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At least 73 records · Page 4Linked to original sources
PubMed1966

Effect of Electrolytes on Differentiation in Achlya sp.

Some factors controlling the differentiation of sporangia and gemmae in an isolate of Achlya sp. were investigated by replacement culture technique. Factors in the replacement medium which affect differentiation were as follows: A) Calcium is required for the differentiation of both sporangia and gemmae. B) Calcium cannot be replaced by magnesium, potassium or sodium. C) Gemmae are induced when the replacement medium contains salt at 40 to 80 mm. D) The salt induction of gemmae is nonspecific, sodium, potassium, magnesium and calcium chlorides are equally effective.

Journal Article↗
PubMed2000

A non-stop antisense reading frame in the grp78 gene of Neurospora crassa is homologous to the Achlya klebsiana NAD-gdh gene but is not being transcribed.

A long non-stop reading frame exists on the antisense strand of the grp78 gene (cDNA and genomic DNA) of Neurospora crassa. Computer analysis revealed a strong similarity of the putative antisense protein to the 10th exon of the NAD-dependent glutamate dehydrogenase gene (NAD-gdh) of Achlya klebsiana, which is itself located on the complementary strand of a transcribed hsc70 gene homologue. In Neurospora, no grp78 antisense mRNA was detected by Northern blot and reverse transcription-coupled polymerase chain reaction analyses, indicating that this long reading frame is not being transcribed. Hypotheses for the presence of such unexpressed non-stop reading frames are discussed.

Blotting, Northern↗
PubMed2001

Heavy metals have different effects on mycelial morphology of Achlya bisexualis as determined by fractal geometry.

The morphological response, as measured by changes to mycelial area, radial extension and border fractal dimension, of the oomycete Achlya bisexualis to Cu, Co, Hg, Zn and Cd at concentrations of between 0.05 and 3 mM is described. All of the metals decreased mycelial area and radial extension. Border fractal dimension increased in the presence of Cu, Co and Hg with individual hyphae extending out beyond the mycelial margin. In the presence of 3 mM Hg these hyphae displayed spiral growth. Zn and Cd had no effect on border fractal dimension. We suggest that all of the metals slow growth and that Cu, Co and Hg may also disrupt the relationship between tip growth and branching at the edge of the mycelium.

Fractals↗
PubMed1967

Role of enzymatic wall-softening in plant morphogenesis: hormonal induction in Achlya.

Sexual hormone A, which induces antheridial branching in male strains of Achlya, also elicits a rise in cellulase. The peak of induced cellulase corresponds in time with the appearance of branches that are the male sexual organ primordia; only those strains that branch in response to the hormone show a concomitant rise in cellulase. The response to the hormone is inhibited by compounds that block protein synthesis, for example, p-fluorophenylalanine and puronmycin. Vegetative branching, induced by substrates such as casein hydrolysate, is also accompanied by a rise in cellulase.

Enzyme Induction↗
PubMed1973

Protein synthesis during the differentiation of sporangia in the water mold Achlya.

During the synchronous differentiation of sporangia in the absence of added nutrients, the water mold Achlya bisexualis (Coker and Couch) actively synthesized protein. Inhibition of protein synthesis at any time during the sporulation process completely inhibited further differentiation. Large changes in the rate of radioactive amino acid uptake resulted in changes in the specific activity of the cellular amino acid pool. The rate of protein synthesis was calculated from the amino acid pool specific activity and the incorporation of isotope into protein. During the 1st h after induction of the sporulation process, the rate of protein synthesis increased to two times the initial value. The amino acid precursors for this synthesis were supplied by the degradation of preexisting protein. Proteolytic enzyme activity assayed in vitro increased in proportion to the in vivo rates of protein synthesis and degradation. Differentiation was accompanied by a slight decline in dry weight of the mycelium as well as by a decrease in the protein content, whereas the relative size of the amino acid pools remained constant.

Amino Acids↗
PubMed1974

Cellulase localization in hyphae of Achlya ambisexualis.

Cellulase (EC 3.2.1.4; beta-1, 4-glucan glucanohydrolase) was localized at the ultrastructural level and found to occur in dictyosomes and vesicles, around the periphery of unidentified storage bodies, between the plasmalemma and the cell wall, and on the outer surface of the cell wall in the male strain (E87) of Achlya ambisexualis after treatment with the sex hormone antheridiol.

