleurotus ostreatus N001

Fluorescence microscopy was used to describe the distribution of nuclei and the organization of the microtubule network in hyphae of Pleurotus ostreatus. Dikaryotic hyphae of P. ostreatus N001 grow by tip extension with two closely spaced nuclei moving slowly forward with the growing hyphal tip. During vegetative growth of the hyphae, cytoplasmic microtubules are found as long filaments oriented longitudinally within fungal hyphae. When the apical cell reaches a length of approximately 150 μm, the two nuclei divide synchronously. Mitosis occurs in association with clamp connection formation, with one of the nuclei dividing in the hook of the developing clamp connection and the other in the main hypha. After mitosis, two daughter nuclei move forward to approximately the center of the apical cell, while the other two move backward to a central position in the subapical cell. Two septa are formed, one in the clamp and the other across the main axis of the hypha to delimit the apical cell. The use of fluorescence microscopy made it possible to examine the changes in the cytoplasmic microtubules, the configuration of the mitotic apparatus, the site of septation and the post-mitotic nuclear migrations during conjugate division in P. ostreatus dikaryotic hyphae.