How a fungus escapes the water to grow into the air.
Fungi are well known to the casual observer for producing water-repelling aerial moulds and elaborate fruiting bodies such as mushrooms and polypores. Filamentous fungi colonize moist substrates (such as wood) and have to breach the water-air interface to grow into the air. Animals and plants breach this interface by mechanical force. Here, we show that a filamentous fungus such as Schizophyllum commune first has to reduce the water surface tension before its hyphae can escape the aqueous phase to form aerial structures such as aerial hyphae or fruiting bodies. The large drop in surface tension (from 72 to 24 mJ m-2) results from self-assembly of a secreted hydrophobin (SC3) into a stable amphipathic protein film at the water-air interface. Other, but not all, surface-active molecules (that is, other class I hydrophobins and streptofactin from Streptomyces tendae) can substitute for SC3 in the medium. This demonstrates that hydrophobins not only have a function at the hyphal surface but also at the medium-air interface, which explains why fungi secrete large amounts of hydrophobin into their aqueous surroundings. (+info)
Update on interconversions of vitamin B-6 with its coenzyme.
Biosynthesis of pyridoxal 5'-phosphate (PLP) depends upon the relatively specific action of two consecutive enzymes, viz. pyridoxal (pyridoxine, pyridoxamine) kinase and pyridoxine (pyridoxamine) phosphate oxidase. Less specific phosphatases catalyze hydrolyses of the 5'-phosphates of the vitamers pyridoxal, pyridoxamine, and pyridoxine. From the recognition a generation ago of these processes by which the three forms of vitamin B-6 and their 5'-phosphates are interconverted, more recent studies have provided a fairly sophisticated understanding of the molecular characteristics of the enzymes involved. The evolutionary retention of homologous portions of pyridoxal kinase in humans as well as bacteria and the most recent finding of a highly conserved region of the pyridoxine (pyridoxamine) phosphate oxidase, also from both prokaryotic and eukaryotic organisms, emphasize the importance of these catalysts in the formation of a coenzyme that is essential for most organisms. Both kinase and oxidase involved in B-6 metabolism are potential targets for pharmacologic agents. (+info)
Cloning and expression of a cDNA encoding the laccase from Schizophyllum commune.
We cloned and analyzed the nucleotide sequence of a cDNA that encodes polyphenol oxidase (laccase) from the white-rot basidiomycete Schizophyllum commune. The nucleotide sequence of the full-length cDNA contained a 1554-base open reading frame that encoded a polypeptide of 518 amino acid residues, including a putative signal peptide of 16 residues. It contained four highly similar regions that are conserved in the deduced amino acid sequences of other laccases, including the region thought to be involved in copper binding. Aspergillus sojae strain 1860 (which has low protease levels) was transformed with the plasmid lacAL/pTPT, which contained the laccase gene under the control of the tannase promoter from Aspergillus oryzae. Laccase was secreted into the medium when transformants A1 and A2 were cultured in tannic acid-containing medium. (+info)
Ultrastructure of an indigotin-producing dome mutant of Schizophyllum commune.
Electron microscopic observations of an indigotin-producing dome mutant of Schizophyllum commune Fr. have shown that large wall ingrowths occur within the hyphae. These ingrowths are coupled with morphological abnormalities produced by the dome mutation. The pigment indigotin appears to be produced by progressive condensation within vacuoles and to a lesser extent within the wall ingrowths. Cytochemical techniques have shown that the wall ingrowths are similar in structure to the hyphal walls. there was no evidence for the passage of condensed indigotin into the medium; the pigment granules found in the medium must therefore form outside the hyphae. (+info)
Studies on basidiospore development in Schizophyllum commune.
The time required for synthesis of the spore components and the effect of different environmental conditions on basidiospore production were studied in the basidiomycete Schizophyllum commune. Both exogenous glucose and storage materials were used in the synthesis of spore components, which took 40 to 45 h to complete. A temperature of 30 degrees C, the presence of 5% CO2, a continuous supply of glucose, or a lack of exogenous glucose, had no effect on the rate of spore production. Light, however, was required for sporulation. Darkness inhibited sporulation between karyogamy and the initiation of meiosis: complete inhibition occurred after 48 h in the dark. Spores were produced 5 h after release from dark inhibition. (+info)
Characterization of trehalose phosphorylase from Schizophyllum commune.