Cell Wall↗
PubMed1982

Alterations in gene expression during heat shock of Achlya ambisexualis.

When exponentially growing cultures of Achlya ambisexualis strain E87 were raised from their normal growth temperature of 30 degrees C to 35 degrees C, the rates of synthesis of a small number of proteins were dramatically increased. The most predominant proteins synthesized in response to heat shock had molecular weights of 70,000 and 78,000, and their increased synthesis was detected as early as 10 min after the shift to 35 degrees C. Changes in the populations of translatable messenger RNAs during heat shock showed that the levels of the mRNA's for all the major induced proteins correlated very closely with the alterations in the in vivo patterns, suggesting a transcriptional level of control of their synthesis. When after a period of heat shock (60 min) the cultures were shifted back to 30 degrees C, recovery of the preshock patterns of protein synthesis was attained after several hours. Different proteins show temporally distinct patterns of recovery. During recovery the levels of translatable mRNA's for the induced proteins also correlated closely with the patterns of in vivo protein synthesis.

Fungal Proteins↗
PubMed1969

Ribonucleic acid synthesis during the differentiation of sporangia in the water mold Achlya.

The role of ribonucleic acid (RNA) synthesis in the development of sporangia in the saprolegniaceous mold Achlya was studied. Methods were developed for growing and treating large populations of mycelia so that the hyphal tips would differentiate into sporangia with considerable synchrony. Under the starvation conditions imposed for the differentiation of sporangia, net RNA, deoxyribonucleic acid (DNA), and protein synthesis ceased. However, incorporation of radioactive precursors into RNA continued at a high rate throughout the period of differentiation, showing that the enzymatic mechanism for RNA synthesis was still in an active state. Actinomycin D inhibited the differentiation of sporangia and the incorporation of labeled precursors into RNA. The level of actinomycin used did not inhibit the normal outgrowth and branching of the mycelia that occurred during differentiation. Thus, DNA-dependent RNA synthesis was required for the differentiation of sporangia. Sucrose gradient analysis of newly synthesized RNA showed that only the ribosomal and soluble fractions of RNA were labeled during vegetative growth. During the differentiation of sporangia, ribosomal and soluble RNA fractions were also labeled, and, in addition, a heterodisperse fraction of labeled RNA which was heavier than ribosomal RNA appeared; this fraction was not evident in the newly synthesized RNA from vegetative mycelia.

Cell Differentiation↗
PubMed1980

Hyphal tip growth in Achlya. I. Cytoplasmic organization.

Growing apices of Achlya ambisexualis Raper hyphae were examined by electron microscopy using cytochemical techniques. Apical vesicles can be grouped into two major classes based upon size and cytochemical reactions. Vesicles of the most prominent class are about 150 nm in diameter and possess contents which appear fibrous in thin section. This fibrous material reacts positively with the periodic acid-silver methenamine (PASM) cytochemical test for polysaccharides. Most of these same vesicles also display IDPase activity, and a smaller number display acid phosphatase activity. Vesicles of the second class are about 80 nm in diameter, and include coated vesicles and others which react positively for IDPase activity. They show a negative PASM reaction in contrast with the larger vesicles. Some of these smaller vesicles are stained by the phosphotungstic acid-chromic acid (PTA-CrO3) stain, whereas 150-nm vesicles are not. The source of at least some vesicles of both major classes appears to be the Golgi apparatus. It is proposed that the IDPase activity and carbohydrate content of the 150-nm cytoplasmic vesicles could serve as useful markers in their isolation.

Cell Membrane↗
PubMed1980

Hyphal tip growth in Achlya. II. Subcellular localization of cellulase and associated enzymes.

The isolation and characterization of cellulase-containing membranes of Achlya ambisexualis Raper was attempted by differential and density gradient centrifugations. Maximum cellulase activity was found at an isopycnic density of 1.19 g/cm3, although some activity was found at other densities. A similar distribution of activity was shown by IDPase, ATPase, UDPG transferase, and by sedimentable carbohydrate. The coequilibration and steady enrichment of these activities during purification suggests their presence in a single type of subcellular particle. It was not possible to identify clearly the particle(s) in question from isolated fractions by electron microscopy, but when compared with the cytochemical localization of carbohydrate and IDPase in intact hypha, cytoplasmic vesicles with 150-mm diameters seem to be likely candidates.

