Zoospore germination in the water mold, Blastocladiella emersonii

Cyclic GMP and cyclic AMP levels during growth and differentiation of B. emersonii were measured by use of chemical, biochemical, and immunologic assays. Of particular interest was the finding that net synthesis of cyclic GMP occurred during a single stage of its life cycle, sporulation, when intracellular levels increased 50-to 100-fold in a process requiring protein and RNA synthesis.Cyclic AMP and cyclic GMP are generally regarded as growth-regulatory agents in animal cells and bacteria (1-4). In general, high intracellular levels of cyclic AMP are associated with conditions that arrest or limit growth and high levels of cyclic GMP with a change to more favorable growth conditions (3). Intracellular cyclic AMP levels in a variety of eukaryotic microorganisms also increase as conditions become less favorable for growth (5-7); however, we are not aware of any report documenting the existence in these organisms of cyclic GMP.This report establishes the presence of both cyclic AMP and cyclic GMP in the aquatic fungus Blastocladiella emersonii (8). In addition, we describe an analysis of cyclic nucleotide levels at different stages of the life cycle. The levels of cyclic AMP and cyclic GMP were found to change markedly during cytodifferentiation. Of particular interest is our finding that net synthesis of cyclic GMP in B. emersonii occurs only as growth ceases during sporulation, when intracellular levels increase 50-to 100-fold. MATERIALS AND METHODSMedia. Glucose-casamino acid and peptone-yeast extractglucose growth media, and buffered CaCl2 solution were as described (9).Cell Growth and Development. Routinely 1 to 2 X 109 zoospores, obtained as described (9), were inoculated into 900 ml of glucose-casamino acid medium in a water-jacketed spinner flask. The temperature was maintained at 270 by circulating water. Germination, assayed by microscopic observation (10), was complete by [45][46][47][48][49][50][51][52][53][54][55][56][57][58][59][60] min, when each zoospore had given rise to a uninucleate germling. Stirring and aeration (11) were then begun and continued for about 5-6 hr. At this time the culture consisted entirely of multinucleate vegetative cells; sporulating cells and zoospores were never detected in vegetative cell populations examined under the phase-contrast microscope. Growth medium was then exchanged by filtration for one-half its volume of buffered CaCl2 to induce sporulation (10, 11). Two hr after the exchange ) 90% of the cells had formed a prominent discharge papillum (11), and by 4 hr >90% had released zoospores.Radioimmune Analysis of Cyclic Nucleotide Levels. At different times in the growth cycle aliquots (50 or 100 ml) were removed from the culture, and the cells were collected by centrifugation (5 min, 2000 X g) at 4°. Zoospores were first filtered over Sargent 500 paper to remove vegetative cell debris (12). The medium was removed by aspiration, and the cell pellets were immediately frozen in an ethanol-solid CO2 bath. Acid-soluble material was extracted at 40 in 1 ml of 1 M...

Section: Methodsmentioning

confidence: 99%

Cyclic nucleotide metabolism coupled to cytodifferentiation of Blastocladiella emersonii.

Silverman¹,

Epstein²

1975

“…We have focused attention particularly on the sequence of cellular changes involved in zoospore germination, primarily because this sequence is characterized by dramatic, abrupt changes in cell structure, and because zoospore populations can be induced to germinate rapidly and semisynchronously (1). A sequence of four morphologically distinct cell types can be unambiguously resolved (see Fig.…”

mentioning

confidence: 99%

“…The initial cell type, the zoospore, swims about by means of a posteriorly situated flagellum and can be maintained for relatively long periods in the absence of exogenous organic nutrients (3). The zoospore contains an impressively ordered array of internal organelles, but lacks a cell wall (1,4,5). Zoospore populations germinate upon exposure to any of certain monovalent salts (3,6).…”

mentioning

confidence: 99%

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Zoospore Germination in Blastocladiella emersonii: Cell Differentiation without Protein Synthesis?

Soll

Sonneborn

1971

Evidence is presented to suggest that several early events of zoospore germination in the water mold, Blastocladiella emersonii, are not dependent upon concomitant protein synthesis. The events involve abrupt, dramatic changes in cell architecture. On account of this evidence, as well as evidence available from other sources, we question whether differential protein synthesis provides an exclusive and sufficient mechanism for phenotypic change (i.e., cell differentiation). Rather, we argue that mechanisms for bringing about structural alterations in the preformed machinery of the cell should also be given attention.One common thread runs through virtually all current thinking regarding the mechanism(s) of cellular differentiationnamely, that cells change phenotype (i.e., differentiate) as a result of differential protein synthesis. Our intention in this paper is certainly not to discredit the usefulness of this hypothesis, but rather to call into question whether this form of phenotypic control provides an exclusive and sufficient mechanism for cellular differentiation.The organism under study is the water mold Blastocladiella emersonii. We have focused attention particularly on the sequence of cellular changes involved in zoospore germination, primarily because this sequence is characterized by dramatic, abrupt changes in cell structure, and because zoospore populations can be induced to germinate rapidly and semisynchronously (1). A sequence of four morphologically distinct cell types can be unambiguously resolved (see Fig. 1 and refs.

“…We present evidence that this change can be effected in vitro by means of a protein phosphatase (phosphoprotein hydrolase, EC yeast extract/glucose agar plates and stored as lyophilized powders, as described (4). Growth-phase cells were prepared as described (10) after adding 8 x 108 zoospores to 14 liters of defined growth medium (11) Fig. 4 for growing cell extracts).…”

mentioning

confidence: 99%

Developmentally regulated interconversions between end product-inhibitable and noninhibitable forms of a first pathway-specific enzyme activity can be mimicked in vitro by protein dephosphorylation-phosphorylation reactions.

Frisa¹,

Sonneborn²

1982