During growth on d-glucose, the basidiomycete Schizophyllum commune produces an intracellular alpha,alpha-trehalose phosphorylase. Specific phosphorylase activity increases steadily during the exponential growth phase, up to a maximum of approx. 0.08 unit/mg of protein, and decreases after the available d-glucose in the medium has been fully depleted. The variation with time of the concentrations of intracellular alpha,alpha-trehalose and Pi is reciprocal to that of trehalose phosphorylase activity, indicating that the enzyme makes temporary use of the pool of alpha, alpha-trehalose (approx. 0.42 mmol/g dry cell) via phosphorolysis. The enzyme has been purified, 150-fold, to homogeneity in 55% yield and characterized. It is a monomeric 61 kDa protein, which seems to lack regulation at the level of enzyme activity. The enzyme catalyses the reversible phosphorolysis of alpha,alpha-trehalose into alpha-d-glucose 1-phosphate and alpha-d-glucose in the absence of cofactors, with a catalytic-centre activity at 30 degrees C of 14 s(-1). Double-reciprocal analysis of the initial velocities for trehalose phosphorolysis and synthesis yields intersecting patterns, and no exchange reaction occurs between alpha-d-glucose 1-phosphate and the phosphate analogue arsenate. Therefore trehalose phosphorylase operates by a ternary-complex, rather than a Ping-Pong, kinetic mechanism. The specificity constants (kcat/Km) of phosphate (6000 M(-1).s(-1)) and alpha-d-glucose 1-phosphate (3500 M(-1).s(-1)) compared with those of alpha,alpha-trehalose (161 M(-1).s(-1)) and d-glucose (260 M(-1).s(-1)), together with the inhibition by NaCl, which is competitive with respect to phosphate with a Ki of 67 mM, suggest an important role for ionic enzyme-phosphate interactions in the catalytic mechanism of trehalose phosphorylase. The isolated enzyme requires alpha,alpha-trehalose (0.1-0.3 M) for its conformational stability. (+info)
Multiple sex pheromones and receptors of a mushroom-producing fungus elicit mating in yeast.
The mushroom-producing fungus Schizophyllum commune has thousands of mating types defined, in part, by numerous lipopeptide pheromones and their G protein-linked receptors. Compatible combinations of pheromones and receptors encoded by different mating types regulate a pathway of sexual development leading to mushroom formation and meiosis. A complex set of pheromone-receptor interactions maximizes the likelihood of outbreeding; for example, a single pheromone can activate more than one receptor and a single receptor can be activated by more than one pheromone. The current study demonstrates that the sex pheromones and receptors of Schizophyllum, when expressed in Saccharomyces cerevisiae, can substitute for endogenous pheromone and receptor and induce the yeast pheromone response pathway through the yeast G protein. Secretion of active Schizophyllum pheromone requires some, but not all, of the biosynthetic machinery used by the yeast lipopeptide pheromone a-factor. The specificity of interaction among pheromone-receptor pairs in Schizophyllum was reproduced in yeast, thus providing a powerful system for exploring molecular aspects of pheromone-receptor interactions for a class of seven-transmembrane-domain receptors common to a wide range of organisms. (+info)
Maxillary sinusitis caused by medusoid form of Schizophyllum commune.
We present a case of maxillary sinusitis in a diabetic female caused by the basidiomycete fungus Schizophyllum commune. Identification of the isolate was hampered by its atypical features. Subcultures formed sterile medusoid structures from nonclamped mycelia until spontaneous dikaryotization resulted in the development of characteristic fan-shaped fruiting bodies. Identification was confirmed by the presence of spicules formed on the hyphae and by vegetative compatibility with known isolates. (+info)