Acid Anhydride Hydrolases↗
PubMed1975

Hormonal stimulation of ribosomal RNA synthesis in Achlya ambisexualis.

The experiments reported show that one of the early effects of the steroid sex hormone antheridiol is on the synthesis of rRNA and ribosomes. This is demonstrated in hormone treated cultures of Achlya ambisexualis (strain E87) by an enhancement of the incorporation of [3H]uridine into 26S and 18S rRNA and by an increase in measurable amounts of ribosomes per milligram dry weight of mycelium. Furthermore, since the hormone does not significantly alter the pool size or the specific activity of uridine triphosphate, this effect appears to represent an increased rate of RNA synthesis.

Fungi↗
PubMed1978

Glucose transport in Achlya: characterization and possible regulatory aspects.

The freshwater fungus Achlya transported D-(+)glucose (glucose) and 2-deoxy-D-glucose (deoxyglucose) by an energy-related system. Their transport4 was inhibited by uncouplers of metabolic energy such as 2,4-dinitrophenol, cyanide, azide, and carbonylcyanide-p-chlorophenylhydrazone. Besides inhibiting each other, glucose and deoxyglucose transport was inhibited by D-(+)galactose, D-(+)mannose, and D-(+)xylose. Many other sugars tested failed to inhibit glucose transport implying a certain degree of specificity. Glucose transport was pH (optimum at 6.5) and temperature (optimum at 30-40 degrees C) dependent. Glucose transport was also inhibited by citrate, N6-substituted adenines (cytokinins), and iodine. None of these agents penetrated the cell membrane within the brief (1-3-min) period in which glucose transport was measured. In every case, transport was inhibited within 10 s (the shortest time in which measurements could be made). When cells were osmotically shocked to release a cell-wall membrane phosphorylated proteoglycan (PPG), they became incapable of transporting glucose for several hours until new PPG material was reisolable from the membrane by osmotic-shock treatment. The osmotically shocked cells could not transport glucose or deoxyglucose. No glucose-binding protein was detected in the shock fluid. Practically all of the glucose transported within 1-2 min was recovered as glucose-6-phosphate. No other phosphorylated sugar was detected suggesting that glucose may be phosphorylated in transport. Related studies have shown that citrate removed calcium bound by PPG; N6-substituted adenines were bound by PPG while three polyphosphorylated dinucleosides, HS3, HS2, and HS1, were displaced from it. Iodine formed stable complexes with the HS compounds. All of these agents inhibited glucose transport without entering the cell. It is therefore possible that HS compounds, calcium and PPG may be involved in maintaining the cell membrane in proper form for glucose transport.

Biological Transport, Active↗
PubMed1984

Analysis of the steroid receptor of Achlya ambisexualis.

We have previously reported the discovery of a specific high-affinity binding protein for the fungal sex steroid pheromone antheridiol in the cytosol of Achlya ambisexualis male cells. In this report, we describe the fractionation of the binding protein from the cytosol by ammonium sulfate precipitation, the optimization of in vitro conditions for radioligand binding assays, and some of the biochemical properties of the binding protein. In the presence of sodium molybdate, the macromolecule has a sedimentation coefficient of 8.3 S in sucrose gradients of low ionic strength, a Stokes radius of 56.6 A (Sephacryl S-300 columns), a molecular weight of approximately 192,000, a frictional ratio of 1.5, and an axial ratio of 8.9. The binding protein can be eluted with 0.24 M KCl as a single peak from DEAE-Sephadex A-25 columns. These results indicate that this steroid-binding protein from a primitive eukaryotic microbe has in vitro biochemical properties that are similar to those of other known steroid receptors in higher organisms.

Cytosol↗
PubMed1978

Protoplast formation and the visualization of nuclei in the eukaryotic microbe, Achlya.

Protoplasts have been released form 21 h germlings of the aquatic fungus, Achlya. The commercial enzyme preparation Driselase was utilized to digest the hyphal walls. Protoplast release began 20 min after incubation at 25 degrees C, and was completed by 2 hr after enzyme addition. The fluorescent dye mithramycin was utilized to observe nuclei both in tract hyphae and in isolated protoplasts.

Cell Nucleus↗